WO2001086250A1

WO2001086250A1 - Gel spot picker device and method

Info

Publication number: WO2001086250A1
Application number: PCT/EP2001/005424
Authority: WO
Inventors: Lars Fagerstam
Original assignee: Amersham Pharmacia Biotech AB; Amersham Bioscience AB
Current assignee: Cytiva Sweden AB
Priority date: 2000-05-12
Filing date: 2001-05-11
Publication date: 2001-11-15
Anticipated expiration: 2002-11-12
Also published as: AU2001267431A1; SE0001780D0

Abstract

The present invention relates to a method and device for removing gel plugs (13) attached to a support plate (3), wherein said device has a picker head with a needle having an inner diameter D and it has control means (17) for displacing said needle sideways after it has been lowered into contact with said plate (3).

Description

Title

GEL SPOT PICKER DEVICE AND METHOD

Field of the Invention

The present invention relates to devices and methods for picking up spots of gel from sheets of gel.

Prior Art Many biochemical analytical methods produce results in the form of sheets of gel upon which the constituents of the analysed substances are grouped in spots. Further analyse of the constituents can be made by cutting out and picking up the cylindrical plugs of gel containing the substances of interest and transferring the plugs to other devices such as microtitre plates or test tubes for further analysis. The plugs are extracted from the sheet of gel by lowering a cylindrical hollow needle through liquid covering the gel and the gel until it reaches the supporting base plate, applying a suction to the upper end of the needle in order to lift the plug off the base plate and into the needle where it is caught by a pieced bulkhead near the tip of the needle. The plug can then be transported by the picker head to a position above a well in a micro-titre plate or a test tube and then ejected out of the needle by pressurised liquid applied to the upper part of the needle.

A problem can occur if the sheet of gel is stuck to an underlying support, as the tensile strength of the adhesive attaching the gel to the support is greater than the tensile strength of the gel in the plug. This means that when a gel plug is sucked up, the top of the plug breaks away from the base of the plug of gel, leaving a stump of gel attached to the support. This means that some of the constituents of the sample of interest can remain behind on the gel sheet and are not available for further analysis.

Summary of the Invention

The present invention seeks to provide a device and a method for overcoming the problem of the prior art devices and methods. The present invention achieves this with a device having the features mentioned in the characterising part of claim 1 and by means of a method having the features mentioned in the characterising part of claim 4. Device and methods having the features of the present invention have the advantage that the whole of a gel plug can be easily removed from a support.

Brief Description of the Figures Figure 1 shows a lateral view of a spot picker head and gel sheet in accordance with the present invention;

Figure 2 shows a section through line I-I in figure 1 ;

Figure 3 shows a view from above of an embodiment of picker head movement in accordance with a first embodiment of the invention;

Figure 4 shows a view from above of an embodiment of picker head movement in accordance with a second embodiment of the invention; and

Figures 5 a) and 5b) show further embodiments of picker head movements.

Detailed Description of Embodiments Illustrating the Invention

Figure 1 shows a lateral view of a picker head 1 for picking up plugs of gel from a sheet of gel 2. The sheet of gel 2 is support on a plate 3 and is covered by a thin layer of fluid 4. Picker head 1 has a tubular body 5. The upper end of body 5 is adapted by means of complementing fastening means (which are well known in the prior art and therefore not shown) to be attached to a picker arm (not shown). The lower end of body 5 has an opening 6 to which a hollow needle 7 is attached. Needle 7 is open at each end and has an internal diameter D. The upper end of body 5 can be connected to a supply of liquid at a pressure lower than atmospheric pressure in order to form a suction at the lower end of needle 7 and it can also be connected to a supply of pressurised liquid in order to form an overpressure at the lower end of needle 7. Needle 7 contains a bulkhead 9 with a centre hole 11. When a gel plug 13 is sucked up from the plate 3, the bulkhead 9 prevents it from being sucked all the way up into the body 5. Picker head 1 is shown in figure 1 in a position where it has been lowered through the fluid 4 and the sheet of gel 2, and is in contact with the plate 3. The needle 7 contains a plug 13 of gel. The base 14 of the gel is attached to the plate 3 by an adhesive layer 15. Normally this prevents the gel from being cleanly lifted of the plate 3 when a supply of liquid at a pressure lower than atmospheric pressure is provided at the upper end of body 5. Instead the gel plug would break some distance from the bottom of the plug - shown by line 16 in figure 1 - and the portion of the gel plug 13 above the break 15 would be drawn up into the needle 7 until it comes into contact with the bulkhead 9. The rest of the gel plug 13 would remain attached to the plate 3. Figure 2 is a cross-section through line I-I of figure 1. In order to avoid the gel plug 13 breaking, in accordance with the present invention, the picker head 1 and needle 7 are controlled by control means such as a computer 17 to move sideways after being lowered into contact with the plate 3. Figure 3 shows a view from above of a first embodiment of a sideways movement of picker head 1 in order to pick up a gel plug 13 containing a spot 18. The inner diameter D of needle 7 is shown by circles, wherein the circle drawn with a solid line shows where the needle 7 is lowered into contact with the plate 3 and the dotted circles show the minimum outer limits of the subsequent sideways displacements of the needle 7 needed to minimise disturbances of the surrounding gel. The minimum sideways movement must half the inner diameter D of the needle if the sideways displacements are in a straight line but in opposite directions in order to ensure that the attachment between the bottom of the gel plug and the plate is broken completely. In this example the needle is first moved a distance of at least D/2 in one direction (e.g. to the right in figure 3) and then a distance of D back in the opposite direction (e.g. to the left). Figure 4 shows a second embodiment of the present invention in which the needle 7 is moved a distance that is at least one needle inner diameter D in a single direction. This movement is quicker than the reciprocating movement described in connection with figure 3 but causes more deformation of the surrounding gel in the direction of the movement of the needle. Other movements of the needle are also conceivable, non-limiting examples of which are shown by arrows in figure 5a) (showing movement in two orthogonal directions) and 5b) (shown movement in a spiral) where the start and end positions of the needles are shown by circles drawn with dashed lines and the plugs which are to be removed are shown by circles drawn with solid lines.

Claims

1. Device for removing gel plugs (13) attached to a support plate (3), wherein said device has a picker head (1) with a needle (7) having an inner diameter D characterised in that it has control means (17) for displacing said needle (7) sideways after it has been lowered into contact with said plate (3).

2. Device in accordance with claim 1 characterised in that said control means (17) controls said needle (7) to first move a distance of at least D/2 in one direction and then a distance of at least D in the opposite direction after it has been lowered into contact with said plate

(3).

3. Device in accordance with claim 1 characterised in that said control means (17) controls said needle (3) to first move a distance of at least D in one direction after it has been lowered into contact with said plate (3).

4. Method for removing gel plugs (13) attached to a support plate (3) by means of a device in accordance with any of claims 1-3 characterised by the steps of: a) lowering said needle (7) until it is in contact with said plate (3); and, b) displacing said needle sideways after it has been lowered into contact with said plate (3).

5. Method in accordance with claim 4 characterised in that in step b) said needle (7) is first moved a distance of at least D/2 in one direction and then a distance of at least D in the opposite direction after it has been lowered into contact with said plate (3).

6. Method in accordance with claim 4 characterised in that in step b) said needle (7) is first moved a distance of at least D in one direction after it has been lowered into contact with said plate (3).