Pyrrole–hyaluronic acid conjugates for decreasing cell binding to metals and conducting polymers

Surface modification of electrically conductive biomaterials has been studied to improve biocompatibility for a number of applications, such as implantable sensors and microelectrode arrays. In this study we electrochemically coated electrodes with biocompatible and non-cell adhesive hyaluronic acid (HA) to reduce cellular adhesion for potential use in neural prostheses. To this end, pyrrole-conjugated hyaluronic acid (PyHA) was synthesized and employed to electrochemically coat platinum, indium–tin oxide and polystyrene sulfonate-doped polypyrrole electrodes. This PyHA conjugate consisted of (1) a pyrrole moiety that allowed the compound to be electrochemically polymerized onto a conductive substrate and (2) non-adhesive HA to minimize cell adhesion and to potentially decrease inflammatory tissue responses. Our characterization results showed the presence of a hydrophilic p(PyHA) layer on the modified electrode, and impedance measurements revealed an impedance that was statistically the same as the unmodified electrode. We found that the p(PyHA)-coated electrodes minimized adhesion and migration of fibroblasts and astrocytes for a minimum of up to 3 months. Also, the coating was stable in physiological solution for 3 months and was stable against enzymatic degradation by hyaluronidase. These studies suggest that this p(PyHA) coating has the potential to be used to mask conducting electrodes from adverse glial responses that occur upon implantation. In addition, electrochemical coating with PyHA could potentially be extended for the surface modification of other metallic and conducting substances, such as stents and biosensors.