Antifouling polyurethanes to fight medical device-related infections

Biofouling is a spontaneous process occurring when a medical device comes in contact with biological fluids. The formation of a conditioning film rich in proteins and cells makes the medical device surfaces more suitable for colonization by bacteria and fungi. For this reason, the reduction of biofouling process is considered a promising approach to prevent medical device-related infections. In this study, to obtain antifouling materials able to hamper microbial adhesion, a series of carboxylated segmented polyurethanes possessing different degrees of hydrophilicity was synthesized. Particularly, the following three madrodiols, polypropylenoxide (PPO), polycaprolactide (PCL) diol and poly-l-lactide (PLA) diol, were employed as the soft phase. In all polymers, methylene bisphenyl diisocyanate and dihydroxymethylpropionic acid were used as the hard phase. Tests of microbial adhesion evidenced as the polymers containing a polar soft phase (PCL or PLA) were able to significantly reduce the adhesion of Staphylococcus epidermidis with respect to the PPO containing polymer. In particular, 2 and 4 log-reductions of bacterial adhesion were obtained for the PCL- and PLA-containing polyurethanes, respectively. The better antifouling properties of the PLA-containing polyurethane were shown to be related, not only to polymer hydrophilicity, but also to its good degree of hard/soft phase segregation that presumably caused the formation of large hydrophilic domains on the polymer surface. The approach pursued in this work is particularly interesting since the developed polymers are intrinsically able to hinder microbial adhesion without the release of antimicrobial agents from the device surface.