Electroactive Polymeric Biomaterials

Conjugated polymers are attractive materials for interfacing electrically conducting devices with biological tissue. These polymers, which can be electrochemically polymerized on metal electrodes, are electrically and ionically conductive, mechanically softer than metals, and have low cytotoxicity. The surface area of conjugated polymers can be tailored to create films with low electrical impedance. In addition, through synthetic chemistry or electrochemical doping, biological molecules can be incorporated into conjugated polymer films. These properties enable conjugated polymers to effectively interface with ionically active tissues, most often nervous tissue. This chapter will focus on the conjugated polymers that have received the most attention for interfacing with tissue, polypyrrole (PPy) and poly(3,4-ethylenedioxythiophene) (PEDOT). Derivatives of these polymers that can covalently bind to biological molecules, such as peptides, have been developed, along with composites of the polymers with hydrogels, which have greater tissue-like properties. Coatings of PPy and PEDOT have been put on devices, including neural probes, and made into fibers for neural regeneration. Many current research projects focus on addressing biological reactions that occur upon implantation of devices, such as inflammation and gliosis. Potential solutions to these problems include electrical actuation of conjugated polymers for drug delivery and in vivo electrochemical polymerization.