Redox cycling for passive modification of polypyrrole surface properties: effects on cell adhesion and proliferation.

The surface properties of electrodeposited poly(pyrrole) (Ppy) doped with sodium dodecylbenzenesulphonate (NaDBS) are modifi ed by two methods: addition of poly(ethylene glycol) (PEG) during the electrodeposition and through redox cycling post electrodeposition. X-ray photoelectron spectroscopy (XPS) was used to ascertain PEG incorporation and to analyze the change in the oxidation state of the polymer. Anodic cycling resulted in the formation of micrometer-sized surface cracks which increased the amount of Rhodamine-B dye adsorbed onto the surface, and played a role in decreasing the wettability of the surface. The change in surface wettability caused by these cracks was mitigated by the presence of PEG in the Ppy matrix. Compared to the incorporation of PEG, redox cycling was more effective in passively modulating the adhesion of NIH 3T3 fi broblast cells on the Ppy surface. Based on the attenuation of surface polarity of the Ppy surfaces by the incorporated PEG, a mechanism is proposed to explain the observed cell adhesion behavior. the presence of a delocalized pi-electron cloud along the backbone of an otherwise insulating structure. The process of polymerizing through electrodeposition provides a facile method to obtain a desired thickness of these polymers on substrates of different sizes and shapes. A doping agent (dopant) is essential for catalyzing the electrodeposition of these polymers and also to stabilize the polymer backbone by carrying charge in the form of extra electrons. [ 3 ] A variety of dopants have been used, including enzymes, antibodies and even entire living cells. [ 4 ] Polypyrrole (Ppy) is the most widely researched among ICPs because of its good mechanical stability, ease of synthesis and higher conductivity compared to other conducting polymers. [ 5 ] Its biocompatibility makes it suitable for use in