Fluorocarbon chain end-capped poly(carbonate urethane)s as biomaterials: blood compatibility and chemical stability...

Previous work has shown the synthesis of fluorocarbon chain (CF(3)(CF(2))(6)CH(2)O-) end-capped poly(carbonate urethane)s (FPCUs) and confirmed the presence of a novel bilayered surface structure in FPCUs, that is, the top fluorocarbon and subsurface hard segment layers (Xie et al., J Biomed Mater Res Part A 2008; 84:30-43). In this work, the effects of such surface structure on blood compatibility were investigated using hemolytic test and platelet adhesion analysis. The chemical stability of the polymers was also determined by Zhao's glass wool-H(2)O(2)/CoCl(2) test and phosphate-buffered saline (PBS, pH = 3.1-3.3) treatment. One of the FPCUs, FPCU-A, and two control materials, a poly(ether urethane) (PEU) and a poly(carbonate urethane) (PCU), were investigated. No significant difference in hemolytic indices was observed among the three materials, whereas the adherent density and deformation of platelets were much lower on FPCU-A compared with on PCU and PEU. Severe surface cracking and surface buckling developed in prestressed PEU and PCU films after H(2)O(2)/CoCl(2) treatment, respectively, whereas smooth surface was observed for the FPCU-A. PBS incubation resulted in parallel ridge-like morphology in PCU whereas PEU and FPCU-A retained their smooth surfaces. Under relatively high stress conditions, all the materials developed well-oriented strip-like surface patterns. Results from ATR-FTIR spectra revealed a surface oxidation mechanism as described in literature. However, observations of universal decrease of molecular weights under stress conditions further suggested the presence of another bulk stress oxidation mechanism. Regardless the degradation mechanisms involved, the unique bilayered surface structure really improved the blood compatibility and chemical stability of FPCU-A, indicating that further in vivo investigations are worthwhile.