Synthesis, characterization, microfabrication, and biological applications of conducting polymers

Electrical stimulation on cell growth has been investigated extensively in vitro, especially on bone cells. This serves a good pre clinical study for treating injured bones since it has been demonstrated electrical stimulation, in spite of the mode, current or field, AC or DC, coupled or induced, continuous or pulsed, can be beneficial in terms of bone regeneration and osteogenesis if appropriately adjusted. The current study is trying to bring conducting polymers (CPs) into this field to replace the metal electrodes here. Not only do CPs offer a cheaper, more convenient, biocompatible alternative, the flexibility in synthesis and structure modification can bring unique properties to the electrode material as well. Based on this concept, we designed the synthesis scheme of our own CPs after we have failed the in vitro biocompatibility tests on several commercially available CPs. The thus synthesized CPs are a series of sulfontated polyaniline (SPAN). We chose these due to reported good conductivity stability of SPAN within a fairly wide range of pH value. After the synthesis, we conducted a thorough physical properties and chemical structure analysis, making sure the thus obtained polymers satisfied all the requirement of this study. In vitro cell culture also indicated generally good biocompatibility. To build the electrical field in a more precise fashion so that we could relate the cellular responses to the electrical stimulation conditions in a more quantitative way, we turned to Microfabrication techniques for processing the thus synthesized CPs. In addition to Interdigitated Electrodes (IDEs), which is the major type of electrical field configuration we used in this study, we developed innovative techniques for making other patterns in miniature size with CPs too. The applications can range from thin film organic transistors to CPs based biochemical sensors. Followed the Microfabrication, we started working on the electrical stimulation of bone cells with our SPAN made electrodes. Both DC and AC electrical field effects are investigated. Not only have we obtained the similar positive results as previous researchers reported, we also found something different. Those common effects are increase in proliferation, membrane permeability as well as calcium deposition and alkaline phosphatase activity. Others particular to this study are non-linear dependency of voltage and frequency. Also we found a unique distribution of cell growth based on our special field strength arrangement. This study is limited to low frequency and low amplitude. Phenomena like altered cell orientation or polarization, dielectrophoresis, etc., due to the applied electrical stimulus have not been observed. In the end, we conducted a detailed survey of all materials involved in the process of cells responding to the electrical stimulation, including the dielectric layer, the electrode SPAN itself, and the cell membrane. We managed to combine all the physics, biology, and electrical engineering theories together, successfully explained all the experimental results we have seen. We believe the current study serves as an excellent guide for bring conducting polymers from lifeless electronics area into the live biological world.