Antimicrobial PVC silver zeolite composites: plasticizers influence

Polyvinyl chloride (PVC) is a polymer widely used in medical field to produce equipments for blood transfusion, medical devices, etc. The replacement of di-2-ethyl hexyl phthalate (DEHP) from PVC processing, reducing or eliminating the health risk caused by its release into environment together with theachievementof antimicrobial properties are undoubtedly important for the development of new PVC products relevant for health care applications. In this study we used PVC plasticized with DEHP, di-isononyl phthalate (DINP) and tris-2-ethyhexyl trimellitate(TOTM) to test the influence of plasticizers on silver release from PVC silver composites. Polymer composites were prepared by mixing PVC pellets with a silver zeolite (SZ) in the amount of 10-20 wt%. The antibacterial activity of PVC SZ composites was tested on Escherichia coli and Staphylococcus epidermidisin culture broth, on agar plate and in sterile urine seeded with these strains for simulation purposes. The results indicate that the addition of large amount of SZ did not influence the processability and the formability of the composites as well as their thermal and mechanical properties, if compared to neat plasticized PVC. Composites showed antibacterial activity against S. epidermidis and E. coli in culture broth, direct inhibition on agar plate andin urine supplemented with bacteria. PVC-DEHP SZ composites exhibited a good antimicrobial activity at 10% wt of silver zeolite, while the best performance of composites of PVC plasticized with DINP and TOTM was at 20% wt of silver zeolite. In sterile urine, composites induced a significant reduction of viability of both strains already at 24 h, inhibiting E. coli growth up to 20 days, whereas their antimicrobial action against S. epidermidis vanished within 5 days. Data on silver release suggest that the different steric hindrance of plasticizers influence the migration and release of the antimicrobial agent from polymeric matrix to the environment.