Biostability and biocompatibility of poly(ether)urethane containing gold or silver nanoparticles in a porcine model

Nanocomposites from polyether-type waterborne polyurethane (PU) incorporated with different amounts of gold nanoparticles (17.4-65 ppm) or silver nanoparticles (30.2-113 ppm) were prepared. Specifically, the nanocomposite containing 43.5 ppm of gold or 30.2 ppm of silver was previously found to possess the best thermal and mechanical properties. The enhanced biostability of the nanocomposite at the specific nanoparticle content was also observed in subcutaneous rats. The latter was probably related to the free radical scavenging ability of the nanocomposite shown in vitro. In this study, the in vivo biostability of the full series of these nanocomposites was assessed by porcine subcutaneous implantation for 19 days followed by microscopic examination and chemical characterization using attenuated total reflectance-infrared spectroscopy (ATR-IR). The nanocomposite at 43.5 ppm of gold ("PU-Au 43.5 ppm") and that at 30.2 ppm of silver ("PU-Ag 30.2 ppm") exhibited superior biostability in pigs to those at higher or lower nanoparticle contents. In particular, evidence of oxidative chain scission and crosslinking of the surface was presented by ATR-IR spectra in the explanted PU and nanocomposites other than PU-Au 43.5 ppm and PU-Ag 30.2 ppm. The extent of biodegradation and that of foreign body reactions were highly associated in these nanocomposites, both of which showing negative correlation with the free radical scavenging ability. The interdependency among antioxidation/biostability/biocompatibility of PU was demonstrated in this porcine model.