IN-VIVO TESTING OF CROSS-LINKED POLYETHERS .1. TISSUE-REACTIONS AND BIODEGRADATION

The in vivo biocompatibility and biodegradation of crosslinked (co)pol yethers with and without tertiary hydrogen atoms in the main chain and differing in hydrophilicity were studied by means of subcutaneous imp lantation in rats. After 4 days, 1 month, and 3 months postimplantatio n, the tissue reactions and interactions were evaluated by light micro s copy (LM) and transmission electron microscopy (TEM). Poly(tetrahydr ofuran) (poly(THF)), poly(propylene oxide) (poly(POx)), and poly(tetra hydrofuran-co-oxetane) (poly (THF-co-OX)) were tested as relatively hy drophobic polyethers, and poly(ethylene oxide) (PEG) and a poly(THF)/P EO blend were used as more hydrophilic materials. In general all polye thers showed good biocompatibility with respect to tissue reactions an d interactions, with low neutrophil and macrophage infiltration, a qui et giant cell reaction, and formation of a thin fibrous capsule. For t he relatively hydrophobic polyethers studied, the biostability increas ed in the order poly(POx) < poly(THF-co-OX) < poly(THF), probably indi cating that the absence of tertiary hydrogen atoms has a positive effe ct on the biostability. Concerning the more hydrophilic materials, cro sslinked PEO showed the highest rate of degradation, probably due to t he mechanical weakness of the hydrogel in combination with the highest presence of giant cells as a result of the high porosity. A frayed su rface morphology was observed after implantation of the crosslinked po ly(THF)/PEO blend, which might be due to preferential degradation of P EO domains. (C) 1996 John Wiley & Sons, Inc.