We report a fabrication process for coating neural probes with an ultrafast degrading polymer to create consistent and reproducible devices for neural tissue insertion. The rigid polymer coating acts as a probe insertion aid, but resorbs within hours post-implantation. Despite the feasibility for short term neural recordings from currently available neural prosthetic devices, most of these devices suffer from long term gliosis, which isolates the probes from adjacent neurons, increasing the recording impedance and stimulation threshold. The size and stiffness of implanted probes have been identified as critical factors that lead to this long term gliosis. Smaller, more flexible probes that match the mechanical properties of brain tissue could allow better long term integration by limiting the mechanical disruption of the surrounding tissue during and after probe insertion, while being flexible enough to deform with the tissue during brain movement. However, these small flexible probes inherently lack the mechanical strength to penetrate the brain on their own. In this work, we have developed a micromolding method for coating a non-functional miniaturized SU-8 probe with an ultrafast degrading tyrosine-derived polycarbonate (E5005(2K)). Coated, non-functionalized probes of varying dimensions were reproducibly fabricated with high yields. The polymer erosion/degradation profiles of the probes were characterized in vitro. The probes were also mechanically characterized in ex vivo brain tissue models by measuring buckling and insertion forces during probe insertion. The results demonstrate the ability to produce polymer coated probes of consistent quality for future in vivo use, for example to study the effects of different design parameters that may affect tissue response during long term chronic intra-cortical microelectrode neural recordings.

We describe a series of fluorocarbon surfactant polymers designed for modifying fluorocarbon surfaces such as poly(tetrafluoroethylene). Novel fluorocarbon surfactant polymers poly(Nvinyldextranaldonamide-co-N-vinylperfluoroundecanamide), in which hydrophilic dextran oligosaccharides and hydrophobic perfluoroundecanoyl groups were incorporated sequentially onto a poly(vinylamine) backbone, were synthesized and characterized by FT-IR, NMR, and XPS spectroscopy. By adjusting the feed ratio of dextran to fluorocarbon branches, surfactant polymers with different hydrophilic/hydrophobic balances were prepared. The surface activity of the surfactants at the air/water interface was demonstrated by significant reductions in water surface tension. Surfactant adsorption and adhesion at the solid PTFE/aqueous interface were examined under well-defined dynamic flow conditions, using a rotating disk system. The surface activity at the air/water interface and adhesion stability on PTFE under an applied shear stress both increase with increasing density of fluorocarbon branches on the polymer backbone. The results show that stable surfactant adhesion on PTFE can be achieved by adjusting the hydrophilic dextran to hydrophobic fluorocarbon branch ratio.

These results suggest that: (1) the degree of mechanical trauma at device implantation and mechanical mismatches at the probe-tissue interface affect long term gliosis; (2) smaller, more flexible probes may minimize the glial response to provide improved tissue biocompatibility when used for chronic neural signal recording; and (3) some degree of glial scarring did not significantly affect neuronal distribution around the probe.

We describe a series of fluorocarbon surfactant polymers designed as surface-modifying agents for improving the thrombogenicity of ePTFE vascular graft materials by the reduction of platelet adhesion. The surfactant polymers consist of a poly(vinyl amine) backbone with pendent dextran and perfluoroundecanoyl branches. Surface modification is accomplished by a simple dip-coating process in which surfactant polymers undergo spontaneous surface-induced adsorption and assembly on PTFE/ePTFE surface. The adhesion stability of the surfactant polymer on PTFE was examined under dynamic shear conditions in PBS and human whole blood with a rotating disk system. Fluorocarbon surfactant polymer coatings with three different dextran to perfluorocarbon ratios (1:0.5, 1:1 and 1:2) were compared in the context of platelet adhesion on PTFE/ePTFE surface under dynamic flow conditions. Suppression of platelet adhesion was achieved for all three coated surfaces over the shear-stress range of 0–75 dyn/cm2 in platelet-rich plasma (PRP) or human whole blood. The effectiveness depended on the surfactant polymer composition such that platelet adhesion on coated surfaces decreased significantly with increasing fluorocarbon branch density at 0 dyn/cm2. Our results suggest that fluorocarbon surfactant polymers can effectively suppress platelet adhesion and demonstrate the potential application of the fluorocarbon surfactant polymers as non-thrombogenic coatings for ePTFE vascular grafts.

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