Macromol. Chem. Phys. zyxwvut 195, 875 -888 zyxwv (1994) zyxwvu 875 zy Synthesis and characterization of new hydrophobic polyurethanes for biomedical applications W Marconi? A. Martinelli, A. Piozzi, D. Zane Department of Chemistry, University of Rome “La Sapienza”, 00185 Rome, Italy (Received: March zyxwvutsr 22, 1993; revised manuscript of June 8, 1993) SUMMARY The synthesis of new segmented polyurethanes containing as chain extender N-hexadecyl- zy 2,2-bis(hydroxymethyl)propionamide (alone or with 1,4-butanediol at different mole ratios) is described. The degree of hydrophobicity and the glass transition temperatures Tg were found to be proportional to the alkyl chain content of the polymers. Also the amount of bonded albumin is proportional to the alkyl group content of the polymer, and platelet adhesion is remarkably lower for the 100% alkylated polymer (PEUHDA) than for the standard non-alkylated polyurethane (PEU). This behaviour was confirmed by SEM evaluation, showing a much lower degree of activation of platelets on albuminized PEUHDA films. It was not possible to ascertain with sufficient reliability a different behaviour, with respect to platelet adhesion, of the polymers containing alkyl chains in the range 9 t 50 mol-Yo, due to the relatively high error of the evaluation systems. Introduction Segmented polyurethanes are widely used in biomedical applications, due to their good physical and mechanical properties and to their fairly good characteristics of biocompatibility and nonthrombogenicity. Several techniques have been investigated to improve their haemocompatibility, as surface heparinization ‘-6), synthesis of polyurethanes containing sulfonic or sulfate groups ’-lo) and employment of polyurethanes containing albumin or groups able to bind it. In particular, since it had been observed that surfaces of thrombogenic polymers (as for example polyethylene) behaved much better with respect to platelet adhesion and aggregation when coated with albumin, this latter was covalently bonded to polymer surfaces. However, this technique generally brings about denaturation of the protein, with partial loss of its antiplatelet activity. Moreover, in the real in vivo conditions, albumin undergoes in a relatively short time proteolytic degradation by circulating proteases. The important observation that albumin binds by hydrophobic bonds to molecules containing long alkyl chains suggested to synthesize polymers of different type (polyamides, polyesters, polyurethanes, etc.) containing, as side groups, normal alkyl chains of 16 or 18 carbon atorns”-l5). This makes it possible, in case of desorption or proteolysis of the adsorbed albumin, to get a continuous “de novo” adsorption of endogeneous albumin for the blood onto the polymer surface. These surfaces have proved to be really able to bond albumin preferentially, and exhibited, in in vivo tests, superior characteristics of haemocompatibility. Usually, the polymers synthesized to this purpose contain the alkyl chains only on their surface, due to the fact that they are introduced, by heterogeneous reaction, onto the preformed polymers films. zy 0 1994, Hiithig zyxwvuts & Wepf Verlag, Basel CCC 1022-1 352/94/$08.00