Towards a Biocompatible, Biodegradable Copolymer Incorporating Electroactive Oligothiophene Units

As part of an ongoing effort to develop biocompatible, biodegradable conducting polymers, we report here the synthesis and characterization of a novel copolymer, 5,5"'bishydroxymethyl-3,3"'-dimethyl-2,2':5',2":5",2"'-quaterthiophene-co-adipic acid polyester (QAPE). This system was designed so as to incorporate alternating electroactive quaterthiophene units and biodegradable ester units into one macromolecular framework, while allowing for facile preparation of the polymer via a polycondensation reaction. In agreement with the design expectations, the ester groups were found to be incorporated into the polymer between the quaterthiophene subunits, as inferred from standard chemical and spectroscopic analyses. QAPE exhibited redox activity as detected by cyclic voltammetry and a new red-shifted absorption peak upon doping, providing support for the notion that the quaterthiophene units maintain electroactivity after incorporation into the QAPE polymer framework. The degradation, likely through surface erosion, of this polymer in the presence of cholesterol esterase was confirmed by the detection of a fluorescence signal at wavelengths corresponding to the quaterthiophene subunit and comparisons to appropriate controls. In vitro cytocompatability studies, carried out over 48 h, indicate that the QAPE polymer is nontoxic to Schwann cells.