Artificial dural sealant that allows multiple penetrations of implantable brain probes

This study reports extensive characterization of the silicone gel (3-4680, Dow Corning, Midland, MI), for potential use as an artificial dural sealant in long-term electrophysiological experiments in neurophysiology. Dural sealants are important to preserve the integrity of the intracranial space after a craniotomy and in prolonging the lifetime and functionality of implanted brain probes. In this study, we report results of our tests on a commercially available silicone gel with unique properties that make it an ideal dural substitute. The substitute is transparent, elastic, easy to apply, and has re-sealing capabilities, which makes it desirable for applications where multiple penetrations by the brain probe is desirable over an extended period of time. Cytotoxicity tests (for up to 10 days) with fibroblasts and in vivo tests (for 12 weeks) show that the gel is non-toxic and does not produce any significant neuronal degeneration when applied to the rodent cortex even after 12 weeks. In vivo humidity testing showed no sign of CSF leakage for up to 6 weeks. The gel also allows silicon microprobes to penetrate with forces less than 0.5 mN, and a 200-microm diameter stainless steel microprobe with a blunt tip to penetrate with a force less than 2.5 mN. The force dependency on the velocity of penetration and thickness of the gel was also quantified and empirically modeled. The above results demonstrate that the silicone gel (3-4680) can be a viable dural substitute in long-term electrophysiology of the brain.