GB2370112A

GB2370112A - Multiwell sample plates

Info

Publication number: GB2370112A
Application number: GB0030683A
Authority: GB
Inventors: William Lindsay; James Courtney
Original assignee: Hybaid Ltd
Current assignee: Hybaid Ltd
Priority date: 2000-12-15
Filing date: 2000-12-15
Publication date: 2002-06-19
Also published as: GB0030683D0

Abstract

A sample well plate 10 includes an array of sample wells 12 and substantially flat top and bottom plate surfaces 14, 16. At least one of the top and bottom plate surfaces is heat conductive. The plate is used in testing or reacting a large number of samples and can provide very small sample wells, for example 5 microlitres or less in volume. The plate may be fabricated from a ceramic, polycarbonate, gold, aluminium, silver etc. The plate optionally provides a path for illumination through or in the wells. Utility is in polymerised chain reaction processes.

Description

REAGENT PLATE

The present invention relates to a sample well plate for holding reagent samples for testing and reaction purposes. The sample well plate is suitable for use in a large variety of tests and reactions including polymerised chain reactions (PCR).

Conventional apparatus provides a sample plate having an array of sample wells depending from a top surface of the sample plate. The reaction or test apparatus includes a temperature regulated block which has an array of recesses arranged such that each sample well of the plate fits within an associated recess of the temperature regulated block. The arrangement provides good thermal contact between a reagent in a sample well and the temperature regulated block since the sample effectively sits within the temperature regulated block. However, the system can only be used with matching sample plates and in practice has a limited minimum sample well size.

The present invention seeks to provide an improved sample well plate and apparatus therefor.

According to an aspect of the present invention, there is provided a sample well plate including an array of sample wells and substantially flat top and bottom plate surfaces, at least one of the top and bottom plate surfaces being heat conductive.

Such a sample well plate can be placed on a substantially flat temperature regulated block, with the result that the arrangement of sample wells can be altered at will without the need to modify the apparatus with which the sample well plate is used. Moreover, as a result of the simplified structure, the volume of the sample wells can be reduced substantially relative to conventional sample well plates, thereby being able to accommodate smaller amounts of reagents. Another important advantage of this structure is that it is possible to provide many more sample wells within a specified area and the applicant has already been able to develop a prototype with 1536 sample wells.

This allows many more samples to be tested at the same time under the same test conditions.

The sample well plate can be formed in a variety of different manners. For example, it may be formed as a unitary structure with the sample wells being cast, moulded or drilled therein. An alternative is to produce the plate in a plurality of layers, for example two, with a first layer being formed with an array of bores and a second unperforated layer forming the bottom surface of the plate and the bottom wall of the sample wells.

The sample well plate may be made of a single material or of a plurality of materials, depending upon the intended applications of the plate. Some examples are described below.

In the preferred embodiment, the sample well plate provides a path for illumination through or in the sample wells, for measurement of a reaction (by suitable detection means) or for initiating the reaction. For example, the bottom surface may be transparent or translucent to allow the passage of light therethrough. Alternatively, the bottom surface may be reflective to reflect light directed into the sample wells. This feature can provide a very convenient arrangement for measuring the light properties, for example fluorescence, of samples in the sample wells.

According to another aspect of the present invention, there is provided apparatus for accommodating a sample well plate as specified herein including a temperature regulated block having a substantially flat sample well plate contact surface. Advantageously, the apparatus includes clamping means operable to clamp one or more sample well plates to the temperature regulated block. The clamping means may be provided on or adjacent the temperature regulated block or on a cover which in use is placed over the temperature regulated block.

The apparatus may be a thermal cycler. It is envisaged that the sample well plate would be tested at a uniform temperature, although it is envisaged that it could be subjected to a temperature gradient, particularly a sample well plate having a large number of sample wells. Suitable means for producing a temperature gradient are disclosed in the applicant's International patent application WO-00/32312.

According to another aspect of the present invention, there is provided apparatus for carrying out a polymerase chain reaction including provision for a sample well plate as specified herein.

According to another aspect of the present invention, there is provided a method of carrying out a polymerase chain reaction in which reagents are reacted in a sample well plate as specified herein An embodiment of the present invention is described below, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of an embodiment of sample well plate ; and Figure 2 is a schematic diagram of an example of illumination and image recording system.

Referring to Figure 1, there is shown an embodiment of sample well plate 10 having 96 sample wells 12 (only some of which are shown in Figure 1). The sample well plate 10 in this example could be said to have a shape and dimensions similar to a microscope slide, although it could have a variety of shapes and dimensions depending upon the desired application. Moreover, plates having substantially more sample wells are possible and a prototype with 1536 wells has been developed by the applicant.

The plate 10 is provided with substantially flat top and bottom surfaces 14,16. The wells 12 are open at the top surface 14 and are closed at the bottom surface 16. In the preferred embodiment, the thickness of the bottom walls of the wells 12, that is the distance from the bottom of each well 12 to the bottom surface 16, is around 0.2 mm.

The actual thickness depends upon the materials chosen for the plate 10 or for its bottom layer if this is formed of different materials, and the size and shape of the sample wells 12. In practice, it is envisaged that this wall thickness will be considerably less than the wall thickness of wells of conventional sample wells, which are typically 0.3 to 0.6 mm

or more. Of course, conventional sample wells must be strong enough to withstand handling despite their exposed nature.

The plate 10 can be made of a variety of materials. Examples are ceramics such as Beryllia, polycarbonate, glass-based materials and metal such as aluminium, gold, copper or silver.

The plate 10 can also be made of several layers, possibly of different materials. For example, there may be provided a top layer providing the top surface 14 and having a plurality of bores therein which would form the sample wells 12, and a bottom unperforated layer which would provide the bottom surface 16 and the bottom walls of the sample wells 12.

Providing different layers can allow the plate 10 to have different characteristics. For example, at least one of the layers could be of a heat conductive material and the other of a light transmissive material.

An instance may be a metallic bottom layer and a glass or transparent plastics upper layer. This example would allow heating from the bottom and detection of optical properties of the samples under reaction or optical initiation of reactions from above (an example is given in connection with Figure 2). In this case, the bottom layer may also act as a light reflective layer for reflecting light from above.

Another instance may be the opposite, for example a metallic or heat conductive upper layer and a light transmissive bottom layer. In this case, the sample plate would be heated from above and light transmitted from below the sample plate. This example can provide an easy arrangement for light sources (below the plate) and optical detectors (above the plate).

To provide heat to the samples, either or both of the top and bottom surfaces of the plate 10 should be heat conductive.

The preferred embodiment of plate 10 has some or all of the following features : 1) Heat transfer properties : the material should preferably be capable of transfer of heat at a level similar to or exceeding that of ceramic Beryllia (260-300 w/m/k). Glass-based chips having substantially lesser conductivity may also be used. However, because of the direct contact between the reaction samples and the reagent plate in the preferred embodiment, materials having lower heat transfer capabilities can be employed.

2) Lack of porosity. No water loss should occur into or through the material at temperatures up to 100 C.

3) Ideally, the material should be sufficiently durable that it can be heated/cooled several thousand times without loss of shape, cracking etc. Besides temperatures of PCR cycling (up to 95OC), the material should preferably withstand higher temperatures for washing (up to 1500C).

4) The surface should be smooth such that repeated cleaning is possible and ideally should be resistant to cleaning agents such as detergents and sterilising agents such as ethanol.

5) There should be no effect on the reagents used in PCR (for example, high protein adsorption and so on).

6) The plate is preferably relatively thin (perhaps of the order of 1 to 2 mm).

7) Each reaction well is preferably less than 5 microlitres volume, more preferably from 1 to 4 microlitres, and most preferably 2 microlitres.

Referring now to Figure 2, there is shown in schematic form an example of apparatus designed for the sample well plate 10 of Figure 1.

The apparatus includes a temperature regulated block 18 having a substantially flat top surface 20 upon which the plate 10 rests. Heaters (not shown), such as Peltier elements are provided to heat and cool the temperature regulated block 18. A suitable arrangement is disclosed in the applicant's International patent application WO-00/32312.

Indeed, with some sample plates, for example larger sample plates, the apparatus may provide temperature gradients as taught in WO-00/32312.

Above the plate 10 there is provided an optical sensor 22, in this example a CCD (Charge Coupled Device) camera. Two light sources 24,26 are provided for illuminating the samples in the sample wells 12 and in this example these are conveniently located at the side of the CCD camera 22.

In a practical embodiment, the CCD camera (and light sources) could be provided in a lid of the apparatus which also acts as a clamp or holding means for holding the sample plate 10 against the temperature regulated block 20. Many other arrangements are also envisaged. For example, as explained above, the top or sides of the plate 10 could be heated with light being directed from below the plate 10. Similarly, light could be directed through the sides of the plate 10 (in the case that the plate or a substantial part thereof is transparent or translucent).

In this regard, the plate 10 may be formed of a material which acts as a light filter in order to radiate the reaction samples with light of the appropriate wavelength to initiate the reaction.

In alternative embodiments, a thermal gradient could be provided by having the lower surface 16 of the plate 10 of different thermal conductivity. For example, the plate 10 may have wells 12 of differing volumes and/or depths, so as to result in a thermal gradient across the reagent plate, depending on the depth of material between the bottom of the plate and the bottom of each well.

Claims

1. A sample well plate including an array of sample wells and substantially flat top and bottom plate surfaces, at least one of the top and bottom plate surfaces being heat conductive.

2. A sample well plate according to claim 1, wherein the plate is formed as a unitary structure.

3. A sample well plate according to claim 1, wherein the plate is formed as a plurality of layers

4. A sample well plate according to claim 1,2 or 3, wherein the plate is made of a single material or of a plurality of materials.

5. A sample well plate according to any preceding claim, wherein the plate provides a path for illumination through or in the sample wells.

6. A sample well plate according to claim 5, wherein the bottom surface is transparent or translucent or reflective.

7. Apparatus for accommodating a sample well plate according to any preceding claim, including a temperature regulated block having a substantially flat sample well plate contact surface.

8. Apparatus according to claim 7, wherein the apparatus is a thermal cycler.

9. Apparatus according to claim 7 or 8, including heating and/or cooling means operable to create a temperature gradient across a sample plate.

10. Apparatus for carrying out a polymerase chain reaction including provision for a sample well plate according to any one of claims 1 to 6.

11. A method of carrying out a polymerase chain reaction in which reagents are reacted in a sample well plate according to any one of claims 1 to 6.