WO2010057264A1 - Essai de détection d’analyte - Google Patents

Essai de détection d’analyte Download PDF

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Publication number
WO2010057264A1
WO2010057264A1 PCT/AU2009/001515 AU2009001515W WO2010057264A1 WO 2010057264 A1 WO2010057264 A1 WO 2010057264A1 AU 2009001515 W AU2009001515 W AU 2009001515W WO 2010057264 A1 WO2010057264 A1 WO 2010057264A1
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WIPO (PCT)
Prior art keywords
particles
wgm
analyte
particle
microspheroidal
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PCT/AU2009/001515
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English (en)
Inventor
Karl Frederick Poetter
Edin Nuhiji
Paul Mulvaney
Original Assignee
Genera Biosystems Limited
The University Of Melbourne
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Publication date
Priority claimed from AU2008906057A external-priority patent/AU2008906057A0/en
Priority to AU2009317878A priority Critical patent/AU2009317878B2/en
Priority to BRPI0921591A priority patent/BRPI0921591A2/pt
Priority to US13/130,566 priority patent/US8617824B2/en
Priority to NZ592953A priority patent/NZ592953A/xx
Priority to JP2011536705A priority patent/JP5588454B2/ja
Application filed by Genera Biosystems Limited, The University Of Melbourne filed Critical Genera Biosystems Limited
Priority to CA2744331A priority patent/CA2744331C/fr
Priority to MX2011005366A priority patent/MX2011005366A/es
Priority to EP20090827053 priority patent/EP2368115B1/fr
Priority to ES09827053.1T priority patent/ES2545232T3/es
Priority to CN200980153782.XA priority patent/CN102272597B/zh
Publication of WO2010057264A1 publication Critical patent/WO2010057264A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
    • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
    • G01N33/53—Immunoassay; Biospecific binding assay; Materials therefor
    • G01N33/543—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals
    • G01N33/54313—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals the carrier being characterised by its particulate form
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y15/00—Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
    • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
    • G01N33/53—Immunoassay; Biospecific binding assay; Materials therefor
    • G01N33/543—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals
    • G01N33/54313—Immunoassay; Biospecific binding assay; Materials therefor with an insoluble carrier for immobilising immunochemicals the carrier being characterised by its particulate form
    • G01N33/54346—Nanoparticles
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/48—Biological material, e.g. blood, urine; Haemocytometers
    • G01N33/50—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing
    • G01N33/58—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving labelled substances
    • G01N33/588—Chemical analysis of biological material, e.g. blood, urine; Testing involving biospecific ligand binding methods; Immunological testing involving labelled substances with semiconductor nanocrystal label, e.g. quantum dots
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
    • G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
    • G01N2021/7769—Measurement method of reaction-produced change in sensor
    • G01N2021/7786—Fluorescence
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/75—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated
    • G01N21/77—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator
    • G01N21/7703—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator using reagent-clad optical fibres or optical waveguides
    • G01N21/7746—Systems in which material is subjected to a chemical reaction, the progress or the result of the reaction being investigated by observing the effect on a chemical indicator using reagent-clad optical fibres or optical waveguides the waveguide coupled to a cavity resonator

Definitions

  • the present invention relates to the field of analyte detection. More particularly, the present invention relates to biosensing and rapid and sensitive analyte detection using a whispering gallery mode (WGM)-based assay.
  • WGM whispering gallery mode
  • WGM whispering gallery modes
  • MDR morphology dependent resonances
  • WGM technology is predicated, in part, on the phenomenon that fluorophores enable a distinctive WGM profile to be generated.
  • the fluorophores are incorporated onto quantum dots which are into the microparticles by diffusion or may be incorporated during their manufacture.
  • the type of fluorophore is unlimited and may for example be an organic dye, a rare earth based lumophore, a semiconductor nanocrystal of various morphologies and compositions, a phosphor or other material which emits light when illuminated. This fluorophore or mixture thereof is then attached to microspheroidal particles. When a target analyte interacts with a binding partner immobilized to the microspheroidal particle, the WGM profile changes, enabling detection of the binding event.
  • WGM allow only certain wavelengths of light to be emitted from the particle.
  • the result of this phenomenon is that the usual broad emission (10-lOOnm wide) bands from, for example, a fluorophore, become constrained and appear as a series of sharp peaks corresponding effectively to standing mode patterns of light within the particle.
  • the WGM profile is extremely sensitive to changes at the surface of the microspheroidal particle and the WGM profile changes when the microspheroidal particle interacts with analytes or molecules within its environment.
  • the present invention provides a sensitive method and reagents based on whispering gallery mode (WGM) detection assays, for, inter alia, detecting analytes in a sample.
  • WGM whispering gallery mode
  • the method and reagents of the present invention are predicated, in one part, on the unexpected determination that the coating of microspheres with a fluorophore per se, as opposed to using discrete quantum dots, enhances the sensitivity of the WGM-based detection.
  • the selection of particle such as a particle with functionalized chemical groups on its surface increases sensitivity when either quantum dots or direct fluorophore coating occurs.
  • the particle is selected having a higher refractive index relative to the medium in which the assay is conducted.
  • the microspheroidal particle has a refractive index greater than 1.40.
  • one aspect of the present invention provides a method of analyte detection in a medium, the method comprising subjecting microspheres coated with a fluorophore and a multiplicity of ligands to WGM detection means to identify a binding event between one or more ligands and a ligand binding analyte.
  • the present invention provides a method of analyte detection in a medium, the method comprising subjecting microspheres wherein the microspheres have a higher refractive index than the medium comprising the analyte coated with a fluorophore and a multiplicity of ligands to WGM detection means to identify a binding event between one or more ligands and a ligand binding analyte.
  • the microspheroidal particle has a refractive index greater than 1.40.
  • Another aspect of the present invention provides a method for detecting a binding event between an analyte and a ligand, comprising the steps of: (i) anchoring a multiplicity of ligands to a population of fluorophore-conjugated microspheroidal particles; (ii) contacting the microspheroidal particles with a negative control sample and determining a baseline spectrum; (iii) contacting the microspheroidal particles with a sample putatively comprising the analyte for a time and under conditions sufficient to facilitate a binding event between the analyte and its respective ligand; and (iv) subjecting the microspheroidal particles to WGM detection means to detect a binding event.
  • Another aspect of the invention comprises, a method for detecting an analyte in a medium, comprising the steps of:
  • the microspheroidal particles are functionalized by chemical moieties such as with azide, alkyne, amine, aldehyde, sulfate or thiol, carboxyl, carboxylate and/or hydroxyl groups.
  • the microspheroidal particles are amine-aldehyde particles such as but not limited to melamine particles or melamine formaldehyde particles.
  • another aspect of the present invention provides a method for detecting a binding event between an analyte and a ligand, comprising the steps of: (i) anchoring a multiplicity of ligands to a population of fluorophore-conjugated functionalized microspheroidal particles; (ii) contacting the functionalized microspheroidal particles with a negative control sample and determining a baseline spectrum; (iii) contacting the functionalized microspheroidal particles with a sample putatively comprising the analyte for a time and under conditions sufficient to facilitate a binding event between the analyte and its respective ligand; and (iv) subjecting the microspheroidal particles to WGM detection means to detect a binding event.
  • the present invention provides a method for detecting a binding event between an analyte and a ligand, comprising the steps of: (i) anchoring a multiplicity of ligands to a population of fluorophore-conjugated amine-aldehyde microspheroidal particles; (ii) contacting the amine-aldehyde microspheroidal particles with a negative control sample and determining a baseline spectrum; (iii) contacting the amine-aldehyde microspheroidal particles with a sample putatively comprising the analyte for a time and under conditions sufficient to facilitate a binding event between the analyte and its respective ligand; and (iv) subjecting the amine-aldehyde microspheroidal particles to WGM detection means to detect a binding event.
  • the amine-aldehyde particles are melamine formaldehyde particles.
  • the present invention provides a method for detecting a binding event between an analyte and a ligand, comprising the steps of: (i) anchoring a multiplicity of ligands to a population of fluorophore-conjugated melamine formaldehyde microspheroidal particles; (ii) contacting the melamine formaldehyde microspheroidal particles with a negative control sample and determining a baseline spectrum; (iii) contacting the melamine formaldehyde microspheroidal particles with a sample putatively comprising the analyte for a time and under conditions sufficient to facilitate a binding event between the analyte and its respective ligand; and (iv) subjecting the melamine formaldehyde microspheroidal particles to WGM detection means to detect a binding event.
  • the particles may also comprise quantum dots.
  • another aspect of the present invention provides a method for detecting a binding event between an analyte and a ligand, comprising the steps of: (i) anchoring a multiplicity of ligands to a population of melamine formaldehyde microspheroidal particles comprising fluorophore-coated quantum dots; (ii) contacting the microspheroidal particles with a negative control sample and determining a baseline spectrum; (iii) contacting the microspheroidal particles with a sample putatively comprising the analyte for a time and under conditions sufficient to facilitate a binding event between the analyte and its respective ligand; and (iv) subjecting the microspheroidal particles to WGM detection means to detect a binding event.
  • Another aspect of the present invention provides a method for detecting a binding event between an analyte and a ligand, comprising the steps of: (i) anchoring a multiplicity of ligands to a population of microspheroidal particles having a higher refractive index than the medium comprising the analyte, the microspheroidal particles encoding a fluorophor; (ii) contacting the microspheroidal particles with a negative control sample and determining a baseline spectrum; (iii) contacting the microspheroidal particles with a sample putatively comprising the analyte for a time and under conditions sufficient to facilitate a binding event between the analyte and its respective ligand; and (iv) subjecting the microspheroidal particles to WGM detection means to detect a binding event.
  • Yet another aspect of the present invention provides a method of detecting an analyte, the method comprising contacting at least one population of microspheroidal particles with a sample putatively comprising the analyte, wherein each particle within a population of microspheroidal particles comprises a fluorophore which emits visible radiation in response to infrared excitation and an immobilized putative binding partner of the analyte wherein each particle population has a defined WGM profile, wherein binding of the analyte to the immobilized binding partner results in a change in the WGM profile of the at least one population of microspheroidal particles which is indicative of the presence of the analyte.
  • the analyte or its respective ligand comprises a molecule selected from the list consisting of: nucleic acid; protein; peptide; antibody; lipid; carbohydrate; and any small molecule or chemical entity, including cells (e.g. cancer cells), bacteria and viruses.
  • the ligands anchored to the microspheroidal particles are nucleic acid molecules and the analytes to be detected are complementary nucleic acid molecules.
  • the nucleic acid ligand or analyte is a DNA molecule comprising a single-stranded DNA sequence.
  • Another aspect of the present invention provides the use of a method comprising the steps of: (i) anchoring a multiplicity of ligands to a population of fluorophore- conjugated microspheroidal particles; (ii) contacting the microspheroidal particles with a negative control sample and determining a baseline spectrum; (iii) contacting the microspheroidal particles with a sample putatively comprising the analyte for a time and under conditions sufficient to facilitate a binding event between the analyte and its respective ligand; and (iv) subjecting the microspheroidal particles to WGM detection means in the manufacture of an assay to detect a binding event between an analyte and a ligand.
  • the microspheres may be re-cycled.
  • the assay may be conducted in any medium such as air or other gas or in a liquid phase such as an aqueous solution, biological buffer or complex biological fluid.
  • the present invention provides a kit comprising fluorophore- conjugated microspheroidal particles and a multiplicity of ligands for anchoring thereto, for detecting a binding event between a ligand and an analyte by WGM detection means.
  • the kit comprises fluorophore-conjugated microspheroidal particles to which a multiplicity of ligands has been attached.
  • the fluorophore may be coated on an organic dye or a quantum dot.
  • the present invention provides a biosensor comprising WGM detection means wherein the biosensor is a self-contained unit comprising a power source, light source, sample-handling chamber and a spectrophotometer.
  • SEQ ID NO Nucleotide and amino acid sequences are referred to by a sequence identifier number (SEQ ID NO).
  • the SEQ ID NOs correspond numerically to the sequence identifiers ⁇ 400>l (SEQ ID NO: I), ⁇ 400>2 (SEQ ID NO:2), etc.
  • a summary of the sequence identifiers is provided in Table 1.
  • a sequence listing is provided after the claims.
  • Figure 1 is a graphical representation of WGM DNA biosensing demonstrating consistent and measurable shifts after binding. These measurements have been carried out in an aqueous solution containing pH buffers and an electrolyte. A demonstrable shift in WGM profile was observed for each of beads 9, 10, 11 and 12 (A 3 B, C and D respectively) after the beads or microspheroidal particles were contacted with a nucleic acid analyte complementary to the nucleic acid analyte-binding partner anchored to the surface of the beads. Each of the beads was 5.6 ⁇ m in diameter.
  • FIG. 2 is a schematic representation of the WGM detection means and apparatus.
  • Figure 3 is a graphical representation of WGM spectra generated with incident light of 6.3 ⁇ W, 50.2 ⁇ W, 214.5 ⁇ W and 1,160.5 ⁇ W (A, B, C and D respectively).
  • the light source had a wavelength of 532 nm and the exposure time was 200 ms.
  • Figure 4 is a graphical representation of WGM profile generated following illumination of microspheroidal particles with incident light (532 nm, 50 ⁇ W) for 10, 60, 200 and 1,000 ms (A, B, C and D, respectively). Visibility decreased gradually up to 5 seconds exposure time (E).
  • Figure 5 is a photographic image of microspheroidal particles of the present invention immobilized on the surface of a glass coverslip.
  • Figure 6 is a photographic representation showing the simplified chemical reaction steps using a silica particle functionalized with mercaptan groups. Through covalent bonding the conjugation of fluorescently labeled acryloyl-single strand oligonucleotide fragments is achieved. This process leads to the robust cost effective fabrication of fluorescent microspheres which propagate WGM.
  • Figure 7 is a graphical representation showing the plot of the peak positions of four major WGM peaks from a single microsphere as a function of the assay stage at which they were recorded. The plot clearly demonstrates the four major peaks red shift during hybridization, blue shift during denaturing and red shift again upon re-exposure to the target.
  • Figure 8 is a photographic representation showing an overview of particle synthesis and WGM hybridization assay.
  • Part A) indicates the key features of the 70 base enl oligonucleotide-modified 7.50 ⁇ m SiO 2 microspheres.
  • TMR dye-label tetramethyl rhodamine
  • Part B) Particle assay plate preparation particles are immobilized on the hybridization substrate which follows the acquisition of emission signal (pre-treatment);
  • Part D) The final step involves the analysis of the pre/post-emission signals from a single particle, the peak positions from the acquired spectra are compared to determine the effect of the treatment solution.
  • Figure 9 is a photographic representation showing typical WGM emission signal outputs and single particle spectroscopy.
  • a typical emission signal captured in air from an excited 7.50 ⁇ m oligo-modified silica particle using two WGM characterization set-ups A) Coupled to an Ocean Optics spectrometer ( ⁇ 0.9 run) and B) Triax spectrometer ( ⁇ 0.05 run); C) The concept of single particle spectroscopy, the schematic shows two particles, labeled microsphere A and B each from the same sample, both particles have been identically chemically modified. Note the emission signals acquired from the individual particles are distinctly unique.
  • Figure 10 is a graphical representation showing single microsphere spectral shift data from a selection of sensors used in a concentration based cDNA hybridization assay.
  • Figure 11 is a schematic illustration of the reaction chemistry utilized to functionalize raw melamine formaldehyde (MF) particles with labeled single-strand- oligonucleotide fragments. Note the reaction is completed in a single step at room temperature using buffer only. The fragments covalently bind with -NH groups on the particle surface.
  • MF melamine formaldehyde
  • Figure 12 is a graphical representation showing particle excitation was achieved through an 80 W mercury lamp and a 420-490 nm filter block. Emission signals captured in air and water from 7.50 ⁇ m 30 base (TMR) oligo-modified microspheres.
  • Figure 13 is a graphical representation showing emission signal measurements, taken using assay plates derived of several composite materials; Particle excitation was achieved through an 80 W mercury lamp and a 420-490 nm filter block.
  • FIG 14 is a graphical representation showing heat stability analysis of oligonucleotide (TMR) functionalized 7.52 ⁇ m MF particles. Particles were immersed in solution under constant heat at 9O 0 C over a 3 hr period in Milli-Q, Buffer or MES (pH 5.4).
  • TMR oligonucleotide
  • a WGM was collected from each test particle utilizing an 80 W mercury lamp and a 420-
  • FIG. 15 is a graphical representation showing thermo-cycled hybridization binding study.
  • a two-step temperature gradient (37 0 C - 72 0 C) was created using a thermo- regulated microscope stage coupled to the confocal/ TRIAX setup.
  • the target DNA (T m 71.2 0 C) was complementary to the rslO434 target fragments attached to the particle.
  • Hybridization cycles were completed on a single microsphere with Milli-Q H 2 O (control) and target DNA.
  • a fluorescence signal was captured at each temperature gradient and the A ⁇ was observed.
  • Figures 16(A) and (B) are graphical representations showing (A) Melamine beads WGM solid lines: Solid lines are WGM of single melamine formaldehyde beads obtained in air. Spectra acquired in aqueous media are shown in dotted lines; (B) Silica beads WGM: Solid lines are WGM of single silica beads obtained in air. Spectra acquired in aqueous media are shown in dotted lines. Acquisition in water yielded very faint fluorescence and no WGM.
  • Figure 17 is a graphical representation of the antibody WGM immuno-assay. A single 7.52 ⁇ m MF particle functionalized with a FITC labeled human ⁇ -IgM antibody was immobilized in a single micro-well.
  • the entire assay was performed at room temperature.
  • the untreated particle was excited through a Ar+ laser to obtain a reference signal, then treated with Milli-Q followed by unlabeled human IgM.
  • the representative peak-set indicates a typical red shift of several nanometres which resulted following IgM treatment. A minimal shift was noted 30 min after the addition.
  • Spectra were acquired through a Triax 550/CCD confocal setup (spectral resolution + 0.05 nm).
  • a ligand includes a single ligand, as well as two or more ligands
  • reference to “an analyte” includes a single analyte, as well as two or more analytes
  • reference to “the fluorophore” includes a single fluorophore, as well as two or more fluorophores
  • reference to “the invention” includes single or multiple aspects of an invention; and so forth.
  • the present invention provides a multiplicity of analyte-binding partners or ligands conjugated to fluorophore-coated microspheroidal particles. When these particles are illuminated, a "baseline" whispering gallery modes (WGM) spectrum or profile is emitted. Each population of microspheroidal particles has a unique WGM baseline signature. This baseline profile is altered by binding of analytes to the analyte-binding partner or ligand on the surface of the microspheroidal particles, causing a detectable shift in the WGM spectrum.
  • WGM whispering gallery modes
  • the microspheroidal particles of the present invention comprise microspheres coated with fluorophores, which, when illuminated, emit fluorescent light. The emitted light is trapped within the microsphere and resonates within the sphere creating a spectrum of discrete wavelengths termed whispering gallery modes or "WGM" .
  • the coating of the microspheroidal particles with a fluorophore as opposed to using discrete quantum dots enhances the sensitivity of WGM-based detection.
  • the present invention extends to microspheroidal particles coated with a fluorophore (i.e. without using quantum dots) or the use of quantum dots in combination with melamine formaldehyde particles.
  • the microspheroidal particles may also be selected on the basis that they have a higher refractive index relative to the medium comprising the analyte. In an embodiment, the microspheroidal particle has a refractive index greater than 1.40.
  • quantum dot or “QD” is to be understood as encompassing particles known in the art as semiconductor nanoparticles, nanocrystals, quantum dots, or Qparticles.
  • microspheroidal particles and “microspheres” are used interchangeably herein and include spherical particles comprising any material, homogenous or otherwise which can produce one or more WGM profiles based on its fluorophore. As will be evident to those of skill in the art, almost any material, homogenous or otherwise, may be used for the microspheroidal particle.
  • the microspheroidal particles contemplated herein may also comprise more than one substance, and as such may comprise shells, alloys or mixtures of organic and/or inorganic substances.
  • the microspheroidal particle comprises a substantially homogenous material with an isotropic refractive index and which is also non-absorbing (other than the fluorophore, which is further described below).
  • the microspheroidal particles of the present invention comprise a material selected from the list consisting of: melamine or a chemical derivative thereof such as melamine formaldehyde; silica; latex; titania; tin dioxide; yttria; alumina; other binary metal oxides; perovskites and other piezoelectric metal oxides; PLGA; sucrose; agarose; and other polymers.
  • the microspheroidal particles are functionalized by chemical moieties such as with amine, aldehyde, sulfate or thiol, carboxyl, carboxylase and/or hydroxyl groups.
  • the microspheroidal particles are amine-aldehyde particles such as but not limited to melamine formaldehyde (MF) particles.
  • MF particles provide a robust conjugation substrate for acryloyl modified target oligonucleotides and proteins to bind. The covalent bond remains intact after exposure to high pH solutions and extreme temperatures, as a high quality WGM can acquire post-treatment.
  • Melamine is a trimer of cyanamide and is also known as: l,3,5-triazine-2,4,6- triamine; 2,4,6-triamino-s-triazine; cyanurotriamide; cyanurotriamine or cyanuramide.
  • the melamine is melamine formaldehyde.
  • the present invention also extends to the use of magnetic particles in the WGM assay. Such particles could be presented in very precise fixed positions. Magnetic facilitated particle immobilization enables discrete single particle analysis and alleviates the need to fabricate custom immobilization substrates.
  • high refractive index particles are selected which support WGM in solution such as colloidal silica, zirconia or titania.
  • microspheres shelled with higher refractive index materials provide useful ideal sensor platform. These particles contain high order radial modes within the adsorbed layer and as a result should enable the acquisition of high Q WGM spectra which contain the high order modes.
  • a fluorescently stable particle which supports WGM in solution may be produced by the adsorption of a monolayer of nanocrystals to a homogenous microsphere followed by a stabilizing high refractive index shell.
  • a list of commercially available high refractive index materials and particles is provided below.
  • fluorophore is general and is not limited to organic dyes, but includes any chemical, molecule or material, which has the property of emitting light of a well defined wavelength when illuminated. This includes but is not restricted to; organic dyes, organometallic complexes, quantum dots (including nanorods, nanowires and other morphologies, coated and uncoated QDs, alloys and mixtures thereof.), rare earth ions or mixtures thereof, upconverters and also infra-red emitting fluorophores, which may be advantageous in absorbing samples. Other materials may also be incorporated such as defective fluorescent materials such as diamond containing Nitrogen induced defects or vacancies.
  • WGMs may be generated by fluorophores that are attached to the surface of the microsphere, but may also be generated when the fluorophore is embedded or distributed within the microsphere.
  • the distribution of fluorophores affects the intensity of different modes of the WGM, but for the purposes of this invention, no distinction is made between fluorophores that are on the surface or within the microsphere.
  • Titania TiO 2 (2.20), Aluminium Al 2 O 3 (1.77), Mylar (1.65), Copper Cu (2.43), Platinum Pt (2.33)
  • the present invention is predicated, in part, on the determination that WGM detection means do not require microspheres to be coated with quantum dots.
  • one aspect of the present invention provides a method of analyte detection in a medium, the method comprising subjecting microspheres coated with a fluorophore and a multiplicity of ligands to WGM detection means to identify a binding event between one or more ligands and a ligand binding analyte.
  • the present invention provides a method of analyte detection in a medium, the method comprising subjecting microspheres wherein the microspheres have a higher refractive index than the medium comprising the analyte coated with a fluorophore and a multiplicity of ligands to WGM detection means to identify a binding event between one or more ligands and a ligand binding analyte.
  • Another aspect of the present invention provides, a method for detecting an analyte in a medium, comprising the steps of:
  • fluorophore refers to any molecule which exhibits the property of fluorescence.
  • fluorescence may be defined as the property of a molecule to absorb light of a particular wavelength and re-emit light of a longer wavelength. The wavelength change relates to an energy loss that takes place in the process.
  • fluorophore may encompass a range of fluorophores such as chemical fluorophores and dyes.
  • the fluorophore may be chosen to emit at any wavelength at which WGM profile may be easily resolved. This depends on the ratio of the wavelength of the emission to the particle radius. Given that the sphere radius is arbitrary, the emission may be suitably chosen from the ultraviolet (wavelength range of about 350nm to about 3nm), visible (wavelength range of about 350nm to about 800nm), near infrared ([NIR)] (wavelength range of about 800nm to about 1500nm) and/or infrared ([IR)] (wavelength range of about 1500nm to about lO ⁇ m) ranges. However, due to the ease of detection, in one particularly preferred embodiment, the fluorophore is detectable in the visible wavelength range.
  • the fluorophore emits visible radiation in response to Infrared excitation.
  • fluorophores are also referred to herein as "upconverters”.
  • another aspect of the present invention provides a method of detecting an analyte, the method comprising contacting at least one population of microspheroidal particles with a sample putatively comprising the analyte, wherein each particle within a population of microspheroidal particles comprises a fluorophore which emits visible radiation in response to infrared excitation and an immobilized putative binding partner of the analyte wherein each particle population has a defined WGM profile, wherein binding of the analyte to the immobilized binding partner results in a change in the WGM profile, when compared to the baseline WGM profile, of at least one population of microspheroidal particles which is indicative of the presence of the analyte.
  • the microspheroidal particles are functionalized by chemical moieties such as with amine, thiol and/or aldehyde groups, sulfate, carboxylate, hydroxyl groups, axide and/or alkynes.
  • amine-aldehyde-based particles such as melamine formaldehyde, provide a usefuls substrate for acryloyl modified target oligonucleotides and proteins to bind.
  • another aspect of the present invention provides a method for detecting a binding event between an analyte and a ligand, comprising the steps of: (i) anchoring a multiplicity of ligands to a population of fluorophore-conjugated functionalized microspheroidal particles; (ii) contacting the functionalized microspheroidal particles with a negative control sample and determining a baseline spectrum; (iii) contacting the functionalized microspheroidal particles with a sample putatively comprising the analyte for a time and under conditions sufficient to facilitate a binding event between the analyte and its respective ligand; and (iv) subjecting the microspheroidal particles to WGM detection means to detect a binding event.
  • the present invention provides a method for detecting a binding event between an analyte and a ligand, comprising the steps of: (i) anchoring a multiplicity of ligands to a population of fluorophore-conjugated amine-aldehyde microspheroidal particles; (ii) contacting the amine-aldehyde microspheroidal particles with a negative control sample and determining a baseline spectrum; (iii) contacting the amine-aldehyde microspheroidal particles with a sample putatively comprising the analyte for a time and under conditions sufficient to facilitate a binding event between the analyte and its respective ligand; and (iv) subjecting the amine-aldehyde microspheroidal particles to WGM detection means to detect a binding event.
  • the amine-aldehyde particles are melamine formaldehyde.
  • the present invention provides a method for detecting a binding event between an analyte and a ligand, comprising the steps of: (i) anchoring a multiplicity of ligands to a population of fluorophore-conjugated melamine formaldehyde microspheroidal particles; (ii) contacting the melamine formaldehyde microspheroidal particles with a negative control sample and determining a baseline spectrum; (iii) contacting the melamine formaldehyde microspheroidal particles with a sample putatively comprising the analyte for a time and under conditions sufficient to facilitate a binding event between the analyte and its respective ligand; and (iv) subjecting the melamine formaldehyde microspheroidal particles to WGM detection means to detect a binding event.
  • quantum dots may also be used.
  • another aspect of the present invention provides a method for detecting a binding event between an analyte and a ligand, comprising the steps of: (i) anchoring a multiplicity of ligands to a population of melamine formaldehyde microspheroidal particles comprising fluorophore-coated quantum dots; (ii) contacting the microspheroidal particles with a negative control sample and determining a baseline spectrum; (iii) contacting the microspheroidal particles with a sample putatively comprising the analyte for a time and under conditions sufficient to facilitate a binding event between the analyte and its respective ligand; and (iv) subjecting the microspheroidal particles to WGM detection means to detect a binding event.
  • Another aspect of the present invention provides a method for detecting a binding event between an analyte and a ligand, comprising the steps of: (i) anchoring a multiplicity of ligands to a population of microspheroidal particles having a higher refractive index than the medium comprising the analyte, the microspheroidal particles encoding a fluorophor; (ii) contacting the microspheroidal particles with a negative control sample and determining a baseline spectrum; (iii) contacting the microspheroidal particles with a sample putatively comprising the analyte for a time and under conditions sufficient to facilitate a binding event between the analyte and its respective ligand; and (iv) subjecting the microspheroidal particles to WGM detection means to detect a binding event.
  • fluorescent dyes which are available in the art which may be used as fluorophores in accordance with the present invention.
  • An important property of a fluorescent dye or other fluorophore, which determines its potential for use is the excitation wavelength of the fluorophore; it must match the available wavelengths of the light source.
  • fluorescent dyes and other fluorophores will be familiar to those of skill in the art, and the choice of fluorescent marker in no way limits the subject invention.
  • Convenient "fluorophores" which may be used for the labeling of a microspheroidal particle comprise any fluorescent marker which is excitable using a light source selected from the group below:
  • Argon ion lasers - comprise a blue, 488 nm line, which is suitable for the excitation of many dyes and fluorochromes that fluoresce in the green to red region.
  • Tunable argon lasers are also available that emit at a range of wavelengths (458 nm, 488 nm, 496 nm, 515 nm amongst others).
  • Diode lasers - have an emission wavelength of 635 nm. Other diode lasers which are now available operate at 532 nm. This wavelength excites propidium iodide (PI) optimally. Blue diode lasers emitting light around 476 nm are also available. Such diode lasers may be conveniently employed to excite WGMs within the microspheroidal particles.
  • HeNe gas lasers - operate with the red 633 nm line. Such lasers may be conveniently employed to excite WGMs within the microspheroidal particles.
  • LEDs Light Emitting Diodes
  • HeCd lasers - operate at 325 nm. Such lasers may be conveniently employed to excite WGMs within the microspheroidal particles.
  • the fluorescent markers are selected from: Alexa Fluor dyes; BoDipy dyes, including BoDipy 630/650 and BoDipy
  • Cy dyes particularly Cy3, Cy5 and Cy 5.5; 6-FAM (Fluorescein); Fluorescein dT; Hexachlorofluorescein (HEX); 6-carboxy-4', 5'-dichloro-2', T- dimethoxyfluorescein
  • Rhodamine Green Rhodamine Green and ROX
  • Carboxytetramethylrhodamine TAMRA
  • Tetrachlorofluorescein TAT
  • Two dyeing techniques are commonly used to fluorescently label microspheroidal particles.
  • the two techniques produce particles with unique properties, each beneficial for different applications.
  • Internal dyeing produces extremely stable particles with typically narrow fluorescence emissions. These particles often display a greater resistance to photobleaching.
  • surface groups are available for use in conjugating ligands (proteins, antibodies, nucleic acids, etc.) to the surface of the bead. For this reason, internally labeled particles are typically used in analyte-detection and immunoassay applications.
  • Surface- labeling involves conjugation of the fluorophore to the microspheroidal particle surface.
  • the fluorophores are on the surface of the particle, they are able to interact with their environment just as the fluorophores on a stained cell.
  • the result is a particle standard that exhibits the same excitation and emission properties as stained cell samples, under a variety of different conditions, such as the presence of contaminants or changes in pH.
  • the "environmentally responsive" nature of surface-labeled particles makes them ideally suited for mimicking biological samples. Externally labeled particles are frequently used as controls and standards in a number of applications utilizing fluorescence detection.
  • the present invention contemplates the association of a particle with a fluorescent label via any means.
  • fluorophore should be understood to also encompass multiple fluorophores, and mixtures of fluorophores. The use of all such fluorophores on microspheroidal particles is to be considered as being within the scope of the methods and reagents described herein.
  • the emission of any particular fluorophore depends on the distribution of the fluorophore in the microspheroidal particle, the type of fluorophore and the concentration of fluorophore.
  • the methods of the present invention are still practicable irrespective of whether the fluorophore is at the surface of the microspheroidal particle, present as a shell within the microspheroidal particle, located at the core of the microspheroidal particle or is present in more than one of the recited locations.
  • the methods of the present invention are not predicated on quenching of the emission from the fluorophore.
  • the methods of the present invention are predicated, in part, on a modulation (i.e. a change) in the WGM profile of the fluorophore as a result of an interaction or association of an analyte with a binding partner immobilized to the surface of a microspheroidal particle.
  • WGM when dealing with electromagnetic radiation, are electromagnetic resonances that can be established when incident light interacts with a particle of higher refractive index than its surrounding medium. WGM occur at particular resonant wavelengths of light for a given particle size, and the nature of the WGM may change with, inter alia, the size of the particle containing the WGM and the refractive indices of both the particle and the surrounding medium. Furthermore, the size of the particle can also affect the WGM established therein. WGM are established when the incident light undergoes total internal reflection at the particle surface.
  • Total internal reflection may occur at the interface between two non- absorbing media.
  • TIR Total internal reflection
  • a beam of light propagating in the medium of higher refractive index meets an interface at a medium of lower refractive index at an angle of incidence above a critical angle
  • the light is totally reflected at the interface and propagates back into the high refractive index medium.
  • the light may be reflected many times within the particle of higher refractive index.
  • the light is concentrated near the circumference of the particle and can be assigned a mode number and a mode order.
  • the mode number, n provides the number of wavelengths around the circumference of the particle
  • the mode order, / provides the number of maxima in the radial dependence of the electromagnetic field within the particle.
  • Fluorescence emitters embedded on a particle display defined WGM profiles. These modes allow only certain wavelengths of light to be emitted from the particle. The result of this phenomenon is that the usual relatively broad emission spectrum of a fluorophore (for example, fluorophores typically emit in a 10-100 nm wide band) becomes constrained and appears as a series of sharp "peaks" corresponding effectively to standing mode patterns of light within the particle.
  • the series of peaks generated as a result of the establishment of a WGM in the microspheroidal particle of the present invention are referred to herein as "whispering gallery mode profiles" or "WGM profiles”.
  • the WGM profile is extremely sensitive to both the position of the embedded fluorophore and their concentration and spatial configuration with respect to each other. Particle size and refractive index are the 2 most important parameters in determining the emission wavelengths seen in a WGM profile.
  • the position and amplitude of one or more peaks in a WGM profile may be strongly influenced by interactions or associations of the microspheroidal particle with molecules in a sample or external environment.
  • association or binding of a molecule to a microspheroidal particle alters the effective refractive index of the microspheroidal particle altering the WGM profile generated by the microspheroidal particle.
  • Any number of means known in the art are suitable for conjugating fluorophores to the surface of microspheres.
  • Microsphere surfaces can be optimized or functionalized for hydrophobic adsorption or covalent attachment of molecules including fluorophores or any biological or chemical molecule.
  • the present invention does not extend to and specifically excludes the use of quantum dots to label the microspheres.
  • microspheres can be functionalized by the addition of any number of functional groups including: azide, alkyne, maleimide, succinimide, epoxide, methacrylate, acryloyl, amine, aldehyde, sulfate or thiol; carboxyl; carboxylate; hydroxyl; etc.
  • nucleic acid molecules are bound covalently to a sulfur-coated surface of a silica microsphere. Silanization with 3-mercaptopropyltrimethoxysilane followed by exhaustive washing is used to create this surface.
  • Nucleic acid molecules for example, DNA oligonucleotides, are manufactured with 5' thiol or acryl groups and are attached to the free sulfurs on the surface.
  • the ligands of the present invention are in no way limited to any one species and include ligands selected from the group consisting of: nucleic acids; antibodies; peptides; polypeptides; carbohydrates; lipids; glycoproteins; lipoproteins; lipopeptides; lipopolysaccharides; small organic molecules and small inorganic molecules.
  • ligands selected from the group consisting of: nucleic acids; antibodies; peptides; polypeptides; carbohydrates; lipids; glycoproteins; lipoproteins; lipopeptides; lipopolysaccharides; small organic molecules and small inorganic molecules.
  • the particles When coated with an antigen or antibody, the particles are used in an "immuno-WGM” assay or "immuno-based WGM” assay.
  • nucleic acids include RNA, cDNA, genomic DNA, synthetic forms and mixed polymers, both sense and antisense strands, and may be chemically or biochemically modified or may contain non-natural or derivatized nucleotide bases, as will be readily appreciated by those skilled in the art.
  • modifications include, for example, labels, methylation, substitution of one or more of the naturally occuring nucleotides with an analog (such as a morpholine ring), internucleotide modifications such as uncharged linkages (eg.
  • synthetic molecules that mimic polynucleotides in their ability to bind a designated sequence via hydrogen bonding and other chemical interactions. Such molecules are known in the art and include, for example, those in which peptide linkages substitute for phosphate linkages in the backbone of the molecule.
  • antibody refers to a protein of the immunoglobulin family that is capable of combining, interacting or otherwise associating with an antigen.
  • An antibody is, therefore, an antigen-binding molecule.
  • antigen is used herein in its broadest sense to refer to a substance that is capable of reacting with or binding to the antigen- binding site of an antibody. With reference to the present invention, an antigen also includes the idiotype of an antibody.
  • immunoglobulin is used herein to refer to a protein consisting of one or more polypeptides substantially encoded by immunoglobulin genes.
  • the recognized immunoglobulin molecules include the K, ⁇ , ⁇ , ⁇ (IgG 1 , IgG 2 , IgG 3 , IgG 4 ), ⁇ , ⁇ and ⁇ constant regions, light chains (K and 1), as well as the myriad immunoglobulin variable regions.
  • One form of immunoglobulin constitutes the basic structural unit of an antibody. This form is a tetramer and consists of two identical pairs of immunoglobulin chains, each pair having one light and one heavy chain.
  • immunoglobulins may exist in a variety of other forms including, for example, Fv, Fab, Fab' and (Fab') 2 and chimeric antibodies and all of these variants are encompassed by the term "antibody” as used herein.
  • immunoglobulins from other animals eg. birds, mammals, fish, amphibians, and reptiles
  • the analyte-binding ligand is a DNA molecule comprising a single-stranded DNA overhang
  • the analyte to be detected is a nucleic acid molecule capable of hybridizing to the ligand.
  • hybridization occurs, a shift in WGM profile is detectable. Conversely, when there is no hybridization between complementary nucleic acid sequences, no shift in WGM profile occurs.
  • the analyte-binding partners or ligands are DNA molecules prepared by: (i) digestion of double-stranded DNA with an enzyme that generates a single-stranded DNA overhang, for example, a restriction endonuclease; and (ii) digestion with an exonuclease enzyme.
  • the resultant digested DNA comprises single- stranded DNA capable of hybridizing to, inter alia, complementary single-stranded nucleic acids.
  • Restriction endonuclease as used herein means a nuclease enzyme that hydrolyses nucleotides at specific sequences within a DNA molecule. Restriction endonucleases comprise Type I, Type II and Type III restriction endonucleases.
  • Table 2 lists a subset of Type I and Type II restriction endonucleases that generate 5'-overhangs of 4 bases.
  • Table 3 lists a subset of Type I and Type II restriction endonucleases that generate 3 '-overhangs, mostly four bases in length.
  • Exonuclease as used herein means a nuclease enzyme that hydrolyzes nucleotides from the ends of DNA strands.
  • an exonuclease enzyme suitable for the preparation of the analyte-binding ligands and/or the analytes to be detected is lambda ( ⁇ ) exonuclease.
  • Lambda exonuclease is a double-stranded DNA exonuclease which degrades double-stranded DNA in a 5'- to 3'- direction. Lambda exonuclease requires the 5'-end of the DNA to be double-stranded and phosphorylated. Lambda exonuclease digestion can be used to preferentially degrade specific strands of double-stranded DNA to generate single- stranded DNA analyte-binding ligands and analytes to be detected.
  • microspheroidal particles of the present invention are coated with nucleic acids derived from a pathogenic agent such as a virus, bacterium, yeast or parasite.
  • the detection of a binding event is indicative of the presence of complementary nucleic acids in the sample and therefore, is indicative of the presence of the agent in the sample and/or at the source of the sample.
  • "Complementary" as used herein refers to the capacity for precise pairing between two nucleobases of an oligomeric compound.
  • a nucleobase at a certain position of an oligonucleotide is capable of hydrogen bonding with a nucleobase at a certain position of a target nucleic acid, said target nucleic acid being a DNA, RNA, or oligonucleotide molecule
  • the position of hydrogen bonding between the oligonucleotide and the target nucleic acid is considered to be a complementary position.
  • the oligonucleotide and the further DNA, RNA, or oligonucleotide molecule are complementary to each other when a sufficient number of complementary positions in each molecule are occupied by nucleobases which can hydrogen bond with each other.
  • the present invention is particularly useful for testing for the presence of a wide array of analytes in a single sample.
  • the present invention is useful for the detection of rare analytes which are present in a sample at low concentrations.
  • the invention is useful for the detection of trace elements or contaminants such as allergens, pyrogens and microbiological or chemical contaminants in foods and medicines; pollutants or toxicants in environmental and industrial samples; explosives; agents of bio-terrorism; etc.
  • trace elements or contaminants such as allergens, pyrogens and microbiological or chemical contaminants in foods and medicines; pollutants or toxicants in environmental and industrial samples; explosives; agents of bio-terrorism; etc.
  • the term "rare” means infrequently occurring or uncommon or relatively few in number or relatively low in concentration.
  • the present invention is also useful for the identification of analytes previously not known to bind to a particular ligand.
  • the microspheroidal particles are coated with an enzyme or a receptor molecule in which the conformation of the catalytic site or putative ligand-binding site is intact.
  • Analytes that bind to such particles represent putative agonists or antagonists of enzyme activity or receptor-ligand binding.
  • the present invention is useful for drug identification and design.
  • Rational drug design permits the production of structural analogs of biologically active polypeptides of interest or of small molecules with which they interact (e.g. agonists, antagonists, inhibitors or enhancers) in order to fashion drugs which are, for example, more active or stable forms of the polypeptide, or which, e.g. enhance or interfere with the function of a polypeptide in vivo. See, e.g. Hodgson (Bio/Technology 9:19-21, 1991). In one approach, one first determines the three-dimensional structure of a protein of interest by x-ray crystallography, by computer modeling or most typically, by a combination of approaches.
  • Useful information regarding the structure of a polypeptide may also be gained by modeling based on the structure of homologous proteins.
  • An example of rational drug design is the development of HIV protease inhibitors (Erickson et al, Science 249:527-533, 1990).
  • target molecules may be analyzed by an alanine scan (Wells, Methods Enzymol. 202:2699-2705, 1991).
  • an amino acid residue is replaced by Ala and its effect on the peptide's activity is determined.
  • Each of the amino acid residues of the peptide is analyzed in this manner to determine the important regions of the peptide.
  • the present invention is useful for the detection of genes or their encoded proteins associated with specific pathological conditions and diseases.
  • the microspheroidal particles of the invention are coated with a specific ligand or library of ligands known to be expressed in human cancer, or conversely, with an antibody or library of antibodies specific for an antigen or antigens known to be associated with cancer. Therefore, the detection of a binding event is indicative of the presence in a sample of an analyte known to be associated with cancer. Due to its sensitivity, the WGM detection means of the present invention provides, inter alia, a method for the early detection of cancer.
  • the ligand or analyte to be detected comprises a single nucleotide polymorphism (SNP) or a specific post-translational modification.
  • SNP single nucleotide polymorphism
  • the methods of the present invention are useful for several applications in the fields of, for example, medicine, veterinary science, agriculture, forensic science, biotechnology, food technology, sports science, nutritional science, manufacturing, drug design and development, biodefence, detection of explosive materials, insecticides, fertilisers and toxins.
  • the methods of the present invention are useful for diagnosis of pathological conditions or diseases including genetic diseases, cancer, autoimmune disorders, allergies, infectious diseases, heart disease, neurological disease, proteopathies, and metabolic diseases, virus and bacterial diseases and contamination, identification of unknown bacteria or viruses or other microorganisms in natural samples..
  • the methods of the present invention are useful for, inter alia, tissue typing, blood typing, genetic testing, drug testing, analysis of blood analytes, alcohol testing, pregnancy testing, etc.
  • a "biological sample” is to be understood as a sample derived from a biological source such as an environmental sample, organism extract, plant or animal extract, serum, urine, exudate, semen, plasma, soil sample, river or sealed sample, extra-terrestrial sample, amongst other sources.
  • biosensor as used herein means a sensor device for detecting quantities of, including very small quantities, or changes in a biochemical or chemical substance, in which an intermolecular binding event is registered and translated into data.
  • Biosensing as used herein means any of a variety of procedures which use biomolecular probes to measure the presence or concentration of biological molecules, biological structures, microorganisms, etc., by translating a biochemical interaction into a quantifiable physical signal.
  • biosensing applications of the invention are in no way limited and include: environmental applications e.g. the detection of pesticides and river water contaminants; remote sensing of airborne bacteria or spores thereof e.g. in counter-bioterrorist activities; detection of pathogens; determining levels of toxic substances before and after bioremediation; detection of organophosphates; routine analytical measurement of biochemical analytes; detection of drug residues in food, such as antibiotics and growth promoters; drug discovery and evaluation of the biological activity of new compounds.
  • environmental applications e.g. the detection of pesticides and river water contaminants
  • remote sensing of airborne bacteria or spores thereof e.g. in counter-bioterrorist activities
  • detection of pathogens determining levels of toxic substances before and after bioremediation
  • detection of organophosphates routine analytical measurement of biochemical analytes
  • detection of drug residues in food such as antibiotics and growth promoters
  • drug discovery and evaluation of the biological activity of new compounds include: environmental applications e
  • the present invention provides, inter alia, an optical biosensor based upon the WGM detection system.
  • the biosensor is compact and portable.
  • the biosensors of the present invention provide a means for the rapid and sensitive detection of analytes.
  • the biosensor is particularly adapted for convenient use in research and analytical laboratories and in the field.
  • the WGM detection apparatus per se is adaptable to self-containment, miniaturization and portability. Importantly, this adaptability allows for rapid and convenient analyte detection on the bench-top or in the field, without any requirement for bulky and expensive components.
  • the WGM detection apparatus does not require a bulky power source or light source, nor an expensive spectrophotometer or optical lens.
  • some embodiments provide a 6OX microscope objective lens and a non-chilled spectrophotometer is used with a 0.5 nm slit width.
  • the WGM detection apparatus is a biosensor.
  • a power source of about 10 ⁇ W to about 2000 ⁇ W is sufficient to generate WGM spectral data according to the methods of the present invention.
  • the fiuorophore-conjugated microspheroidal particles of the present invention are exposed to light for about 20-2000 milliseconds.
  • Light at a wavelength of 532 nM is particularly suitable for generating WGM spectra according to the present invention.
  • the microspheroidal particles of the invention are immobilized by "baking" to a solid support matrix, e.g. glass.
  • the solid support comprises material through which light in the infra-red, visible and ultra-violet spectra can travel.
  • microspheres are dried to a glass surface for times greater than 10 minutes at temperatures above 4O 0 C.
  • a key requirement of the system is that spectra can be automatically compared and differences between before and after binding can be quantified. This has been accomplished by using a log transformation of the time-mode spectrum.
  • kits for analyte detection by WGM means comprise fiuorophore-conjugated microspheroidal particles to which a multiplicity of analyte-binding ligands is attached.
  • the microspheroidal particles are immobilized to a glass surface.
  • the multiplicity of ligands to be anchored to the microspheroidal particles can be designed to detect a specific array of analytes. For example, in a specific embodiment, an environmental sample is tested for the presence of one or more human pathogens of public health significance, e.g.
  • the microspheres are coated with a library of nucleic acids derived from a number of different pathogens.
  • the combinations of ligands for anchoring to the microspheroidal particles is not limited.
  • the kit may also contain quantum dots.
  • Environmental sample as used herein means a specimen of any material collected from an environmental source, such as air, water or soil.
  • An “environmental source” as used herein relates to the natural environment, man-made environment or the extraterrestrial environment. Other samples include food samples.
  • the WGM assay is useful for the food industry, environmental water testing, the agricultural industry, bio- terrorism testing and pharmacological testing.
  • the particles may also be re-cycled for continual use and for high throughput screening.
  • the changes to the WGM indicate the presence of an analyte. It is also possible to glean further information from changes in the relative intensities, line widths and wavelengths of the WGM peaks of a particular microsphere.
  • Fluorophore-conjugated microspheroidal particles conjugated to a multiplicity of DNA ligands demonstrated a measurable and consistent difference after binding of specific analyte.
  • Microspheroidal particles either 4.87, 5.6, 6.8, or 7.5 ⁇ m in diameter were conjugated to a multiplicity of 22-mer DNA molecules with a TMR tag at nucleotide position 1.
  • WGMs were acquired before and after hybridization with complementary 22-mer ( Figure 1).
  • FIG. 2 provides a schematic illustration of the WGM detection system.
  • the power of the light source was varied to determine its effect on WGM resolution.
  • An incident power for the light source (532 nm, 200 milliseconds) of 6.3, 50.2, 214.5 or 1160.5 ⁇ W was sufficient to resolve WGMs (Figure 3B).
  • Such power is achievable with a standard low cost laser (light pointer).
  • the excitation time was varied in order to determine its effect on WGMs.
  • WGMs were assessed following exposure for 10, 60, 200 and 1000 milliseconds of incident light (50 ⁇ W, 532 nm). It was determined that an exposure time as short as 200 ms was sufficient to resolve WGMs (Figure 4C) with visibility decreasing up to 5 seconds exposure time (Figure 4E).
  • the prototype WGM biosensor is built to specifications that result in well-resolved WGM spectra before and after binding of an analyte to a microspheroidal particle.
  • the device is approximately 30 x 15 x 15 cm and 2-5 kg, and is completely self-contained comprising a power source, light source, sample handling chambers and spectrophotometer.
  • Microspheroidal particles (QSand [trademark: silica particles]) were immobilized to the surface of a glass microscope slide coverslip in a random configuration ( Figure 5). The coverslip with immobilized QSand (trademark) particles was able to be coupled directly into the slit of the spectrometer.
  • WGM whispering gallery modes
  • Succinimidyl ester dye-label tetramethyl rhodamine (TMR), Bodipy 630/650 and Alexa 647 was purchased from Olecular Probes, Eugene, USA. Milli-Q grade (R > 18 M ⁇ cm) water was used throughout. Acryloyl modified oligonucleotides were designed in-house and constructed by Integrated DNA Technologies, Coralville, Iowa, USA. The oligonucleotide constructs were received dry and resuspended to 200 ⁇ M with ultra-purified Milli-Q H 2 O before use.
  • the spectral resolution (+ 0.9 nm) defines the accuracy with which a fluorescence peak wavelength can be measured. Peak shifts in a WGM response curve can be routinely observed between 0.1 nm up to several run. The optical resolution stated by the manufacturer indicates peaks with 0.14 nm - 7.7 nm FWHM can be routinely detected.
  • microspheres were also collected using a Philips XL-30 field- emission SEM. To do this, microspheres were washed with Milli-Q H 2 O and immobilized directly onto 12 mm circular silica substrates, which were then mounted onto SEM studs. The samples were sputter coated with 3-5 nm of gold using an Edwards S 150B Sputter Coater.
  • Oligonucleotide fragment design and construction [0154] The following single-stranded target and complementary oligonucleotide sequences were randomly designed and named for the sole purpose of this investigation; therefore homologies to known gene sequences are coincidental and should be disregarded. Designed sequences were synthesized and ordered from integrated DNA technologies, Coralville, Iowa, USA. The oligonucleotides were maintained as 200 ⁇ M working stocks in ultra-pure Milli-Q H 2 O.
  • the oligonucleotide sequences and the shorthand names used throughout this Example are provided below.
  • the modification "iAm” provides a free internal amine group (e.g. used to attach fluorophores) on the DNA fragment which essentially is a T nucleotide base with the free -NH group attached.
  • AAT CCG CAG GAT GGG CCT TAC A - 3 1 (SEQ ID NO:6) [0156]
  • the sequence /Acrd/ denotes a 5'acryloyl group (Acrydite-trademark, Integrated DNA Technologies, USA) group attached to the oligonucleotide sequences and /iAm/ specifies the position of a modified T nucleotide base which possesses a free internal amine group used for fluorophore attachment (Integrated DNA Technologies, USA).
  • Microsphere surface functionalization [0157] The silica microspheres used in this investigation were functionalized with thiol groups using standard literature procedures (Battersby et al, Chemical Communications 74:1435-1441, 2002; Corrie et al, Langmuir 22 (6) :2731-27 '37, 2006; Miller et al, Chemical Communications 35:4783-4785, 2005; Johnston et al, Chemical Communications 7:848- 850, 2005; Verhaegh and Vanblaaderen, Langmuir 70f5j:1427-1438, 1994).
  • Functionalized spheres were washed at 1800 rpm with 2-propanol and resuspended in 10 mL of fresh 2-propanol. This microsphere slurry was divided into aliquots and pelleted at 8000 rpm for 5 s and dried in a desiccator under nitrogen for 230 min. Finally, they were agitated and heat cured to ensure complete 2-propanol evaporation (9O 0 C) for 30 min on a heating block. All functionalized microspheres were stored desiccated at 4 0 C under nitrogen. The above procedure leads to reproducible, dense functionalization of the silica surface, and further ensures quantitative repeptization of the microspheres after storage. Surface layered nanocrystal doped microsphere synthesis
  • CdSe@ZnS nanocrystal core/shells were used which emitted orange with emission maximum 593 nm; FWHM 32 run. Aliquots were taken from a 10 ⁇ M stock solution. MPS functionalized silica beads were combined with CdSe@ZnS core shell nonocrystals in a 1 :2.5 ratio, manually shaken, then put onto a rotator at minimum rpm for 15 min - 1 hr.
  • the polar amide group within the pyrrolidone ring on the PVP molecule most probably facilitates chemisorption to the nanocrystal surface via covalent bonds.
  • the coating offers stability to the microsphere (hydrophobicity and stability in water) and allows the molecule to be absorbed onto many surfaces. This increases the affinity of the particle to the final silica shell coating without the employment of a coupling agent. The following day reacted particles were washed several times (8000 rpm; 5 s) in 2-propanol and maintained 4 0 C in 2-fresh propanol.
  • microspheres were capped in a 1 :200 solution of TEOS, 1 mL of 4.2% (in H 2 O) NH 3 solution was utilized per 1 mL of PVP capped particles in reaction and 1 :200 TEOS volume (100 ⁇ L per 0.005 g of PVP capped microspheres).
  • TEOS was added under stirring and allowed to react overnight followed by several washes in 2-propanol.
  • AU microspheres were kept suspended in 2-propanol and maintained at 4 0 C.
  • the preparation was treated with a mixture of 58 ⁇ L Milli-Q H 2 O, 10 ⁇ L NaOAc, and 200 ⁇ L of ethanol, which were added directly to the reaction and the solution was then stored in a -2O 0 C freezer for 30 min. Samples were then centrifuged for 20 min at 13,800 rpm and the supernatant removed. These steps were repeated until the sample supernatant was free of excess fluorophore. Finally, the labeled oligonucleotides were diluted to a 200 ⁇ M working stock with 100 ⁇ L of ultra-pure Milli-Q H 2 O and stored in a -2O 0 C freezer.
  • ⁇ cryloyl oligonucleotide coupling to microspheres [0160] Thiol functionalized microspheres were derivatized with enl and Control target 5' acryloyl modified oligonucleotides using standard protocols (Hermanson, Bioconjugative Techniques, Sand Diego: Academic Press Incorporated, 785, 1996) as follows: In an eppendorf tube 0.002 g of functionalized MPS microspheres were weighted out and then saturated with 100 ⁇ L of methanol via microcentrifugation (8000 rpm for 5 s), and the supernatant discarded.
  • the pellet was resuspended in fresh 0.5 M MES (pH 5.4), followed by the addition of 15 ⁇ L of 200 ⁇ M acryloyl-modified TMR-labeled oligo-sequence (enl or Control) along with 100 ⁇ L fresh 10% w/v ammonium persulfate (w/v).
  • the reaction was vortexed and then gently mixed on a motorized wheel for 1 hour.
  • the coupled microspheres were washed with Phosphate Buffer Saline (Buffer) [ph 9.0] and pelleted in a microcentrifuge (8000 rpm for 5 s) to remove the supernatant.
  • a sample of 200 ⁇ M stock cDNA solution was diluted with PBS (1:40), and the sample was vortexed. A 120 ⁇ L aliquot was applied to each array plate (enough to completely immerse the gridded array area). Each particle-mounted array then underwent 90 s single hybridization cycle.
  • each grid was treated with 120 ⁇ L of the control solutions: Milli-Q H 2 O followed by buffer (PBS), non-specific DNA and cDNA (as above) and a hybridization cycle of 90 s was run for each treatment plate. All arrays were allowed to stand at RT for 5 min then gently washed with 100 ⁇ L portions of Milli-Q H 2 O to remove any solution phase (unreacted) DNA. Unless otherwise noted, excess water in all assays post cDNA treatment was removed by evaporation on a heating block (9O 0 C). The fluorescence excitation and emission signal measurements from treated spheres were then captured in air.
  • Hybridization was carried out as above and then denaturation was effected by heating the hybridized samples on a 9O 0 C heating block for 30 s.
  • the buffer was immediately removed by several 100 ⁇ L washes with Milli-Q H 2 O.
  • the denaturation steps were repeated three times, followed by the evaporation of excess liquid and finally the measurement of emission from selected particles.
  • the initial goal of this Example involved the surface functionalization of silica microspheres ( ⁇ 10 ⁇ m) with CdSe core shells (emitter) to enable a WGM signal to be created via ultraviolet (UV) illumination (Gomez et al, Small l(2):23S-24l, 2005).
  • the NC particles were then capped with several organic stabilizing layers and the final functional layer was intended to be with a selected bio-molecule.
  • the stability of the nanocrystals utilized in the experiments was compromised; progressive treatments led to consistent photodegradation and a loss of discernable WGM peaks before any possible conjugation with a biological molecule could be performed. The significant loss of photoluminescence was probably due to the desorption/break down of the nanocrystal layer.
  • Every single functionalized microsphere exhibits a unique WGM fingerprint. Consequently, it is necessary for bioassays to be carried out on the same particles before and after exposure to a test solution.
  • the particles were immobilized onto a gridded-silica array and a detailed microsphere map of the e «/-target and Control assay grids was collected.
  • Each microsphere was numbered according to the other of its emission signal being measured; its specific location was then mapped out using the corresponding scan-number which was noted on a graphical schematic that represented a single etched grid.
  • the same microsphere could be routinely relocated after exposure to various test solutions and controls.
  • the refractive index of the microspheres is quite low and it was difficult to obtain high-quality WGM spectra from microspheres immersed in solution due to the low refractive index contrast. This was a fundamental problem and unexpected.
  • the refractive index mismatch between colloidal silica and water is insufficient to support a WGM. Consequently, the protocols were designed so that all spectra could be collected in air.
  • the array plates were treated with a 120 ⁇ L does of the target complement a-enl.
  • the initial hybridization step involved the assay grids being placed on a 9O 0 C heating block; by slowly heating the solution, any oligomeric or aggregated DNA that is present in the target solution is peptized to facilitate hybridization with the probe DNA on the bead.
  • the acryloyl/sulfhydryl bond formed when probe oligonucleotide was conjugated to the microspheres surface effectively tethered and immobilized the target-probe sequence to the spheres surface and was not effected by subsequent heating 9O 0 C.
  • the arrays were cooled for 5 min at RT to allow sufficient time for the a-enl cDNA probes to anneal to enl target microspheres.
  • the grids were then washed and all excess water was removed by evaporation on a heater block.
  • Following treatment with the a-enl probe the same individual particles were relocated and a second set of spectra were collected in air.
  • a fluorescence spectrum of the dye-label TMR employed to label enl and control oligonucleotide target sequences was fluorometrically analyzed.
  • the emission range of the dye demonstrated the expected range of the microsphere emission signal which should be defined by the emission range of the selected fluorophore.
  • the WGM emission signal falls within the excitation range of the TMR dye.
  • the WGM spectra show a clear red-shift, though not every peak shifts equally.
  • the peak displacements observed post cDNA a-enl hybridization measured at wavelengths 575 (1.1 nm), 585 (1.5 nm), 595 (1.1 nm) and 605 nm (1.1 nm) are all to longer wavelengths compared to the pre- hybridization emission signal, i.e. hybridization lead to red-shifts of the major peaks in the WGM spectrum.
  • a control assay was then established to investigate the effects of control reagents on gallery mode signal.
  • a single assay plate was treated with Milli-Q H 2 O, a non-specific DNA sequence and finally the cDNA probe.
  • a 90 s hybridization cycle was run for each stage treatment, the selected spheres were relocated and the fluorescence spectra collected after each stage.
  • Milli-Q and non-specific DNA treatment there was no consistent peak shift observed.
  • red-shifts were observed when the microsphere was exposed to cDNA (a-enl).
  • Example 5 showed that single silica colloids functionalized with single-strand oligonucleotide fragments and can delineate between differences of 10 nucleotide bases of a cDNA target probe.
  • the results demonstrate that the WGM based system is capable of rapid, target-specific detection of complementary DNA fragments at room temperature (RT), at sub-picomolar concentrations and within just a few minutes using samples of several microlitres. The results indicate that attomole detection of unlabeled DNA fragments is possible on a routine basis.
  • Particles were excited through a Melles Griot X2 multi-line Ar+ laser (Melles Griot, USA) typically at an excitation power of 350 ⁇ W.
  • Emission signals were typically collected with the wavelength centre point at 600 nm through a 550 nm cut-off filter with a 2 s integration time.
  • a 'real' assay environment is one in which functionalized particles are exposed to various control reagents, specific and non-specific unlabeled analyte and hybridization buffers under various reaction conditions as prescribed in Example 5.
  • a competitive detection platform in the current market should be able to routinely detect sub-picomolar concentrations of analyte.
  • This Example investigates whether the WGM assay can be performed at room temperature and the detection limit of the system presented in Example 5 is determined. Unless otherwise stated, the assays performed in this Example were as prescribed in Example 5.
  • the array-plates were washed with Milli-Q H 2 O to dilute the saline reaction buffer, and ensure that when excess reactant was evaporated off that salt-crystal deposition on the assay plate was minimized. Particles were then recovered and the relevant 'post-hybridization' emission signals measured.
  • the arrays were then run for a single hybridization cycle of either 10 s, 30 s, 60 s, 180 s or 300 s at RT.
  • Post-treatment array-plates were allowed to stand for 5 min at RT, washed with Milli-Q H 2 O and dried. Sensors were then recovered and the relevant emission signals measured.
  • Gallery mode signatures were acquired from 7.50 ⁇ m silica particles functionalized with TMR labeled 70 base-oligonucleotide fragments using two characterization set ups. The first a TE2000-S Nikon fluorescence microscope coupled to an ocean optics CCD ( ⁇ 0.9 run ) detector ( Figure 8A) and higher resolution spectra were acquired using an Olympus Fluoview laser Scanning Microscope 1X71 (Olympus, USA) coupled to a TRIAX spectrometer ( ⁇ 0.05 nm) Figure 8B. The key feature of the developed recognition platform is the 'single-particle' method utilized for particle scoring.
  • Figure 8C illustrates the fundamental reason for the chosen format and why it is crucial in a WGM based system.
  • the key point to take from the schematic is that to use the optical properties of WGM in a detection platform, averaging spectra from ensemble results can not be performed successfully as the example shows two identically modified particles, from the same sample have unique emission signatures.
  • a single particle acts as its 'own-reference', thus a single particle can be seen as a single experiment.
  • This parameter formed the fundamental analytical variable in the developed hybridization assay.
  • the spectral resolution of the CCD set-up generally employed in this investigation could limit the sensitivity of the WGM sensors.
  • the sensitivity depends critically on the spectral resolution of the detector employed.
  • the Ocean Optics detector has a resolution of 0.9 nm, and the WGM emission peaks are damped due to the low spectral resolution. Hence, there is no information that can be gleaned from the mode shapes. Nevertheless, these simple spectrometers enable the assay to be carried out cheaply and could be done in the field routinely.
  • Hybridization induced red-shifts are routinely observed with 70 base-oligo- modified particles treated with sub-picomolar cDNA concentrations from a 120 ⁇ L dosage volume.
  • Benchtop, LN2-cooled CCDs and grating monochromators are necessary to properly observe and characterize the WGM modes of the microspheres, but for assay purposes such high resolution is not a pre-requisite.
  • At the lowest DNA concentrations one can observe small, random blue- shifts from post hybridized particles. These indicate that the WGM emission can be influenced by small perturbations such as minute changes in the solution refractive index due to temperature fluctuations and electrolyte concentration. This determines the ultimate practical limit in sensitivity possible for these bioassays in aqueous media. Consequently, only consistent red-shifts of four or more peaks are taken to indicate a positive detection event.
  • a disadvantage of silica-based WGM platform is it cannot be used entirely in solution.
  • the limitations associated with the current WGM system are alleviated by designing a conjugation protocol along with the development of a highly- sensitive, whispering gallery mode (WGM) solution based genotyping system.
  • the system comprises a uniform, highly-cross linked melamine formaldehyde microsphere ( ⁇ 7.52 ⁇ m) functionalized with a fmorophore and a monolayer of single-strand oligonucleotides.
  • Using a microplate-well system an assay can be completed entirely in solution.
  • the WGM label-free system can score polymorphic amplified DNA targets at sub-picomolar sensitivity.
  • the frequency shifts detected in water can be used to monitor the denaturation of the double-stranded post-hybridization complex at elevated temperatures. Controlled by a two-step temperature gradient the optical switching capability of the polymer based sensor is also demonstrated as the WGM shifts can be reversed and re-activated routinely.
  • biocompatible melamine composite particles are commercially available in a wide range of particle sizes (300 nm - 12 ⁇ m).
  • the material's high refractive index (n r 1.68) which is greater than that of polymethylmethacrylate (n r 1.48), silica and most other glass materials (n t 1.47 - 1.50) offers a clear advantage.
  • the increased refractive index mismatch between an MF particle and an external water-medium (n r 1.33) should improve the quality factor of the WGMs.
  • the mismatch is large enough that it enables simplified assays to be carried out in solution.
  • This Example examines the development of a single particle, label-free WGM 'wet-assay' for oligomeric target detection.
  • the particles possess Q factors similar to those of silica microspheres of the same size in air.
  • the assay can routinely detect sub-picomolar levels of unlabeled oligonucleotide fragments in solution in a micro-well plate bench-top format.
  • the findings presented show that fluorescent WGM signals in highly cross-linked melamine formaldehyde (MF) microspheres ( ⁇ 10 ⁇ m) positively discriminate a single nucleotide polymorphism (SNP) between unlabeled PCR amplified fragments of genomic DNA (gDNA) of three individuals carrying a different nucleotide at a particular loci.
  • MF melamine formaldehyde
  • SNP single nucleotide polymorphism
  • a microscope PElOO-NI system inverted peltier stage was utilized for thermocycling hybridization studies.
  • the system comprised a diaphot range of inverted scopes with XY table customized for a Nikon TE200/300 microscope table.
  • the stage temperature range (- 5 to 99 0 C) was controlled with a PElOO-I heating/cooling peltier stage.
  • the stage was coupled to a water circulation pump to regulate stage temperature.
  • GAA - 3' SEQ ID NO:8
  • T a- rs 10434 B (mismatch) 5'- CAG GAG [C]CC AC/iAm/ GGC AGA TGT CCC GGC
  • PCR amplified regions of gDNA containing the rs 10434 SNP labeled Individual 1 [A/ A]; Individual 2 [A/G]; Individual 3 [G/G] were provided by the International Diabetes Institute (Melbourne, Australia). Genotyping was carried out using the Mass ARRAY system (Sequenom, San Diego, CA), as previously described (Peyrefitte et al, Mechanisms of Development 104(l-2):99- ⁇ 04, 2001). Briefly, PCR primers were designed for rslO434 using SpectroDESIGNER to amplify a 97 bp fragment surrounding the variant site.
  • Reactions were performed using 2.5 ng genomic DNA, 2.5 mmol/L MgCl 2 , standard concentrations of other PCR reagents and 0.1 unit HotStar Taq DNA polymerase (Qiagen, Germany) in a total reaction volume of 5 ⁇ L. Fragments were isolated by electrophoresis using Qiaquick gel extraction kit (Qiagen, Germany) as per the manufacturer's instructions.
  • Aery loy I mediated conjugation of oligonucleotide fragments to microspheres [0191]
  • the raw melamine particles were washed several times in Milli-Q (8000 rpm for 5 s) and stored dry and desiccated at 4 0 C under nitrogen. Washed MF particles (2 mg) were weighed in an eppendorf tube.
  • the native surface chemistry of the melamine particles (Gao et al, Macromolecular Materials and Engineering 286(6):355-361, 2001) provided a robust conjugation surface to immobilize the single-strand oligonucleotide fragments.
  • Microspheres were initially diluted in a series of four dilutions by taking 1 ⁇ L stock microspheres (2 mg / 1 mL) and resuspending it in 1 mL of Milli-Q (dilution 1) and vortexing. Then 250 ⁇ L of the dilution was resuspended in 1 mL of Milli-Q H 2 O and vortexed. This process was repeated with the new dilution three times. A 1 ⁇ L aliquot from dilution 3 or 4 would typically contain 1 particle / ⁇ L.
  • the heating stage temperature was increased to 37 0 C and allowed to equilibrate for 2 min and then a single spectrum was captured. 5 ⁇ L of Milli-Q or a 2 ⁇ M target probe solution was then applied to the well. The stage-temperature was increased to 72 0 C and held for 2 min followed by spectral acquisition. Finally the stage temperature was decreased to 37 0 C or room temperature.
  • oligonucleotide fragments used to functionalise the microspheres were designed and constructed to mimic a 30 base strand spanning the rs 10434 SNP region of the human genome. The sequence is homologous to the region on chromosome 6.
  • VEGF vascular endothelial growth factor receptor
  • the hyperglycaemia experienced by diabetic patients causes abnormal vascular cell function, in particular in the endothelium at later stages of the disease. These individuals commonly experience progressive degeneration of the micro- and macro-circulation which consequently leads to organ damage (Laselva et al, Acta Diabetologica 30( ⁇ :190-200, 1993; Ciulla et al, Acta Ophthalmologica Scandinavica 80(5) ⁇ 68-477, 2002). Studies have demonstrated that the selected SNP region could potentially be used as a marker for T2D and related illnesses. The findings presented here demonstrate the validity of the optimized WGM platform as an effective diagnostic tool to routinely score known human disease related SNP targets.
  • the oligo-modified MF particles have a diameter of 7.52 microns and were directly bioconjugated with 5' acryloyl modified TMR labeled target oligonucleotides.
  • MF particles ability to support a WGM in solution led to the next investigation, which was to select a hybridization substrate which facilitates routine acquisition of relatively high-Q WGMs in solution.
  • Presenting the particles in a micro-titre plate format moves a step closer towards the direction of a high throughput automated assay.
  • the analysis was based on WGM signal quality that could be collected from the oligo-modified MF particles while immobilized on a micro-well and assay plate substrate.
  • Modified MF particles were immobilized on a silica gridded array plate, within a single well 384 well polycarbonate cytoplate, 384 well optical plate and a 96 well polymer cell culture plate. Emission signals were collected from selected particles while immersed in standard hybridization buffer.
  • Figure 12 illustrates a representative emission profile obtained using each selected substrate. Due to the small working width of the substrate it was expected that the silica gridded array would produce high signal outputs from a selected MF particle ( Figure 12A). However for a high throughput format, a well-based system was the desired direction. The first micro-plate system analysis was carried out with a common plastic based 96 well culture plate ( Figure 12B). The collected emission signal indicates a WGM profile consisting of several broad low intensity peaks. This was simply due to a large width of the base of each well and to the fact that plastic has high scattering properties. Also the use of a lower objective magnification power (x 40) to allow for a large working distance reduced the overall signal.
  • x 40 objective magnification power
  • Each well had a smaller total working volume (polymer based plate: base width 100 ⁇ m; well area, 0.05 cm 2 / well with a total working volume, 120 ⁇ L / well). Also the flat bottom well geometry and visible transparency allowed easy access to the plate and manipulation using the microscope X/Y oriented working stage.
  • Figure 12C shows an example of a typical emission signal from an MF particle. Present are a series of identifiable narrow, high intensity fluorescent peaks. A 384 optical plate was also employed with the same working dimensions and volumes as the polymer plate. However, the base width was narrower (50 ⁇ m) and the well base did not hold a positive charge. Nine distinct emission peaks are noted within the WGM profile as indicated in Figures 13 A and C.
  • the reference photoluminescence (PL) signal was measured from selected particles and the plate was heated to standard hybridization assay temperature (9O 0 C). The temperature was maintained for three hours during which time the selected particles were relocated and the emission signal regularly collected.
  • Figure 14 presents normalized WGM spectra acquired from the selected particles after 3 hours of heat exposure. Over the 3 hr period the greatest effect was noted in the particle immersed in MES (black dashed line) which exhibited a significant loss of PL signal compared with particles immersed in hybridization buffer (black solid line). The strongest signal following heat treatment was observed in the control particle which was maintained in Milli-Q only (grey solid line). The emission signal level did vary between samples. However, a clear WGM profile with several identifiable peaks could still be obtained from each particle after 3 hrs heating.
  • a single 7.52 ⁇ m MF-rslO434 target particle was cycled through a two-step gradient (37°C-72°C).
  • An initial hybridization reaction was completed following the addition of 5 ⁇ L of Milli-Q.
  • Spectra acquired at a 2 s integration time at each gradient temperature through several cycles indicated no consistent movement of the WGM peaks Figure 15A-B.
  • the experimental conditions were repeated with addition of the target probe DNA (5 ⁇ L of a 2 ⁇ M stock).
  • DNA fragments of approximately 20 bases were amplified using primers which spanned the rs 10434 SNP region.
  • the genotypes of the above individuals were determined using the Sequenom Mass ARRAY genotyping platform. Each individual had a different genotype. Individual 1 was homozygous for the A allele (A/A), individual 2 was heterozygous (AlG) and individual 3 was homozygous for the G allele (G/G) at this locus.
  • the aim here was to determine whether a single base pair difference could be detected from the PCR amplified samples using the WGM system.
  • a single rslO434-MF particle specific for the A allele of the rs 10434 DNA variant was immobilized in a micro-plate well; the particle was then exposed to the 3 different analytes over separate hybridization reactions. Each hybridization was completed at 90 0 C for 5 min after a 2 ⁇ L addition of the DNA sample (Individual 1-3). Emission signals were collected after each hybridization reaction respectively after the reaction temperature gradient had been decreased to ambient room temperature. WGM signatures acquired after each treatment relative to the reference signal (black spectra) were determined. The peak positions were analyzed relative to the un-treated WGM profile and the L ⁇ noted. The spectra obtained show the peak wavelength positions as a function of the peak-shift about the given reference wavelength.
  • Exposure of a single particle to both target probes resulted in a blue shift of all major fluorescence gallery mode peaks post a- rs 10434 B treatment, if the particle was initially exposed to a- rs 10434 A target fragments.
  • the native surface of the MF particles facilitates conjugation of a dense monolayer of acryloyl modified oligonucleotide fragments.
  • the conjugation is essentially the covalent linkage of a melamine molecule with an acrylic acid.
  • the oligonucleotide modified particles are highly resilient when exposed to high pH solutions at elevated temperatures (90 0 C) as high quality WGM signals can be collected from the particles after prolonged exposure. Data demonstrate that FITC labeled human ⁇ -IgM antibodies can also bind effectively to the un-modified MF particles. These particles can then be utilized in antibody-antigen binding assays.
  • DNA has a higher refractive index in the single-stranded (denatured) conformation (Parthasarathy et al, Applied Physics Letters 87(11) ⁇ 13901-3, 2005). In its native form the refractive index of DNA is similar to that of typical organic polymers (Samoc et al, Chemical Physics Letters 431(1-3):U2-134, 2006). Naturally double-stranded DNA exists as a dielectric material, and alternatively in the denatured form it becomes a semiconductor with a band gap of a few hundred milli-electronvolts (Rakitin et al, Physical Review Letters 86(16):3670, 2001).
  • the WGM shifts described in this Example are governed by a decrease or increase in the relative refractive index at the microsphere surface in direct association with an increase in the microspheres diameter (Niu and Saraf, Smart Materials and Structures 11(5):778-7S2, 2002). How these parameter(s) influence the WGM specifically is yet to be elucidated, however in contrast the characteristic shifts are routinely reproducible using both composite particles.
  • the position of the fluorophore at the first nucleotide base of the tethered acryloyl oligonucleotides facilitates the routine total-internal-reflection of the excited light in air and water mediums.
  • the system described in the current Example does not utilize optic- fibre coupling methods to excite a WGM which drastically simplifies the assay. Attomole volumes of target DNA probe solution can be routinely detected. The cyclically reversible WGM shifts observed in the MF microspheres importantly indicates the particles can be recycled. The WGM peak shifts were shown to be reversible when the local temperature was oscillated above and below the T m of the target probe; hence, the spectral red-shifts are specifically due to hybridization of complementary DNA. The binding affinity of a target probe is significantly decreased when a DNA fragment has a single base mismatch.
  • Nonspecific binding although found to be negligible can cause small blue-shifts in a particle's WGM spectra if the same particle is initially exposed to a complementary target.
  • the compared WGM emission spectra indicate a specific target probe has a far greater binding affinity as opposed to a fragment containing a single base mismatch.
  • This Example reports on the development of a series of optimized parameters to routinely excite high quality whispering gallery modes (WGM) in the fluorescent colloids.
  • WGM whispering gallery modes
  • TSOM target specific oligonucleotide-modif ⁇ ed silica and melamine microspheres (7.50 - 7.52 ⁇ m) [Microparticles Germany GmbH] presented in Examples 5 to 7 are utilized throughout.
  • Coupling position effects [0215] Using the confocal set-up, an angle-resolved spectroscopic technique was designed to characterize the WGM emission as a result of altering the laser excitation position. Cover glass array slides were prepared with TSOM silica and MF particles as prescribed previously (Examples 5 to 7). The confocal system employed was utilized to alter the excitation position around the circumference of the particle using the acquired particles' transmission image as a reference. At a 350 ⁇ W radiation power selected particles were excited through a multi-line Ar+ laser. The emission spectra were collected at a 2 s integration time. For all confocal work herein an Ar+ laser was used for particle excitation.
  • the excitation position was altered at 45° increments over a 360° rotation around the microspheres peripheral boundary relative to the 0° (reference) co-ordinate.
  • a particle's WGM is excited on the confocal set-up the excitation position 0° is normally utilized, this results in the routine acquisition of high quality WGMs.
  • excitation at the selected positions through 360° also results in the collection of strong WGM spectra.
  • Analysis of the spectra-set for the selected example demonstrates no detectable peak shifts are observed for the selected excitation positions (within the spectral resolution of the Triax 550 spectrometer ⁇ 0.05 nm). In some cases a peak distortion can occur. The distortion was consistently observed in each WGM spectra acquired at the given wavelength.
  • a selected MF particle was then scanned in air under the same conditions. Analysis of the WGM spectra-set demonstrates that relative to the 0° spectra, detectable peak shifts are observed (spectral resolution of the CCD ⁇ 0.05 nm. Blue shifts are observed in the selected example, however, it is unlikely the particles refractive index has changed to cause the observed shifts. These effects could be due to the movement of the excitation position but are more likely the result of reaching the threshold limits of the CCD. The total internal reflection of light through a TSOM-MF particle immobilized in solution was demonstrated in Example 7. A single MF particle immersed in solution was then excited at the selected radial positions.
  • the particles were immobilized on cover glass arrays, the substrates were then mounted on a confocal microscope. Selected silica and MF microspheres were excited in air through the 0° excitation position (integration time 2 s). Spectra set acquired at a 2 s integration time from the selected silica microsphere. The WGM photointensity (PI) significantly decreases in fluorescence intensity after the series of scans. Ten distinct peaks were identified in Scan 1 and 9-10 peaks from the Scan 20.
  • the next step was to repeatedly excite a single TSOM MF particle in solution (Milli-Q H 2 O).
  • a single particle was lased at position 0° and set of spectra were captured at a 2 s integration time.
  • the number of identified peaks decreased within the selected scan range (eight) in comparison with the air measurements. However, the peak number remained unchanged after the scans were complete (scan 1-20). A six-fold decrease in the Q-factor is observed between scan 1 and 20, respectively.
  • the sensitivity of a spectrometer has an important role in WGM measurements during a working assay.
  • the spectrometer determines the amount of spectral information one can acquire from an excited particle and the sensitivity limits of the WGM detection platform.
  • microscope set-ups and sensitivity of the CCD detectors are compared.
  • a silica particle was first excited (position 0°) in air, and the spectra collected with a Triax 550 spectrometer (spectral resolution ⁇ 0.05 nm) at an integration time of 2 s. A spectrum was then acquired from the same particle through a mercury lamp (excitation output power 35.52 mW). A QE6500 Ocean Optics system (spectral resolution ⁇ 0.9 nm) at an 2 s integration time was utilized to acquire a spectrum. A clear broadening is observed of several major peaks from the spectra acquired with the QE6500 spectrometer.
  • the spectra acquired through the Triax 550 indicates several peaks ( ⁇ nax - 577.54 nm, 588.47 nm, 594.35 nm and 599.95 nm) are not present in the QE6500 spectra.
  • the spectrum acquired through the Triax 550 indicates a loss of several peaks results when the QE6500 is utilized for WGM acquisition 578.81 nm, 584.65 nm, 588.07 nm, 597.73 nm and 608.08 nm).
  • the FWHM values Triax (0.72 nm) and QE6500 (1.27 nm) further indicate the difference in spectral quality.
  • the WGM peak shift between spectrometers is simply due to the differing sensitivity of the spectrometers.
  • the spectral resolution of the instrument defines the accuracy in which a peak position can be measured as a 'true' ⁇ nax -
  • the Ocean Optics system ( ⁇ 0.9 nm) is less accurate in relation to the 'true I max ' for each observed WGM peak compared with the TRIAX system ( ⁇ 0.05 nm). Therefore based on these conditions it is expected that there will be variability between the WGM response curves.
  • a bleaching threshold of the microspheres was determined while under constant excitation through a fixed coupling position.
  • Figures 17(A) and (B) show a comparison of the WGM profile obtained using silica particles (B) and melamine formaldehyde particles (A).
  • the solid lines in (A) and (B) were the profiles obtained in air and the dotted lines represent the profiles when the particles were in aqueous media.
  • An immuno-based WGM assay provides a setting for a diagnostic platform. Data demonstrate a fluorescent WGM signal entitled from an antibody (Human ⁇ -IgM) modified MF particle can be utilized to discriminate between a control reagent and target antigen ( Figure 17) in a room temperature reaction.
  • the immuno-WGM assay provides an alternative recognition format with tunable specificity to a plethora of biomolecular targets such as proteins, antibodies, animal and plant pathogens, bacteria, interleukins, peptides, RNA, niRNA and prions. Immuno-WGM assay has potential in applications in the food hygiene industry, environmental water testing, agricultural industry, military (biowarfare), virology, microbiology diagnostics and pharmacological screening.

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Abstract

La présente invention concerne un essai de détection d’analyte rapide et sensible basé sur des modes de galerie de particules microsphéroïdales marquées par fluorescence. Des ligands pour l’analyte, tels que des acides nucléiques, sont ancrés aux particules. Les marqueurs fluorescents peuvent comprendre des fluorophores ou des points quantiques. Dans le dernier cas, les particules peuvent comprendre du mélamine-formaldéhyde. L’essai peut être utilisé pour détecter des analytes dans des échantillons aqueux.
PCT/AU2009/001515 2008-11-21 2009-11-20 Essai de détection d’analyte WO2010057264A1 (fr)

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CN200980153782.XA CN102272597B (zh) 2008-11-21 2009-11-20 分析物检测试验
BRPI0921591A BRPI0921591A2 (pt) 2008-11-21 2009-11-20 métodos de detecção de analito num meio e de evento de ligação entre analito e ligante e respectivos usos
US13/130,566 US8617824B2 (en) 2008-11-21 2009-11-20 Analyte detection assay
NZ592953A NZ592953A (en) 2008-11-21 2009-11-20 Analyte detection assay using melamine formaldehyde
JP2011536705A JP5588454B2 (ja) 2008-11-21 2009-11-20 分析物検出アッセイ
AU2009317878A AU2009317878B2 (en) 2008-11-21 2009-11-20 Analyte detection assay
CA2744331A CA2744331C (fr) 2008-11-21 2009-11-20 Essai de detection d'analyte fonde sur des particules microspheroidales marquees de maniere fluorescente
MX2011005366A MX2011005366A (es) 2008-11-21 2009-11-20 Ensayo de deteccion de analitos.
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CA2744331A1 (fr) 2010-05-27
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EP2368115A1 (fr) 2011-09-28
US8617824B2 (en) 2013-12-31
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US20110256528A1 (en) 2011-10-20
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