Biocompatibility of silver-modified polyester for antimicrobial protection of prosthetic valves

Background and aims of the study: The biocompatibility of a silver- coated polyethylene terephthlate PET, polyester) fabric for the inhibition of prosthetic valve endocarditis (PVE) associated with mechanical heart valves (MHVs) was assessed. The infrequency of PVE is outweighed by mortality rates commonly exceeding 50%. These high mortality rates rave been attributed to the poor effect of antibiotic-therapy on colonized valves and infected myocardial issue. Silver has been used as an antimicrobial for centuries due to its general effectiveness and relative lack of toxicity. Our previous work has shown PET polyester fabric coated with metallic silver by an ion beam- assisted deposition (IBAD) process to: (i) be effective in vitro in the inhibition of microbial attachment and colonization; (ii) be tightly adherent and low leaching; and (iii) promote tissue ingrowth and the organization of tissue pannus in a short-duration (five weeks) sheep mitral mechanical heart valve model. Methods: This paper addresses additional biocompatibility assessment consisting of a cell compatibility assay in which serum extracts of silver-coated fabric were exposed to fibroblasts for 48 hours, after which cell viability and function were measured. The amount of silver in the extract was measured using elemental analysis techniques. Results: No signs of toxicity were seen in the cells until the extract concentration reached 1200 p.p.m. Ten-week duration mechanical valve replacement studies in sheep with uncoated or coated polyester sewing cuffs showed comparable tissue ingrowth and mature pannus with a suggestion of a thinner pannus on the silver-coated fabric. Additional antimicrobial testing confirmed the effectiveness of this coating in inhibiting colonization of polyester fabric. Conclusions: These current results, together with the earlier data, suggest that IBAD silver coating on poly-ester facilitates healing and may provide protection against PVE.