This invention relates to a membrane with anti-viral properties, to a method of imparting anti-viral properties to a membrane, and to products such as surgical gloves and condoms made of such a membrane, which itself may typically be of rubber, such as latex rubber, or polyurethane. An important virus whose activity it would be appropriate to curb with such products is the human immuno-deficiency virus HIV.

It had been thought from laboratory studies in the mid-1980s that the spermicide nonoxynol-9 killed this virus, but more recent studies suggest that this compound can increase the chance of HUV transmission compared with using a placebo (Guardian, 3 November 1993). Therefore the search for a different anti-viral agent is urgent.

It has been suggested by a group from Emory University, Atlanta, Georgia, USA, that the football-shaped carbon compound buckminsterfullerene Cgø should block the action of the enzyme "reverse transcriptase", with which the virus converts its RNA into the DNA essential for replication (Neue Zϋrcher Zeitung 1 December 1993). Independently, Friedman et al. from the University of California postulated and verified that Cgø was of just the right size to block the enzyme HIV-protease, which has the form of an open cylinder in the bore of which is a site where two aspartic acid groups catalyse the hydrolysis (i.e. destruction) of the peptide bonds of the protein being attacked by the enzyme. The Cgø molecule snugly fits this site, stopping the enzyme from functioning (J. American Chemical Society, 1993, pp 6510-2).

However, the possibility of exploiting these welcome properties in the context of membrane products has not been considered because it is such an improbable combination technically, in that a strong chemical bond uncharacteristic of buckminsterfullerene is normally required for a monomolecular layer to adhere to a substrate.

Independently of this, Williams et al of the University of Durham have succeeded in forming Langmuir-Blodgett films of fullerenes on to various rigid bulk substrates,

namely glass, single-crystal silicon, quartz and aluminium-coated glass (Synthetic Metals.

55-57 (1993) 2955-2960), and Goldenberg et aL (J. Chem. Soc, Chem. Comm.. 1993. p 1310) have improved on this, but still on rigid bulk substrates only, by using the substituted compound l-tertbutyl-l,9-dihydrofullerene-60. A membrane of for example polyurethane or rubber, e.g. latex rubber, according to the invention carries a coating of from one to ten, preferably 1 or 2, layers of one or more fullerenes. The fullerene(s) may be applied by way of dispersion in a gel or lubrication layer, applied conventionally to the membrane, or as follows.

A method of coating a membrane, according to the invention, comprises applying one or more Langmuir-Blodgett coatings of fullerene to the membrane. The fullerene may be dissolved in an aromatic and/or hydrophobic compound on a hydrophilic (e.g. water) subphase. The fullerene may be codissolved with a phospholipid or fatty acid, e.g. arachidic acid, in a mole proportion of 1 :(1-10) and/or may be substituted with alkyl chains C _j -C _j g or with functionalised chains containing amine, hydroxyl or carboxy lie acid groups, e.g. may be 1 -tertbutyl- 1.9-dihydrofullerene-60.

The invention extends to products such as surgical gloves and condoms made of a membrane which has a coating as set forth above.

The invention will now be described by way of example.

A Langmuir-Blodgett trough of a constant perimeter design of floating boom was housed in a microelectronics-grade clean room. The subphase in the trough was ultra-pure water (pH 5.7 ± 0.1, temperature 20 ± 2°C) obtained by reverse osmosis, deionization and

UV sterilization.

Onto the subphase and inside the adjustable perimeter floating on the surface of the subphase were placed a few drops (150 μl) of a concentrated solution of 1 mole part Cgø fullerene and 4 parts arachidic acid in benzene. One hour was allowed to pass, to ensure complete evaporation of the benzene. The perimeter was adjusted until the fullerene plus arachidic acid formed a close-packed and ordered arrangement, this being established by compressing the perimeter such as to maintain a surface pressure of 30 milliNewtons/m.

This arrangement is believed to be of vertically aligned fatty acid molecules in a close-packed ordered arrangement on the subphase (water) surface, with the fullerene

molecules on tog. This arrangement is transferred "as is" to a solid substrate dipped into the Langmuir-Blodgett trough.

When a substrate is dipped into the trough and removed, it may have adhering to it a layer of aligned molecules which became attached: on the downstroke only (X-type deposition), on the downstroke and again on the upstroke (Y-type deposition), or on the upstroke only (Z-type deposition). The thoroughness or efficiency of deposition is measured by the deposition ratio, defined as (change in enclosed surface area of trough)/(dipped area of substrate).

Initially, attempts were made to dip on to commercially available condoms, which were first washed in a mild detergent/warm water solution to remove any lubrication. Dipping was, however, unsuccessful as residual lubrication turned out to have remained on the condom, transferring to the subphase surface as the substrate was lowered into the subphase. This was monitored by an increase in surface area of the floating film, instead of the expected decrease which accompanies loss of material from the subphase surface. Further attempts to clean the condoms resulted in a deterioration of the latex rubber. LB film transfer was unsuccessful.

A pair of hospital-grade starch-free latex rubber surgeon gloves was obtained and a finger was removed from a glove. The finger was stretched over a 1 cm diameter glass test tube. Once again, on transferring the substrate through the subphase a surface area increase was monitored. It was, however, found possible to remove this unknown coating by repeatedly dipping the substrate through a clean subphase/air interface. Following this cleaning procedure, Y-type Langmuir-Blodgett deposition occurred at a dipping speed of - 7.5 mm min"*. The deposition ratio was 1.0 ± 0.05 and the film thickness estimated to be 7.2 nm. This was too thin to affect the appearance of the substrate. Z-type deposition was recorded for a dry condom, supplied by the London Rubber

Company, with a deposition ratio approaching 1.0.