Nanocomposites from a polyester-type waterborne polyurethane (PU) containing various low concentrations (15-75 ppm) of silver nanoparticles (nano Ag, size approximately 5 nm) were prepared. The PU-Ag nanocomposites exhibited good nanoparticle dispersion up to 30 ppm of nano Ag, confirmed by the transmission electron microscopy. Distinct surface morphology at different concentrations of nano Ag was shown by the atomic force microscopy. The oxidative degradation of PU-Ag was inhibited in all concentrations of nano Ag tested, especially at 30 ppm ("PU-Ag 30 ppm"). This may be related to the free radical scavenging ability observed for the nanocomposites. PU-Ag 30 ppm showed enhanced fibroblast attachment and endothelial cell response, as well as reduced monocyte and platelet activation, relative to PU alone or nanocomposites at the other silver contents. The rat subcutaneous implantation confirmed the better biocompatibility of the nanocomposites. The adhesion of Bacillus subtilis, Escherichia (E.) coli or Ag(+)-resistant E. coli on PU-Ag nanocomposites was significantly lower at all concentrations of nano Ag tested. Besides, the nanocomposites demonstrated microbiostatic effect while pure PU did not. The commercial catheters coated with PU-Ag 30 ppm were inserted into rat jugular veins for evaluation. The results showed milder inflammation for PU-Ag after 3 months compared to the non-coated catheters or pure PU-coated catheters. The enhanced performance of PU-Ag over that of pure PU was a result of extensively modified surface morphology in the presence of a very small amount of nano Ag. The dispersion of nano Ag was highly associated with the overall performance.
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