FR2794861A1 - Device for reading a biochip comprises a light source for illuminating the biochip in the form of a strip covering at least one line of discrete zones - Google Patents

Abstract

Device for reading a biochip comprising at least one line of discrete zones comprises a light source for illuminating the biochip in the form of a strip covering at least one line of discrete zones and a detector for detecting the fluorescence emitted by the biochip. An Independent claim is also include for a biochip comprising: (a) at least one line of discrete zones, each containing a substance capable of emitting fluorescent light when the surface of the chip is illuminated; and (b) a series of synchronization zones permitting movement of the chip and fluorescence detection to be synchronized.

Description

TECHNICAL FIELD AND PRIOR ART The invention relates to a device for reading a biological chip.

More particularly, the invention relates to a nucleic acid chip reading device commonly referred to as a DNA chip (DNA for Deoxyribonucleic Acid).

The invention has applications in many fields such as, for example, the field of molecular biology for the recognition of antibodies and antigens, genome sequencing, the search for mutations responsible for diseases, and the like.

The biological chip reading devices use the fluorescence technique.

The fluorescence technique consists in mixing a substance whose identification and / or concentration is to be determined with a substance having the ability to emit fluorescent light under the action of light radiation.

A DNA chip consists of a matrix of N x M pads, each pad containing a mixture of substances as mentioned above, that is to say likely to emit fluorescent light by illumination. According to the known art, the reading of a DNA chip is carried out either by simultaneous illumination of all the pads of the chip, or by scanning the chip plot by pad.

US-A-5 578 832, WO-97 4361 and US-A-5 646 411 disclose reading devices comprising a scanning microscope used in confocal or non-confocal to parcel plot a DNA chip.

US-A-5 585 639 discloses a linear array reading device for sequential reading of the chip and reconstruction of the 2D image of the fluorescence of the chip.

The reading device performs a linear scan of the different pads of the chip. A motor drives a rotating mirror to allow a light beam to scan along a line. The complete scanning of the chip is obtained by translation of a support on which the chip is positioned.

Reading devices such as those mentioned above require the DNA chip to be positioned with great accuracy with respect to the light beam. It is also necessary that an almost perfect focusing of the light beam on the surface of the chip be carried out.

Such devices are difficult to develop. The adjustment time that precedes the start of the fluorescence measurements can be relatively long.

The invention does not have these disadvantages. Indeed, the invention relates to a fluorescence reading device of a biological chip comprising at least one line of M pads, the device comprising means for illuminating the biological chip and means for detecting a fluorescent light from the chip. The means for illuminating the biological chip comprises means for illuminating the chip in the form of a strip of light covering at least one line of M pads.

The invention also relates to a biological chip comprising at least one line of M pads, each pad containing a substance that can emit fluorescent light under the action of a lighting means of the surface of the chip, the fluorescent light emitted being detected by a detection means. The biological chip comprises on its surface means for synchronizing a movement of the chip and the detection of fluorescent light.

An advantage of the invention is that it does not require precise positioning of the chip with respect to the illumination means of the chip.

BRIEF DESCRIPTION OF THE DRAWINGS Other characteristics and advantages of the invention will appear on reading a preferred embodiment of the invention with reference to the appended figures among which: FIG. 1 FIG. 2 represents a first embodiment of the biological chip reading device according to the invention; FIG. 3 represents a biological chip corresponding to a reading device according to the first embodiment of the invention, - Figure 4 shows a second embodiment of the biological chip reading device according to the invention.

In all the figures, the same references designate the same elements.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION FIG. 1 represents a block diagram of a biological chip reading device according to the invention.

The reading device comprises a lighting means (F, 1) of a biological chip 5 and a means (2, 3, 4) for detecting the fluorescent light coming from the biological chip.

The illumination means of the chip comprises an optical element 1, such as, for example, a Pauwell lens, for transforming a laser beam F into a band B of laser light making it possible to illuminate at least one line of M Plots Pl , P2, ..., PM of the chip 5.

Preferably, a single row of pads is illuminated by the band B of light. As will be described in more detail in FIG. 3, the width e of the band B is then slightly greater than the width of the pads P1, P2,..., PM of the same row of pads. By way of non-limiting example, a Pauwells lens makes it possible to obtain a strip of laser light approximately 100 μm wide by 5 mm long, at a distance of 30 mm from the chip and at an incidence close to 45 mm. . For a laser beam of power substantially equal to 10 mW, the power density obtained on the surface of the chip is then about 0.02 uW / um2. An advantage of the invention is to be able to use a relatively low power microlaser while guaranteeing a relatively high power density on the illuminated pin line. Such a microlaser has a MTBF of 30000 hours. The biological chip reading device according to the invention then has high reliability.

est égale à

où W (communément appelé "waist") est la largeur de la bande de lumière à 1/e2 et k la longueur d'onde de la lumière. The depth of field of the laser light band, that is, the distance over which the width of the band increases by a factor

Equals

where W (commonly called "waist") is the width of the light band at 1 / e2 and k the wavelength of light.

In the example chosen, the depth of field is thus equal to 15 mm. Advantageously, according to the invention, there is therefore no problem of positioning, in height, the chip vis-à-vis the lighting means of the chip.

The means for detecting the fluorescent light from the biological chip 5 comprises an objective 2, an optical filter 3 and a detector 4. The detector 4 is preferably a CCD (Charge Coupled Device) type detector comprising a large number of image pixels.

Dans le cas de l'application de l'invention à une puce

de dimensions 0, 8mm x 1, 6mm, l'objectif 2 est choisi, par exemple, avec un grossissement de 5. Le champ image est alors de 4mm x 8mm. Le détecteur 4 peut être, par exemple, une barrette de type TDI (TDI pour "Time Delay Integration") comprenant des pixels image de 250 um x 250 um. The invention finds a particularly advantageous application in the case where the biological chip is of relatively small dimensions (for example 1 mm x 2 mm) and where the pads of the same line are relatively few (for example 10 to 100) and well spaced from each other (for example 100 um edge to edge). Such a chip may be, for example, a chip type

In the case of the application of the invention to a chip

dimensions 0, 8mm x 1, 6mm, the objective 2 is chosen, for example, with a magnification of 5. The image field is then 4mm x 8mm. The detector 4 may be, for example, a TDI (Time Delay Integration) type array comprising image pixels of 250 μm × 250 μm.

For an objective as mentioned above, that is to say magnifying 5 times, the opening can be of the order of <B> 0.1 </ B> and the positioning tolerance in height typically equal at 50 μm. It follows that the chip can be positioned with a tolerance of <B> 0.1 </ B> mm. For a chip having, for example, a length of 2 mm, the inclination that can present the axis defined by a line of pads relative to the axis defined by the detection strip can then advantageously reach 3.

The detection bar operates by summing the CCD lines. This results in excellent detection sensitivity (for example, a few tens of photons / um '/ s) as well as excellent dynamics (typically a dynamic of 16 bits).

Advantageously, the summation of the detected signals makes it possible to take into account all the power of the fluorescent light emitted by a pad, and this even in the case where the chip is inclined at an angle of a few degrees (typically less than or equal to 3, as in the example described above).

FIG. 2 represents a first embodiment of the biological chip reading device according to the invention.

The illumination means of the chip 5 comprises a radiation source 7, an optical element 6, a Pauwell lens 1 or a sphero-cylindrical optic.

The radiation source 7 is preferably a microlaser emitting in the green. By way of nonlimiting example, a microlaser having a power of the order of 10 mW and a beam diameter of the order of 200 μm can be used. The optical element 6 makes it possible to reduce by a factor of 2 the diameter of the laser beam. It is then possible to obtain a laser beam of diameter substantially equal to <B> 100 </ b> um at the output of the optical element 6.

The elements 1, 6, 7 which constitute the lighting means and the elements 2, 3, 4 which constitute the means for detecting the fluorescent light are integrated in a structure 9 of the card reader type having a slot 11. The chip Biological 5 is fixed on a support 8. The structure 9 comprises a motorized translation table 10 which allows the introduction of the support 8 in the structure 9 by the slot 11. The motorized translation table 10 is driven at a substantially constant speed . Advantageously, it is not necessary that the speed of translation of the table is controlled.

According to the first embodiment of the invention, it is during the gripping motion of the support 8 that the scanning of the chip 5 by the laser beam from the lighting means takes place. To this end, the device according to the invention comprises means (not shown in FIG. 2) for triggering the scanning of the chip during the introduction of the support 8 into the slot 11.

By way of non-limiting example, the support 8 on which is fixed the biological chip 5 may be in credit card format and the drive system of the support a drive system such as that of the bank card dispensers.

FIG. 3 represents a biological chip corresponding to a reading device according to the first embodiment of the invention.

Le nombre N est alors compris entre 1 et 1000 et le nombre M entre 1 et 100. Les plots d'une même ligne Pjl, Pj2, ..., PjM sont espacés, bord à bord, d'une distance d'environ 100 um. The biological chip 5 comprises N lines of M pads Pjl, Pj2,..., PjM (j = 1, 2, ..., N). The biological chip 5 is, for example, a chip of the type

The number N is then between 1 and 1000 and the number M between 1 and 100. The pads of the same line Pjl, Pj2, ..., PjM are spaced, edge to edge, a distance of about 100 um.

At each line of pads Pj1, Pj2, ..., PjM are associated synchronization pads aj, bj, cj, dj (j = 1, 2, ..., N).

The synchronization pads are arranged so as to define two tracks located on either side of the chip 5. The invention also relates to the case where the synchronization is obtained by a single track of pads. The presence of two tracks makes it possible to improve the synchronization and, possibly, to compensate for an inclination of the chip. A first track consists of the succession of synchronization pads al, cl, a2, c2, a3, c3, ..., aN, cN. A second track consists of the succession of synchronization pads b1, d1, b2, d2, b3, d3,..., BN, dN. The pads aj and bj (j = 1,2, ..., p) define an axis parallel to the axis defined by the line of pads <B> pi 1, <I> pi </ I> </ B> <I> 2, </ I> ..., PiM. The pads cj and dj also define an axis parallel to the line of pads Pjl, Pj 2,. . . , PJM.

The synchronization pads are able to reflect the light they receive from the lighting means. The light reflected simultaneously by a pair of pads (aj, bj) is detected by the detection means in the form of a pulse triggering the integration of the charges in the detector 4. Similarly, the light reflected simultaneously by a pair of pads (cj, dj) is detected by the detection means in the form of a pulse stopping the integration of the charges in the detector 4.

By way of nonlimiting example, the distance L1 which separates the synchronization pads aj and cj (respectively bj and dj) may be equal to 75 μm and the distance L2 which separates the synchronization pads cj and aj + 1 (respectively dj and bj + 1) may be 25 μm. For an illumination time of 100 ms between two successive integrations of charge charges into the detector 4, it is then possible to reserve the first 75 ms for the integration of the charges in the detector and the last 25 ms for the evacuation of integrated loads.

The scanning speed of the chip 5 can therefore be equal to <B> 100 </ B> μm / 100 ms, ie 1 mm / s. Advantageously, a complete scan of the chip can then be performed in a few seconds.

According to the embodiment of the invention described above, the synchronization between the movement of the chip and the detection is made using synchronization pads arranged on the chip.

The invention also relates to other modes of synchronization. This may be, for example, the use, in conjunction with magnetic encoders, magnetic tracks located on the surface of the chip or synchronization by drive system with encoder wheel.

FIG. 4 represents a second embodiment of the biological chip reading device according to the invention.

According to the embodiment of FIG. 4, the band B of laser light is scanned on the surface of the biological chip 5 by means of a deflector means 12 such as, for example, an acousto-optical deflector, a mirror galvanometric, etc.

According to this second embodiment of the invention, the scanning of the chip is not performed during the introduction of the support 8 into a structure 9. It is then not necessary that the biological chip comprises elements (pads synchronization, magnetic tracks) that participate in the synchronization between the scanning of the chip and the detection of fluorescence. The synchronization is then performed by any known means.

Claims (17)

1. A fluorescence readout device of a biological chip (5) comprising at least one line of M pads (Pj 1, Pj 2, ..., PjM), the device comprising means (F, 1) for illuminating the biological chip (5) and means (2, 3, 4) for detecting the fluorescent light from the biological chip (5), characterized in that the means (F, 1) for illuminating the biological chip (5) comprises a means (1) for illuminating the chip in the form of a strip (B) of light covering at least one line of M pads (Pjl, Pj2, ...., PjM). 2. Device according to claim 1, characterized in that it comprises a scanning means (10, 12) for the strip (B) of light sweeps the entire surface of the biological chip (4). 3. Device according to any one of claims 1 or 2, characterized in that it comprises synchronization means between the scanning means (10, 12) and the means (2, 3, 4) for detecting the fluorescent light . 4. Device according to any one of claims 2 or 3, characterized in that the scanning means (10, 12) is a motorized translation table (10). 5. Device according to any one of claims 2 or 3, characterized in that the scanning means (10, 12) is a deflector means (12) of the light from the means (1) for illuminating the chip (5) . 6. Device according to claim 4, characterized in that the synchronization means comprise signal processing means from the biological chip (5). 7. Device according to claim 6, characterized in that the signal processing means from the biological chip comprise magnetic coders. 8. Device according to any one of claims 3 to 5, characterized in that the synchronization means comprise a drive system with an encoder wheel. 9. Device according to any one of the preceding claims, characterized in that the means (2, 3, 4) for detecting the fluorescent light comprises a CCD detector (4). 10. Device according to any one of the preceding claims, characterized in that the means (2, 3, 4) for illuminating the biological chip (5) comprises a microlaser (7). 11. Device according to claim 10, characterized in that the microlaser (7) has a power substantially equal to 10 mW. 12. Device according to any one of the preceding claims, characterized in that the means (1) for illuminating the chip (5) in the form of a strip (B) of light covering at least one line of M pads (Pjl , Pj2, ..., PjM) is a Pauwells lens. 13. Device according to any one of claims 2 to 12, characterized in that it comprises a slot (11) by which is introduced a support (8) on which is fixed the biological chip (5). 14. Device according to claim 13, characterized in that it comprises means for triggering the scanning of the chip during the introduction of the support (8) in the slot (11). 15. Biological chip (5) comprising at least one line of M pads (Pjl, Pj2, ..., PjM), each pad containing a substance that can emit fluorescent light under the action of a lighting means of the surface of the chip, the fluorescent light emitted being detected by a detection means, characterized in that it comprises on its surface means (aj, bj, cj, dj) for synchronizing a movement of the chip and the detection of fluorescent light. 16. Biological chip (5) according to claim 15, characterized in that the means (aj, bj, cj, dj) for synchronizing the scanning of the chip and the detection of the fluorescent light are reflective pads defining at least one track. 17. Biological chip (5) according to claim 16, characterized in that the means (aj, bj, cj, dj) for synchronizing the movement of the chip and the detection of the fluorescent light comprise at least one magnetic track.