Method for the manufacture of filter wells

Plastic and nonmetallic article shaping or treating: processes – With severing – removing material from preform mechanically,... – Punching article from sheet material

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Details

264250, 264255, 264DIG48, B29C 4514

Patent

active

058854991

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to the production of filter wells useful for separating a solid phase from a liquid.
Separating a solid phase from a solution is a common process in a biotechnological laboratory and is carried out mainly either by centrifugation or by collecting the solid phase on a filter. As examples, the preparation of nucleic acids from bacteria, bacteriophages, DNA-synthesis, PCR products, etc., can be mentioned. Normally, such filtering is carried out in so called filter wells, i.e. a small tube or the like containing a filter through which the liquid phase is forced by applying vacuum on the underside of the filter or pressure on the upside of the filter. A device for carrying out biochemical reactions in microtitre plates, where a solution is forced through filter wells by means of gas pressure, is described in our U.S. Pat. No. 5,273,718. Relative to the application of vacuum, the use of a positive pressure on the upside of the filter has i.a. the advantages that the solid phase as well as the liquid phase easily can be collected and that a greater pressure difference between the upside and the underside of the filter is possible (greater than 1 bar) but requires on the other hand a very good sealing between the filter and the wall of the filter well in order to avoid a leakage of liquid past the filter.
A method of providing the necessary sealing upon filtering by means of vacuum is described in WO 86/07606, where a test plate of microtitre well type is produced in that a filter membrane is placed between an upper part and lower part which are then pressed together so that a number of wells provided with filters, are formed. The sealing between the wells is secured in that the upper and lower parts between the well portions are provided with matching ridges and recesses so that the filter membrane breaks upon pressing the parts together when a ridge is forced into the corresponding recess. The upper and lower parts are then fused together in these portions by means of heat, e.g. by use of ultrasound. However, this method is limited to a microtitre well format with fixed wells.
Systems based on separate filter wells offer greater flexibility. Holders can i.a. be supplied for a varying number of filter wells of one and the same type. However, for this case, no sealing method which is sufficient in all respects has been described so far. Thus, at least under certain conditions, fixing the filter in the well by glueing causes release of contaminating substances to the passing liquid. Ultrasound welding as in the above WO 86/07606, has turned out to destroy the filter. A sealing arrangement of O-ring type is possible per se but results in a construction which for most purposes is too complicated and thereby expensive.
EP-A-328 038 describes the production of a filter well by injection moulding of the filter well in one piece and at the same time casting the filter edge integral with the wall of the well. This method has i.a. the disadvantage that it does not allow the forming of any support surface for the filter. Moreover, the filter is compressed during the forming process which can cause damages to the active filtering surface of the filter. Furthermore, in the method as specifically described, only one side of the filter is fixed in the wall of the filter well.
U.S. Pat. No. 4,113,627 describes the production of a filter for infusion liquids where two preformed filter housing halves with a filter clamped therebetween, are sealed at the outer edge by injection moulding of a thermoplastic resin. Besides the fact that the manufacturing process is relatively complicated, the clamping of the filter between the housing parts can damage the filter surface. Moreover, only one side of the filter is cast integral with the thermoplastic resin.
The present invention relates to a method of producing separate filter wells, which does not exhibit the disadavantages and inconveniences mentioned above at the same time as it in combination with a simple procedure secures an extraordinary sealing of th

REFERENCES:
patent: 4113627 (1978-09-01), Leason
patent: 5269917 (1993-12-01), Stankowski
patent: 5273718 (1993-12-01), Skold et al.
patent: 5443723 (1995-08-01), Stankowski et al.
patent: 5556541 (1996-09-01), Ruschke

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