WO2008104637A1

WO2008104637A1 - Luminescence energy transfer based homogeneous bioassay and kit therefore

Info

Publication number: WO2008104637A1
Application number: PCT/FI2008/050087
Authority: WO
Inventors: Tero Soukka; Leena Kokko; Ulla Karhunen
Original assignee: Hidex Oy
Priority date: 2007-02-28
Filing date: 2008-02-26
Publication date: 2008-09-04
Also published as: FI20070171A0

Abstract

This invention relates to a luminescence energy transfer based homogeneous bioassay wherein measurement of phosphorylated or dephosphorylated peptide or protein is carried out. The bioassay comprises a) a first group labelled with an energy donor; wherein the first group is a particulate comprised of a polymer or an inorganic crystallic structure, and the first group is i) a long-lifetime luminescent lanthanide label if the particulate is a polymer, or ii) an up-conversion luminescent lanthanide label or down-conversion luminescent lanthanide label if the particulate is an inorganic crystallic structure. The first group is able to transfer fluorescence energy to an acceptor of a second group, and the first group i) is coated with a trivalent metal ion binder through passive adsorption, achelate structure or a polymeric structure, or ii) has trivalent metal ions incorporated into the crystallic structure. The second group is labell ed with the energy acceptor, wherein the acceptor is a short-lifetime fluorescent label, and the second group comprises a peptide or protein with at least one phosphorylatable amino acid within 10 nm from said acceptor. After a sample and reagents of the bioassay, the reagents including the first and second groups, and trivalent metalions if not incorporated in the second group, have been brought into contact with each other, the first group is excited and resulting emission of the second group, the emission relating to energy transfer from donor to acceptor due to phosphorylated peptides and/or proteins of the second group being attached to the trivalent metal ions bound to or incorporated into the first group, is measured. The present invention also relates to kits for bioassays according to the invention.

Description

LUMINESCENCE ENERGY TRANSFER BASED HOMOGENEOUS BIOASSAY AND KIT THEREFORE

FIELD OF THE INVENTION

This invention relates to measurement of biological activity or its modulation or analyte concentration using a luminescence energy transfer based homogeneous bioassay.

BACKGROUND OF THE INVENTION

The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated by reference.

Kinases and phosphatases are important enzymes, because they regulate the activity of other proteins through phosphorylation and dephosphorylation of certain amino acids. These enzymes are an important part of many cellular processes (e.g. growth, proliferation, apoptosis, differentiation and cell cycle control). Especially kinases are currently a very important class of potential targets in high throughput screening. There are over 500 known kinases, of which 85 % catalyse the phosphorylation of serine or threonine amino acids while the rest catalyse the phosphorylation of tyrosine amino acid.

There are several assay methods suitable for high throughput screening of novel drugs. Many of the developed assays are homogeneous, since they are less laborious than heterogeneous assay due to the lack of separation steps. In homogeneous assays used in high throughput screening the components of the assay are mixed and after an optimised incubation time the signal generated by the assay is measured and the effect of a potential drug screened in the assay can be deduced from the obtained signal. The first reported and still widely used homogeneous assay method is scintillation proximity assay (SPA), which utilizes isotopic labels and scintillant-impregnated particles to generate a measurable signal. Binding of molecules containing a weak energy isotope like ³H or ¹²⁵I on the scintillant embedded particle stimulates the light emission. Radioactivity of the molecules cannot penetrate long distances in aqueous solutions, thus those isotopes, which are not bound onto the scintillant embedded particles, cannot generate a measurable signal. However, the SPA produces radioactive waste, which is expensive to decimate. [Hart HE and Greenwald EB (1979) Scintillation proximity assay (SPA) - a new method of immunoassay. Direct and inhibition mode detection with human albumin and rabbit antihuman albumin. MoI Immunol 16: 265-267; Udenfriend S, Gerber LD, Brink L and Spector S (1985) Scintillation proximity radioimmunoassay utilizing 1251- labeled ligands. Proc Natl Acad Sci USA 82: 8672-8676]

LOCI (luminescent oxygen channeling immunoassay), commercially known as AlphaScreen (Perkin Elmer Life and Analytical Sciences, Boston, MA), utilizes two different particle or bead labels. When a polystyrene particle dyed with photosensitive dye (e.g. phthalocyanine) is irradiated e.g. at 680 nm, it releases singlet oxygen, which can travel a short distance to a chemiluminescent particle dyed with e.g. thioxene in close proximity. Singlet oxygen initiates a chemiluminescence reaction, which leads to measurable luminescence emission at 580 - 620 nm. The distance which the singlet oxygen can travel is up to 200 nm. [Ullman EF, Kirakossian H, Singh S, Wu ZP, Irvin BR, Pease JS, Switchenko AC, Irvine JD, Dafforn A, Skold CN and Wagner DB(1994) Luminescent oxygen channeling immunoassay: Measurement of particle binding kinetics by chemiluminescence. Proc natl Acad Sci USA 91 : 5426-5430; Ullman EF, Kirakossian H, Swithchenko AC, lshkanian J, Ericson M, Wartchow CA, Pirio M, Pease J, Irvin BR, Singh S, Singh R, Patel R, Dafforn A, Davalian D, Skold C, Kurn N and Wagner DB (1996) Luminescent oxygen channeling assay (loci): Sensitive, broadly applicable homogeneous immunoassay method. Clin Chem 42: 1518 - 1526] The AlphaScreen method has been used for many high throughput screening assays, including kinase and phosphatase activity assays (US 2006/0063219 A1 ) . Another commercially available assay method for measurement of kinase activity is IMAP (immobilised metal affinity for phosphate, Molecular Devices), (WO 00/75167 A2). IMAP technology utilises fluorescence polarisation for the detection, thus it is a homogeneous assay method. When the substrate peptide conjugated with a fluorescent label is bound onto the surface of the IMAP particle, the fluorescence polarisation of the label is altered compared to substrate peptides not bound on the particle. Traditionally homogeneous kinase assays use antibodies, which recognise and bind to the phosphorylation site of the substrate peptide or protein. IMAP, like previously mentioned AlphaScreen, however, utilise trivalent metal ions complexed with suitable structures as binders. It is well reported that certain trivalent metal ions [e.g. Ga(III), Fe(III), AI(III), In(III), Ru(III), Sc(III), Y(III)] can bind to phosphate groups with relatively high specificity and affinity. Trivalent metal ions are generic binders, since they do not recognise the sequence surrounding the phosphorylation site of the protein or peptide. Thus trivalent metal ions have been used as binders in many assays measuring the presence of phosphorylated proteins and other biological macromolecules. (US 2006/0121544, US 2005/0014197, US 2006/0063219, WO 2005/114198)

Different lanthanide chelates or cryptates have been used in commercial homogeneous fluorescence resonance energy transfer based high throughput screening assays. [LANCE (WO 98/15830), LanthaScreen (WO 96/00901 ) and HTRF (WO 92/13264)]. In FRET based assays two fluorescent labels are used: a donor and an acceptor. When a lanthanide label is used as the donor, the acceptor label has a short fluorescence lifetime. When the donor and the acceptor are in close proximity, the emission of the donor label can excite the acceptor label and sensitised emission is generated. Because the donor label has a long fluorescence lifetime, the sensitised emission can also be measured using time- resolved detection. The lanthanide ions themselves have a poor absorption capacity, thus specific chelate (or cryptate) structures are needed: The chelate must have an organic chromophore (antenna), which absorbs the excitation energy and transfers it to the lanthanide ion held in place by metal binding groups (chelators). The chelate also contains an active group, which can be used for bioconjugation of the label. Lanthanide chelates have undeniable benefits compared to traditional organic fluorophores: Unusually large Stokes' shift of the chelates separates the excitation and emission wavelengths by hundreds of nanometers. Thus scattering of the excitation light is not likely to cause background in the measurement. Each lanthanide chelate has a wide excitation spectrum in the UV range, but a narrow emission spectrum in visible light range. Main emission peaks are clearly separated from each other enabling multiplex assays. Fluorescence generated by the lanthanide chelates has a significantly longer lifetime than traditional organic fluorophores. This enables time-resolved detection, which efficiently eliminates the background caused by e.g. short lifetime autofluorescence of biological material. [Gudgin Dickson EF, Pollak A, Diamandis EP (1995) Time-resolved detection of lanthanide luminescence for ultrasensitive bioanalytical assays. J PhotoChem Photobiol B 27: 3 - 19, Hemmila I, Laitala V (2005) Progress in lanthanides as luminescent probes. J Fluoresc 15: 529 - 542]

Lanthanide chelates can be packed inside a nanoscale polystyrene shell to produce a particulate fluorescent label. Commercially available Eu(lll)-chelate dyed nanoparticles (Seradyn Inc., Indianapolis, IN) contain several thousands of Eu(lll)-β-diketone chelates inside a single polystyrene shell, but also particles dyed with Tb(III), Sm(III) and Dy(III) chelates have been produced and used as labels in immunoassays. The polystyrene shell of the particles is known to form a protective environment, which prevents fluorescence quenching of the embedded lanthanide chelates caused by e.g. bivalent metal ions. Carboxyl acid groups on the surface of the particle enable covalent conjugation of proteins e.g. antibodies or streptavidin. Eu(lll)-chelate dyed nanoparticles have been used successfully as labels in both heterogeneous and homogeneous immunoassays. [Harma H, Soukka T, Lόvgren T (2001 ) Europium nanoparticles and time-resolved fluorescence for ultrasensitive detection of prostate-specific antigen. Clin Chem 47: 561 - 568; Huhtinen P, Kivela M, Kuronen O, Hagren V, Takalo H, Tenhu H, Lόvgren T, Harma H (2005) Synthesis, characterization, and application of Eu(III), Tb(III), Sm(III), and Dy(III) lanthanide chelate nanoparticle labels. Anal Chem 77: 2643 - 2648; Kokko L, Lόvgren T, Soukka T (2007) Europium(lll)-chelates embedded in nanoparticles are protected from the interfering compounds present in assay media. Anal Chim Acta 585:17-23] An alternative source of long-lifetime lanthanide photoluminescence is inorganic rare earth-based crystals that are commonly used in fluorescent lamps to convert ultraviolet to visible light. Bulk micron-sized phosphor material (e.g., europium- activated yttriumoxysulphide) can be either ground to submicron particle size or nanocrystals composed of rare earth oxides or fluorides, or phosphates containing europium as a doping element can be synthesized directly. Submicron phosphor particles have been stabilized with surface ligands and coated with proteins (e.g., antibodies) and nucleic acids to produce functional conjugates to be employed in ligand binding assays, time-resolved fluorescence microscopy, and in a homogeneous fluorescence energy transfer assay. These lanthanide phosphors generate photoluminescence typical to the corresponding lanthanide chelates but provide an improved photostability and have slightly different absorption bands for excitation. The lanthanide phosphors designed for mercury discharge lamps have typically excitation bands in a range of discharge from 254 to 365 nm. The excitation in deep ultraviolet at 254 nm is, however, very weakly suitable for use in fluoroimmunoassays due to the resulting exceedingly high instrument background, which generally also has a long decay time. In addition to the excitation bands at ultraviolet, the europium phosphors have been reported to be excited efficiently enough using either violet (390-400 nm) or blue light (465-470 nm), which can moderate the price of the detection system by allowing the use of highpower light emitting diodes as excitation light sources. [Soukka T, Kuningas K, Rantanen T, Haaslahti V and Lόvgren T (2005) Photochemical characterization of up- converting inorganic lanthanide phosphors as potential labels. J Fluoresc 15: 513- 528; (Beverloo HB, van Schadewijk A, Zilmans HJ, Tanke HJ (1992) Immunochemical detection of proteins and nucleic acids on filters using small luminescent inorganic crystals as markers. Anal Biochem 203: 326 - 334]

A new type of particulate reporter, that of up-converting phosphor technology introduced in the late 1990s, provided a novel solution to the problem of instrument background and autofluorescence in fluorescence based immunoassays. Up-converting phosphors consist of an inorganic crystal lattice with thvalent rare earth dopands (e.g., yttriumoxysulphide activated with erbium and ytterbium) and the upconverting phosphors can be fairly similar in structure to the previously described lanthanide phosphors, but possess a unique feature of being capable to convert infrared to visible light via non coincident absorption of two or three infrared photons. The efficiency of the up-conversion process in these phosphors, however, is greatly enhanced compared to simultaneous two-photon excitation, because thvalent lanthanides commonly have long-lifetime excited states, which can operate as a metastable state excited from a ground state to be excited again to an emission state (or transfer its energy to another ion). This property is so exceptional that no autofluorescence is produced from any biological material at the visible wavelengths by an infrared light flux used to excite the up-converting phosphors; i.e. anti-Stokes photoluminescence (up-converted emission) can be measured entirely free of autofluorescence and scattered excitation light. In principle, the anti-Stokes photoluminescence background is equivalent to that achieved in luminescence counting, where the dark counts of the photomultiplier set the limit of detection. Further, up-converting phosphors possess the favourable characteristics associated with lanthanide photoluminescence, including narrow emission bands and large Stokes shift (in this case anti-Stokes shift). The major advantage of the up-converting phosphors as a label in an immunoassay would be the availability of a low limit of detection with an uncomplicated detection system; anti-Stokes photoluminescence can be measured without temporal resolution using an inexpensive infrared laser diode for excitation, standard long-pass colour glass as an excitation filter, a photomultiplier for photon counting and a narrow band-pass filter with adequate infrared blocking for selection of the appropriate emission wavelength. [Soukka T, Kuningas K, Rantanen T, Haaslahti V and Lόvgren T (2005) Photochemical characterization of up-converting inorganic lanthanide phosphors as potential labels. J Fluoresc 15: 513-528; WO2004/086049; Kuningas K, Rantanen T, Karhunen U, Lόvgren T, Soukka T (2005) Simultaneous use of time-resolved fluorescence and anti-stokes photoluminescence in a bioaffinity assay. Anal Chem 77: 2826-34]

All particulate lanthanide labels can be used as reporters in heterogeneous and homogeneous assays. Fluorescent properties of lanthanides are not significantly changed, when the ions or chelates are embedded into particle structures. All lanthanide particles can be used as donor labels in homogeneous immunoassays based on FRET. Homogeneous assays using nanoparticles as donors include both sandwich-type non-competitive assays for proteins and competitive assays for haptens [Valanne A, Lindroos H, Lόvgren T, Soukka T (2005) A novel homogeneous assay format utilising proximity dependent fluorescence energy transfer between particulate labels. Anal Chim Acta 539: 251 - 256; Kokko L, Sandberg K, Lόvgren T, Soukka T (2004) Europium(lll) chelate-dyed nanoparticles as donors in a homogeneous proximity-based immunoassay for estradiol. Anal Chim Acta 503: 155 - 162; Kuningas K, Rantanen T, Ukonaho T, Lόvgren T, Soukka T (2005) Homogeneous assay technology based on upconverting phosphors. Anal Chem 77:7348 - 7355] These assays have been employed e.g. in automated high throughput screening of novel drugs. [Kokko L, Johansson N, Lόvgren T, Soukka T (2005) Enzyme inhibitor screening using a homogeneous proximity-based immunoassay for estradiol. J Biomol Screen 10:348 - 354; Kokko L, Jaakohuhta S, Lindroos P, Soukka T (2006) Improved homogenous proximity- based screening assay of potential inhibitors of 17β-hydroxysteroid dehydrogenase. ASSAY Drug Dev Tech 4:671 - 678]

Many kinases require Mn²⁺ as a cofactor, but Mn²⁺ is a very effective, reversible quencher of intrinsically fluorescent lanthanide chelates [Kokko L, Lόvgren T, Soukka T. Europium(lll)-chelates embedded in nanoparticles are protected from interfering compounds present in assay media. Anal Chim Acta. 2007 Feb 28;585(1 ):17-23]. Thus, conventional TR-FRET based kinase assays based on intrinsically lanthanide chelates are susceptible to interference by Mn²⁺ and addition of EDTA (or other chelator) is required to eliminate this effect. EDTA also chelates other ions such as Mg²⁺ and thus also stops the phosphorylation reaction.

OBJECT AND SUMMARY OF THE INVENTION

One object of the present invention is to provide a luminescence energy transfer based homogeneous bioassay wherein measurement of phosphorylated or dephosphorylated peptide or protein is carried out. Another object of the present invention is to provide a kit for a homogenous bioassay according to the method of the invention. The present invention provides a luminescence energy transfer based homogeneous bioassay wherein measurement of phosphorylated or dephosphorylated peptide or protein is carried out; and said bioassay comprises a) a first group labelled with an energy donor; wherein said first group is a particulate comprised of a polymer or an inorganic crystallic structure, and said first group is i) a long-lifetime luminescent lanthanide label if the particulate is a polymer, preferably polystyrene, or ii) an up-conversion luminescent lanthanide label or down-conversion luminescent lanthanide label if the particulate is an inorganic crystallic structure, preferably a phosphor particle; being able to transfer fluorescence energy to an acceptor of a second group; and said first group i) is coated with a thvalent metal ion binder through passive adsorption, a chelate structure or a polymeric structure, or ii) has trivalent metal ions incorporated into said crystallic structure; and b) said second group labelled with said energy acceptor, wherein said acceptor is a short-lifetime fluorescent label, said second group comprises a peptide or protein with at least one phosphorylatable amino acid within < 10 nm from said acceptor; and after a sample and reagents of said bioassay, said reagents including said first and second groups, and trivalent metal ions if not incorporated in said second group, have been brought into contact with each other; said first group is excited and resulting emission of said second group, said emission relating to energy transfer from donor to acceptor due to phosphorylated peptides and/or proteins of said second group being attached to said trivalent metal ions bound to or incorporated into said first group, is measured.

The present invention also provides a kit for a homogenous bioassay according to any of the assays defined above wherein said kit comprises reagents including reagents comprising a) a first group labelled with an energy donor; wherein said first group is a particulate comprised of a polymer or an inorganic crystallic structure, and said first group is i) a long-lifetime luminescent lanthanide label if the particulate is a polymer, preferably polystyrene, or ii) an up-conversion luminescent lanthanide label or down-conversion luminescent lanthanide label if the particulate is an inorganic crystallic structure, preferably a phosphor particle; being able to transfer fluorescence energy to an acceptor of a second group; and said first group i) is coated with a thvalent metal ion binder through passive adsorption, a chelate structure or a polymeric structure, or ii) has trivalent metal ions incorporated into said crystallic structure; b) said second group labelled with said energy acceptor, wherein said acceptor is a short-lifetime fluorescent label, said second group comprises a peptide or protein with at least one phosphorylatable amino acid within < 10 nm from said acceptor; and c) trivalent metal ions if not incorporated in said second group.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates the components of a composition suitable for conducting the bioassay for measurement of kinase or phosphatase activity in accordance with the present invention.

Figure 2 illustrates a plot of sensitized emission measured as described in Example 1.

Figure 3 illustrates a plot of specific sensitized emission (sensitized emission generated with non-phosphorylated peptides was reduced from sensitized emission of the phosphorylated peptides) measured as described in Example 2. Figure 4 illustrates a plot of specific sensitized emission measured as described in Example 3.

Figure 5 illustrates a plot of signal to background ratios (sensitized emission of phosphorylated peptides divided by sensitized emission of the non-phosphorylated peptides) measured as described in Example 4.

Figure 6 illustrates the effect on sensitized emission of uncoated and coated nanoparticles as described in example 5.

Figure 7 demonstrates sensitised emission of a homogenous assay according to the invention using aspartic acid and octylamine coated nanoparticles as described in example 6.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

In this disclosure, the term "first group" shall be understood to include any particulate lanthanide label, which can be used as a donor label in fluorescence resonance energy transfer (FRET) based assay with an acceptor label and where trivalent metal ions are bound onto the surface or the particles.

The term "second group" shall be understood to cover acceptor containing peptides or proteins, which are phosphorylated or can be phosphorylated or dephosphorylated by kinases and phosphatases, respectively. An acceptor label can be used in FRET based assays together with a donor. The acceptor label can be covalently conjugated with the analyte or the acceptor label can bind to the analyte via an association reaction.

In the context of the present application the term "bioassay" shall be understood to include association assays, which measure the activity of kinases or phosphatases or the concentration of the phosphorylated or dephosphorylated proteins or peptides. The term "homogeneous bioassay" shall be understood to cover bioassays requiring no separation steps. Single or multiple steps of each; addition of reagents, incubation and measurement are the only steps required. The term "separation step" shall be understood to be a step where a labelled bioassay reagent bound onto a solid-phase, such as for example a microparticle or a microtitration well, is separated and physically isolated from the unbound labelled bioassay reagent; for example a microtitration well is washed (liquid is taken out and, to improve the separation, additional liquid is added and the well emptied) resulting in separation of the solid-phase bound labelled bioassay reagent from the labelled bioassay reagent not bound onto the solid-phase.

The term "trivalent binder metal" and "binder containing a trivalent metal ion" shall be understood to include Lewis' metal ions capable to bind phosphorylate groups, especially Ga(III), Fe(III) and Y(III) ions coupled onto a donor particle surface using either passive adsorption, a specific chelate structure or polymer, and trivalent metal ions incorporated into the inorganic lattice of the phosphor labels.

The term "analyte" shall cover all proteins or peptides, which contain serine, threonine or tyrosine amino acids, which either are phosphorylated or can be phosphorylated or non-phosphorylated by a function of kinases and phosphatases, respectively.

The term "fluorescence" shall be understood to cover photoluminescence, i.e. luminescence excited by light, conventional short-lifetime fluorescence, delayed fluorescence with microsecond or millisecond fluorescence lifetime, ionic photoluminescence, up-conversion based anti-Stokes photoluminescence, and phosphorescence.

The term "fluorescent label" or "fluorescent compound" shall be understood to cover dye molecules, chelates, proteins, polymers, particles, dyed particles and phosphors, which express fluorescence.

The term "long-lifetime fluorescence" and "long-lifetime fluorescent compound" shall be understood to cover fluorescence and fluorescent compounds having a luminescence lifetime equal to or more than 1 microsecond (the lifetime being calculated as the time wherein luminescence emission intensity decays to the relative value of 1/e, i.e. to approximately 37 % of the original luminescence emission intensity). The compounds capable of long-lifetime fluorescence include, but are not limited to, lanthanide chelates, lanthanide-chelate dyed-nanoparticles, lanthanide phosphors and up-converting phosphors.

The term "short-lifetime fluorescence" and "short-lifetime fluorescent compound" shall be understood to cover fluorescence and fluorescent compounds with a luminescence lifetime of less than 1 microsecond.

The term "light" and "excitation light" and "emission light" shall be understood as electromagnetic radiation at wavelengths from 200 nm to 1600 nm. These wavelengths cover ultraviolet, near-ultraviolet, visible, near-infrared and infrared light.

The terms "acceptor", "acceptor label" and "acceptor compound" mean luminescent compounds having typically, but not necessarily, absorption spectra at least partially overlapping with the emission spectra of the donor and essentially capable of fluorescence resonance energy transfer from the donor.

The terms "donor" and "donor label" shall be understood as fluorescent compounds capable of fluorescence resonance energy transfer to an acceptor.

The terms "energy transfer", "fluorescence energy transfer" and "fret" shall be understood as transfer of excited state energy from donor compound to acceptor or quencher compound in proximity. Typically the energy transfer is based on Fόrster type fluorescence resonance energy transfer, but especially in case of lanthanide labels other mechanism can be prevalent.

The terms "sensitized emission" and "sensitized acceptor emission" shall be understood as emission of the acceptor label generated by energy transfer from the donor label in proximity upon excitation of the donor label. In case of long- lifetime donor label the sensitized emission has also prolonged fluorescence lifetime. The term "lanthanide" shall be understood here to be equivalent to "rare earth metal ion" and to include single lanthanide elements and combination of several different lanthanide elements from the following: neodymium, praseodymium, samarium, europium, promethium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and yttrium, especially europium, terbium, samarium, dysprosium, erbium, praseodymium, thulium, and ytterbium.

The terms "luminescent lanthanide label" and "lanthanide label" shall be understood to include a lanthanide chelate or chelate structure, containing one or more lanthanide ions, an inorganic lanthanide containing phosphor particle, or a polymeric nanoparticle containing either the described lanthanide chelates or phosphor particles. The lanthanide can represent one single lanthanide element or a combination of several different lanthanide elements.

The term "long-lifetime fluorescent lanthanide label" shall be understood as a long- lifetime fluorescent compound, i.e. a luminescent lanthanide label being able to emit long-lifetime fluorescence upon excitation enabling temporal resolution in fluorescence detection with delay time and gate times equal or greater than 1 microsecond. The long-lifetime lanthanide labels include long-lifetime fluorescent lanthanide phosphors, long-lifetime fluorescent lanthanide-chelate dyed nanoparticles, and long-lifetime fluorescent lanthanide chelates and chelate structures with or without light harvesting moiety. In addition to lanthanide-based compounds the term shall be understood to include platinum and palladium porphyrins and derivatives with similar long-lifetime fluorescence properties.

The term "long-lifetime fluorescent lanthanide phosphor" and "long-lifetime fluorescent lanthanide-chelate dyed nanoparticle" shall be understood as a particulate luminescent lanthanide label capable of long-lifetime fluorescence. The long-lifetime fluorescent lanthanide phosphor is an inorganic phosphor crystal doped with emissive lanthanide ions. The long-lifetime fluorescent lanthanide- chelate dyed nanoparticle is a polymeric particle dyed with long-lifetime fluorescent lanthanide chelates. The diameter of the particulate phosphor or particle is equal or greater than 4 nm and smaller than 1 μm. The term "up-converting lanthanide phosphor" shall be understood as a particulate luminescent lanthanide label capable of up-conversion, wherein a particulate absorbs long wavelength radiation and emits light at shorter wavelength as result of energy pooling of sequential absorption of long wavelength radiation. In certain types of phosphors, a priming dose of energy at shorter wavelength is required to excite and pre-load the phosphor before the up-conversion of long wavelength radiation is possible. The up-converting phosphor can be able to delocalise its excitation from a part or the entire volume of the particulate by internal transfer of energy between similar excited states within the particulate to a single or a few acceptor molecules. This means that a single acceptor can be excited by lanthanides which would otherwise be too far away for energy transfer to be efficient. The diameter of the particulate phosphor is equal or greater than 4 nm and smaller than 1 μm.

The term "up-conversion fluorescence" and "up-conversion fluorescent compound" means fluorescence produced by and fluorescent compounds converting lower energy incident light to higher energy emitted light. It is also called anti-Stokes fluorescence or anti-Stokes photoluminescence. Anti-stokes photoluminescence material converts low energy light to high energy light. In "up-conversion fluorescence" two or more lower energy photons of the same or different energy are absorbed sequentially, in two or more stages, to generate a single higher energy photon, contrary to simultaneous absorption in two-photon or multi-photon excitation.

In the context of the present invention hydrophilic moieties typically are polar or charged compounds soluble in water or aminodehvatives of such compounds. In the context of the present invention hydrophobic moieties typically are nonpolar compounds that prefer other neutral molecules and nonpolar solvents and are not soluble in water or aminoderivatives of such compounds.

Preferred embodiments of the invention

Objects of the present invention are to provide a homogenous bioassay for use in measurement of biological activity of enzymes (kinases and phosphatases), to use the assay for screening of potential new molecules influencing on the activity of the enzymes and for measurement of other analytes containing phosphorylated amino acids. The bioassay technology described here typically a) has relatively high signal to background ratio (S/B) b) has a large dynamic range (S-B) c) is homogeneous d) is non-radioactive e) does not require antibody specific for phosphorylated amino acid f) can be measured using either time-resolved detection mode or anti-Stokes' fluorescence g) can be measured at near-infrared area h) is not sensitive for environmental interference.

The assay utilizes a particulate lanthanide label as the donor and a short lifetime fluorescent dye as the acceptor. The donor particle is typically coated with a trivalent metal ion [Ga(III), Fe(III) or Y(III)] using either passive adsorption, specific chelate structure (e.g. NTA), a polymeric structure containing the metal ion or the trivalent metal ions are incorporated into the lattice of phosphor particles. The acceptor fluorophore is typically either covalently conjugated to the analyte (protein, peptide, which may contain a phosphoryl group) or the acceptor fluorophore is conjugated to another biological entity capable of binding to the analyte (e.g. analyte is biotinylated and the acceptor is conjugated with streptavidin). When the analyte contains a phosphoryl group, it will bind to the trivalent metal ions, which are on the surface of the particulate donor label. The binding of the analyte brings the donor and the acceptor in close proximity. When the donor and the acceptor are in close proximity, the emission of the donor label can excite the acceptor label and sensitized emission is generated. Because the donor label has slow fluorescence decay, the sensitized emission can also be measured using time-resolved detection. When up-converting phosphors are used as donor labels, the sensitized emission can be measured using anti-Stokes' fluorescence. The present invention provides an improved luminescence energy transfer based homogeneous bioassay, suitable to be used in measurement of biological activity of kinase and phosphatase enzymes or presence of phosphoryl group containing analytes. The invention further provides assays which can be carried out by using either long-lifetime luminescent or up-converting luminescent particulate labels as donors to improve signal intensity and limit of detection, which do not need any separation steps and can be measured by fluorometers or other instruments capable of measuring time-resolved fluorescence or up-conversion photo- luminescence, and in case of up-converting luminescent label, which can be performed with a strongly colored sample.

Thus, a typical embodiment of this invention concerns a luminescence energy transfer based homogeneous bioassay comprising a first group labeled with an energy donor and a second group labeled with an energy acceptor, wherein the energy acceptor is a short-lifetime fluorescent label - the energy donor is a particulate long-lifetime luminescent label or a particulate up-conversion luminescent label being able to transfer fluorescence energy to acceptor,

- the first group may or may not be coated with separate polymeric surface, the first group comprises a binder containing trivalent metal ions (Ga(III), Fe(III) Or Y(III)), o the first group can be coated with the trivalent metal ion binder using either passive adsorption, specific chelate structure (e.g. NTA) or a polymeric structure or, o the first group can have the trivalent metal ions incorporated into the inorganic host lattice of phosphor particle the second group comprises a peptide or protein, which kinase can phosphorylate or phosphatase can dephosphorylate or a peptides and proteins, which contain phosphoryl groups o the second group is either covalently conjugated with the acceptor or, o the second group contains a tag (e.g. biotin), which can be recognized by a recognizing agent (e.g. streptavidin) conjugated to the acceptor, the increase or decrease in energy transfer from the donor to the acceptor resulting from shortening or lengthening of the distance between the said labels is observed by exciting the energy donor and measuring the increase or decrease in emission of the energy acceptor, respectively. o the maximum distance of the first group and the second group is 10 nm o the suitable distance of the said labels can be achieved using an analyte, where the phosphorylation or dephosphorylation site and the acceptor are in close proximity or, o the analyte, which is either phosphorylated or dephosphorylated, has a three-dimensional structure, which brings the first group and the second group in close proximity.

According to a typical embodiment of the invention, the assay is performed by contacting the first group and the second group with the sample, - the assay is incubated for biological activity, its modulation or binding of the analyte, the emission of the energy acceptor is measured by exciting the energy donor to measure the distance between the first group and the second group.

According to preferred embodiment, the first group is in the form of particulate, each particulate comprising at least a single said donor and said binder, and preferably comprising multiple of said donors and said binders. Preferably the particulate is in the form of microparticle, having a diameter less than 10 micrometers, more preferably in the form of nanoparticle, having diameter less than 400 nanometers, and most preferably in the form of nanoparticle, having diameter less than 100 nanometers.

In typical embodiments of the invention the first group is a polymer shell, preferably polystyrene, wherein the lanthanide chelates are embedded, or a phosphor particle containing the lanthanide ions, i.e. an up-converting or down- converting lanthanide phosphor. The lanthanide is typically selected from the group consisting of europium, terbium, samarium, dysprosium, erbium, praseodymium, thulium, ytterbium and any combination thereof; and is preferably europium.

The acceptor is typically a single luminescent molecule or combination of different luminescent molecules selected to allow an increased Stokes' shift, preferably selected from the group consisting of rapidly decaying, short-lifetime fluorophores, semiconducting materials, polymeric particles embedded with any of or any of combination of these, and a near-infrared fluorescent protein.

The trivalent metal ion or ions bound to or incorporated in the particle of the first group are preferably Ga(III), Fe(III) and/or Y(III) ions, most preferably Ga(III) ions.

The first group particulate typically has a diameter of < 10 μm, preferably < 400 nm, and more preferably < 100 nm.

In preferred embodiment the first group particulate, i.e. the donor, comprises a surface coating, preferably a polymeric coating.

In some preferred embodiments also the second group, i.e. the acceptor, is in particulate format, preferably with a diameter from 1 nm to 10 μm.

In especially preferred embodiments the first group comprises hydrophilic and/or hydrophobic moieties coupled covalently onto the particulates of said first group resulting in decreased binding of non-phosphorylated peptides and/or proteins of the second group. Such moieties can be coupled covalently onto the particulates by coating as demonstrated in examples 1 , 2, 4, 5 and 6.

In embodiments with hydrophilic moieties they are typically selected from the group consisting of moieties that are negatively charged, comprise at least one carboxyl acid group and have a molecular weight of less than 2000, preferably less than 600 and most preferably less than 200, and any combination thereof. (Aminooxy)acetic acid or aspartic acid moieties are preferred alternatives. In embodiments with hydrophobic moieties they are selected from the group consisting of moieties that are not charged, comprise a hydrocarbon chain from 2 to 16 carbons and have a molecular weight less than 2000, preferably less than 600 and most preferably less than 200, and any combination thereof. Octylamine moieties are preferred.

The typical and preferred embodiments disclosed above relate both to the assay according to the invention as well as for kits to these embodiments.

Any generic inhibitor, such as staurospohn, can be employed to stop the phosphorylation reaction. In an assay according to the present invention chelation of Mn²⁺ to restore the fluorescence is not needed in contrast to assays based on intrinsically fluorescent lanthanide chelates.

The invention provides a unique combination of features to improve homogeneous, non-separation bioassays based on luminescent detection:

1 ) the signal of the assay (sensitized accepter emission) is strictly dependent on the distance between two labels, a donor and an acceptor, since fluorescence resonance energy transfer is dependent to inverse sixth power of distance,

2) the signal of the assay can be amplified by using a particulate donor or multiple donors, enabling high signal when the donor and the acceptor are in close proximity, yet enabling low background signal when the donor and the acceptor are not in close proximity,

3) the replacement of antibodies with thvalent metal binders simplifies the assay significantly and lowers the production costs, since the single assay can be used for measurement of all the kinases and phosphatases,

4) the signal of the assay can be measured at near-infrared area, where biological components cannot quench the acceptor fluorescence,

5) the fluorescence stability of lanthanide ions or chelates is improved, since they are embedded inside the polymer shell or inside inorganic crystalloid structure and they are completely protected from the assay environment, 6) the signal of the assay based long-lifetime fluorescent donor can be measured free of autofluorescence with temporal resolution, and

7) the signal of the assay based up-converting fluorescent donor can be measured free of autofluorescence and scattered excitation light without temporal resolution at a wavelength range were most of the biological samples are practically transparent.

Description of the drawings

Figure 1 illustrates the preferred composition of components required for performing a homogeneous fluorescence resonance energy transfer based assay for measurement of enzymatic activity of kinases or phosphatases or presence of analytes containing phosphoryl groups. A thvalent metal ion binder (101 ) is coupled on the surface of a donor particle (100), which is preferably a polymer (e.g. polystyrene) dyed with lanthanide(lll)-chelates, down-converting lanthanide(lll)-phosphor or up-converting lanthanide phosphor. Coupling of the metal ion can be done using passive adsorption of the ions on the particle surface, the metal ion can be coupled to specific chelate structure or polymer (102) or the metal ion can be directly incorporated into the phosphor label lattice. Also hydrophilic and/or hydrophobic moieties, if present, are coupled covalently onto the particulates (102). The analyte (103) contains tyrosine, threonine or serine amino acids, which can be phosphorylated or non-phosphorylated (104). The analyte also contains an acceptor label (105), which can be covalently coupled to the analyte, or acceptor label can bind to the analyte via bioaffinity reaction. When the donor and the acceptor are bound to each other, energy is transferred from the donor to the acceptor and the generated sensitized emission can be measured with time-resolved detection (when using down-converting donor label) or with anti-Stokes' excitation (when using up-converting donor label).

Preferred donor labels

All the donor labels are in particulate format with size of 1 nm - 10 μm.

The lanthanide chelates [preferably Eu(III), Tb(III), Dy(III) or Sm(lll)-chelates] are embedded inside a nanoscale polymer shell, which is preferably polystyrene. The label can be commercially available (e.g. Seradyn Inc) or prepared using published protocols. [Huhtinen P, Kivela M, Kuronen O, Hagren V, Takalo H, Tenhu H, Lόvgren T, Harma H (2005) Synthesis, characterisation, and application of Eu(III), Tb(III). Sm(III), and Dy(III) lanthanide chelate nanoparticle labels. Anal Chem 77: 2643-2648] One polymer shell, depending on its size, can harvest thousands of chelates. Thus the specific activity of the label is extremely high. The polymer shell of the particle can protect the lanthanide chelates from interfering factors (e.g. bivalent metal ions), which may be present in assay media.

Down-converting lanthanide phosphors are composed of long lifetime lanthanide ions (preferably Eu(III), Tb(III), Dy(III) or Sm(III)) embedded into host lattice. These lanthanide phosphors generate photoluminescence typical to the corresponding lanthanide chelates but provide an improved photostability and have slightly different absorption bands for excitation.

Up-converting lanthanide phosphors are composed lanthanide ions (preferably erbium, praseodymium, thulium, and ytterbium), which are embedded into host lattice. Unlike down-converting phosphors, the up-converting phosphor particles absorb long wavelength radiation and emit light at shorter wavelength as result of energy pooling of sequential absorption of long wavelength radiation. In certain types of phosphors, a priming dose of energy at shorter wavelength is required to excite and pre-load the phosphor before the up-conversion of long wavelength radiation is possible. The up-converting phosphor can be able to delocalise its excitation from a part or the entire volume of the particulate by internal transfer of energy between similar excited states within the particulate to a single or a few acceptor molecules. This means that a single acceptor can be excited by lanthanides which would otherwise be too far away for energy transfer to be efficient. Optical properties of the phosphors are unaffected by their environment, e.g. buffer pH or assay temperature, since the up-conversion process occurs with the host crystal.

The donor particle can also be a phosphor particle containing lanthanide ions and trivalent binder metal ions incorporated as part of the host lattice of the phosphor. Thus the particle itself contains both the luminescent label component and the trivalent binder component.

In all the donor particles lanthanide ions or chelates are either embedded inside a polymer shell or phosphor host lattice. Thus the lanthanides are protected from known fluorescence quenching caused by e.g. low pH or presence of bivalent metal ions and also protected from potential quenching caused by the presence of trivalent binder metal ions.

Preferred acceptor labels

Luminescent acceptor label can be a single luminescent molecule or combination of different luminescent molecules selected to allow an increased Stokes' shift.

The preferred luminescent acceptor label is selected from the group consisting of rapidly decaying, short-lifetime fluorophores (fluorescence lifetime below

1 microsecond), semiconducting materials (Chan WC and Nie S, Science

1998;281 :2016-2018) such as quantum dots available from Quantum Dot Corp (www.qdots.com), and polymeric particles embedded with any or any combination of the above mentioned labels (US 5326692; Roberts DV et al. J Lumin 1998; 79:

225-231 ; Han M et al., Nat Biotechnol 2001 ; 19:631-635) available e.g. with trade names FluoSpheres and TransFluoSpheres from Molecules Probes

(www.probes.com). The luminescent acceptor label or a part of it can also be a near-infrared fluorescent protein (Trinquet E et al. Anal Biochem 2001 ;296:232-

244; Kronick MN, J Immunol Methods 1986;92:1 -13; Fradkov AF et al., FEBS Lett

2000;479:127-130).

If the acceptor is in particulate format, the preferred size of the acceptor particle ranges from 1 nm to 10 μm in diameter.

Especially suitable acceptor fluorophores are e.g. Alexa and BODIPY series available from Molecular Probes (www.probes.com), Cy-dyes from Amersham Biosciences (www.amershambiosciences.com), EVOblue and DY-dyes from Dyomics (ww.dyomics.com), Atto-Dyes from Atto-tec (www.atto-tec.de) and Oyster-dyes from Denovo Biolabels (www.biolabel.de). Dimeric fluorescent energy transfer dyes, tandem dyes and energy-transfer cassettes, comprising two fluorescent molecules are preferred for their property of large and tunable Stokes' shift (US 5,565,554; WO 99/39203; EP 0747700; Burghart, A et al., Chem Commun 2000; 22: 2203-2204) enable utilization of optimal excitation and emission wavelengths.

The preferable acceptor label should be selected to have an excitation spectrum, which overlaps at least partially with peaks of the emission spectrum of the donor label and has an emission maximum between the emission and acceptor wavelengths of the donor.

The up-converting label and the luminescent acceptor label can be selected so that both the excitation and the emission of the up-converting label and the optional sensitised emission of the acceptor label are at wavelengths with minimal absorbance and interferences of variation in optical properties of biological samples. Up-converting labels in combination with an acceptor label enable homogeneous assays to be performed regardless of the sample matrix enabling almost identical signal levels requiring no correction of the absorption when buffer based standards and biological fluids are employed.

EXAMPLES

Used reagents and devices

Assay buffer contained 10 mM Tris-HCI, pH 7.0, 100 mM NaCI and 0.1 % (w/v) Tween-20, and it was used in all dilutions unless otherwise mentioned. All assays were performed on 96-well MaxiSorp™ -plates (Nunc, Roskilde, Denmark). All measurements were made with Plate Chameleon V (Hidex Oy, Turku, Finland) equipped with a 730 nm band-pass emission filter with a 10 nm bandwidth and a

340 nm DUG11 excitation filter using 1 ms cycle time, 200 Hz, 75 μs delay and 50 μs measurement window.

Preparation of acceptor labelled peptides

Peptides containing lysines at the carboxyl terminus were conjugated with an acceptor fluorophore (e.g. with a near-infrared dye AlexaFluor 680 succinimidyl ester purchased from Molecular Probes, Eugene, OR, USA). The peptide sequence also contained phosphorylated or non-phosphorylated serine, threonine or like in this example tyrosine at the optimal position. The conjugation reactions contained 50 μg of phosphorylated or non-phosphorylated peptide and a 2-fold molar excess of AlexaFluor 680 (A680) dissolved in 50 mM carbonate buffer, pH 9.3 with 10 % (v/v) dry DMF in a total volume of 100 μl. The reactions were incubated at +4 ⁰C over night and purified with HPLC using a C2/C18 RP column (Amersham Biosciences, Sweden). The correct products (phosphorylated peptide- A680 and non-phosphorylated peptide-A680 conjugates) were identified with MALDI-TOF mass spectrometry (Voyager DE Prot, Perseptive Biosystems, Boston, MA, USA).

Preparation of streptavidin labeled with the acceptor

Streptavidin (SA), purchased from Societa Prodotti Antibiotici (Italy), was labeled with an acceptor (e.g. a near-infrared dye AlexaFluor 680 succinimidyl ester from Molecular Probes). SA, 500 μg, and a 6-fold molar excess of AlexaFluor 680 were dissolved in 50 mM carbonate buffer, pH 9.3 with 10 % (v/v) dry DMF in a total volume of 100 μl. The reaction was incubated at RT over night and purified using gel filtration with Sephadex G-25 (Amersham Biosciences).

Example 1

Preparation of Ga(III)-NTA coated nanoparticles

Donor nanoparticles (in this example europium(lll) chelate-dyed nanoparticles with a 92-nm diameter purchased from Seradyn, Indianapolis, IN, USA) were covalently coated with N_α,N_α-Bis(carboxymethyl)-L-lysine hydrate (NTA, Sigma- Aldrich, St. Louis, MO, USA). Nanoparticles were suspended in 20 mM MES buffer, pH 6.8, and the carboxyl acid groups on their surface were activated with 24 mM /V-(3-dimethylaminopropyl)-/V-ethylcarbodiimide hydrochloride (EDC) and 180 mM Λ/-hydroxysulfosuccinimide sodium salt (NHS) purchased from Fluka (Switzerland). After activation, the particles were suspended in 20 mM MES buffer, pH 6.8, and NTA was added in the same buffer. In the coating reaction, we used 2.45 x 10¹² nanoparticles and 2.97 x 10^~5 mol of NTA in a total volume of 400 μl. NTA was attached to the nanoparticles when activated carboxyl groups on the particle surface and amino groups of NTA formed covalent bonds. After the coupling of NTA on the surface of the particle for two hours, the remaining activated carboxyl groups were saturated with 50 mM (aminooxy)acetic acid (Sigma-AIdrich, St. Louis, MO). Coated particles were separated from the unbound NTA using Nanosep Omega 300 kDa centrifugal devices (Pall Corp., Ann Arbor, Ml, USA) by washing the particles five times with 400 μl of assay buffer.

Ga(III) ions were allowed to conjugate to the NTA on the surface of the nanoparticles. NTA coated nanoparticles (2 x 10¹⁰ pes) were incubated with 10 mM Ga(lll)Cl₃ (Sigma-AIdrich) in assay buffer for one hour at RT in a total volume of 50 μl. Ga(lll)-NTA-particles were stored at RT.

Homogeneous assay using Ga(lll)-NTA-particles and Alexa680-labeled peptides

In this example, 2 x 10⁸ Ga(lll)-NTA-nanoparticles in 50 μl and 50 μl of 300 nM Alexa680-labeled peptides, which were either phosphorylated or non- phosphorylated were added into the microtiter wells using three assay replicates. The wells were protected from light with aluminium foil and incubated at RT for 15 min and the sensitised emission from the energy transfer was measured. The incubation was continued for 1 or 2 hours and the measurement was repeated. The results are shown in figure 2.

Example 2

Preparation of Ga(lll)-octylamine coated nanoparticles

Donor nanoparticles (in this example europium(lll) chelate-dyed nanoparticles with a 92-nm diameter purchased from Seradyn, Indianapolis, IN, USA) were covalently coated with octylamine (Sigma-AIdrich, St. Louis, MO, USA). Nanoparticles were suspended in 20 mM MES buffer, pH 6.8, and the carboxyl acid groups on their surface were activated with 24 mM Λ/-(3- Dimethylaminopropyl)-/V-ethylcarbodiimide hydrochloride (EDC) and 180 mM N- Hydroxysulfosuccinimide sodium salt (NHS) purchased from Fluka (Switzerland). After activation, the particles were suspended in 20 mM MES buffer, pH 6.8, and octylamine was added. In the coating reaction, we used 2.45 x 10¹² nanoparticles and 2.86 x 10^~5 mol of octylamine in a total volume of 200 μl. Octylamine was attached to the nanoparticles when activated carboxyl groups on the particle surface and amino group of octylamine formed covalent bonds. After the coupling of octylamine on the surface of the particle for two hours, the remaining activated carboxyl groups were saturated with 50 mM (aminooxy)acetic acid (Sigma-Aldrich, St. Louis, MO). Coated particles were separated from unbound octylamine using Nanosep Omega 300 kDa centrifugal devices (Pall Corp., Ann Arbor, Ml, USA) by washing the particles five times with 400 μl of assay buffer.

Ga(III) ions were absorbed on the surface of octylamine coated nanoparticles. Octylamine-nanoparticles (2 x 10¹⁰ pes) were incubated in assay buffer containing 10 mM Ga(lll)Cl3 (Sigma-Aldrich) for one hour at RT in a total volume of 50 μl. Ga- octylamine-nanoparticles were stored at RT.

Homogeneous assay using Ga(lll)-octylamine-particles and Alexa680-labeled peptides

In this example, Ga(lll)-octylamine-nanoparticles (2 x 10⁸) in 50 μl and 50 μl of 0- 500 nM Alexa680-labeled phosphorylated or non-phosphorylated peptides were added to the microtiter wells using three assay replicated. The wells were protected from light with aluminium foil and incubated at RT for 15 min. Sensitised emission from the energy transfer with the non-phosphorylated peptide (background) and the phosphorylated peptide (signal) was measured. The difference of the measurements (signal - background) is shown in figure 3.

Example 3

Preparation of Ga(III) coated nanoparticles

In this example, Ga(III) ions were absorbed on the surface of europium(lll) chelate-dyed nanoparticles (Seradyn, Indianapolis, IN, USA) with a 92-nm diameter. Nanoparticles (2 x 10¹⁰⁾ were incubated with 10 mM Ga(lll)Cl3 (Sigma- Aldrich) in assay buffer for one hour in room temperature in a total volume of 50 μl. Ga-nanoparticles were stored at RT. Homogeneous assay using Ga(lll)-nanoparticles and Alexa680-labeled peptides

Ga(lll)-nanoparticles (2 x 10⁸ pes) were added in 50 μl of assay buffer to wells. Alexa680-labeled phosphorylated or non-phosphorylated peptides, diluted to 0- 500 nM in assay buffer, were added to the nanoparticles in a volume of 50 μl in three replicates. The wells were protected from light with aluminium foil and incubated at RT for 15 min. Sensitised emission from the energy transfer with the non-phosphorylated peptide (background) and the phosphorylated peptide (signal) was measured. The difference of the measurements (signal - background)is shown in figure 4.

Example 4

Homogeneous assay using biotinylated peptides, streptavidin labelled with Alexa680 and Ga-octylamine-nanoparticles

In this example, the phosphorylated and non-phosphorylated peptides contained a biotin at the carboxyl end of the peptide. In total volume of 200 μl, 100 nM peptides and 0-150 nM SA-Alexa680 were incubated for 30 min at RT. Thus the biotinylated peptides were bound to SA labelled with Alexa680. After binding reaction, 50 μl of each reaction was added to wells in three replicates. Ga-octylamine-nanoparticles were diluted to 2 x 10⁸ pes in a volume of 50 μl and added to the wells. The wells were protected from light with aluminium foil and incubated at RT for 15 min and the sensitised emission from the energy transfer was measured. The incubation was continued for 1 and 2 hours and the measurement was repeated. Sensitised emission from the energy transfer with the non-phosphorylated peptide (background) and the phosphorylated peptide (signal) was measured. The ratio of the measurements (signal / background) is shown in figure 5. Example 5

Homogeneous assay using variously coated Ga-particles and Alexa680-labeled peptides

Europium(lll) chelate dyed nanoparticles with a 92 nm diameter were used either uncoated or covalently coated with octylamine or (aminooxy)acetic acid. Ga(III) ions were absorbed on the surface of these nanoparticles when 2 x 10¹⁰ pes of the nanoparticles were incubated in assay buffer containing 10 mM Ga(lll)Cl3 for one hour at RT in a total volume of 50 μl. Ga(lll)-nanoparticles (2 x 10⁸) in 50 μl and

50 μl of 100 nM Alexa680-labeled phosphorylated or non-phosphorylated peptides were added to the microtiter wells using three assay replicates. The wells were protected from light with aluminium foil and incubated at RT for 15 min. Sensitised emission from the energy transfer was measured and is shown in figure 6.

Example 6

Homogeneous assay using aspartic acid and octylamine coated Ga-particles and Alexa680-labeled peptides

Europium(lll) chelate dyed nanoparticles with a 92 nm diameter were covalently coated with aspartic acid and octylamine. Ga(III) ions were absorbed on the surface of these nanoparticles when 2 x 10¹⁰ pes of the nanoparticles were incubated in assay buffer containing 10 mM Ga(lll)Cl3 for one hour at RT in a total volume of 50 μl. Ga(lll)-nanoparticles were diluted to a concentration of 2 x 10⁸ pes in 50 μl and added to the wells of a microtiter plate. Alexa680-labeled phosphorylated or non-phosphorylated peptides, diluted to 0-200 nM in assay buffer, were added to the nanoparticles in a volume of 50 μl in three replicates. The wells were protected from light with aluminium foil and incubated at RT for 15 min. Sensitised emission from the energy transfer with the non-phosphorylated peptide (background) and the phosphorylated peptide (signal) was measured. The difference of the measurements (signal - background) is shown in figure 7. Other preferred embodiments

It will be appreciated that the methods of the present invention can be incorporated in the form of a variety of embodiments, only a few of which are disclosed herein. It will be apparent for the expert skilled in the field that other embodiments exist and do not depart from the spirit of the invention. Thus, the described embodiments are illustrative and should not be construed as restrictive

Claims

1. A luminescence energy transfer based homogeneous bioassay wherein measurement of phosphorylated or dephosphorylated peptide or protein is carried out; and said bioassay comprises a) a first group labelled with an energy donor; wherein said first group is a particulate comprised of a polymer or an inorganic crystallic structure, and said first group is i) a long-lifetime luminescent lanthanide label if the particulate is a polymer, preferably polystyrene, or ii) an up-conversion luminescent lanthanide label or down-conversion luminescent lanthanide label if the particulate is an inorganic crystallic structure, preferably a phosphor particle; being able to transfer fluorescence energy to an acceptor of a second group; and said first group i) is coated with a thvalent metal ion binder through passive adsorption, a chelate structure or a polymeric structure, or ii) has trivalent metal ions incorporated into said crystallic structure; and b) said second group labelled with said energy acceptor, wherein said acceptor is a short-lifetime fluorescent label, said second group comprises a peptide or protein with at least one phosphorylatable amino acid within < 10 nm from said acceptor; and after a sample and reagents of said bioassay, said reagents including said first and second groups, and trivalent metal ions if not incorporated in said second group, have been brought into contact with each other; said first group is excited and resulting emission of said second group, said emission relating to energy transfer from donor to acceptor due to phosphorylated peptides and/or proteins of said second group being attached to said trivalent metal ions bound to or incorporated into said first group, is measured.

2. The assay according to claim 1 characterized in that first group is either a polymer shell, preferably polystyrene, wherein the lanthanide chelates are embedded, or a phosphor particle containing the lanthanide ions, i.e. an up- converting or down-converting lanthanide phosphor.

3. The assay according to claim 1 or 2 characterized in that the lanthanide is selected from the group consisting of europium, terbium, samarium, dysprosium, erbium, praseodymium, thulium, ytterbium and any combination thereof; and is preferably europium.

4. The assay according to any of any of the preceding claims characterized in that the acceptor is a single luminescent molecule or combination of different luminescent molecules selected to allow an increased Stokes' shift, preferably selected from the group consisting of rapidly decaying, short-lifetime fluorophores, semiconducting materials, polymeric particles embedded with any of or any of combination of these, and a near-infrared fluorescent protein.

5. The assay according to any of the preceding claims characterized in that the thvalent metal ion or ions bound to or incorporated in the particle of the first group are Ga(III), Fe(III) and/or Y(III) ions, preferably Ga(III) ions.

6. The assay according to any of the preceding claims characterized in that the first group particulate has a diameter of < 10 μm, preferably < 400 nm, and more preferably < 100 nm.

7. The assay according to any of preceding claims characterized in that the first group comprises hydrophilic and/or hydrophobic moieties coupled covalently onto the particulates of said first group resulting in decreased binding of non- phosphorylated peptides and/or proteins of the second group.

8. The assay according to claim 7 characterized in that the hydrophilic moieties are selected from the group consisting of moieties that are negatively charged, comprise at least one carboxyl acid group and have a molecular weight of less than 2000, preferably less than 600 and most preferably less than 200, and any combination thereof.

9. The assay according to claim 8 characterized in that the hydrophilic moieties are (aminooxy)acetic acid or aspartic acid moieties.

10. The assay according to claim 7, 8 and/or 9 characterized in that the hydrophobic moieties are selected from the group consisting of moieties that are not charged, comprise a hydrocarbon chain from 2 to 16 carbons and have a molecular weight less than 2000, preferably less than 600 and most preferably less than 200, and any combination thereof.

11. The assay according to claim 10 characterized in that the hydrophobic moieties are octylamine moieties.

12. A kit for a homogenous bioassay according to any of preceding claims characterized in that said kit comprises reagents including reagents comprising a) a first group labelled with an energy donor; wherein said first group is a particulate comprised of a polymer or an inorganic crystallic structure, and said first group is i) a long-lifetime luminescent lanthanide label if the particulate is a polymer, preferably polystyrene, or ii) an up-conversion luminescent lanthanide label or down-conversion luminescent lanthanide label if the particulate is an inorganic crystallic structure, preferably a phosphor particle; being able to transfer fluorescence energy to an acceptor of a second group; and said first group i) is coated with a thvalent metal ion binder through passive adsorption, a chelate structure or a polymeric structure, or ii) has trivalent metal ions incorporated into said crystallic structure; b) said second group labelled with said energy acceptor, wherein said acceptor is a short-lifetime fluorescent label, said second group comprises a peptide or protein with at least one phosphorylatable amino acid within < 10 nm from said acceptor; and c) trivalent metal ions if not incorporated in said second group.

13. The kit according to claim 12 characterized in that first group is either a polymer shell, preferably polystyrene, wherein the lanthanide chelates are embedded, or a phosphor particle containing the lanthanide ions, i.e. an up- converting or down-converting lanthanide phosphor.

14. The kit according to claim 12 or 13 characterized in that the lanthanide is selected from the group consisting of europium, terbium, samarium, dysprosium, erbium, praseodymium, thulium, ytterbium and any combination thereof; and is preferably europium.

15. The kit according to any of claim 12 to 14 characterized in that the acceptor is a single luminescent molecule or combination of different luminescent molecules selected to allow an increased Stokes' shift, preferably selected from the group consisting of rapidly decaying, short-lifetime fluorophores, semiconducting materials, polymeric particles embedded with any of or any of combination of these, and a near-infrared fluorescent protein.

16. The kit according to any of claims 12 to 15 characterized in that the trivalent metal ion or ions bound to or incorporated in the particle of the first group are Ga(III), Fe(III) and/or Y(III) ions, preferably Ga(III) ions.

17. The kit according to any of claims 12 to 16 characterized in that the first group particulate has a diameter of < 10 μm, preferably < 400 nm, and more preferably < 100 nm.