Cell culture products

Details Cell culture products Cell culture products

2000-02-11

2004-10-05

Witz, Jean C. (Department: 1651)

Drug, bio-affecting and body treating compositions

Whole live micro-organism, cell, or virus containing

Animal or plant cell

C424S445000

Reexamination Certificate

active

06800282

ABSTRACT:

The present invention relates to the culturing of mammalian anchorage dependent cells onto a carrier substrate. More particularly, the present invention relates to wound dressings suitable for treating e.g. partial thickness wounds such as bums or skin graft donor site and to systems for the preparation of such dressings.
The current widely practised approach to the treatment of severe skin trauma necessitates the removal of dead tissue which might otherwise support the proliferation of pathogenic micro-organisms. However, this procedure often leaves massive open wounds which require closure and the use of autologous skin grafts is not particularly desired for a number of reasons, not least because there may be, in cases of serious burns for example, a limited supply of unaffected tissue. Cadaver skin grafts have been used to temporarily close a wound site but its limited supply and the perceived concern with cross-contamination with bacterial or viral pathogens has led to a search for alternatives.
In recent years, techniques for the in vitro cultivation of keratinocytes from human epidermis have been developed for culturing on epidermal sheets to cover full thickness bums. In the earliest versions of this approach, a confluent usually mutilayered keratinocyte sheet was grown on tissue culture plastic in vitro. The cell layer would then be detached from the culture plastic using degradative enzymes, inverted and placed upon the wound. Reports on the efficiency of this approach indicate that substantial practical difficulties exist (see, for example, J Bum Care Rehab. 13, 174-180).
More recently keratinocytes have been cultured on flexible, biocompatible membranes to facilitate the transfer of cell sheets onto the wound site. See for example, our patent application WO91/13638. Other illustrative examples of this approach include those disclosed in WO88/08448, EP 0364306, EP 0387975 and U.S. Pat. No. 5,266,480. One difficulty with prior art approaches is that the use of membranes optimised for keratinocyte attachment thereto during the culturing phase can often inhibit the migration of the cells from the membrane onto the wound, following the application of the wound dressing. Indeed, the prior art has tended to concentrate on improving the attachment of cells to the membrane, see for example U.S. Pat. No. 5,558,861 where the use of microbially produced cellulose is disclosed having an animal cell adhesive protein physically or chemically bonded thereto, the express aim of which is to provide a cellulose gel having an excellent adhesion to epidermal cells.
It is therefore an object of the present invention to provide a wound dressing which comprises a carrier layer that promotes the culturing and anchoring of anchorage dependent cells in vtro thereto yet following application to a wound, the dressing becomes substantially non-adherent to cells.
In accordance therefore with the present invention provides a wound dressing comprising a carrier layer having a wound-facing surface, said surface being non-adherent to anchorage-dependent cells and having disposed thereon a biodegradable cell anchoring layer.
By the term “biodegradable cell anchoring layer” we mean a layer, capable of anchoring cells thereto, that is susceptible to degradation or breakdown following application of the dressing to the wound.
It is preferred that the dressing is conformable i.e the dressing will conform to changes in contours of the body portion to which the dressing is applied.
In preferred embodiments the carrier layer is in the form of a gel, e.g. hydrogel, a film or sheet. A film is particularly preferred. Films suitable as the carrier layer may be continuous or apertured e.g formed into a net. The film may be flat or contoured. The contours may be produced for example by embossing. Suitably contoured films may also have apertures.
The carrier layer may comprise a material which is inherently non-adherent to cells or alternatively the material may be surface treated e.g coated, with a non-adherent to cell material, to provide a carrier layer having a non-adherent to cell wound facing surface. It is observed that when a material is non-adherent to cells, the cells when suspended in a suitable aqueous medium in contact with the non-adherent material appear rounded up and do not attach to the material. In contrast, where a material is adherent to cells, the cells will attach to the material and “sit down”. Furthermore, the cells will resist detachment when washed gently with physiological compatible saline.
Useful materials that are non-adherent to cells include cross-linked cellulose derivatives. Preferred examples thereof include cross-linked hydroxyalkyl celluloses e.g. hydroxyethyl cellulose, hydroxypropyl cellulose, methyl, thyl and methyl thyl celluloses (available from Sigma Co and Aldrich). Cross-linked carboxyalkyl celluloses are also preferred e.g. carboxymethyl cellulose (CMC, available from Hercules Ltd, Lancashire, UK) cross-linked with ethylene glycol diglycidyl ether (EGDGE) or 1,4 butanediol diglycidyl ether. Other preferred materials include polyvinyl alcohol (PVA, Sigma Co), Cell-Form™ (ICN), agarose e.g Sepharose™.
Alternatively a material which is adherent to cells maybe surface treated e.g by coating or by chemical/physical bonding with a non-adherent to cell material so as to provide a carrier layer having a non-adherent to cell wound facing surface. Illustrative examples of adherent materials employed in the present invention include polymers, particularly synthetic polymers, such as those disclosed in our patent applications WO 91/13638 and WO 97/06835. Apt polymers therefore include polyhydroxyethylmethacrylic acid (polyHEMA), cross linked polyvinylalcohol (PVA), polyacrylic acid cross linked with triallylsucrose (Carbopol), polyvinylpyrrolidone, polyetherpolyesters, polyetherpolyamides, polyacrylamides and polyethylene oxide and polyurethanes. Other apt polymers include copolymers such as those containing vinyl acetate residues such as ethylenevinyl acetate copolymers. Suitable ethylene-vinyl acetate copolymers are those containing not more than 20% vinyl acetate. A preferred material, known as EVA 538/539 contains 16% vinyl acetate. Other suitable polymers include essentially hydrocarbon based materials such as polybutadienes, polypropylene and polystyrene. Further examples include block copolymers having hard end blocks and softer mid blocks. Apt block copolymers include stryene based rubbers such as styrene-butadiene styene (manufactured under the trade name CARIFLEX or KRATON, Shell chemical Co). The adherent mat rial may then be coated on the wound facing surface with phosphoichloline, or silicone, polyethylene glycol or polytetrafluroethylen (PTFE).
The carrier layer may comprise a material which is biodegradable or non-biodegradable following application of the dressing to the wound site. Illustrative examples of biodegradable materials include photopolymerizable hydrogels such as those disclosed in U.S. Pat. No. 5,410,016, incorporated herein by reference, and sold under the trade name FOCAL (Focal Inc, USA).
The carrier layer may also comprise a backing layer disposed on a non-wound facing surface to increase the robustness of the wound dressing. Accordingly, the wound dressing may comprise a carrier layer in the form of a laminate film comprising a carrier layer described hereinbefore having a backing layer disposed on a non wound-facing surface. The backing layer may be fabricated from imaterials commonly used in the manufacture of wound dressings such as polypropylene, polyurethanes, polyesters and polyethylene. Particular preferred are polyurethanes. Preferred polyurethane backing layers include cyclic polyether polyurethanes, ESTANE 5714™ (BF Goodrich) OPSITE IV3000™ hydrophilic polyurethane film (Smith & Nephew). Polyurethane backing layers may be chemically modified with treatments such as plasma treatment with nitrogen, ammonia or air, corona discharge treatment or flame treatment to increase the surface energy of the surface of the backing layer which contact

Affiliated with

Also associated with

Rating

Cell culture products does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Cell culture products, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cell culture products will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3312659