BIODEGRADATION OF A POLY(ESTER)UREA-URETHANE BY CHOLESTEROL ESTERASE - ISOLATION AND IDENTIFICATION OF PRINCIPAL BIODEGRADATION PRODUCTS

Synthesized poly(ester)urea-urethanes with C-14-labeled toluene diisoc yanate or C-14-labeled chain extender ethylene diamine were incubated with cholesterol esterase in a phosphate buffer solution at 37 degrees C. A number of biodegradation products, generated at the level of 2.8 mu g/cm(2) of polymer surface area, were isolated from this simulated physiologic system. Individual products were obtained by separation w ith reversed-phase high-performance liquid chromatography. The two dif ferent radiolabels were used to assist in the identification of degrad ation products from hard- and soft-segment domains. Approximately 20 d egradation products were isolated; however, toluene diamine (TDA) was not detected from the chromatographic separation. Two principal produc ts were identified by tandem mass spectrometry. Both products are TDA derivatives (secondary aromatic diamine) substituted with end units of the polyester segment at N and N' positions of TDA. The absence of fr ee TDA suggests that there could be a stabilization of urethane and ur ea linkages within the toluene diisocyanate (TDI) segments of the poly urethanes. For TDI-synthesized polymers, this finding raises awareness to the potential biological importance of degradation products other than TDA, particularly to their interaction with surrounding cells. (C ) 1997 John Wiley & Sons, Inc.