FR2858689A1 - Apparatus for the detection of the presence and/or quantity of molecules in a liquid, e.g. nucleic acids and proteins, comprises colored magnetic micro-balls specific to the molecules of interest with movement by magnets - Google Patents

Abstract

Apparatus (10) for the detection and/or dosage of molecules, within a liquid, comprises a support (12) for a reaction chamber (13) to hold the liquid, and other chambers. Apparatus (10) for the detection and/or dosage of molecules, within a liquid, comprises a support (12) for a reaction chamber (13) to hold the liquid, and other chambers. At least one colored magnetic micro-ball (20) is specific for each molecule of interest, for indexing by color to show the presence and/or quantity of molecules of interest. The apparatus has a magnet (21) and a mechanism to shift the magnet and support to displace a magnetic micro-ball within the magnetic field from the reaction chamber in the other chamber. The support carries a washing chamber (14), a development chamber (15) and a scanning chamber (16). At least one dry zone (17-19) separates at least two of the chambers for the transfer of micro-balls between chambers within the apparatus.

Description

METHOD AND DEVICE FOR DETECTING AND / OR ASSAYING MOLECULES.

  The present invention provides a method and a device for detecting and / or assaying molecules. It applies, in particular, to the immunoassay and to the nucleic acid assay. More particularly, the present invention relates to a method and a device for multiple detection (i.e., of several molecules, for example nucleic acids and proteins) in the field of in vitro diagnostics using colored magnetic microbeads whose The purpose is to generate a measurable signal.

  The use of magnetic microbeads in the field of immunoassays or nucleic acids is a well known method. Indeed, the magnetic microbeads make it possible to extract a target molecule from a sample and to transport microbeads from one reaction medium to another.

  The use of plastic disposables in which the reactions are practiced has also been practiced for a long time since these objects remain manageable by the manufacturers and make it possible to guarantee the proper conduct of a diagnostic test.

  More recently, diagnostic systems have evolved into solutions that can detect multiple analytes in a reactive medium, often called multiplexing. A parallel trend is also to detect multiplexing analytes in increasingly smaller volumes, which increases the potential for multiplexing, but also allows substantial savings in reagent.

  Also, we have recently seen devices called biochips, where reactions are carried out on a glass surface or a polymer membrane, ligands being fixed, in the form of dots or "spot", on these supports to capture target molecules. which are then revealed by other ligands capable of generating a signal, thanks to a reagent that reacts simultaneously on all spots. The position of the different spots is known, and the spot reading performed for example by a charge transfer device camera or "CCD" which detects a color change of a spot.

  These biochips therefore make it possible to reveal more than one analyte in the same reaction medium and thereby allow savings in reagents. The biochip system also offers the advantage of a disposable device that provides good quality control and additional safety for the user. But the biochip system suffers from the disadvantage of lacking flexibility for diagnosis. Indeed, the fabrication of each biochip freezes the geometry and the composition of the spots. Since the analysis rarely requires all the analytes fixed, costly waste ensues.

  ## STR1 ## wherein: ## STR1 ## Other systems derived from flow cytometry, such as that marketed by the company Luminex (trademark), use colored microbeads on which ligands which capture target molecules as described above.

  The microbeads, after reaction, are sent by a liquid flow into a narrow reading cell and pass two laser beams. The signal is read by measuring the light re-emitted by the microspheres which provide two information on each microbead, the first concerning the color, which is indexed to the type of molecule sought, and the second, for example the fluorescence generated, indicating the presence of the target molecule; in addition, the counting of the microbeads is carried out, which makes it possible to know how many microbeads have detected which molecule sought.

  This system offers a good flexibility of use because the choice of multiplexing can be carried out before use of the microspheres, but it remains however limited to a reading system which is unique and requires numerous and expensive washes between the counts of the microbeads. which are essential, if not cross contaminations appear.

  Other recent developments, such as that of the company Febit (trademark) described in the document WO 00/12123, use the same principle previously described of colored microbeads, but associated with a transparent plastic device which keeps them side by side in a plan because their density does not allow good sedimentation. This device then allows a reading with a camera like biochips. This plastic device is associated with an inlet which leads to the device in plan and requires a circulation of a liquid which will carry the microbeads.

  This solution combines the advantage of a good flexibility in defining the analytes of the multiplexing associated with microbeads and the advantage of a disposable device containing the microbeads, all of which is disposable. On the other hand, the plastic object requires a carrier liquid which contains the microbeads, and a reading cell which holds the microbeads in a plane; this remains a source of problem associated with the microfluidics and thus with the friction which hinders the smooth flow of the microbeads in the planar part.

  The present invention aims to overcome these disadvantages and, in particular to reduce the waste of reagents, the need for washing and the risk of rubbing balls against the walls of a cell.

  For this purpose the present invention aims, in a first aspect, a device for detecting and / or dosing molecules in a liquid, characterized in that it comprises: a support comprising at least one reaction compartment in which is placed said liquid, and another compartment, for each desired molecule, at least one colored magnetic microbead specific to said molecule of interest, for indexing, by color, the presence and / or the quantity of said desired molecule, a magnet and respective moving means of said magnet and said support for moving each colored magnetic microbead placed in the magnetic field of said magnet from the reaction compartment in said other compartment.

  Thanks to these provisions, the desired molecules are detected according to the colors of the microbeads and their displacement is performed by moving respectively the magnet and the support.

  Thus, the colored magnetic microbeads can successively be used to effect a reaction in the reaction compartment, followed by revelation in a revealing compartment and then reading in a reading compartment without leaving the support. It is observed that certain compartments may have several functions successively, it being understood that at least two compartments are provided in the; device object of the present invention.

  The colored magnetic microbeads, which remain in the magnetic field of the magnet are moved relative to the disposable to move from one compartment to another. It is observed that the respective movement of the magnet relative to the disposable can be performed by holding the disposable and moving the magnet and / or holding the magnet fixed and moving the disposable.

  According to particular features, said support comprises a disposable 25 comprising at least the reaction compartment, at least one revealing compartment and at least one reading compartment, and at least one dry separation zone of at least two of said compartments, each compartment and each dry zone of separation being adapted to receive colored magnetic microbeads and to allow their displacement from one compartment to another inside the disposable. By passing through dry areas, the colored magnetic microbeads avoid contamination of the baths present in the various compartments of the device.

  According to particular features, the device as briefly described above comprises means for controlling the respective displacement of the magnet relative to the disposable.

  Thanks to these provisions, the operations can be performed automatically.

  - - - - - - - '.- -'. - _ ..,, __. 11, I - 1. . .,. ... 1 - l -.,., .. -. . According to particular features, the device as briefly described above comprises a filling means and a purge means of at least one compartment.

  Thanks to these provisions, on the one hand, a cleaning of the colored magnetic microbeads can be carried out in several baths successively placed in the same compartment and, on the other hand, the same compartment can be used for several steps of the detection method and or dosage.

  According to particular features, the device as briefly described above comprises a plurality of reservoirs each containing at least one colored magnetic microbead specific for a desired molecule and a means for selectively feeding colored magnetic microbeads originating from a molecule. part of the plurality of tanks.

  Thanks to these provisions, depending on the molecules whose detection and / or dosage is sought, the colored magnetic microbeads from different reservoirs are used and the waste of reagents and / or colored magnetic microbeads is avoided.

  According to particular features, the selective feed means comprises a carousel on which the various tanks are supported. Thanks to these provisions, the supply means is particularly simple to implement.

  According to particular features, the device as briefly described above comprises a magnetic pipetting arm. Thanks to these provisions, colored magnetic microbeads can be removed and moved easily and carrying a small amount of liquid.

  According to particular features, the carrier is adapted to carry out a polymerase chain reaction known as polymerase chain reaction PCR in the reaction compartment. Thanks to these provisions, small amounts of molecules, in particular nucleic acids, can be used.

  According to particular features, the device as briefly described above comprises a temperature control means of a reaction compartment. With these provisions, a chain polymerization reaction can be carried out in a reaction compartment.

  According to particular features, the device as briefly described above comprises means for analyzing the kinetics of appearance of read signals.

  Thanks to these provisions, the detection and / or dosage of the desired molecules is more precise.

  - 1 1.. .:. I. - - - 1 _ - -. - -_ - - -, - --- - - - 7, - --- - -. - - Mr 1 -I 1 1 - -. 1 -. ,. -. , - 1, - - 1 -, - - - - 1- - - - - -__ _ -1 - - 1 - - - -, - = - - -,,. According to particular features, the device as briefly described above comprises an optoelectronic sensor. Thanks to these provisions, the detection and / or dosage of the desired molecules is performed by electronic means, possibly digital, which allows a better reliability and automaticity of the results.

  According to particular features, the optoelectronic sensor is an electronic camera comprising a lens provided with a polarizing filter whose polarization axis is crossed with respect to a polarization axis of each polarizing filter associated with a light source illuminating the battery compartment. reading.

  According to particular features, the light source illuminating the reading compartment is an annular illumination centered on the optical axis of the camera lens.

  Thanks to each of these provisions, the direct reflections on the colored magnetic microbeads are reduced and the image analysis is improved.

  According to a second aspect, the present invention aims a method for detecting and / or assaying molecules in a liquid, characterized in that it comprises: a filling step during which said liquid is placed in a reaction compartment a support comprising at least said reaction compartment and another compartment, - a placement step during which, for each molecule sought, is placed in the reaction compartment, at least one colored magnetic microbead specific to said molecule sought, to index, by color, the presence and / or the amount of said desired molecule and - a respective step of moving a magnet and said support to move each colored magnetic microbead placed in the magnetic field of said magnet since the reaction compartment in said other compartment.

  According to particular features, the process as briefly described above comprises a step of selective sampling of at least one colored magnetic microbead specific to a desired molecule in at least one part of a plurality of reservoirs each containing at least one less a colored magnetic microbead specific to a molecule that may be sought in a liquid.

  According to particular features, the process as succinctly set forth above comprises a polymerase chain reaction step known as PCR for polymerase chain reaction.

  According to particular features, the method as briefly described above comprises a reading step with an optoelectronic sensor.

  According to particular features, the method as briefly described above comprises a step of analyzing the kinetics of appearance of read signals.

  Since the advantages, aims and particular characteristics of the method that are the subject of the present invention being similar to those of the device that is the subject of the present invention, they are not recalled here.

  Other advantages, aims and features of the present invention will become apparent from the following description, given for the purpose of explanation and in no way limitative, with reference to the appended drawings, in which: FIG. 1 represents, schematically, in partial top view, In a particular embodiment of the device which is the subject of the present invention, FIG. 2 schematically represents, in partial elevational view, the particular embodiment of the device of the present invention illustrated in FIG. 1 and FIGS. 313 represent a particular embodiment of the method which is the subject of the present invention.

  It is noted that in Figures 1 and 2, the scales are not respected. In particular, the vertical and horizontal scales are not identical.

  FIGS. 1 and 2 show a device 10 for detecting and / or assaying molecules 11, comprising a device 12 having, itself, a reaction compartment 13, a washing compartment 14, a revealing compartment 15 and a reading compartment 16.

  The disposable 12 is preferably made of a transparent plastic material, for example polystyrene or molded methacrylate.

  Dry zones of separation 17, 18 and 19 separate the compartments so that the liquids contained in these compartments can not mix. The dry zones 17, 18 and 19 take the form of siphons or thresholds containing air in their upper part.

  Each compartment and each dry zone of separation is adapted to receive colored magnetic microbeads 20 and to allow them to move from one compartment to another inside the device 12.

  Ligands specific to the desired molecules, or target molecules are attached to the surface of the colored magnetic microbeads 20 to extract said target molecule, specific to the microbead and therefore to its color, of a sample, the magnetism of the microbeads making it possible to transport them. one reaction medium to another. The target molecules are then revealed in the revealing compartment by other ligands causing a change in the color of the colored magnetic microbead. The reading of the detection or the quantity of each molecule sought is then carried out by analyzing the color of the microbeads, the color being indexed to the type of molecule sought and varying according to the presence or absence of the molecule sought.

  A movable magnet 21 is disposed below the device 12. A means 22 for displacing the magnet 21 and the device 12 respectively, move the magnet 21 and / or the device 12 from each respective position in which the magnet 21 magnet 21 is facing a compartment to each other respective position in which the magnet 21 is facing another compartment, passing through a position in which the magnet 21 is facing a dry zone of seperation.

  Control means (not shown) for respective displacement of the magnet 10 relative to the disposable controls the displacements of the displacement means 22. The displacement means 22 is, for example, constituted of a stepper motor controlled by a PLC or a computer (not shown) constituting the control means.

  Filling means 24 and purge means 25 act on the washing compartment 14 to alternately fill and empty it to perform successive washings of colored magnetic microbeads described below.

  It is observed that the filling and purging means of others: compartments are not shown in the figures, for the sake of clarity thereof. They are, however, substantially identical to those of the washing compartment.

  The filling and purging means are, for example, constituted by pipettes connected to pumps for pouring, respectively sucking, liquid into the washing compartment 14.

  A plurality of reservoirs 26 to 29 each contain a type of colored magnetic microbeads 20, for example preserved in physiological saline. A means for selectively feeding colored magnetic microbeads from a portion of the plurality of reservoirs 26 to 29 includes a carousel 32 on which the various reservoirs 26 to 29 are supported and a magnetic pipetting arm 33. The carousel is controlled by rotation by a PLC or computer (not shown).

  The colored magnetic microbeads 20, constituted according to known techniques and having diameters preferably between 7 and 50 μm, allow the color to be indexed by the parameter to be assayed and to carry out a flexible multiplexing.

  associated with a reading of the multiplexed colored magnetic microbeads, by an optoelectronic sensor 34, for example a color camera with a charge transfer device known under the name of CCD for chargecoupled device.

  Thus, the magnet 21 allows the colored magnetic microbeads 20 to pass from one compartment to another of the disposable device 12 by passing through dry or threshold zones separating the compartments containing different reagents which must not mix.

  In addition, no liquid is used to carry the colored magnetic microbeads, but the colored magnetic microbeads are moved by the magnet 21 which moves them in the different compartments of the device 12.

  In addition, it is the magnet 21 which keeps the colored magnetic microbeads in a plane against the wall of the disposable 12, which is preferable for reading by the camera 34. This characteristic also makes it possible to overcome the problems The flow of the colored magnetic microbeads is absent because there is no geometrical stress for the colored magnetic microbeads.

  The reading compartment 16 has, alternatively, privileged positions in which the colored magnetic microbeads are positioned spontaneously. For example, the preferred positions are regularly spaced hollows formed by molding in the bottom of the reading compartment. Thus, the colored magnetic microbeads are spaced from one another and the reading of a microbead is not disturbed by the reflections and the color of the other colored magnetic microbeads.

  The optoelectronic sensor 34 is an electronic camera comprising a lens 36 provided with a polarizing filter 37 whose polarization axis is crossed with respect to a polarization axis of a polarizing filter 38 associated with a light source 39 illuminating the beam. reading compartment. The light source 39 is, preferably, an annular illumination centered on the optical axis of the objective 36 of the camera 34.

  Apparatus for analyzing the appearance of read signals 35 receives the image signals from the camera 34 and analyzes them, on the one hand, image by image, to detect the apparent color variations of the colored magnetic microbeads and On the other hand, in the long run, to process the speed of these color variations.

  For example, the analysis means consists of a digitization card of signals from the optoelectronic sensor 34 and a computer (not shown) implementing an appropriate image processing software.

  The assay means then determines the presence and / or amount of desired molecules in the liquid initially placed in the reaction compartment.

  In the embodiment described and shown in the figures, the disposable 12 is adapted to perform a polymerase chain reaction known as polymerase chain reaction PCR. For this purpose, the device 10 comprises a temperature control means 40 of the reaction compartment 13. The operation and the reagents used in the PCR reaction are known per se and are not described here.

  The temperature control means 40 comprises, for example, a resistor whose heating is controlled by a computer or an automaton (not shown).

  The different computers mentioned in the description with reference to FIGS. 1 and 2 are preferentially merged into a single computer. Likewise, the various automata mentioned in the description with reference to FIGS. 1 and 2 are preferentially merged, possibly in the form of a PLC card of the aforementioned computer.

  FIG. 3A and 3B show the succession of the following steps: positioning of a new disposable, step 60, displacement of the magnet under the reaction compartment, step 61, programming of the molecules to be detected, step 62, filling of the reaction compartment with the liquid product in which the molecules are sought, step 63, PCR, optionally, step 64, sampling of the corresponding colored magnetic microbeads in the cells.

  reservoirs, by movement control of the carousel and the magnetic pipetting arm, step 65, - deposition of the colored magnetic microbeads in the reaction chamber by displacement and inversion of magnetic polarity of the magnetic pipetting arm, step 66, - reaction between the liquid in which molecules are searched for and the ligands of the colored magnetic microbeads, step 67, - filling of the washing compartment, for example with water, step 68, - displacement of the magnet to move the colored magnetic microbeads in the zone drying or threshold separating the reaction compartment from the washing compartment, step 69, - moving the magnet to move the colored magnetic microbeads in the washing compartment, step 70, moving the magnet to move the colored magnetic microbeads 30 in the dry zone or threshold separating the reaction compartment from the washing compartment, step 71 - purging the washing compartment, step 72, - filling the washing compartment, for example with water, step 73, - moving the magnet to move the colored magnetic microbeads in the washing compartment, step 74 , optionally repeating the washing steps (symbolized by a dotted arrow), - moving the magnet to move the colored magnetic microbeads in the dry zone separating the washing compartment from the revealing compartment, step 75 (FIG. 3B), filling the revealing compartment with revealing products, step 76, moving the magnet to move the colored magnetic microbeads in the revealing compartment, step 77, filling the washing compartment, for example with water , step 78, - moving the magnet to move the colored magnetic microbeads in the washing compartment, step 79, - washing as indicated above step 80, moving the magnet to move the colored magnetic microbeads in the dry zone separating the washing compartment from the reading compartment and then into the reading compartment, step 81, taking an image or reading the images. beads in the reading compartment, step - processing of the image taken, step 83, - repetition of the last two steps, at time intervals, preferably regular, - processing of the kinematics of color variation, step 84 and - determination of presence and / or quantity of molecules sought, step 85.

  An example of a test of the device illustrated in FIGS. 1 and 2 is given below.

  Magnetic stained microspheres with a diameter of 50 μm and of yellow and red color are coated with a DNA probe directed against the bacterium Ecoli and the bacterium B.subtilis respectively and specifically.

  A solution 1 containing amplified E. coli DNA is prepared in phosphate buffer pH 5.2, 0.15 M NaCl. This solution is obtained by PCR amplification using a pair of primers, or primers. , one of which is biotinylated.

  A solution 2 containing amplified B.subtilis DNA is prepared in phosphate buffer pH 5.2, 0.15 M NaCl. This solution is obtained by PCR amplification using a pair of primers, or primers, one of which is biotinylated.

  A solution 3 containing amplified DNA of B. subtilis and E. coli is prepared by mixing the two previous ones.

  _-,. : _ Z, - .-- -, - -. -. A reagent is prepared, containing a visualization system consisting of a peroxidase enzyme, or marker, in solution bound to a molecule of streptavidin, molecule used. in PCR.

  The enzyme is revealed by the degradation of a tetramethylbenzidine substrate (TMB) into a precipitating blue deposit.

  Three disposables whose capacity of each compartment is 200 μl each receive about 50 yellow microbeads and about 50 red microbeads coated with E.coli probes and B.subtilis respectively in 50 μl of buffer solution.

  The three solutions are distributed at a rate of 50 μl per reaction compartment, each disposable receiving only one solution, and incubated for 30 minutes at 60 ° C.

  A magnet is then applied under the reaction compartment and the microbeads are conveyed into the washing compartment, the microbeads being retained and moved under the influence of the magnet. 100 μl of wash buffer are put in place and emptied, or purged, using the magnet to hold the microbeads. This washing operation of the microbeads is repeated three times.

  The microbeads are then transported into the revealing compartment where the enzyme linked to streptavidin is placed at 50 μl per revealing compartment and incubated for 30 minutes at 37 ° C.

  After washing as before, in the washing compartment, 50 μl of TMB is dispensed per revealing compartment.

  The magnetic microbeads are then conveyed in the reading compartment, where they are all positioned in the same plane at the bottom of the reading compartment under the action of the magnet and the reading compartment is then read from above at intervals of time. regular for 30 minutes by an electronic camera. The images are analyzed and processed, both one by one and in the progression of the color variations, and make it possible to highlight the results, ie the detection or the determination of the desired molecules, by the modification of the colors.

  The biotinylated DNAs hybridize with the corresponding probes on the microbeads of corresponding color. The hybridized DNAs then affinityate between biotin and streptavidin, retain the enzyme which allows local deposition of the blue color, inducing a color change of the microbead.

  The first disposable contains yellow microbeads and dark red to violet microbeads, which corresponds to the revelation of the B. subtilis DNA solution.

  Precipitation of TMB blue substrate changes the color of the dark red / violet red microbeads revealing the presence of B. subtilis.

  - 1 - - -------- The second disposable contains green microbeads and red microbeads, which corresponds to the revelation of E. coli DNA. TMB blue substrate precipitation changes the color of green yellow microbeads to reveal the presence of B. subtilis.

  The third disposable contains green microbeads and red microbeads, which corresponds to the revelation of E. coli and B. subtilis DNA. TMB blue substrate precipitation changes the color of yellow to green microbeads and red microbeads to dark red / violet revealing the presence of B. subtilis and E. coli.

  The present invention is particularly applicable to immunoassay and nucleic acid assay, particularly for multiple detections (i.e., multiple molecules, e.g., nucleic acids and proteins). . It finds applications in the field of in vitro diagnostics.

Claims (14)

CLAIMS:   1 - Device for detecting and / or dosing (10) molecules in a liquid, characterized in that it comprises: - a support (12) comprising at least one reaction compartment (13) in which said liquid is placed, and another compartment (14, 15, 16), for each desired molecule, at least one colored magnetic microbead (20) specific for said molecule of interest, for indexing, by color, the presence and / or the quantity of said molecule sought, -a magnet (21) and - a respective moving means (22) of said magnet and said support for moving each colored magnetic microbead placed in the magnetic field of said magnet from the reaction compartment in said other compartment.   2 - Device according to claim 1, characterized in that said support comprises a disposable (12) comprising at least the reaction compartment (13), at least one revealing compartment (15) and at least one reading compartment (16) and at least one dry zone (17, 18, 19) for separating at least two of said compartments, each compartment and each dry separation zone being adapted to receive colored magnetic microbeads (20) and to allow their displacement. from one compartment to another, inside the disposable.   3 - Device according to any one of claims 1 or 2, characterized in that it comprises a respective displacement control means of the magnet relative to the disposable.   4 - Device according to any one of claims 1 to 3, characterized in that it comprises a filling means (24) and a purge means (25) of at least one compartment.   - Device according to any one of claims 1 to 4, characterized in that it comprises a plurality of reservoirs (26 to 29) each containing at least one colored magnetic microbead specific to a desired molecule and a supply means selective (32, 33) colored magnetic microbeads from a portion of the plurality of reservoirs.   6 - Device according to claim 5, characterized in that the selective feed means comprises a carousel (32) on which are supported the various reservoirs (26 to 29).   7 - Device according to any one of claims 1 to 6, characterized in that it comprises a magnetic pipetting arm (33).   8 - Device according to any one of claims 1 to 7, characterized in that the carrier (12) is adapted to perform a polymerization chain reaction: known as PCR for polymerase chain reaction, in the compartment of reaction (13).   9 - Device according to any one of claims 1 to 8, characterized in that it comprises a temperature control means (40) of a reaction compartment (13).   - Device according to any one of claims 1 to 9, characterized in that it comprises a read signal kinetics analysis means read (35).   11 - Device according to any one of claims 1 to 10, characterized in that it comprises an optoelectronic sensor (34).   12 - Device according to claim 11, characterized in that the sensor: optoelectronic (34) is an electronic camera comprising a lens (36) provided with a polarizing filter (37) whose polarization axis is crossed with respect to a polarization axis of each polarizing filter (38) associated with a light source (39) illuminating the reading compartment.   13 - Device according to claim 12, characterized in that the light source (39) illuminating the reading compartment is an annular illumination centered on the optical axis of the lens (36) of the camera (34).   14 - Method for detecting and / or assaying molecules in a liquid, characterized in that it comprises: - a filling step (63) during which said liquid is placed in a reaction compartment (13) of a support (12) comprising at least said reaction compartment and another compartment (14, 15, 16), - a placing step (65, 66) during which, for each desired molecule, is placed, in the reaction chamber, at least one colored magnetic microbead (20) specific to said desired molecule, for indexing, by color, the presence and / or quantity of said desired molecule and - a step of moving (69, 70, 71, 74, 75, 77, 79, 81) of a magnet (21) and said holder for moving each colored magnetic microbead placed in the magnetic field of said magnet from the reaction compartment into said other compartment.   - Process according to claim 14, characterized in that it comprises a step of selective sampling (65) of at least one colored magnetic microbead specific to a molecule sought in at least a part of a plurality of reservoirs (26 to 29) each containing at least one colored magnetic microbead specific for a molecule that can be searched for in a liquid.   16. The process according to any of claims 14 or 15, characterized in that it comprises a chain polymerization reaction step (64) known as PCR for polymerase chain reaction.   17 - Process according to any one of claims 14 to 16, characterized in that it comprises a reading step (82, 83) with an optoelectronic sensor (34). 18 - Process according to any one of claims 14 to 17, characterized in that it comprises a step of analysis of kinetics of appearance of read signals (84).