Patent Application
20230213503
The present invention generally relates to a device and method for rapid automated quantitative determination of analytes in liquid samples by immunoassays at a Point Of Care (POC), particularly assays incorporating labels and magnetic particles.
Immunodiagnostics are increasingly used to detect many types of diseases and health conditions ranging from cancer and heart-attack to infections such as Covid-19. There are basically two types. One relies on the use of heavy (non-transportable) equipment such as auto-analyzers which provide accurate results with high through-puts but long turnaround times, typically of more than one hour. (See Euroimmun: https://www.euroimmun.com/products/automation/chlia/; Abbott Labs, https://www.corelaboratory.abbott/int/en/offerings/brands/architect). It should be noted that there is traditionally no provision in these auto-analyzers for vigorously and thoroughly mixing the reactants during the reaction process because ample time is allowed for the incubation and the reactants are usually non-particulate in nature. However, there are instances where very brief mixing is effected e.g., by centrifuging the reaction mixture and then bringing the motion to a sudden halt.
The other type comprises simple rapid tests, typically of less than 30 minutes, that can be manually performed at POC settings, but which provide results that are generally less accurate. In these tests, the results are often read by eye although recently, small image sensors or fluorescence readers (not auto-analyzers that actually perform tests) have been employed to improve the scoring of results such as those based on the lateral-flow technique. (See Quidel, https://www.quidel.com/immunoassays/sofia-tests-kits; Creative Diagnostics, https://www.creative-diagnostics.com)
In most immunodiagnostics, the antibody or antigen employed as the reagent to detect properties of the analyte of interest is used in its free naked form, or conjugated with a label, or immobilized on the surface of a reaction well (tube). Recently, however, several systems have used magnetic microspheres in suspensions to immobilize either the antibody or the antigen and used as suspensions. These particles have a magnetic core and a polymer shell with a functionally modified surface. The advantage here is the ease by which the bound reagent can be separated from the unbound reagent in solution through the use of magnetic force. The use of such particles in immunoassays, however, which dates back to the pioneering work done by the applicant (see Lim P L, Ko K H, Choy W F. 1989. J. Immunol. Methods 117:267-273. https://doi.org/10.1016/0022-1759(89)90149-X) is still relatively uncommon.
It is even less common to use another microsphere besides the magnetic particle to immobilize the antibody or antigen reagent. Such a two-particle system is used in the TUBEX® test developed by the applicant (Lim P L, Tam F C H, Cheong Y M, Jegathesan M. 1998. J. Clin, Microbiol. 36:2271-8. DOI: 10.1128/JCM.36.8.2271-2278.1998; Yan M Y, Tam F C H, Kan B, Lim P L. 2011. PLOS ONE 6:e24743. https://doi.org/10.1371/journal.pone.0024743). In this rapid POC test, the magnetic particle is coupled with an antigen, while the second microsphere, which also has a polymer shell but lacks a magnetic core, is coloured to serve as the reaction indicator and is coupled with the corresponding antibody. Both particles are used in liquid suspensions. The two particles will bind to each other specifically and rapidly when mixed together, and both will settle to the bottom of the well when magnetic force is applied. However, if the relevant antigen or antibody is present in a sample to be analyzed, this will block the interaction between the pair of microspheres and cause the indicator microspheres to remain suspended in solution, thus giving a positive score. The results are visually read based on the colour intensity (semi-quantitative). The assay format is as such based on inhibition unlike the direct-binding or capture (sandwich) format used by the majority of immunodiagnostic systems.
Vigorous multi-directional mixing of the reactants during the whole incubation period is a crucial feature of the TUBEX® test, and distinguishes it from most other systems, such as ones based on the lateral-flow technique or ELISA. Mixing not only enhances the chances of collision between the two microspheres to speed up the interaction, but also ensures that the binding between the two particles, as well as between each particle and the analyte, is real (specific) and not spurious (equivalent to the effect achieved by traditional washing). This type of mixing is different from the brief mixing of reactants done by pipetting or vortexing that is sometimes used in some diagnostic systems when the reagents are first introduced. This is also different from the mono-directional light rinsing (washing) of reactants due to the capillary flow of fluid in the lateral-flow technique.
Achieving thorough mixing in a small container is a challenge. In TUBEX®, this is done manually by first sealing the mouth of the V-shaped multi-channel reaction wells with tape (to prevent leakage of contents) and laying the set of reaction wells flat on their face (to provide a large surface for mixing), and then shaking the wells vigorously in a forward-and-backward motion for several min.
It is apparent that the manual TUBEX® test, although simple and fairly accurate, has several shortcomings. One is the mixing step, since this is cumbersome and can be incorrectly performed by some users. Another is the subjectivity and difficulty associated with reading of the colorimetric results by eye.
Thus, there exists a need for a device and method for performing rapid automated quantitative analyses of an analyte in a fluid sample which provides a more homogeneous analyte and reagent mix in the sample for enhancing the accuracy of the analysis. It is particularly desirable to provide a device that is small and portable or transportable for use in a POC rapid test but which offers the high-precision of an auto-analyzer.
Disclosed herein is a device that can autonomously perform the TUBEX® test without the inherent problems of the manual test but with much enhanced sensitivity. Critically, a way was found to mix the TUBEX® reagents effectively without the need for capping the reaction well nor laying it flat i.e. while the reaction well is stood upright, open-mouthed. Sensitivity was improved by changes made to the TUBEX® reagents and assay method, and the provision of a photosensitive detector in the device which can read the two-colour fluorescence of the new TUBEX® reagents.
Table 1 shows the results of an experiment aimed at finding out whether tiny mechanical stirrers (see
Table 2 shows the results of an experiment aimed at finding out whether a rocking platform could be used to mix a small volume of TUBEX® reagents in a reaction well while standing the reaction well upright on the platform. The results show the great potential of this method at the conditions used.
Table 3 shows the results of an experiment aimed at extending the experiment of Table 2 to find a design of the reaction well (see
In a further study using the original V-shaped reaction wells in an upright position, mixing was done by manually pipetting the reaction mixture up and down repeatedly for up to 2 min, but only <90% completion could be achieved (data not shown).
According to one aspect of the present invention there is provided an immunoassay device for use in performing rapid immunodiagnostic tests to quantitatively measure an amount of an analyte in a fluid sample, comprising:
a set of reaction wells;
a transport which moves the set of reaction wells along a path;
first and second reagent holders disposed alongside the path for holding respective reagents;
a dispenser configured for withdrawing reagent from the reagent holders and dispensing the reagent into ones of the reaction wells, wherein the reagents comprise: a labelled reagent including one of a binding pair coupled with a label, and a magnetic reagent including a magnetic particle coupled with the other of the binding pair;
a magnet disposed alongside the path for applying a magnetic field in a magnetization direction to the contents of the set of reaction wells such that bound pairs are thereby separated;
a photosensitive detector configured to quantitatively measure the amount of analyte; and
a controller operable to coordinate movement of the transport with operation of the dispenser for dispensing of the reagents and operating the transport to reciprocate the set of reaction wells along the path for mixing the fluid sample with the reagents.
Advantageously, the resulting mixing performance substantially contributes to a more homogeneous analyte and regent mix in the sample, while allowing for the relatively simple configuration of the machine. In addition to the controller operating the transport to reciprocate the set of reaction wells along the path for mixing the fluid sample with the reagents, the controller may operate the transport to reciprocate the set of reaction wells along the path after dispensing one of the reagents and before dispensing the other of the reagents for mixing the fluid sample with the one of the reagents. In addition, following mixing of the fluid sample and reagents, the results may be resolved by operating the magnet to separate the bound pairs of reagents from the unbound label. Thus, the device can autonomously perform the TUBEX test, and it avoids the need to make a colour determination manually, and offers greater sensitivity by the use of a photosensitive detector.
Preferably the label comprises one of a fluorescent label, a chemilumiscent label and a dye. Preferably the labelled reagent further comprises a non-magnetic particle, the non-magnetic particle coupled to the label and to the one of antigen and antibody.
Preferably the set of reaction wells comprises like reaction wells arrayed in a longitudinal direction, each well extending down from an opening to a closed end, each well having substantially the same cross section throughout its height.
Preferably the reaction wells are generally trapezium-shaped in cross section, with a pair of transversely opposing outer walls forming bases of the trapezium, the transversely opposing outer walls comprising at least opposing windows of transparent material, the outer walls aligned substantially parallel to the path.
Preferably the trapezium is an acute trapezium, the opposing walls are aligned in the longitudinal direction of the array and the reaction wells of the set are integrally formed.
Preferably the openings are arrayed in a top flange that is generally flat and elongated in the longitudinal direction and serves to integrally connect tops of the reaction wells.
Preferably the path is linear and parallel to the longitudinal direction.
Preferably the dispenser comprises first and second pipette modules, each pipette module dispensing reagent from a respective one of the reagent holders. Alternatively, the dispenser may comprise a single robotic arm that holds a different dispensing device to dispense each reagent.
Preferably the controller operates each pipette module to alternately draw in and expel the fluid sample and reagent for further mixing of the fluid sample with each reagent.
Preferably the controller operates each pipette module to draw in a first volume and subsequently dispenses a fraction of the first volume into each of the reaction wells. By not using the pipette module to mix the reagent and each sample, no pipette washing step is required.
Preferably the controller operates each pipette module to alternately draw in and expel one or each of the reagents for mixing the reagent prior to dispensing the reagent.
Preferably the device further comprises opposing jaws mounted on the transport, resilient means for urging one of the jaws toward the other from a released position to an engaged position in which the set of reaction wells is clamped between the jaws.
Preferably the jaws are elongated in the longitudinal direction and clampingly engage at least one of the outer walls, at least one of the jaws having a respective array of windows, such that each window can be disposed in registration with one of the outer walls of each reaction well.
Preferably the transport is moveable along the path under control of the controller to a release station, wherein the release station comprises at least one actuator that is moveable under control of the controller to abut and move the at least one of the jaws from its engaged position to its released position.
Preferably a pair of parallel linear guides on the transport support longitudinally opposing ends of the one of the jaws for transverse movement and the at least one actuator comprises a corresponding pair of actuators, each actuator moveable simultaneously under control of the controller to abut and move the at least one of the jaws from its engaged position to its released position.
Preferably each actuator comprises a shaft mounted in a linear bushing for movement between a retracted position and an extended position for abutting the one of the jaws, each actuator driven by a rotary motor that turns a cam, wherein a cam follower engaged with the cam is connected to the shaft such that a lobe of the cam displaces the cam follower and the shaft to the extended position.
In another aspect, the invention provides an immunoassay method for quantitatively measuring an amount of a first analyte in a fluid sample, comprising:
providing a transport that moves along a path;
providing a set of reaction wells holding a fluid sample mounting the set of reaction wells to the transport;
providing in respective ones of two reagent holders a) a labelled reagent including one of a binding pair coupled with a label, and b) a magnetic reagent including a magnetic particle coupled with the other of the binding pair;
operating a dispenser for withdrawing reagent from one of two reagent holders;
coordinating movement of the transport with operation of the dispenser to dispense the withdrawn reagents into one of the reaction wells, and,
operating the transport to reciprocate the set of reaction wells along the path for mixing the fluid sample with the reagents,
before subsequently applying a magnetic field in a magnetization direction to the contents of the set of reaction wells such that bound are thereby separated, and
operating a photosensitive detector to quantitatively determine the amount of the first analyte.
Preferably the method is performed using the immunoassay device described above, wherein one of the magnetic reagent and labelled reagent is dispensed into the reaction wells by the first dispenser of the immunoassay device and other of the magnetic reagent and labelled reagent is dispensed into the reaction wells by the second dispenser of the immunoassay device.
Alternatively the method is performed using the immunoassay device described above, wherein one of the magnetic reagent and labelled reagent is dispensed into the reaction wells by the dispenser of the immunoassay device and other of the magnetic reagent and labelled reagent is dispensed into the reaction wells outside of the immunoassay device.
Preferably the method comprises first and second mixing periods during which the transport is operated to reciprocate the set of reaction wells along the path for mixing, the first mixing period following the dispensing of one of the magnetic reagent and labelled reagent, the second mixing period following the dispensing of the other of the magnetic reagent and labelled reagent.
Preferably the label comprises one of a fluorescent label, a chemilumiscent label and a dye.
Preferably the labelled reagent further comprises a first particle, the first particle coupled to the label and to the one of the binding pair.
Preferably the method further comprises adding to the fluid sample a second reagent pair, the second reagent pair having a specificity and label differing from those of the first reagent pair, and
operating the photosensitive detector to quantitatively determine the amount of a second analyte.
In this manner advantage is also taken of the availability of many different types of fluorophore with distinct excitation and emission frequencies to mix two or more fluorophores together in a single test, so that multiple specificities can be simultaneously examined.
Preferably, for the detection of an antigen, the binding pair comprises an antigen and antibody pair and the first particle is coupled with the antibody, and the second particle is coupled with the antigen, and the transport first reciprocates the reaction wells to mix the analyte and one of the reagents of the first reagent pair, before dispensing of the other of the reagents of the first reagent pair.
Preferably, for the detection of an antibody, the binding pair comprises an antigen and antibody pair and the first particle is coupled with the antigen, and the magnetic particle is coupled with the antibody, and the transport first reciprocates the reaction wells to mix the analyte and one of the reagents of the first reagent pair, before dispensing the other of the reagents of the first reagent pair.
Preferably the photosensitive detector is used to measure one of florescence, chemiluminescence and colour.
Preferably the results derived from the photosensitive detector are output in analog form, with an indicator highlighting where a result lies on a scale.
The method may further comprise adding to the fluid sample a second reagent pair, the second reagent pair having a specificity and label differing from those of the first reagent pair, and
operating the photosensitive detector to quantitatively determine the amount of a second analyte.
Preferably the antibody used for coupling the first particle is a mixture of monoclonal antibodies.
Preferably the antibody used for coupling the magnetic particle is a mixture of monoclonal antibodies.
Preferably the dispenser comprises first and second pipette modules, and wherein operating the dispenser comprises withdrawing reagent from a respective one of the two reagent holders using a respective one of the first and second pipette modules.
In still another aspect, the invention provides an immunoassay method for quantitatively measuring an amount of a first analyte in a fluid sample, the sample further comprising a first reagent pair comprising a) a labelled reagent including one of a binding pair coupled with a label, and b) a magnetic reagent including a magnetic particle coupled with the other of the binding pair, the method comprising:
providing a transport that moves along a path;
providing a set of reaction wells holding a fluid sample
mounting the set of reaction wells to the transport;
operating the transport to reciprocate the set of reaction wells along the path for mixing the fluid sample with the reagents,
before subsequently applying a magnetic field in a magnetization direction to the contents of the set of reaction wells such that bound are thereby separated, and
operating a photosensitive detector to quantitatively determine the amount of the first analyte.
Preferably the reaction wells are generally trapezium-shaped in cross section, with a pair of transversely opposing outer walls forming bases of the trapezium, the transversely opposing outer walls comprising at least opposing windows of transparent material, the outer walls aligned substantially parallel to the path.
Preferred forms of the present invention will now be described by way of example with reference to the accompanying drawings, wherein:
As used herein, the terms “antibody” and “antibodies” refer to serum proteins classified as immunoglobulins (Ig); and includes (a) the various isotypes such as IgM and IgG, (b) intact whole molecules or fragments such as single-chain Fv or camelids, (c) both natural and re-engineered forms, and (d) both monoclonal and polyclonal sources including mixtures of monoclonal antibodies.
A ‘surrogate antibody’ can substitute for an antibody, and means any substance with a structure different from that of an antibody, that is natural or chemically-synthesized, and that has a suitable binding affinity for the antigen. Surrogate antibodies can come human, viral and plant sources. For instance, a suitable ligand for the Covid-19 spike protein is the angiotensin-converting enzyme receptor protein (ACE2); another is the various plant lectins that bind to various glycoproteins.
‘Antigen’ refers to any substance containing one or more antigenic sites (epitopes), natural or chemically-synthesized, intact or fragmented, that can be bound by an antibody through the epitopes; the size can range from small chemical groups with a single epitope such as tyvelose, to serum proteins or microbial extracts with multiple epitopes, and to even larger entities such as whole microorganisms, viruses, and blood cells. Sub-specificities refers to the different epitopes present in an antigen that are recognized by individual monoclonal antibodies.
A ‘binding pair’, includes a ‘complementary binding pair’, and comprises an antigen and antibody pair, and an antigen and surrogate antibody pair.
‘Microsphere’, ‘bead’ or ‘particle’ refers to particulate matter composed of polystyrene or silica with a diametric size ranging from 10 nm to 10 μm. Particles are coated or coupled with an antigen or antibody by covalent or non-covalent means, directly or indirectly via spacers or adaptors such as protein G, using conventional methods known to those skilled in the art.
Referring particularly to
As best seen in
Transverse walls 24, 25 of each well are also flat and join the outer walls 22, 23 forming legs of the generally trapezium-shaped cross section that are acutely inclined to the longitudinal axis 19 such that the trapezium is an acute trapezium, particularly an isosceles trapezium. The outer walls 22, 23 and transverse walls 24, 25 may have the same thickness. In the generally trapezium-shaped cross section, the long wall 22 may have a length, in the direction of the longitudinal axis 19, of between 150-250% of the length L of the short wall 23, with the transverse spacing between the walls of between 80-120% of the length L. A top flange 26 that may be generally flat and elongated in the longitudinal axis 19 serves to integrally connect tops of the reaction wells 11a-11f, while a web 73 may extend vertically between the closed end 21 and the flange 26 to connect tapered ends of adjacent ones of the wells 11a-11f throughout their length. As shown in
The above-described set of reaction wells 11 has been found to offer advantageous mixing performance that substantially contributes to a more homogeneous analyte and regent mix in the sample, while allowing for the relatively simple configuration of the machine. This is achieved by aligning the longitudinal axis 19 parallel to the linear path 34, and operating the transport 12 to reciprocate linearly along the path 34. It is believed, without wishing to be limited by theory, that, owing to inertial effects, a rotational component of movement is imparted to the fluid when it impacts the transverse walls 24, 25 when the wells are sharply decelerated at the opposing ends of its longitudinal movement. This rotational component is in opposite directions at the opposite ends of the longitudinal movement, and so reciprocating with a sufficiently high amplitude and suitable frequency, such as an amplitude greater than or equal to the longitudinal dimension of the long wall 22 at between 10 and 50 Hz, ensures a turbulent flow regime that promotes vigorous mixing. By ensuring the wells are between no more than about 20 or 30% full with liquid ensures that no loss or overflow through the openings 20 occurs, so it is unnecessary to provide a closure over the openings 20.
A pair of reagents for use in the device 10 may comprise a labelled reagent including antigen-bound fluorescently labelled microspheres and a magnetic reagent including magnetic microspheres bound with a corresponding antibody. For instance, for a Covid-19 assay to detect antigen from a nasal swab, the magnetic reagent may include magnetic microspheres coated with an antibody specific to the nucleocapsid (NP) of the Covid-19 virus, while the labelled reagent may include microspheres dyed with fluorescein of a certain colour and coated with the corresponding Covid-19 nucleocapsid antigen. When mixed together with the liquid sample, the fluorescein-labelled microspheres and magnetic microspheres bind to one another in the antigen-antibody reaction and, if Covid-19 antigen is absent from the sample, when the magnetic microspheres and unbound fluorescein-labelled microspheres are separated by the application of a magnetic field, no fluorescein-labelled microspheres will be left in suspension and the result will thus be negative. However, when Covid-19 antigen (or the corresponding antibodies) are present in the liquid sample, these antigen or antibodies will block the binding between the pairs of microspheres. Significant amounts of fluorescein-labelled microspheres will be left unbound and remain suspended after the magnetic microspheres are separated by the application of a magnetic field, the degree depending on the amount of inhibitor (antigen or antibodies) present in the sample. The fluorescence detector 17, by measuring fluorescent intensity provides quantitative measurement.
In a preferred embodiment, two reagent pairs, each pair with a different specificity and different fluorophore, are added to a single well. The emission of both is measured and different analyte concentrations are calculated from these two emission signals, allowing two tests to be performed simultaneously from the same sample. For instance, one of the pairs (of a first test) may include antibody-bound microspheres labelled by a fluorophore with an emission wavelength of 525 nm (and the corresponding antigen-bound magnetic particles), while the other of the pairs (of the second test) includes microspheres conjugated with an antibody of a different specificity and labelled by a fluorophore with a different emission wavelength e.g. 575 nm. The first pipette module 15 is shown separate from the device 10 in
As shown in
Referring to
The transport 12 is moveable along the path 34 under control of the controller 18 to a release station 40, wherein longitudinally opposite ends of the transport 12 are disposed adjacent actuators 41, 42 and the set of reaction wells 11 is intermediate therebetween. Clamping the set of reaction wells 11 to the transport 12, the well holder 79 has a fixed jaw 43 which may be integral with the table 36 and which cooperates with an opposing moving jaw 44. A pair of parallel linear guides 45, 46 may be fixed to longitudinally opposing ends of the moving jaw 44 and received to slide in respective bushings 47, 48 mounted to the table 36 to support the moving jaw 44 for transverse movement. Springs 49, 50 are mounted about respective support bars 51, 52 aligned parallel to the linear guides 45, 46 and resiliently urge the moving jaw 44 toward the fixed jaw 43 and its engaged position. The jaws 43, 44 are elongated in the longitudinal axis 19 and have respective upright planar faces that abut and clampingly engage the set of reaction wells 11, with the moving jaw 44 abutting the outer walls 23 and the opposing fixed jaw 43 abutting the outer walls 22. Features (not shown) on one of the jaws 43, 44 may ensure that the set of reaction wells 11 can be accurately clamped in only one position and orientation. The fixed jaw 43 may include an array of windows 53, each disposed in registration with one of the outer walls 22 of each reaction well, and disposed opposite an aligned array of windows in the moving jaw 44.
With the transport 12 at the release station 40, the actuators 41, 42 are moveable simultaneously under control of the controller 18 to abut and move the moving jaw 44 from its engaged position to its released position. The actuators 41, 42 are of like construction, and differ only in handedness. Each actuator may comprise a shaft 54 mounted in a linear bushing 55 for movement between the retracted position shown and an extended position (not shown) in which it abuts the moving jaw 44. Each actuator 41, 42 may be driven by a rotary motor 56 that turns a cam 57, wherein a cam follower 58 engaged with the cam 57 is connected to the shaft 54 such that a lobe 59 of the cam 57 displaces the cam follower 58 and the shaft 54 to the extended position. A spring (not shown) may serve to retract the shaft 54 and urge the cam follower 58 into engagement with the cam 57. In the extended position, the shafts 54 pass through apertures 60, 61 in the fixed jaw 43 to abut the opposite ends of the moving jaw 44.
The fluorescence detector 17 may include two like reader instruments 65, 66 adjacent one another and spaced apart along the path 34, each with a respective optical channel orthogonal to the path 34. Each optical channel is also orthogonal to the plane defined by the outer walls 22 of the wells 11. In this manner, diffraction losses are mitigated and the transport 12 may be moved along the path 34 in a stepwise manner, to align each optical channel with one of the wells 11a, 11b, 11c, 11d etc successively to perform the fluoroscopy. The spacing between the reader instruments 65, 66 along the path 34 may equal the longitudinal spacing between adjacent ones of the wells, allowing adjacent wells to be read simultaneously. Each reader instruments 65, 66 may include excitation 70 and emission 71 filters, a light source 68, plano-convex lens 69 and an emissions sensor 67. The emissions sensors 67 generate an output voltage in response to fluorescence emissions excited by the light source 68. The light source 68 is preferably an LED with a dispersion angle of about 15°. These emissions sensors 67 may include photodiodes, photovoltaic devices, phototransistors, avalanche photodiodes, photoresistors, CMOS, CCD, CIDs (charge injection devices), photomultipliers, and reverse biased LEDs, for instance. By the use of two emissions sensors 67 the fluorescence detector 17 is thus adapted to perform the above-described two different measurements simultaneously. The pair of exciter parts of the instruments 65, 66 on one side of the path 34 may comprise an exciter subassembly 81, with the opposing pair of receiver parts comprising a separate receiver subassembly 82 (shown schematically by rectangles in
The fluorescence signals are instantaneously processed and calibrated against a standard curve by an onboard chip and eventually displayed as digital (numerical) values. In addition, the results are also colour-coded to simplify interpretation for POC users. For example, ‘brown’ can be used to denote results that fall between the 0th and 10th percentile which are considered ‘negative’, ‘yellow’ as ‘borderline positive’ for values that lie between the 11th and 20th percentile, ‘green’ as ‘positive’ for values that lie between the 21st and 50th percentile, and finally, ‘blue’ as ‘strong positive’ for values over the 51st percentile.
Position sensors associated with moving parts of the device 10 provide feedback to the controller 18 to ensure each moving part is correctly configured at each stage of operation before moving to a subsequent stage, in the manner well known in the automation arts.
The device 10 may be operated with the labelled reagent and magnetic reagent in the reagent holders 13, 14. In use, with the moving jaw 44 released, and after placing a patient's fluid samples in the wells 11a, 11b, 11c, 11d, the operator may place the set of reaction wells 11 between the jaws 43, 44 where it may rest upon the table 36. In this position, the device 10 is ready to be started. Optionally, if the batch size is smaller than the number of wells not all of the wells will contain samples, and so the operator provides an initial input to the controller, as via a key pad (not shown) to identify the wells holding samples. After the operator provides a start command, the controller 18 operates the actuators 41, 42 to move together to their retracted positions, allowing the moving jaw 44 to move under the resilient action of the springs 49, 50 and firmly clamp the wells 11 between the jaws 43, 44. The controller 18 operates the first and second pipette modules 15, 16, controlling the robot arm to move a tip of the pipette 27 down into each container 32. To mix the reagents, a volume of reagent is repeatedly drawn in and expelled, before the pipette 27 draws in a predetermined amount sufficient to complete the batch. The controller 18 may then operate the transport 12 to place each well in turn in a first filling position on the path 34 adjacent the first pipette module 15. At this first filling position the pipette 27 is lowered into the well and a predefined volume of the labelled reagent of a first reagent pair is dispensed, before the pipette 27 is withdrawn, this operation of the first pipette module 15 being alternated with stepwise movement of the transport 12. After each well has received the labelled reagent of the first reagent pair in this manner, the pipette returns to the container 32 and ejects remaining reagent into the container. The controller 18 controls the transport 12 to reciprocate along the path 34, as at 30 Hz with an amplitude of 5 mm for two minutes, to mix the reagents and sample. The controller 18 operates the transport 12 to move each well in turn in a second filling position on the path 34 adjacent the second pipette module 16 and the corresponding filling steps are performed in the same manner to dispense the magnetic reagent of the first reagent pair into each of the wells. Next, the controller 18 controls the transport 12 to reciprocate along the path 34 in the above-described manner for a pre-defined period to mix the reagents and sample. A different labelled reagent and magnetic reagent, comprising a second reagent pair with a specificity different to that of the first reagent pair, are then dispensed into each well in a like manner.
The controller 18 operates the transport 12 to place the wells 11 over the electromagnets 38 which are then supplied with current to draw the magnetic microspheres and bound fluorescein-labelled microspheres down to the closed ends 21. After a predetermined time sufficient to complete the magnetic separation, the controller 18 operates the device 10 to perform the fluoroscopy. Readings are taken by the fluorescence detector 17 for each sample. The reader instrument 65 receives the first well 11a and the fluoroscopy is completed on the contents of this first well 11a, before the wells 11 are indexed forward one step so that reader instrument 65 receives the second well 11b and reader instrument 66 receives the first well 11a. In this position, and corresponding positions between the first and last, the reader instruments 65 and 66 are operated simultaneously. The reader instruments 65 and 66 have differing excitation 70 and emission 71 filters, and thus measure different emissions for different simultaneous tests.
By aligning, in turn, each well and corresponding window 53 with the reader instruments 65, 66 by stepwise displacement of the transport 12. The transport 12 may be maintained stationary, or else each scan may be performed following a like movement profile, while the fluorescence detector 17 is operated to produce the fluoroscopic reading for each sample. The controller 18 processes signals from the fluorescence detector 17 to quantitatively measure the amount of analyte, producing a reading for each sample analysed and which may be formatted by the controller 18 and sent to a display 72, to a printer 78 or, for instance, wirelessly to a connected computer.
Referring to
The same O9 antigen-coupled magnetic particles were used throughout and the same monoclonal anti-O9 antibody was coupled to both the coloured and fluorescent indicator particles (all particles purchased from Merck Co., Paris, France). It is apparent that the device (invention)-based results are superior, particularly in the case of antigen detection where the analyte was pre-mixed (2 min) with the indicator particles before mixing with the magnetic particles (4 min). Mixing was performed in trapezium-type reaction wells using the device (see Table 3) or manually in V-shaped reaction wells in a shaker. Details of the latter method including the reagent particles used are described in Yan M Y, Tam F C H, Kan B, Lim P L. 2011. PLOS ONE 6:e24743. https://doi.org/10.1371/journal.pone.0024743
A second embodiment of the immunoassay device 210 is shown in
The well holder 279, best seen in
The magnet mount 280 mounts permanent magnets 238 in a linear array upon a beam 88 fixed in a cantilevered manner to project from an upright linear actuator 89 disposed alongside the guideway 35. The upright linear actuator 89 may be of the screw type, where the screw (not shown) is turned by a rotary electric motor 90. By adjusting the height of the permanent magnets 238, by a command from the controller 18, the magnetic field applied during operation to the contents of the set of wells 11 may be varied from zero, or a negligible level, up to the design level when raised to the position shown in
In operation, the well holder 279, lacking motorised parts of the first embodiment, securing the set of wells 11 is simpler, and once the operator has pushed the set of wells 11 into the recess between the jaws 43, 243 it is held securely. Once the reagents have been dispensed and the above-described mixing steps completed, the controller 18 operates the upright linear actuator 89 to expose the mixture to the magnetic field, performing the separation that pulls the magnetic microspheres toward the closed ends 21.
The immunoassay device 10, 210 is programmed to perform (in a full auto-analyzer mode, and after the set of wells 11 are secure in the machine) the consecutive steps, a) adding one reagent, b) reciprocating the wells for mixing, c) adding the other reagent, d) reciprocating the wells for mixing, e) magnetic separation and f) fluoroscopy, as these steps are described above. For added versatility, the machine is provided with additional user-selectable operating programmes for performing different subsets of these steps a) to f). For instance, for a small batch of tests the user may manually add the reagents, before selecting a programme that performs only the above steps d) to f). Alternatively, only the magnetic separation and fluoroscopy steps e) and f) may be performed by a different programme, as might follow manual addition of the reagents and mixing. Another programme may provide only for the steps d) and e), perhaps when a visual check of a colour change would suffice, so fluoroscopy is not required. Yet another programme may allow the device the device to be used as a benchtop mixer, only reciprocating the wells for mixing.
In a preferred embodiment of the invention to detect antigen (e.g., osteopontin or OPN) from an unknown sample, the following protocol is adopted based on the current configurations of the immunoassay device 10, 210:
For samples that contain only small amounts of antigen, the following modification is used to increase the sensitivity of the test:
In another preferred embodiment of the invention but this time to detect antibodies (e.g., anti-Salmonella LPS antibodies) from an unknown sample, the following protocol is adopted based on the current configuration of the fluorescence reader and the reaction wells:
For samples that contain only small amounts of antibodies, the following modification is used to increase the sensitivity of the test:
Mixing periods during which the transport is operated to reciprocate the set of reaction wells along the path for mixing are critical to the immunoassay method. There are two separate mixing periods. Table 4 below illustrates, for an analyte comprising Covid-NP antigen, the influence of the first mixing period on the sensitivity of the quantitative measurement, while keeping the second mixing period constant. Table 4 also illustrates the greater sensitivity that could be achieved using a mixture of monoclonal antibodies of different sub-specificities than a single monoclonal antibody.
Aspects of the present invention have been described by way of example only and it should be appreciated that modifications and additions may be made thereto without departing from the scope thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022200014 | Jan 2022 | AU | national |
