In vivo evaluation of tetrahedral amorphous carbon

The in vivo behavior and tissue reaction to tetrahedral amorphous carbon (ta-C) has been evaluated for periods of up to 6 months in SV129 mice. Two sample types were tested-silicon die coated with ta-C (n=53) and micromachined particles (n=40). The coated samples were compared to uncoated silicon die (n=22). Die samples were implanted subcutaneously, and tissue reaction and capsule formation were evaluated at various time points. Micromachined particles of 1, 3 10, and 30 mum were injected adjacent to the sciatic nerve, and tissue samples were examined histologically at various time points (4 days-6 months). Tissue reaction to ta-C was mild and was localized to the area of the injection or implantation. Samples with a higher ratio of 3-fold bonding appeared to shed material during the experiments; this was not observed on samples with a higher level of 4-fold bonding. nor on uncoated silicon die. The results strongly suggest that films with greater 4-fold bonding character (more diamondlike) are more resistant to in vivo fragmentation than films with higher 3-fold character (more graphitic) (C) 2004 Elsevier Ltd. All rights reserved.