Biodegradation of the outer silicone insulation of endocardial leads.

BACKGROUND Silicone catheter insulation, larynx prostheses undergo biodegradation. The aims of the study were to verify the conviction that outer silicone lead insulation is biostable and inert in addition to determining the role of macrophages (M) and Staphylococcus aureus (S aureus) strains in the silicone lead insulation degradation. METHODS AND RESULTS Leads removed from 8 patients because of infective and noninfective indications were analyzed with stereomicroscope and classified according to Banacha abrasion classification, and additional analysis using scanning electron microscope was performed. The examination revealed excavations of different shape and depth in the abraded areas. Fresh silicone-insulated lead was cut into fragments. The fragments were cultured with RAW 264.7 macrophage cell line for 9 weeks. Additional lead fragments were placed with S aureus strains: ATCC 25923, ATCC 29213, and K9328H. Lead fragments were also cocultured with the bacterial strains and RAW M. In scanning electron microscope analysis, diminution in silicone was observed. All S aureus strains provoked insulation damage after 9 weeks. The lowest level of degradation of insulation concerned ATCC 25923. Silicone lead fragments in cocultures presented a further gone level of silicone biodegradation. CONCLUSIONS S aureus, macrophages separately, and S aureus and macrophages cocultures initiate the biodegradation of silicone insulation. Differences in the level of biodegradation between strains of S aureus were observed, with the most aggressive reaction toward silicone visible in the cocultures. In vivo silicone biodegradation is initiated by tearing among surfaces of the lead insulation, macrophages may be the crucial cells for the process that may be aggravated by pathogen colonization.