The miniaturization of neuroprosthetic technology has led to an urgent need for thin, conformal, insulating coatings that retain their biocompatibility and stability over long periods. Silicone coatings have long been used in the medical device industry for their biocompatibility and electrically insulating properties. However, conventional silicone encapsulation technologies are unfit for many miniature medical devices including implantable, chronic microelectrode arrays used in some neuroprosheses. Initiated Chemical Vapor Deposition (iCVD) is an attractive alternative to conventional polymer coatings applied using solvent-based techniques such as dip/spray and curing. iCVD has the benefits of thinness, conformality (conforms very well to complex shapes) and high purity. The goal of this work is to produce electrically insulating, biostable iCVD coatings for chronic neural prosthetic devices. In Phase I, we have demonstrated that iCVD silicone coatings exhibit prolonged stability in simulated in-vivo environments under constant sweeping voltage bias (6+ years under soak without any loss in resistivity), show excellent adhesion and flexibility, are bioinert, and meet USP Plastic Class VI requirements. Furthermore, we have demonstrated a three folds increase in deposition rate via the codeposition of a linear siloxane spacer molecule, making the process even more economically viable for commercialization. In Phase II, GVD will qualify promising deposition conditions and de-insulation methods for neural probe coatings. A serives of in-vitro tests will allow us to downselect the most promising conditions. GVD will partner with Dr. William Shain (Seattle Children's Research Institute) to confirm the suitability of selected probe coating methods through staggered in vivo studies. Upon successful performance demonstrated during the in vivo studies, GVD will design an upgraded coating system optimized for cost-effective commercial production of successful coatings. The ultimate goal of this work is to achieve single step encapsulation of three-dimensional neural probe arrays and of neural prosthetic assemblies. The development of a stable, durable, biocompatible insulating coating under this Phase II will enable that goal to be achieved.
The success of this Phase II will allow GVD to offer to researchers &manufacturers a proven, effective tool for the biocompatible insulation and encapsulation of neuroprosthetic devices capable of augmenting impaired function of the nervous system. The coating developed under this work will overcome shortfalls of other encapsulants and provide greater flexibility in the design of devices, the choice of materials used, and the minimum dimensions which can be achieved in neuroprosthetic devices. Therapeutically, the coating will provide safe and effective protection and enhanced reliability of devices in chronic applications. The long-term impact will be to de-bottleneck the development of devices and accelerate their proliferation as treatments for neurological disorders.