WO2012131167A1 - Appareil et procédé de traitement d'échantillons - Google Patents

Appareil et procédé de traitement d'échantillons Download PDF

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Publication number
WO2012131167A1
WO2012131167A1 PCT/FI2012/050318 FI2012050318W WO2012131167A1 WO 2012131167 A1 WO2012131167 A1 WO 2012131167A1 FI 2012050318 W FI2012050318 W FI 2012050318W WO 2012131167 A1 WO2012131167 A1 WO 2012131167A1
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WIPO (PCT)
Prior art keywords
dosing
microwells
sample
solution
optical
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PCT/FI2012/050318
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English (en)
Inventor
Jukka Tuunanen
Jaakko Kurkela
Katja Eklin
Original Assignee
Finnzymes Oy
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Filing date
Publication date
Priority claimed from US13/078,720 external-priority patent/US9422604B2/en
Application filed by Finnzymes Oy filed Critical Finnzymes Oy
Publication of WO2012131167A1 publication Critical patent/WO2012131167A1/fr

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Classifications

    • 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
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/27—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands using photo-electric detection ; circuits for computing concentration
    • G01N21/274—Calibration, base line adjustment, drift correction
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12Q—MEASURING OR TESTING PROCESSES INVOLVING ENZYMES, NUCLEIC ACIDS OR MICROORGANISMS; COMPOSITIONS OR TEST PAPERS THEREFOR; PROCESSES OF PREPARING SUCH COMPOSITIONS; CONDITION-RESPONSIVE CONTROL IN MICROBIOLOGICAL OR ENZYMOLOGICAL PROCESSES
    • C12Q1/00—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions
    • C12Q1/68—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions involving nucleic acids
    • C12Q1/6844—Nucleic acid amplification reactions
    • 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
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G01N21/64—Fluorescence; Phosphorescence
    • G01N21/645—Specially adapted constructive features of fluorimeters
    • G01N21/6452—Individual samples arranged in a regular 2D-array, e.g. multiwell plates
    • 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
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
    • G01N21/251—Colorimeters; Construction thereof
    • G01N21/253—Colorimeters; Construction thereof for batch operation, i.e. multisample apparatus

Definitions

  • the invention relates to detection of sample dosing failures in (bio)chemical assays
  • the invention relates to a method of detecting pipetting failures in multi- component assays, such as Polymerase Chain Reaction (PCR) amplification, in particular quantitative PCR (qPCR) amplification.
  • PCR Polymerase Chain Reaction
  • qPCR quantitative PCR
  • all necessary components i.e. reagents
  • One of the components that usually must be added separately is the sample under study.
  • the number of samples, tubes or sample wells in a microtiter plate can be hundreds or even thousands per setup.
  • PCR master mixes or buffers that contain some visible dye to help pipeting and tracking of electrophoresis runs. These mixes typically also have some component to increase density of the solution to help in electrophoresis gel loading.
  • US 6942964 discloses a product using a pipetting aid dye which is also used as a gel loading and tracking dye. The colorant has been incorporated with the polymerase, which helps the user to see whether the polymerase has been pipetted to the PCR mix or master mix.
  • a similar product is Bio Line Accuzyme Red.
  • USB Corporation's RubyTaq features a polymerase including a mixture of two dyes which are separated during the agarose gel run: magenta (runs between 500 bp [2% gels] and 1500 bp [0.8% gels]) and yellow (runs less than 10 bp).
  • Fermentas and Promega have also added a colorant to the enzyme reaction buffer.
  • Fermentas' DreamTaqTM Green reaction buffer can be seen as green, but the color separates into a blue and yellow bands during gel electrophoresis.
  • Promega GoTaq and GoTaq Green Mastermix behave similarly.
  • NEB provides a product (Crimson Taq) featuring a dye Acid red added to the DNA polymerase reaction buffer.
  • the product also uses 6% dextran as a density enhancer.
  • Qiagen's CoralLoad dye is available both as a concentrate in a separate tube, for being added to an uncolored master mix, and also as an optional ready-made lOx PCR buffer. It contains two gel tracking dyes (orange and red).
  • KR 2002/0045167 discloses freeze-dried PCR mixes containing a colorant to confirm dissolution of the PCR components.
  • US 6153412 discloses also freeze-died reaction mixtures which are used for identifying the existence of a lyophilized PCR reagent and to ensure complete mixing of the PCR reagent and the test sample.
  • US 5565339 discloses the use of a dye in a hot start wax, which does not dissolve into the reaction mixture.
  • Absolute Blue QPCR Master Mix contains an inert blue dye to ease pipetting in reaction set-up.
  • WO 2007/088506 discloses a dyed master mix. Applied biosystems has ROX passive reference dye included in their qPCR products. The purpose of the dye is to provide a steady fluorescence level which can be used to normalize against any non PCR related fluorescence variation between the different reactions and in one sample during a reaction. The method is also suggested to normalize at least partly against deviations in pipetting accuracy.
  • One specific aim is to make the detection of errors easier in various stages of pipetting when preparing multi-component assays, for example PCR assays..
  • the sample processing apparatus comprises
  • a holder for a microtiter plate comprising a plurality of micro wells
  • a computing unit configured to analyse the optical responses in order to detect dosing failures in said plurality of microwells, and, if a dosing failure has been detected in one or more of the microwells, to communicate the existence of the dosing failure to a user of the apparatus through signaling means or to store data indicative of the dosing failure to data storage means for further use.
  • the optical measurement unit is capable of spectral resolution and the computing unit is configured to determine whether the the spectral response of the samples meet predefined criteria of a dosing failure.
  • the optical measurement unit is capable of measuring the optical absorption of the samples.
  • a light source unit there may be provided, on one side of the samples, a light source unit, and on the opposing side of the samples, a light detector unit. This embodiment can be used, in particular, if a transparent microtiter plate is used and if there is optical access to the plate both from above and below. In pipetting apparatuses, this condition can be normally satisfied.
  • the optical measurement unit is capable of measuring optical scattering of the samples. Scattering measurement can be performed from one side of the microtiter plate only, typically from above. There may be provided a light source unit and a detector unit at least one of which is arranged to emit or collect light, respectively, at an oblique angle with respect to the microtiter plate (i.e. deviating from the normal axis of the surfaces of the samples). This arrangement has the advantage that potentially harmful reflection from the surface of the samples can be minimized (mostly scattered, not reflected, light is collected).
  • the optical measurement unit is capable of measuring the fluorescence of the samples. Fluorescence measurement may further increase the detection accuracy but necessitates the presence of suitable fluorescent agents in the sample.
  • the optical measurement unit comprises a light source unit and a detector unit at least one of which is capable of emitting light or detecting light at multiple wavelength channels.
  • a colorimetric measurement i.e., a measurement providing information about the spectral properties of the sample.
  • colorimetric data can be obtained by performing sub-measurements at each of the channels separately and analyzing the sub- measurement data in the computing unit. If both said devices can operate at a plurality of wavelength channels (e.g. white light source and multichannel detector), the measurement of each microwell or even the whole plate can be performed at one shot.
  • the optical measurement unit can be adapted to measure the microwells sequentially using a single-head measurement unit or it may comprise a plurality of light sources and/or light detection units for each of the microwells separately but simultaneously.
  • camera-based detection allows for measurement of the whole plate quickly.
  • the optical measurement unit is configured to produce two- dimensional images of the samples in the microwells
  • the computing unit is configured to determine, based on said image, whether the surface shape and/or area of the samples meet predefined criteria of a dosing failure.
  • the well shape of the microtiter plate must be such that the determination is possible, i.e. varying in shape or size in the depth-dimension of the well.
  • the computing unit may be configured to determine, based on the surface shape and/or area of the samples, the surface level of the samples in a varying-diameter or varying-shape microwell.
  • the present automatic sample processing apparatus may be a pipetting or another type liquid dispensing apparatus, whereby it additionally comprises means for (pipetting) dispensing one or more substances to the microwells.
  • the present sample processing apparatus can be adapted to automatically perform a
  • the apparatus can be a PCR apparatus comprising means for performing a PCR process to the contents of the microwells.
  • the invention can be used for detecting dosing failures in before, during and after a PCR process.
  • the apparatus may be configured to perform the optical measurement before, after or both before and after performing the PCR process. If the optical measurement both before and after the PCR process, the computing unit may be adapted to compare the optical responses of the same microwell before and after the PCR process. The measurements can be carried out through a sealing layer which may be attached on top of the microtiter plate in order to prevent spilling and evaporation.
  • the computing unit is adapted to compare the optical responses of two or more different microwells of the same microtiter plate with each other in order to detect the dosing failure. Evaluation based on mutual comparison of the wells may provide sufficient level of certainty in many applications. Additionally, reference data may be used in order to improve certainty.
  • the apparatus in particular plate holder thereof, must be designed to receive microtiter plates with conical, i.e. v-bottomed, microwells.
  • This well shape has proven to be not optimal for absorbance measurement, whereby scattering- or fluorescence-based measurements are preferred.
  • present method for detecting dosing failures in a chemical or biological assay performed in one or more instruments comprises - pipetting a first reagent solution comprising at least one substance required for performing said assay to a measurement space, the first reagent solution further comprising first colorant providing the solution a first color,
  • a second reagent solution comprising at least one other substance required for performing said assay to a measurement space, the second reagent solution further comprising second colorant providing the solution a second color different from the first color
  • the mixed solution having, due to said first and second colorants, a third color different from the first and second colors,
  • the reagent solutions are mixed for obtaining the final mixture which is subjected to PCR.
  • the reagent solutions are colored with different initial colorants, which, upon mixing produce a distinguishable color different from the colors of the initial colorants.
  • the method comprises - providing a first reagent solution comprising at least one substance required for performing the assay and a first colorant providing the solution a first color,
  • one of the reagent solutions is a sample solution, that is, a solution containing or intended to receive a biological sample to be amplified in the PCR assay, and the other of the reagent solutions contains some other at least one other substance required for performing the assay, for example the polymerase solution or master mix.
  • the sample solution may be a buffered solution (hereinafter "a sample buffer solution").
  • a sample buffer solution indicates that there is only sample solution without other reagents, e.g. master mix, in the well.
  • a microwell with second color indicates that master mix has been added but there is no sample yet.
  • a microwell with third color implies that sample has been properly added to the master mix. The inspection of the color can be made visually or by automatic optical means.
  • one of the reagent solutions is an elution buffer, such an elution buffer used in combination with a nucleic acid purification kit.
  • one of the reagent solutions is a dilution buffer used to facilitate lysis of a solid-state sample to release nucleic acids.
  • the reagent solution can also be used to dilute, digest or precipitate released components before PCR.
  • one of the reagent solutions is a solution used in cDNA synthesis reaction, reverse transcriptase reaction or bisulphite reaction.
  • one of the reagent solutions is some other solution used for preparing the sample for the PCR process.
  • the invention also provides a new use of dyes for producing two or more colored PCR reagent solutions, which are capable of forming a mixed solution having a color distinguishable from the initial colors of the reagent solutions.
  • a particular aim of the invention is to achieve a pipetting aid solution which is compatible with quantitative PCR. This is achieved by using such colorants and colorant
  • the reaction mixture subjected to qPCR is transparent or translucent at least at the qPCR excitation and emission wavelengths. This generally means that the maximum absorbance of the of the reaction mixture is less than 0.5, in particular less than 0.15 (measured using 1 mm light path) and that the absorption window of the colorant does not overlap, at least significantly, with the excitation or emission wavelengths of the fluorescent qPCR dye(s) or modified DNA oligonucleotide probe(s) used.
  • a reaction mixture for quantitative PCR is prepared, the reaction mixture comprising fluorescent dye, primer or probe, and wherein the absorbance peaks of any of said colorants do not overlap with the emission or excitation wavelength of said fluorescent dye, primer or probe. If overlap exists, it should not significantly weaken the qPCR signal, generally implying that the total absorbance of the reaction mixture at said wavelengths is less than 0.05, preferably less than 0.03, in particular less than 0.1.
  • the invention provides considerable advantages. As the initial solutions and the resultant solution are mutually of different colors, one not only distinguish between the initial solutions, but also between the initial solutions and their mixture.
  • the colors make it easier to see if there is any liquid splashed or spilled in wrong places where they could potentially cause contamination, microwell sealing problems etc.
  • any liquid in the sealing contact can compromise the seal and thus the whole PCR assay.
  • the present invention can also be used together with the mechanical solutions to lower their error rate even more, if the pipetting steps performed are visualized using the colorants.
  • dyes and other colorants used in the present manner can help keeping track in reaction setup and especially during loading reagents into reaction plate.
  • the approach provides considerable help and increased certainty for pipetting samples.
  • qPCR there is no need to load the amplified products into a gel after a PCR reaction.
  • the present solutions may be free of density enhancer or contain only minor amounts of density enhancer (i.e. less than required for gel electrophoresis).
  • one or more additional reagent solutions comprising additional colorants providing the solutions different colors.
  • the solutions are capable of forming, on mixing, additional solutions having, due to said additional colorants, further distinguishable colors.
  • the invention can be used not only for aiding the pipetting in one particular stage of the process, e.g. pipetting of the of the sample to master mix, but also for aiding the pipetting during other steps, in particular the steps previous or subsequent to the sample pipetting step.
  • the method may comprise providing a third reagent solution comprising at least one further substance required for performing said assay, the third reagent solution containing a third colorant providing the solution a fourth color different from the first, second and third colors mentioned above, and mixing the third reagent solution with the first and second reagent solutions for providing a mixed reagent solution having, due to said first, second and third colorants, a fifth color different from the first, second, third and fourth colors.
  • the first reagent solution may be a sample
  • the third reagent solution may be a primer solution.
  • the order of application is not essential, unless otherwise defined in assay instructions.
  • the method may comprise providing a third reagent solution containing third colorant providing the solution a fourth color different from the first, second and third colors, and individually mixing the first reagent solution with said second and third reagent solutions for obtaining first and second mixed solutions having third and fifth colors, respectively, different from each other and the first, second and fourth colors.
  • the second reagent solution may contain one set of primers and the third reagent solution may contain a second set of primers.
  • the colors of all initial ingredients and all resultant mixtures are unique.
  • the two abovementioned embodiments can also be chained such that the second and third reagent solutions are ultimately individually mixed with a reagent solution which is itself prepared by mixing at least two different colored reagent solutions.
  • Other kinds of combinations are possible too.
  • a "reagent solution” is any solution containing at least one reagent needed or
  • Most typical ingredients are polymerase, nucleotide, primer, ions, magnesium, other salt, pH buffering agent, dNTPs or fluorescent qPCR dye or probe, oligonucleotide, nucleic acid binding agent, a nucleic acid template.
  • the reagent may also be other polymerase reaction additive, which has an influence on the polymerase reaction or its monitoring.
  • sample solution covers both buffered and non-buffered sample solutions which are still free of template or into which the template to be amplified using PCR has already been added, unless otherwise specified.
  • sample solution is covered by the term “reagent solution”.
  • master mix refers to a mixture of all or most of the ingredients or factors necessary for PCR to occur, typically all except for the template and primers which are sample and amplicon specific.
  • Commercially available master mixes are usually concentrated solutions.
  • a master mix may contain all the reagents common to multiple samples, but it may also be constructed for one sample only. Using master mixes helps to reduce pipetting errors and variations between samples due to differences between pipetted volumes. It also minimizes the time spent for pipetting.
  • a qPCR master mix is a master mix intended for performing a qPCR reaction. Thus, it may contain fluorescent dye or fluorescently tagged oligonucleotide primers or probes.
  • premix refers to a master mix that contains all the necessary components for a PCR reaction except for the template.
  • color herein means any detectable spectral response (of a solution) to white light in the visual range.
  • there is at least one wavelength range in the absorbance spectrum of the solution which provides a colored visual appearance for the solution (in contrast to the nearly 100 % transmittance of water).
  • White, black and shades of grey are herein counted as colors.
  • an absorbance higher than about 0.01 (1 mm light path) gives a visually perceivable color for a solution whereas an absorbance higher than about 0.001 (1 mm light path) can be relatively easily detected by hardware- based spectral detection means.
  • different colors means that the colors are distinguishable, preferably by the naked eye, but at least with spectral detection means.
  • “different colors” may have maximum peaks in their absorption spectrum separated by at least 30 nm.
  • the different colors are selected from the groups of: red, yellow, blue or cyan, magenta, yellow and visually distinguishable combinations and shades thereof, such as green, orange, and violet.
  • colorant means any substance which is capable of being homogeneously mixed or dissolved within a solution and capable of giving the solution a perceivable color.
  • the colorant is a dye, in particular an aqueous dye, preferably a non-oxidizing aqueous dye.
  • transparent or “translucent” colorant-containing solution refers, in particular, to a solution which has an optical transmission window at at least some fluorescence excitation and/or emission wavelenghs that can be used for performing qPCR, the wavelengths depending on the fluorophores, fluorescent dye(s), and/or modified DNA oligonucleotide probe(s) contained in the reaction mixture.
  • the excitation wavelength is between 350 and 690 nm, in particular between 490 and 650 nm.
  • the emission wavelength is typically between 350 nm - 730 nm, in particular 515 nm - 680 nm.
  • a transparent solution is optically essentially non-diffusive, whereas a translucent solution passes light diffusely.
  • sample refers to a solid material or a solution that contains the nucleic acid of interest or is to be analyzed for the presence of nucleic acid of interest.
  • dilution buffer refers to a solution that can be used for sample pretreatment before PCR setup. Pretreatment can include sample lysis for realeasing nucleic acids, dilution, binding, chemical lysis, precipitation and enzymatic digestion of some components.
  • preparative process refers to any reaction, pipetting step or pretreatment which yields a product which can in total or in part be used as a sample in a subsequent PCR reaction.
  • dosing failure should be interpreted broadly as comprising e.g. underdosing, overdosing, undesired sample component proportions and the presence of foreign substances or bodies in the sample space.
  • Conspsing refers to a dosing which is acceptable for the assay concerned.
  • the concept of "detection of a dosing failure" covers practical implementations using criteria for unacceptable dosing as wells as acceptable dosing.
  • pipetting covers manual pipetting, automatic pipetting and any other liquid- dispensing techniques equivalent to pipetting
  • wavelength channel refers to a single wavelength or a band of wavelengths which can be distinguished from wavelength(s) of other wavelength channels by the measurement setup used.
  • the third color achieved by mixing the solutions with the first and second colorants, is a chromatic combination of the first and second colors of the solutions.
  • the third color may be produced as a sum spectrum of the spectra of the first and second colors.
  • FRET fluorescence resonance energy transfer
  • Fig. 1 A shows in cross-sectional view three microwells containing colored sample buffer, colored reagent solution and their colored mixture, respectively.
  • Fig. IB shows a top view of a microtiter plate containing empty wells and wells containing colored sample buffer, colored reagent solution, their colored mixture mixture and wells with optically clear liquid.
  • Fig. 2a and 2b illustrate as a flow chart exemplary ways of carrying out the invention.
  • Fig. 3 shows a flow chart of the present process according to one embodiment of the invention.
  • Figs. 4a - 4d show standard series obtained with master mix and sample with (4a and 4b) and without (4c and 4d) pipetting aid dyes.
  • Figs. 5a - 5d show absorbance spectra relating to a absorbance measurement example.
  • Figs. 6a - 6c and 7a - 7c illustrate the use of colorant in a cDNA synthesis reaction.
  • Figs. 8a-8c illustrate exemplary measurement arrangements for detecting dosing failures.
  • a dye combination that helps keeping track of pipetting master mix, samples and mixing of these, in the pipetting phase of (q)PCR process.
  • the dyes are preferably optimized so that they will have minimal effect on qPCR reaction (e.g. will not influence the sample or DNA polymerase used) and will not significantly affect optical detection of fluorescence.
  • the dyes used are compatible with the qPCR assay.
  • Typical fiuorophores used for qPCR purposes include Alexa 350, FAMTM, TETTM, VICTM, JOETM, HEXTM, CY®3, TAMRATM, ROXTM, Texas Red®, CY®5, CY®5.5 and
  • Fig. 1A illustrates the basic principle of the invention.
  • the microwell 12A contains colored sample buffer 14A having a first color (horizontal lines).
  • the microwell 12B contains colored master mix 14B having a second color (vertical lines).
  • the microwell 12C contains colored mixture of the sample buffer and colored master mix, having a third color
  • Fig. IB illustrates a microtiter plate 10 which, in addition to the solutions shown and marked as in Fig. 1A, contains empty wells 12 and non-colored liquid 14D having no color (dots).
  • a diluted reaction mixture 14E which is achieved by diluting the initial reaction mixture 14C with the non-colored liquid 14D, the diluted reaction mixture having the same basic color as the initial reaction mixture 14C, but with increased transparency, i.e. reduced absorbance (sparse horizontal and vertical lines).
  • the dyes can preferably be both detected and distinguished from each other visually, i.e. by naked eye.
  • the different colors are spectrally relatively densely distributed and no special equipment is needed.
  • colors more finely distributed on the spectral scale can be used, without compromising the ability to distinguish between different colors.
  • the combination comprises a blue master mix and yellow sample buffer. When mixed together these form clearly green solution. Blue color in the plate indicates that master mix has been added but there is no sample yet. When sample is added color turns green. If solution in the well is yellow it means that there is only sample without mastermix.
  • the blue dye comprises Xylene cyanol.
  • the yellow dye comprises Quinoline yellow. These dyes have been found to be compatible with the polymerase and sample buffer, respectively.
  • the dyes are strong enough to give a visually perceivable color for the respective solutions, but weak enough not to disturb fluorescence detection and/or weak enough not to interfere with gel electrophoresis migration tracking with other dyes commonly used for that purpose.
  • the abovementioned Xylene cyanol and Quinolene yellow belong to this group of dyes.
  • electrophoresis dye can be added to the amplified mixture. Moderate dyeing also maintains the general visual appearance of the solutions transparent or translucent. A suitable concentration of the dye depends on the dye itself. According to one
  • the concentration of the dye in the initial solution is adjusted to result in an absorbance of 0.001 - 0.5 at its maximum absorption wavelength (1 mm light path).
  • the concentration of the dye is adjusted to result in an absorbance of 0.01 - 0.5, in particular 0.03 - 0.5, at its maximum absorption wavelength (1 mm light path).
  • the absorbance is 0.03 - 0.15, which ensures both visual detectability of the color and negligible or small effect on the qPCR
  • the total absorbance at the qPCR excitation and/or emission wavelength is less than 0.05, preferably less than 0.03, in particular less than 0.01 (1 mm light path), regardless of the maximum absorbance.
  • the two (or more) initial solutions have differently colored dyes, there is no significant cumulative absorbance at any particular wavelength.
  • the above absorbances are the preferred absorbance of solutions diluted to the desired PCR processing concentration. If the solutions are delivered as concentrates, the preferred absorbances are respectively higher.
  • At least one of the solutions is provided with dye, which is both suitable to be used in qPCR (i.e. does not affect the fluorescence detection at the wavelengths used) and strong enough to detected in gel electrophoresis, and runs on an appropriate distance at the gel with respect to the samples.
  • dye which is both suitable to be used in qPCR (i.e. does not affect the fluorescence detection at the wavelengths used) and strong enough to detected in gel electrophoresis, and runs on an appropriate distance at the gel with respect to the samples.
  • a separate loading buffer is not necessarily needed.
  • the sample buffer containing a dye may be delivered either as a dilute or concentration, depending on the intended use.
  • Fig. 2 illustrates the general concept of pipetting a colored sample solution (step 20) and at least one reagent solution (step 21, optionally 22) into a single container and mixing the solutions (step 23). The color of the mixed solution is checked (step 24) before subjecting the mixture to PCR (step 25). It should be noted that there may be other pipetting and processing steps which are not shown in Fig. 2 for simplicity.
  • a plurality of colored sample buffer solutions in which different colorants are used to give the sample buffers different colors.
  • mixing the plurality of colored sample buffers with the same colored reagent mixture yields reaction mixtures of different colors.
  • a yellow sample buffer and a red sample buffer mixed with a blue master mix could give green and magenta reaction mixtures, from which one can immediately verify not only the proper mixing, but also the type of the sample.
  • a master mix and a plurality of colored primer mixes in which different colorants are used to give the mixes different colors
  • a plurality of master mixes or other premixes (steps 31, 32) which are provided with different colorants to render the premixes differently colored (say, premix 1 : color 2, premix 2: color 3, ... premix n: color n+1) and a sample having a further color (color 1) (step 30).
  • the premixes are individually mixed with the sample (steps 33a, 33b) and the colors of the resulting solutions are checked (steps 34a, 34b).
  • the colors are preferably chosen so that each combination of a premix solution and sample solution solutions yields a unique color rendering the solutions distinguishable from each other and the initial premix and sample solutions.
  • the solutions are, in principle, ready for PCR. It should be noted that there may be other pipetting and processing steps which are not shown in Fig. 3 for simplicity.
  • a plurality of initial solutions each containing a component needed in the PCR reaction, e.g. polymerase, primer, ions, dNTPs or fluorescent qPCR dye or probe, or other additives
  • a component needed in the PCR reaction e.g. polymerase, primer, ions, dNTPs or fluorescent qPCR dye or probe, or other additives
  • the colors are preferably chosen so that each combination of solutions yields a unique color rendering the solutions distinguishable from the other solutions.
  • nucleic acids for molecular biology experiments are usually purified from complex sample material. There are various methods for purification including methods based on extraction, precipitation, hybridization and different modes of chromatography or filtering etc. In most of the techniques nucleic acids are either dissolved or eluted in selected solution. Precipitated nucleic acids can be dissolved in a variety of solutions. When using other method that are based on other DNA interactions there are more requirements for the elution buffer such as suitable ionic strength. Purification methods based on DNA binding to silica in high ionic strength conditions are widely used.
  • Bound DNA is eluted from silica matrix with low ionic strength buffer or with pure water.
  • Many kits based on the silica binding method are available and usually the kit contains the elution buffer.
  • the colorant can be included in the elution buffer or the buffer provided with the kit can be replaced with the colored buffer. By doing this, the user does not have to add the color in a separate step.
  • the sample buffer containing the dye can be used as a sample elution buffer in combination with many commercial or homebrew DNA purification kits.
  • the elution buffer provided with many of the available kits can be just simply replaced with the sample buffer containing the dye.
  • a small amount of dye concentrate can be added in the elution buffer provided with the kit without diluting the sample too much.
  • the other colored reagent solution may be any other solution needed for the process, as discussed above.
  • New enzyme technology has made it possible to significantly simplify sample preparation for PCR and it is even possible to put the unpurified sample directly to the PCR.
  • the sample needs to be separated in to several reactions and it is often preferable to be able to store some of the sample for possible repeats or other purposes.
  • direct PCR protocols where sample is lysed and dissolved in a special sample buffer are very popular.
  • the dilution buffer may contain different agents that lyse the sample.
  • a colorant can be added to the dilution buffer to make subsequent pipeting steps easier.
  • the other colored reagent solution may be any other solution needed for the process, as discussed above.
  • Two cDNA synthesis reaction series were prepared one with the yellow colorant, in final concentration of 10 fold compared to the concentration instructed for the qPCR , the other without the additional dye.
  • HeLa total RNA dilution series with lOOOng, 500ng, lOng lng, lOOpg and 10 pg dilutions were used as template. Reactions were otherwise done according to the manual (Product number F-470, Finnzymes). A 1,5 ⁇ aliquot of each reaction was then used as a template in qPCR with DyNAmo SYBR Flash qPCR master mix.
  • the dye can be brought into the reaction with the transcriptase, with the sample, with the buffer solution or separately as a concentrate.
  • dye can also be added to any component taking part in a bisulphite treatment prior to mixing the sample thereby obtained with a second reaction solution.
  • the dye can be present not only when mixing the final PCR reaction mixture but also in preparative process steps, in particular those relating to sample preparation, such as reverse transcription reaction (e.g. in cDNA synthesis), bisulphite reaction, sample elution or sample dilution.
  • sample preparation such as reverse transcription reaction (e.g. in cDNA synthesis), bisulphite reaction, sample elution or sample dilution.
  • the dye can be introduced also into these reactions in various ways, for example, with the enzyme, with reaction buffer, with the sample or separately.
  • At least one colored solution is brought when mixing the final reaction solution, e.g. with the polymerase or master mix.
  • Fig. 2b illustrates, at a general level, the principle of introducing at least one colored reagent solution (step 20') to the process prior to at least one preparative process step 29'.
  • the pretreatment may involve the introduction of one or more other substances too (step 28').
  • the process can be continued similarly to as explained above, by mixing the product (or aliquot thereof) of the preparative process step with second colored reagent solution (steps 2 ⁇ and 23'), checking the color of the mixed solution (step 24') and proceeding to (q)PCR (step 25').
  • step 28' the process can be continued similarly to as explained above, by mixing the product (or aliquot thereof) of the preparative process step with second colored reagent solution (steps 2 ⁇ and 23'), checking the color of the mixed solution (step 24') and proceeding to (q)PCR (step 25').
  • the different colors are distinguishable by the naked eye.
  • hardware- aided optical measurements capable of distinguishing between colors can be utilized too, irrespective of whether the colors are distinguishable by the naked eye.
  • Figs. 8a-8c show schematic examples of how the measurement can be carried out in an apparatus.
  • the microtiter plate 80 having the microwells 81 is placed into a suitable plate holder (no shown).
  • the samples 82 are pipetted in one or more steps to the microwells 81 before or after placement of the plate 80 to the holder.
  • An absorbance measurement individually for each well can be carried out using a light source 83a and light detector 85a placed on opposite sides of the plate 80.
  • a scattering measurement individually for each well can be carried out using a light source 83b and light detector 85b placed on the same side of the plate 80. Both measurement can be carried out for a plurality of wells simultaneously.
  • a scattering measurement can be carried out using a light source 83b and camera 85b placed on the same side of the plate 80, the illumination and detection optionally taking place through a lens 87.
  • the lens 87 can correct the perspective of imaging so that each well, irrespective of its position in the plate, is illuminated and imaged similarly to other wells.
  • the light source 83a-c and/or the detector 85a-c are in each of the embodiments can be a single- or multichannel device for being able to measure with spectral resolution.
  • the light source 83a-c and the detector 85a-c are in each of the embodiments connected to a control unit (not shows) controlling the measurement sequence.
  • the detector is connected to a computing unit (not shown) for analyzing the measurement results and for making the decision on pipetting failures.
  • audial and/or visual means for signaling potential pipetting failures to the used or the apparatus or storage means (memory) for storing information of incorrectly pipetted microwells.
  • condition of one or more microwells to be pipetted is checked at least once during the pipetting process automatically by optical means capable of spectral resolution.
  • condition of the microwells is automatically checked at least two times in different stages of the pipetting process. Preferably such checking is carried out after every separate pipetting step.
  • the concentration of the colorant decreases and the color of a colored solution become weaker due to every addition of non-colored, i.e. optically clear, liquids.
  • addition of colored substances changes the shade of the color.
  • the strength and/or shade of color of a solution within a well is indicative of the stage of pipetting.
  • the abovementioned monitoring is carried out using a computer program, which is adapted to compare the measured spectral responses after the desired pipetting steps with predefined limits for these steps. Such limits are designed to reflect the correct shade and/or strength of the color of the solution, taking into account the reagents added.
  • a microwell, for which the measured value is not within an accepted range is flagged incorrectly pipetted.
  • the optical measurements are carried out before sealing and/or after removal of the seal.
  • the measurements can be carried out through the seal, too by a suitable method.
  • fluorescence-based methods are insensitive to reflection effects from sealing layers.
  • Sealing is typically used at least in (q)PCR assays.
  • the detection of the color of a solution may be based on absorbance or transmission (photometric) measurement, scattering measurement or fluorescence measurement, to mention some examples.
  • the detection instrumentation which may be an integral part of an automatic pipetting apparatus or a (q)PCR thermal cycling apparatus, for example, contains suitable measurement means, i.e. a light source, a light detector and means for determining the desired optical response of the contents of a microwell at least at one wavelength or wavelength range.
  • the measurement equipment can be the partly or entirely the same as used during monitoring the PCR process.
  • the measurement means comprise a spectrophotometer configured for absorbance or transmission measurements.
  • a spectrophotometer configured for absorbance or transmission measurements.
  • photometric measurement usually will need a good quality bottom window of microwells and the diameter of the window must be wide enough.
  • PCR wells are very conical, whereby the bottom window area is small.
  • the wells are non-transparent (typically white), which prevents transmission measurements. This is the case frequently in qPCR because white well color will enchance the qPCR fluorometric signal level compared with e.g. transparent wells.
  • a white well wall enhances also other than PCR-related scattering measurements.
  • a white light source e.g. LED
  • a color detector e.g, CCD or CMOS camera
  • Scattered light measurement can use visual filtering as in color camera case but also very color specific wavelenght separation can be used. This is specially convenient with separate LEDs with monochrome camera.
  • a potential problem of scattered light measurement is that both the liquid surface and potential cover of the PCR plate will reflect back excitation light which can interfere the scattered light measurement. This problem can be avoided using fluorometric measurement where the excitation wavelenght is filtered out so that reflection of liquid surface and cover of the well will not interfere liquid measurement.
  • Fluorescence detection will make system simpler in qPCR environment because it is more straightforward to tailor the fluorometer instrument for fluorometric color separation measurements.
  • the reflection problem is overcome using a scattering measurement utilizing polarization filter means arranged so as to eliminate or reduce the influence of light reflected from the surface of the sample on the measurement.
  • this can be achieved using polarizing filters with different polarization properties in front of the light source and the detector. For example, if a linearly polarizing filter with S polarizing direction is arranged in front the light source and a linear polarizing filter with P polarizing direction (preferably 90 degrees rotated) is arranged in front of the detector, S- polarized light reflected from the surface of the sample cannot pass to the detector.
  • a combination of a linear polarization filter and a circular polarization filter arranged in tandem (one after another) in the optical paths of the incident and reflected/scattered light is utilized.
  • the linear polarizing filter will first polarize the incident light in a first linear direction.
  • the circular polarizing filter will then give the light a circular polarization in a first circular direction.
  • Light reflected from the sample will be circularly polarized in the opposite (second) circular direction.
  • the circular filter will then polarize the reflected light in a second linear direction
  • the linear polarization filter will not transmit this light.
  • Depolarized scattered light, or suitable components thereof, will, however, pass the filters to the detector.
  • a silicon detector and 3 LEDs or a color sensitive silicon detector (for example three silicon detectors with filters) and a single LED can be used.
  • the reliability of pipetting and PCR assay can be improved, as even small changes in shades and strengths of colors, and thus in the contents of the wells can be detected.
  • the detection instrumentation is contained in a separate apparatus to which the reaction solutions can be transferred either automatically or manually after critical pipetting steps. In the separate apparatus, a quick plate read is carried out before the plate is transferred for further processing.
  • the invention also provides an apparatus for monitoring pipetting, comprising means for receiving a microtiter plate containing a plurality of microwells and means for measuring the optical absorbance of contents of the microwells.
  • Said means for detecting the absorbance are adapted to detect the spectral absorbance profile of the sample (for color detection) and/or color intensity of the sample (for dilution detection).
  • the apparatus is capable of both the abovementioned functions for being able to monitor the entire pipetting process.
  • the optical detection means are preferably connected to a computing unit which analyses and stores the measured absorbances and performs a calculation or comparison of the measurement data with pre-stored data.
  • the detection instrumentation may contain a microplate-receiving block which can be cooled for keeping the temperature of the reactions solutions low enough. For most hot- start polymerases cooling is not necessary.
  • the microwells may be separate or be contained in microtiter strips or plates of any known type.
  • the wells are manufactured from transparent material, allowing the visual inspection or spectral measurements to be carried out through the wall of the well.
  • Xylene cyanol as a colorant was added to DyNAmo Flash SYBR® green qPCR and DyNAmo Flash Probe qPCR master mixes from (Finnzymes, Finland) in the concentration of 0.0026% (w/v). The result was a clearly blue transparent solution.
  • Quinolene yellow was added to a sample buffer in the concentration of 0,00174% (w/v).
  • the sample buffer contained 1 mM Tris - HCL pH 8,5 and 0,lmM EDTA. As a result, a clearly yellow transparent solution was obtained.
  • the colored sample buffer and the colored master mix were mixed, resulting in a clearly green transparent mixture.
  • Figs. 4a - 4d show standard series obtained with master mix and sample with (Figs. 4a and 4b) and without (4c and 4d) the pipetting aid dyes of Example 1. Both series were done by amplifying human genomic DNA sequence with DyNAmo Flash Probe master mix according to the protocol in the product manual. Primer sequences were
  • Detection was based on hydrolysis probe with a sequence TGGCCCCTTGAAGACAGCAG. Amplicon size was 121 bp.
  • a colored (blue) 2x mix was thoroughly mixed with primers and probes, additives and water for obtaining a premix for several reactions.
  • the premix was pipetted to several wells of a microtiter plate (15 ⁇ /well).
  • the resulting solution is ready to be subjected to (q)PCR.
  • the reagents are preferably centrifuged to the bottoms of the wells.
  • Tables 1 - 7 show the results obtained with preferred dyes to be used with FAM or SYBR, whereas Tables 4 - 7 show comparative examples obtained with commercially available colored PCR solutions.
  • the absorbance maxima of the solutions of Tables 1 - 3 are relatively far from the fluorescent wavelengths of FAM and SYBR dyes.
  • the absorbance spectrum (lx dilution) of the reaction mixture of Table 3 is shown in Fig. 5a. From the data is can be concluded, that the dyes tested proved to be suitable to be used in the initial solutions and also together in a qPCR reaction mixture as colorants with these fluorescent dyes.
  • the buffer of Table 4 has absorbance maximum at 510 nm which is close to FAM and SYBR fluorescence maxima. Absorbance would decrease qPCR signals with these dyes significantly.Thus, the use of this mix in qPCR would not be feasible.
  • the mix of Table 5 has very strong absorbance at 419 nm. As the absorbance peaks are not very sharp it also has significant absorbance at 495 nm (0.17 with 1 mm light path), which is the the range where FAM and SYBR dyes are excited. Absorbance would decrease qPCR signals with these dyes.
  • the absorbance spectum (lx dilution) is shown in Fig. 5c.
  • the mix of Table 6 has very strong absorbance at 485 nm. As the absorbance peaks are not very sharp it also has significant absorbance at 495 nm (0.982 with 1 mm light path), which is the the range where FAM and SYBR dyes are excited. Absorbance would decrease qPCR signals with these dyes significantly.
  • the absorbance spectum (lx dilution) is shown in Fig. 5d.
  • the mix of Table 7 has very strong absorbance at 475nm. As the absorbance peaks are not very sharp it also has significant absorbance at 495nm (0.393 with 1 mm light path), which is the the range where FAM and SYBR dyes are excited. Absorbance would decrease qPCR signals with these dyes significantly.
  • the absorbance spectrum (lx dilution) is shown in Fig. 5b.
  • Perceivable range is dependent on the wavelength but in general color providing a absorbance above 0.01 - 0.1 with 1 mm light path seems to be visually distinguishable from the clear liquid. When absorbance is raised to 0.1 - 0.2, the color appears very clear to the eye. However, sophisticated instruments are more sensitive and thus dyes providing absorbance above 0.001 could be used when e.g. a spectrophotometer, scattering detector or a fluorescence detector is used for color measurement.

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Abstract

L'invention concerne un appareil de traitement d'échantillons comprenant un support pour plaque de microtitrage comprenant une pluralité de micropuits, une unité de mesure optique pour mesurer les réponses optiques d'échantillons dosés sur les micropuits, et une unité de calcul conçue pour analyser les réponses optiques afin de détecter des défaillances de dosage dans ladite pluralité de micropuits, et si une défaillance de dosage a été détectée dans un ou plusieurs des micropuits, pour communiquer l'existence de la défaillance de dosage à l'utilisateur de l'appareil par un moyen de signalisation ou pour stocker des données indiquant la défaillance de dosage dans un moyen de stockage de données pour les utiliser ultérieurement. En particulier, l'invention concerne la détection de défaillances de dosage avant, pendant et après un procédé de PCR.
PCT/FI2012/050318 2011-04-01 2012-03-29 Appareil et procédé de traitement d'échantillons WO2012131167A1 (fr)

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CN116837077A (zh) * 2023-07-07 2023-10-03 苏州依科赛生物科技股份有限公司 一种qPCR反应程序中指示溶液存在的方法

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