Biocompatibility of implants in plastic surgery and allergenic potential of materials

The present study investigated the tissue compatibility and allergenicity of three implant materials, titanium, silicone, and polyurethane, which are commonly used in cosmetic and reconstructive surgery, by combining in vitro, in vivo, and clinical assessments. In vitro, human lung fibroblasts (MRC-5) and monocytes (THP-1) were treated with the three materials, and their cytotoxicity was assessed by measuring cell viability. The results showed that the titanium group exhibited the highest cell viability (97.4% for MRC-5 and 95.9% for THP-1), indicative of no significant cytotoxicity; the silicone group showed moderately reduced viability (88.1% and 85.6%, respectively), indicative of weak cytotoxicity; and the polyurethane group displayed markedly reduced viability (62.5% and 59.8%, respectively), indicative of strong cytotoxicity. Correspondingly, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) concentrations in the cell supernatants were minimal with titanium exposure, moderately increased with silicone, and markedly increased with polyurethane. In vivo, titanium implantation in rabbits caused a short-term inflammatory reaction, silicone induced moderate, partially reversible alterations, and polyurethane provoked permanent inflammation with necrosis. Titanium induced a thin stable capsule, silicone induced moderate fibrosis with lymphohistiocytic infiltration, and polyurethane induced chronic inflammation and immature fibrosis. Epicutaneous testing on 78 volunteers indicated no reactions to titanium, mild reversible reactions to silicone in 5.1% of subjects, and severe reactions to polyurethane in 16.7% of subjects, mostly among women under 35. Titanium was the most biocompatible and immunologically inert, while polyurethane was the most sensitizing, requiring a cautious clinical approach.