In-vivo biocompatibility testing of diamond, cobalt and titanium alloy particulates

Objective: The aim of this study was to evaluate the inflammatory reactions to simulated wear debris (diamond, titanium and cobalt alloy) particulates from biomaterials for TMJ prosthesis using rat subcutaneous air pouch model. Materials and methods: Imaging was used to analyze the size, shape and the concentration of the particulates. Particulates were sterilized and suspended in a sterile saline and FBS mixture at 107particles/ml followed by ultra-sonication for even distribution in the suspension. Limulus amebocyte lysate test was performed to ensure the absence of endotoxin. Rats were divided into 3 groups of 4 each, and pouches were prepared according to the method of Edwards et. al. using a subcutaneous injection of twenty milliliters (ml) of air. After 4 days the pouches were reinjected with 10 ml of air and on day six 5 ml of particulate suspensions were injected. Twenty four hours later, under sedation, the pouches were irrigated with 5 ml of sterile saline, fluids were withdrawn and centrifuged and the supernatant was assayed for Tumor Necrosis factor Ą (TNF Ą), and Interleukin 6 (IL-6). Rat were Euthanized following the pouch aspiration and the entire pouch was harvested and preserved in formalin for histology. Results: Rat pouch H&E histology studies for acute inflammation were done by counting polymorphonuclear cells per region using 3 regions per slide. Statistically there was no significant difference in the inflammatory reaction between the three groups. The cytokine results showed levels of TNF Ą and IL-6 that were similar to controls and prior literature. Conclusion: Studies of simulated wear debris from diamond coatings on titanium and cobalt alloys demonstrated biocompatibility profiles that were mild to moderate and similar to prior analysis of wear debris products in synovial pouch models. NIDCR Grant # 1 RO1 DE 13952-O1A1.