Engineering a Biologically Inspired Condom

Diminished sensation during the use of contemporary elastomeric male condom designs is the primary deterrent for condom demand and compliance. Condoms made from GI mucosa solved this problem long ago, and men still prefer ‘sheepskin’ because of improved sensation. In this project we will be the first to use a class of hydrophilic polyurethane elastomers to make hydrated condoms that feel and mechanically behave like mucosal tissue, but are also impermeable to viruses and are capable of being manufactured using cost-effective elastomer processing technology. In the ancient era condoms were made from gut tissue. And even today men prefer gut condoms because they allow for improved sensation during vaginal intercourse; however, condoms made from GI mucosa suffer from biological variability in source material, are not effective in preventing diffusion of viruses(1, 2), and are expensive. Therefore, synthetic materials are required in this public health context. We argue that the condom design field needs materials that have the manufacturability, cost and barrier properties of synthetic materials but the tactile sensation of hydrated mucosa to increase pleasure by mimicking the penis-vagina biointerface tribology more closely than current materials. If such a material is used in the manufacture of condoms it could have a disruptive effect on the condom market and greatly increase their use. Standard polyurethane condoms are made from hydrophobic polymers containing water insoluble polyethers. Less well known are the hydrophilic polyurethanes (HPU) that synthetically include a fraction of a water-soluble polyether polyethylene glycol component. HPU films are unique elastomeric hydrogel materials. When hydrated with aqueous buffer they feel much like GI mucosa. This is because there is a tribologically active hydrated layer of surface polymer creating a low-friction interface much like the extracellular matrix left over after processing the GI mucosa of animals. The most common use of HPU in the biomedical device industry is in coatings on catheters and stents, because the low coefficient of friction provided by the HPU allows facile manipulation of the device when in contact with tissue.(3) In many ways HPUs are unusual materials because they are not brittle like other hydrogels but are strong, elastic and resilient. Yet when dry, they can be manufactured with technology already used in the condom industry: by dip coating a mandrel, by film extrusion, or by injection molding. Mechanically, HPUs are more robust than latex rubbers with higher tensile strength and better tear and abrasion resistance especially when wet. Due to their impressive mechanical properties, HPU films can be as thin as 0.03mm, and thinner materials provide greater tactility. HPUs are also more compatible with lubricants (1) and are much more biocompatible than latex and much less expensive than silicone. Latex has failed many of the ISO 10993 tests for biocompatibility. HPUs used in this project have already passed most of the FDA required biocompatibility tests, including cytotoxicity, hemocompatibility, mutagenicity, acute implantation, mucosal contact and pyrogenicity. This project will succeed because much is known about the materials science and biocompatibility of these HPU materials. There are many condom patents and others have tried to address the problem of increasing male pleasure with stiffeners, accordion structures and lubricants, but none have tried to simply mimic the salient properties of mucosal tissue condoms. A variety of medial grade HPUs