P a t e n t s

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Patents This is a list of recently published patents covering designs and inventions relevant to synthetic membrane technology. Where the same device or process has been patented in several countries, we normally give the same UK patent number. If there is no UK patent we give the number of an English language patent, if one exists.

The patents list is compiled from international sources by BHR Group's information service. This facility can also be used to do full retrospective patent searches - to test the validity, novelty or infringement of existing patents or new ideas. BHR Group, Cranfield, Bedford, MK43 OAJ, UK will provide free estimates on request.

Countries can be identified from the code in front of the number, as follows:

AT Austria IR Eire AU Australia IT Italy BE Belgium IP Japan BR Brazil KP North Korea CH Switzerland LI Liechtenstein DD East Germany LU Luxembourg DE West Germany NL Netherlands DK Denmark NO Norway EP European RO Romania

patent SE Sweden ES Spain SU Soviet Union FI Finland US United States FR France WO World patent GB Britain (Patent Treaty HU Hungary Cooperation IL Israel Publication

BHR Group does not operate a document delivery service for patents, but you can obtain full copies of the original patent documents from the following addresses:

The British Library Patent Express 25 Southampton Buildings London WC2A lAW, UK Fax: 071-323 7230 (The British Library will also supply a list of UK libraries included in the Patent Information Network.) US Patent Office Scientific Library 15th and E Streets NW Washington DC 20231 USA

The Japanese Patent Office 4-3 Kasumigaseki 3-chome Chiyoda-ku Tokyo 100 Japan.

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Immunoassay test kit Infectious diseases are commonly assayed by extracting body fluids (e.g. serum from Herpes simplex sores} and then extracting appropriate antigens from these fluids. The extraction process requires a coarse filter to remove extraneous matter, then another device which captures the relevant antigen and antibodies, while allowing unbound substances to pass through (the 'bound]free' separation step}. Some bound/free separations have shown a tendency to clog, if the coarse filter has allowed some particles to pass through.

This invention comprises (in part} a multiple-level filter device for a container used to process body fluids for an immunoassay, using a binding membrane to trap detectable substances. The filter device is a holder which transmits fluid flow through the device, with at least two filters of different pore sizes. The smaller- pore-size filter has pores of a size substantially the same as the binding membrane, and is itself a membrane.

Fig. 1: Filter device in US 4948561

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The other part of the invention employs this filter in a kit for extracting and testing an antigen from body fluids. The kit contains an extraction tube, a filter tip for insertion into the tube after body

Fig. 2: Immunoassay device

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12 Membrane Technology

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fluid and an extracting agent have been added to the tube, the test device containing a membrane, and a container of labelled antibody for the antigen.

Details of the filter device are shown in Fig. 1. The extraction tube is first removed, the body fluid and an extraction agent are added to it, and then the filter tip is inserted into the open end of the extraction tube. The whole assembly is then inverted and placed in one of the wells of the immunoassay device (Fig. 2).

The extraction tube walls are flexible and the seal between the tube and the filter resists pressure, so when the tube is squeezed, the contents of the assembly are forced through the coarse filter and the second, fine (membrane) filter, through the open tip and into the well. The coarse filter is a plug of polyester fibres or moulded porous polyethylene, with pores able to remove particles larger than 22-25 microns.

The fine filter is a nylon membrane with a pore size of 5- 10 microns, which corresponds to the pore size in the assay device. This range of sizes is set by two characteristics: below 5 microns the antigen itself starts to be filtered out, above 10 microns the sensitivity of the test decreases because more background colour occurs, so a positive reading is more difficult to distinguish.

Once the filtrate is in the well of the immunoassay device, capillary action draws it through the membrane in the well, because the underside of that membrane is in contact with material which absorbs the relatively small volume of fluid delivered to it. The membrane is made of material which captures the complexed antigen, and antibodies are then added to assay the presence of the antigen.

In an alternative embodiment, the filter tip can contain a second membrane filter with a pore size between those of the coarse and fine filters, for example 20-40 microns if the fine filter pore size is 10 microns, or 10 microns if the fine filter pore size is 5microns.

Patent number: US 4948561 Date: 14 August 1990 Inventor: C.C. Hincldey, T.J.

Cummins, S.S. Sullivan Applicant: Eastman Kodak Co.

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Double-acting pump for air separation Altering the nitrogen:oxygen ratio of air from its normal 78:21 proportions is achieved by several different processes. Where total separation is not required, just a degree of enrichment, membranes provide a cheap alternative to cryogenic or pressure-swing adsorption methods. The membrane passes oxygen preferentially, giving a retentate gas stream with an increased nitrogen content and a permeate stream with raised oxygen content.

This pump, shown in the Figure, supplies compressed air to one side of a membrane, here in hollow-fibre form. Passage of the oxygen through the membrane is enhanced by creating a partial vacuum on the permeate side. The patented pump design has at least two heads, one to supply compressed air, the other to draw off the oxygen-enriched stream.

A third head can be fitted in series with the second, to pull higher vacuum levels. In this way it is possible to avoid the expense and space requirements of separate compressors and vacuum pumps. It is also possible to use the third head to produce a further pressure drop in a second membrane cartridge, so that the permeate from the first separation stage can be further enriched in oxygen. Patent number: US 4950315 Date: 21 August 1990 Inventor: A.Z. Gollan Applicant: A/G Corporation

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Ammonia removal from cell cultures Mammal cell culturing is hampered by the build-up of ammonia in the cell growth medium: this reduces cell growth rates and lowers end-product yields. The medium can simply be thrown away and replaced by a fresh batch. In some cases an ammonia-resistant line of cells can be used, but not many such lines exist. Control can be exercised over the level of glutamine in solution, but this compromises cell metabolism.

This invention employs gas or

Double-acting air-separation pump in US 4950315

hollow-fibre membrane cartridge /

nitrogen- enriched air

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oxygen: enriched air

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