James A. Braatz

A new hydrophilic polymer for biomaterial coatings with low protein adsorption

BIOPOL polyurethane polymers, an extension of the HYPOL Polymer series of foamable hydrophilic polymers, have been developed which exhibit improved performance for selected biomedical applications. Members of the BIOPOL polyurethane polymer series, with molecular weights in the range of 7000 to 30,000, are larger molecules than HYPOL polymers (MW less than 3000) and produce hydrogels, rather than foams, when mixed with water. The prototype material in this series, BIOPOL XP-5, is a liquid prepolymer which chain extends in water and forms a hydrogel which can contain greater than 85% water. The time required for polymerization with water was dependent on the prepolymer: water ratio. This prepolymer was coated onto silica and medical grade tubing and then cured in place with water to form a stable coating which was resistant to non-specific protein binding. In addition, soluble, isocyanate-free forms of the prepolymer were tested for toxicity and shown to produce no adverse effects when injected intravenously into mice or when applied to a chicken chorioallantoic membrane. BIOPOL polymers can be useful in applications where protein adsorption is an undesirable event.

Biocompatible Polyurethane-Based Hydrogel

A polyurethane polymer developed at W. R. Grace has been evaluated for a variety of biomedical applications. The primary property of the polymer exploited for these applications is its ability to prevent protein adsorption when coated on a surface. The prepolymer consists of a trifunctional poly(ethyleneoxide-propylene oxide) triol end capped with isophorone diisocyanate. The prepolymer is reactive with water and can be converted to a hydrogel, a thin coating, or a soluble conjugate with another compound. Each category lends itself to separate biomedical applications which are described in detail. The non-toxic nature of the polymer was demonstrated in a number of systems and suggests its utility in biomedical applications.