New anti-infective coatings of medical implants show promise
Implantable devices are highly susceptible to infection and therefore a major risk in surgery. The present work presents a novel strategy to prevent formation of a biofilm on PTFE grafts. Methods: PTFE grafts were coated with gentamicin and teicoplanin incorporated in different lipid-like carriers under aseptic conditions in a dipping process. Poly-D, L-lactic acid, tocopherol acetate, the diglyceride Softisan®649 and the triglyceride Dynasan®118 were used as drug carriers. Drug release kinetics, anti-infective characteristics, biocompatibility and haemocompatibility of developed coatings were studied. Results: All coatings showed an initial drug burst followed by a low continuous drug release over 96 hours. The dimension of release kinetics depended on the carrier used. All coated prostheses reduced bacterial growth even beyond pathologically relevant concentrations drastically over 24 hours. Different cytotoxic levels could be observed bringing up tocopherol acetate as the most promising biocompatible carrier. A possible reason for the highly cytotoxic effect of Softisan®649 could be assessed by demonstrating incorporated lipids in the cell soma with the Oil Red O staining. The performance of tromboelastography studies, ELISA assays and an amidolytic substrate assay could confirm haemocompatibility of individual coatings. Conclusions: The development and in-vitro studies of described biodegradable drug delivery systems highlight the most important requirements for an effective as well as compatible anti-infective equipment of PTFE grafts. Through continuous local release, high drug levels can be obtained at only the targeted area, physiological bacterial proliferation can completely be inhibited while at the same time biocompatibility as well as haemocompatibility can be ensured.
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