GB2322121A

GB2322121A - Multi-well plate closure

Info

Publication number: GB2322121A
Application number: GB9702950A
Authority: GB
Inventors: Richard Michael Ireland
Original assignee: Porvair PLC
Current assignee: Porvair PLC
Priority date: 1997-02-13
Filing date: 1997-02-13
Publication date: 1998-08-19
Also published as: GB9702950D0

Abstract

A flexible moulded closure for a multi-well sample plate comprises a plurality of downwardly depending cups 24d adapted to be a force fit in the openings of the sample plate. Each cup has a slot 22 in its base defining a thinned region which is rupturable for instance by a probe. The width of the slot y is greater than the thickness z of the thinned region, and is preferably greater than the cup wall thickness x. The slot width y may be between 0.25 and 1.5 mm, and the slot may have a plurality of arms. The slot length may be at least half as long as the diameter or diagonal of the cup. In use, the closure is fitted to a sample plate, and a probe can gain access to any of the plate wells by rupturing the relevant cup.

Description

Multi-well Plate Sealing Cap The present invention relates to a closure device for application to a multi-well sample plate. These multi-well plates are commonly referred to as microtitre plates or microplates. These microplates are commonly used to hold a large number of samples in a rectangular array of wells, e.g. 24 wells (4 x 6) or 96 wells (8 x 12). To prevent spillage and to protect the samples from contamination while they are stored the wells are sealed with a cap.

Often samples have to be removed from one plate and transferred to another either using automated liquid handling instruments or transferred manually. Currently the force fit sealing caps employed have to be removed to allow access to the sample wells. This is both time consuming and may also lead to contamination of adjacent samples as the liquid is added or removed or as the lid is removed. Another option is to seal the wells with an adhesive film scored with crosses at each well position.

This is then weak enough to allow penetration of the film without removal. However, this has the disadvantage of an adhesive which may contaminate the samples via contact with the probe as it enters and leaves the well.

In addition, the production of the film involves several steps, namely scoring the crosses and the application of adhesive. Application of the film to the multi-well plate also involves the need to register the crosses with the wells in the microplate. As a result, this makes automation impractical when using such a film.

The present invention seeks to overcome the problem of sealing the wells in a way which allows samples to be taken without contaminating other samples.

According to the present invention a flexible moulded closure comprising a number of downwardly depending cups adapted to be a force fit in the openings of a multi-well plate is provided, in which each downwardly depending cup has a wall thickness of (x) and has a slot in its base affording a thinned region, the width (y) of the slot being greater than the thickness (z) of the thinned region, and preferably greater than the thickness of the base of the well i.e. such that y > z and preferably y > x. Preferably the ratio z:x is in the range 2:15 to 8:15.

This overcomes the problems with the prior art in that the closure is a force fitting into the multi-well plate thereby avoiding the need for an adhesive. The slot in the base of the downwardly depending cup being thinner than the walls of the cup can be penetrated by a metal probe. This avoids the need to remove the seal before taking the sample and the risk of contamination by adhesive when a film closure is used. The film closure can also be cored by the probe thus introducing risks of the probe being blocked. The closure also allows individual samples to be removed without contamination of the remainder of the samples since they remain sealed.

Preferably the width of the slot in the base of the cup of the closure is between 0.25 and 1.5 mm e.g. 0.5 to 1.0 mm. This will allow probes of dimension up to 3.2 mm (1/8 inch) to access the samples since as the probe is pushed into the slot, the thinned walls of the slot split along the slots and the walls of the cups are pushed outwardly. Preferably the slot in the base is of multiarmed form. This arrangement means that once the probe has pierced the cup and the thinned wall has split the walls of the well can spread out like a flower. The slot can be in the form of a V or a single line, but a multi armed shape is preferred such as a cross or a star shape e.g. of 5 or more arms e.g. 3 to 7 arms.

Preferably the length L5 of the slot is at least 50% of the diagonal or of the diameter of the downwardly depending cup.

Preferably the closure is made of a sufficiently flexible and resilient material that on removal of the probe the walls of the cup return to their original position. Preferably the closure is made of a copolymer of ethylene and vinyl acetate (EVA copolymer). This is chosen for its flexibility and its elasticity. Another preferred material is low density polyethylene (LDPE).

In preferred embodiments of the closure there is a sufficient lip to the array of downwardly depending cups for there to be included an alphanumeric well identification.

The invention may be put into practice in various ways and one specific embodiment will be described to illustrate the invention with reference to the accompanying drawings in which: Figure 1 is a plan view from above of the flexible moulded closure; Figure 2 is an elevational view from one side of the flexible moulded closure; Figure 3 is an enlarged plan view from above of one of the downwardly depending cups; Figure 4A is an enlarged perspective view looking towards the line A-A in figure 3; Figure 4B is an enlarged cross section along the line A-A in figure 3; and Figure 5 is an enlarged perspective view of the flexible moulded closure in position in a multi-well plate.

Referring to the drawings, figure 1 shows a flexible moulded closure 10 in accordance with the invention. The embodiment shown is designed to cooperate with a 96 well microplate (12 x 8) with square wells. These wells are typically of a depth to hold 1 to 2 ml of fluid. The flexible moulded closure comprises an upper web 11 with an upper surface ila and lower surface lib. Depending downwardly from this web 11 are 96 cups 20 arranged in rows and columns to correspond to those of the microplate. These cups 20 each have thinned regions in the form of slots 22 in the shape of a cross in their base 26.

Alphanumeric well identification 12 is located around the edge of the upper surface lla again corresponding to any identification on the microplate.

This enables the user to accurately determine from which well the sample should be removed.

The moulded closure 10 has typical dimensions of 120 mm by 77 mm and is manufactured of a copolymer of EVA.

This is chosen for its flexibility and its ability to return to its original position after removal of the probe. Although square wells are shown in this embodiment this invention could equally be applied to other shapes of well e.g. circular.

From figure 2 it can be seen that the cups 20 depend essentially perpendicularly from the upper web 11 for a distance L1 before defining a generally hemispherical shape of radius R1. The distance of the base 26 of the cup 20 below the lower surface lib of the upper web 11 is L2. The thickness of the upper web 11 is L3. A typical set of dimensions which may be suitable is: L1=1.5 mm; L2=5.0 mm; L3=1.0 mm; R1=3.5 mm.

Figure 3 shows an enlarged plan view of one of the cups 20 which depend from the upper web 11 of the moulded closure 10. The square cup shown in figure 3 has a side length L4 which may typically be 6.75 mm. The cup 20 has at its base 26 a slot 22 in the shape of a cross. Each arm is of width y (typically 1.0 mm) and the diagonal length of the cross is L5 (typically 5.0 mm). The significance of the slot 22 is that it is thinner than the surrounding walls of the cup 20 and that it has a significant width as can be seen from figure 4.

In use, a probe (not shown) is positioned at some point on the slot and is then pushed through the closure into the sample. As the probe extends through the cup 20, the walls of the slot split and resultant flaps 24a 24b, 24c and 24d of the cup are pushed outwardly. Being made of a resilient material, when the probe is removed the walls return substantially to their original position.

Figure 4A shows more clearly the relationshiE between the dimensions L1, L2, L3 and R1. Figure 4B showy a cross section along the line A-A in figure 3 from which it can clearly be seen that the slot 22 at the base 26 oi the cup 20 is thinner than the walls 24d. The walls arc of thickness x and the slot is of thickness z. The ratic of the thicknesses z:x is in the range 2:15 to 8:15 anc typical values for the thicknesses are x=0.75 mm anc z=0.20 mm i.e. z:x is 4:15.

Figure 5 shows the moulded closure 10 in use as < seal. The moulded closure 10 is positioned over thc microplate such that the walls 30 of the microplatc extend up between the cups 20 to the lower surface llb oi the upper web. The closure 10 is dimensioned so as to bc a force fit into the tops of the wells of the microplatc thereby avoiding the need for any adhesive.

Claims

1. A flexible moulded closure comprising a number of downwardly depending cups adapted to be a force fit in the openings of a multi-well plate, in which each downwardly depending cup has a wall thickness of (x) and has a slot in its base affording a thinned region, the width (y) of the slot being greater than the thickness (z) of the thinned region, and preferably greater than the thickness of the base of the well i.e. such that y > z and preferably y > x.

2. A flexible moulded closure as claimed in claim 1, in which the ratio z:x is in the range 2:15 to 8:15.

3. A flexible moulded closure as claimed in claim 1, in which the width y of the slot is between 0.25 and 1.5 mm.

4. A flexible moulded closure as claimed in any preceding claim, in which the slot in the base is of multi-armed form.

5. A flexible moulded closure as claimed in any preceding claim, in which the length L5 of the slot is at least 50% of the diagonal or of the diameter of the downwardly depending cup.

6. A flexible moulded closure constructed and arranged substantially as herein specifically described with respect to and as shown in figures 1 to 5 of the accompanying drawings.