Synthesis and characterization of conducting polymers for use in protein chromatography on a MEMS fabricated micro open parallel plate separators (muOPPS)

The electron conducting polymers, polypyrrole, polyaniline, poly (pyrrole-co-aniline-m-sulfonic acid) and poly (pyrrole-co-2-methoxyaniline-5-sulfonic acid), were successfully synthesized onto a model substrate, i.e., porous silica gel, thorough aniline monomer or 3-aminopropyltriethoxysilane Self-assembled monolayer (SAM). When 3-aminopropyl-triethoxysilane-SAM was used, polymer deposition was maximized. Protein adsorption behavior on these grafted surfaces was studied. These studies included the effects of pH and salt concentration. Copolymerizing only 10 ∼ 20 mol-% sulfonic acid groups substituted aniline to pyrrole monomer dramatically changed protein adsorption. Sulfonic acid groups introduced electrostatic interactions besides hydrophobic interactions, and electrostatic interactions were found to have an important role in protein adsorption and repulsion. When 1M ammonium sulfate was added to lysozyme solution, protein adsorption behavior was influenced by hydrophobic and electrostatic interactions. Polypyrrole and polyaniline homopolymers showed interesting protein adsorption behavior when BSA was used as the model protein. They showed much higher BSA adsorption capacities than bare silica gel, depending on pH. Poly (pyrrole-co-aniline-m-sulfonic acid) and poly (pyrrole-co-2-methoxyaniline-5-sulfonic acid) showed a strong dependence of adsorption capacity on pH.