Microarrayer

Abstract: A manual microarrayer 20 is disclosed which includes an integral visual magnification system 20, alphanumeric counter 2 and LED display for tracking samples in a microtitre plate 1. The microarrayer 20 is preferably reversible so as to provide left and right handed user formats.

Description: At the simplest level, a microarrayer is used for transferring material from one location, the source, to a second location, the target. In practice, source material is usually biological material contained in a microtitre plate, and the target is either a glass microscope slide or nylon filter. Microarrayers are used to spot DNA or other biological material onto glass slides or other rigid substrates. It is possible to produce microarrays using either an automated system or by hand. Robotic systems have several advantages: they are fast and accurate and produce large numbers of identical arrays. They are, however, also relatively expensive from the point of view of initial purchase costs. A robotic arrayer is disclosed in nature genetics supplement, vol. 21, january 1999, p. 15-19. It is feasible to produce an array by hand if only a few slides, each with 200 different samples or less, are required. However, hand-spotting an array is only really practical with a feature pitch of approximately 1.0 mm (the feature pitch is the centre to centre distance between adjacent spots). Using a pitch of 1.0 mm and an 8 x 12 grid layout, which corresponds to a standard 96 well microtitre plate, allows up to 6 grids fitted on to a standard microscope slide. However, this does not leave much of a handling margin. Therefore, conventionally only two grids per slide are usually provided. Each grid can be different, or they can be duplicates. Because the most time-consuming element of producing an array is the cleaning cycle, it is common to work on several slides at the same time. It is desired to provide apparatus to assist in producing microarrays which is substantially cheaper than fully automated systems and which enables an operator to produce a microarray more quickly, accurately and at a smaller pitch spacing than is reliably possible using a naked eye. According to the present invention there is provided the combination of a band top workstation for facilitating hand spotted arrays and a pin for manually collecting a sample from a microtitre plate and for spotting said sample on a slide as claimed in claim 1. Preferably, the microarrayer further comprises a sample tracking device for indicating which wells of a microtitre plate have been sampled. The sample tracking device may comprise an array of LEDs, preferably arranged in a 8 x 12 or 16 x 24 format. The sample tracking device may be switched on and/or off, or may be otherwise operated by a foot pedal. Preferably, the visual magnification system provides at least a two-fold magnification. The visual magnification system may be a four-fold, six-fold, eight-fold or ten-fold magnification system. The visual magnification system may also have a magnification selected from the group of: (a) at least x5; (b) at least x10; (c) at least x20; and (d) at least x40. The visual magnification system may comprise a stereo zoom microscope, and/or it may comprise a head-up display. Preferably, the microarrayer further comprises an integral light source, further preferably dichroic. An advantage of the present invention is that more microarrays can be arranged on a single slide then is conventionally possible. Various embodiments of the present invention will now be described, by way of example only, and with reference to the accompanying drawing in which: Fig. 1 shows a preferred microarrayer. A microarrayer 20 according to an embodiment of the present invention is shown in Fig. 1. The microarrayer 20 has a wash bath section 11, a sample tray section 12, a body 13, a slide plate section 14, a counter section 15, and a fascia 16. The microarrayer 20 accommodates a sample tray 1 and has an integral sample well counter 2 (preferably alphanumeric), a storage compartment with a storage access lid 3 shown in a closed position, a magnification system 4, a pin storage area 5, a storage access lid 6, a slide storage area 7, a plate storage area 8, and a wash bath 9. A reference frame 10 (indexed A-H, 1-12 or A-P, 1-24) is also preferably provided. Separate sheltered storage areas for clean and arrayed slides, as well as for spotting pins, are provided. Each workstation or microarrayer 20 preferably has a cleaning station or wash bath section 11 consisting of four stainless steel or plastic trays (approx. 55 x 35 x 20mm deep), a sample source holder for one or more microtitre plates (86 x 128 mm), a slide spotting area 14 for three slides (total area 75 x 75 mm), a pin storage area 5 for 40 to 75mm long pins, an instrument rest (handle is approx. 10mm diameter), a counter 2, and a stereo zoom microscope or an eyepieceless low magnification stereo spatial imaging system. The counter 2 in one embodiment is capable of sequentially indicating 96 wells (A1 to H12) and/or 384 wells (A1 to P24), and can be reset at any time. Various different pitch spacings can be achieved using the apparatus of the present invention. For reference, at a feature pitch of 1.0 mm, single copies of 96 samples will occupy an area 8 x 12 mm; at a feature pitch of 0.5 mm, single copies of 96 samples will occupy an area of 4 x 6 mm; and at a feature pitch of 0.2 mm, single copies of 96 samples will occupy an area of 1.4 x 2.2 mm. The bench-top workstation or microarrayer 20 according to the preferred embodiment has been designed to facilitate the production of hand spotted arrays. Preferably a stereo zoom microscope with an integral light source is provided which enables arrays pitched at e.g. 1.0mm, 0.5 mm, 0.2 mm or less to be produced. The system preferably has a magnification within the range of x5 to x40 (with a conventional stereo zoom microscope) or x2 to x10 with an eyepieceless low magnification stereo spatial imaging system or viewer. According to the preferred embodiment a stereo zoom microscope at six fold magnification is provided which enables 0.5 mm, 0.4 mm, 0.3 mm, and 0.2 mm or smaller pitch arrays to be produced. These formats enable many grids to be put on a single slide. Grids may be laid with the aid of a template placed underneath the slide. This can be a piece of graph paper taped to the underside of the slide, an indexed printed grid, or an engraved stage similar to a microscope stage. According to another embodiment an indexed adhesive label is used for each slide. This provides a permanent means for identifying each sample within a grid. According to a particularly preferred embodiment, a grid template may be provided above the slide, and used as a guide for an operator. Samples may be spotted out using a printing pin similar or substantially identical to those used in automated apparatus. Spots are produced by gently touching the pin down onto the slide surface. The first few spots should preferably be made onto a waste area, as they are inevitably uneven until excess sample material on the side of the pin has drained away. To produce a circular spot the pin should be held as vertically as possible. If the angle is much less than 80°, the spots will be oval. Pins should be touched down gently but firmly. If not, then the spots tend to end up comma shaped. The dwell time (how long the pin actually touches the surface) also affects the volume that is deposited. Too much sample results an uneven "cracked" spot or a doughnut effect. Neither such shapes are good for reading the array following hybridisation. The effectiveness of the cleaning protocols can be checked using fluorescent dyes. The pin must be cleaned between successive samples. A simple 4-stage process is adequate. The pin is first touched down onto a blotting pad to remove sample material, then washed in distilled water and rinsed in 95% ethanol. Finally, the pin is dried by blotting onto a second pad. Following the completion of each set of slides, the pin is cleaned using ultrasound. Sample material is colorless and dries almost instantly when spotted out, making it extremely easy for an operator to lose track of where he/she is. Accordingly, conventionally it has been problematic to keep track of which samples have been spotted out and of their locations within a microarray. A particuarly preferred embodiment includes a sample tracking device (preferably a LED display) and an alphanumeric counter which are provided to indicate to a user which wells of a microtitre plate have been sampled. This reduces the likelihood that samples will be over-spotted, omitted, or duplicated which is a very real problem with conventional track spotting techniques, and hence this preferred feature provides significant advantages over conventional techniques. According to an embodiment, the following protocol is used: 1. using a sampling pin mounted in a holder, the operator collects a sample from the first well (A1) on a microtitre plate; 2. moving to the slide area, the first spot is made by placing the pin over the required position and "touching off" the sample onto the slide; 3. washing the sampling pin by: (a) blotting in a wash bath; (b) twice dipping into the wash bath; and then (c) blotting again in wash bath; 4. indexing the alphanumeric counter to indicate the next sample well (A2); 5. repeating cycle for the next sample well. According to another preferred feature, the microarrayer 20 may comprise a base platform and an upper platform on which all the elements are provided. The upper platform can be turned around so as to change the "handedness" of the apparatus and hence provide both left and right handed user formats.

Claims: The combination of a bench-top workstation for facilitating hand spotted arrays and a pin for manually collecting a sample from a microtitre plate and for spotting said sample on a slide, said bench-top workstation comprising a wash bath (11), sample tray reception means (12) for receiving a sample tray, slide reception means (14) for receiving said slide, a visual magnification system (4) for viewing a slide and an integral alphanumeric sample well counter (2). The combination as claimed in claim 1, wherein said bench-top workstation further comprises a sample tracking device (2) for indicating which wells of a microtitre plate have been sampled. The combination as claimed in claim 2, wherein said sample tracking device (2) comprises an array of LEDs. The combination as claimed in claim 3, wherein said array of LEDs are arranged in a 8 x 12 or 16 x 24 format. The combination as claimed in claim 2, 3 or 4, wherein said sample tracking device (2) is switched ON and/or OFF or is otherwise operated by a foot pedal. The combination as claimed in any preceding claim, wherein said visual magnification system (4) has a magnification selected from the group of: (a) at least x2; (b) at least x5; (c) at least x10; (d) at least x20; and (e) at least x40. The combination as claimed in any preceding claim, wherein said visual magnification system comprises a stereo zoom microscope and/or a head-up display. The combination as claimed in any preceding claim, further comprising an integral light source. The combination as claimed in claim 8, wherein said light source is dichroic.

Inventors: BURKE JULIAN, BURKE, JULIAN
Applicants: GENETIX LTD, GENETIX LIMITED
Application year: 2000
Main classification: B01L11
IPC codes: B01L11, B01J19, G01N35, G02B25, C40B60