Leaching Rate and Antifungal Effect of Triclosan Incorporated into Silicone

Objective: This study compared three methods to incorporate Triclosan (2,4,4'-trichloro-2'-hydroxydiphenylether) into medical grade silicone (Prestige, UK) in order to evaluate its rate of release from silicone and colonisation by fungi. Three levels of Triclosan (0.2, 0.5, 1%) were assessed, relative to control formulations: without silica, in the presence of silica (1.7%) and pre-adsorbed onto silica. Methods: Test pieces were placed into 20 ml of distilled water at 37°C for 1 day and 1, 2, 4 and 8 weeks. UV spectroscopy was used to quantify the amount of Triclosan leached out and the test pieces were placed onto diagnostic sensitivity testing plates seeded with Candida albicans to observe for zones of inhibition. Mid-level silicone formulations (0.5%) were incubated with C.albicans for 1 and 24 hours at 37°C and cell retention measured as percentage area coverage using image analysis. Results: Release of Triclosan was relative to the concentration present in silicone, with more progressive leaching over the first week in formulations containing silica encapsulated Triclosan. Zones of inhibition were also proportional to the concentration of Triclosan in silicone. Silica encapsulated high dose formulations showed a degree of controlled release behaviour. Yeast cell retention to Triclosan doped silicone was significantly reduced (P<0.05) after 24 hours. Conclusions: This preliminary study has demonstrated in vitro a way of reducing fungal contamination of silicone which could be used to improve the longevity of medical devices. Pre-adsorption of Triclosan onto silica was the preferred method of incorporation as it showed potential controlled release behaviour.