BIOCOMPATIBILITY OF SILVER-MODIFIED POLYESTER FOR ANTIMICROBIAL PROTECTION OF PROSTHETIC VALVES

Background and aims of the study: The biocompatibility of a silver-coa ted polyethylene terephthlate (PET, polyester) fabric for the inhibiti on of prosthetic valve endocarditis (PVE) associated with mechanical h eart valves (MHVs) was assessed. The infrequency of PVE is outweighed by mortality rates commonly exceeding 50%. These high mortality rates have been attributed to the poor effect of antibiotic therapy on colon ized valves and infected myocardial tissue. Silver has been used as an antimicrobial for centuries due to its general effectiveness and rela tive lack of toxicity. Our previous work has shown PET polyester fabri c 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 leachin g; and (iii) promote tissue ingrowth and the organization of tissue pa nnus in a short-duration (five weeks) sheep mitral mechanical heart va lve model. Methods: This paper addresses additional biocompatibility a ssessment consisting of a cell compatibility assay in which serum extr acts 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 extra ct concentration reached 1200 p.p.m. Ten-week duration mechanical valv e replacement studies in sheep with uncoated or coated polyester sewin g cuffs showed comparable tissue ingrowth and mature pannus with a sug gestion of a thinner pannus on the silver-coated fabric. Additional an timicrobial testing confirmed the effectiveness of this coating in inh ibiting colonization of polyester fabric. Conclusions: These current r esults, together with the earlier data, suggest that IBAD silver coati ng on polyester facilitates healing and may provide protection against PVE.