Construction Of Polypyrrole-based Bioactive Interface For Detecting Cell Behaviors: Toward Cell-Electronics

The new term “Cell-electronics” in this thesis used the “Genoelectronics” for reference. The term “Genoelectronics” was first introduced by Joseph Wang in 1999 and was used to describe the interface between nucleic acid molecular- recognition system and electronic system. Its ultimate goal was directly translating the specific DNA recognition reaction into electrical signal. In this project, “Cell-electronics” was expected to build an effect interface between cell biological system and electronic system for signal two-way transfer between them. Future, this “Cell-electronics” interface could be used for detecting the cell biology behavior(cell information into electrical signals) and regulating the cell biology behavior(control cell by external electrical signal). In addition, for the research of “Cell-electronics”, it will involve complementary knowledge, such as material science, electronics, cell biology, surface science, etc., so its research will be full of challenges and opportunities.Polypyrrole(PPy), as a new conjugated conducting polymer, provided an opportunity for the research of “Cell-electronics”. It has been presented that PPy not only provided a robust biological activity surface for cell adhesion and proliferation, but also acted as excellent “molecular wires” to connect the cell biology system and electronics system. Based on these knowledge, our works focused on the construction of coupling interface between cell biology system-electronics detection system with different characterizations using the doping mechanism of PPy. This PPy based coupling interface could be used to regulate the cell biology behaviors and translate the cell behavior information into electronic impedance signal. Based on principle mentioned above, cell-based impedance biosensor could be built for detecting cell bio-behavior information. In addition, these work will make a contribution for the development of “Cell-electronics” in future.In our thesis, four aspects of works have been done:(1) Fabrication of a simple interface between cell and electronic impedance detection system based on dry film Photoresist-indium tin oxide(DFP-ITO) electrode for detecting the cellular information. Results showed that the DFP-ITO electrodes with different diameters had similar impedance characteristics. Fully cured dry film photoresist could provide an appropriate surface for A549 cell adhesion and had no obvious cytotoxicity. The cellular impedance sensor based on the DFP-ITO electrode could be used to obtain the morphological data and analyze the changes of the cytoplasm membrane capacitance, cell-cell gap resistance and cell-ITO electrode gap resistance during the process of adhesion and proliferation of A549 cell by optical microscope and impedance spectrum technology respectively.(2) Polypyrrole(PPy) layer was electrodeposited on the surface of the Indium tin oxide(ITO) microelectrode by electrochemical cyclic voltammetry to from the PPy-ITO microelectrode. Then the PPy-ITO microelectrode was used as coupling interface between cell and electronic impedance detection system for detecting the cellular information. The results showed that the PPy-ITO microelectrode prepared under optimal parameter(electrodeposition for five cycles) had a lower electrical impedance and a better cell compatibility than the naked ITO microelectrode. The changes of cytoplasm membrane capacitance, intercellular resistance and the gap resistance between cell and polypyrrole during the processes of adhesion, proliferation and epithelial-mesenchymal transition(EMT) of A549 could be detected by a cell impedance biosensor based on the PPy-ITO microelectrodes.(3) Fabricaiton of a graphene oxide/polypyrrole-indium tin oxide(GO/PPy-ITO) microelectrode for detecting cell adhesion and proliferation. Results showed that the GO/PPy nanocomposite electrodeposited on the surface of the ITO microelectrode had a special structure of smooth surface and abundant micro-pore distribution. Compared with bare ITO microelectrode, GO/PPy-ITO microelectrode had a lower impedance and higher electrochemical activity. Meanwhile, A549 cells cultured on GO/PPy-ITO could attach, spread and proliferate more rapidly than pure PPy. Finally, as the adhesion and proliferation of A549 cells on the surface of GO/PPy-ITO microelectrode would change the impedance spectrum characteristics of the electrode system, the information on the cell adhesion and proliferation could be obtained by fitting the impedance spectrum data with the equivalent circuit model.(4) A biomimetic RGD peptide doped polypyrrole(PPy/RGD) film was synthesized on indium-tin-oxide(ITO) microelectrode for electrochemical impedimetric sensing of cell proliferation and cytotoxicity. The results showed that compared to the ITO electrode and PPy/PSS films, PPy/RGD films can promote the spread of A549 cells, adhesion and proliferation. PPy/RGD-ITO based impedimetric cell sensor can characterize cell proliferation, cell membrane capacitance, cell-cell gap resistance, and quantitatively measure the paridis saponins I induced cytotoxicity.