Fabrication of ITO/Gold nanoparticle/RGD peptide Composites to Enhance Electrochemical Signals from Human Neural Stem Cells Tae-Hyung Kim * , Waleed Ahmed El-said ** and Jeong-Woo Choi *** * Department of Chemical & Biomoleucular Engineering, Sogang University, #1 Sinsoo-dong, Mapo-Gu, Seoul 121-742, Korea, thkim0512@gmail.com ** Interdisciplinary Program of Intergrated Biotechnology, Sogang University, #1 Sinsoo-dong, Mapo-Gu, Seoul 121-742, Korea, waleed@sogang.ac.kr *** Department of Chemical & Biomoleucular Engineering and Interdisciplinary Program of Intergrated Biotechnology, Sogang University, #1 Sinsoo-dong, Mapo-Gu, Seoul 121-742, Korea, jwchoi@sogang.ac.kr ABSTRACT Gold nanoparticles (GNP) and RGD peptide modified indium tin oxide (ITO) electrode was fabricated to enhance the electrochemical signals from neural stem cells (HB1.F3). Aminopropyltrimethoxylane (APTMS) was self- assembled on ITO electrode surface to immobilze GNP and its topological characteristics were confirmed by scanning electron microscopy (SEM). Thereafter, cysteine containing RGD peptide (RGD-MAP-C) was self-assembled on GNP immobilized surfaces via strong Au-S bond. Cells were seeded on the fabricated surface, and their electrochemical characteristics were analyzed by cyclic voltammetry (CV). As a result, ITO/GNP/RGD peptide composite was found to give highest redox signals compared to the bare ITO, ITO/RGD peptide and ITO/GNP substrate. Finally, the cell proliferation on different substrates were also analyzed by trypan blue assay to verify the effects of ITO/GNP/RGD peptide composites on human neural stem cells. Our newly fabricated substrate can be usefully applied for both electrochemical and optical study of stem cells. Keywords: ITO electrode, gold nanoparticle, RGD peptide, electrochemical method, stem cell chip 1 INTRODUCTION A cell chip was recently introduced to increase the reliability and sensitivity of in vitro assay by detecting redox behavior of living cells 1 . A variety of electrochemical tools have been employed to detect the electrochemical response of living cells, such as open circuit potential at the cell/electrode interface 2 , electric cell-substrate impedance sensing (ECIS) 3 , cyclic voltammetry (CV) 4 and differential pulse voltammetry (DPV) 5 . All these electrochemical methods were proven as efficient tool for the determination of cell viability with high sensitivity and accuracy. However, the working electrodes mainly composed of gold (Au) or other metals used for the sensitive detection of electron-transfer or generation of living cells were found to be improper for the integration of other valuable techniques such as confocal microscopy, Raman spectroscopy and optical microscopy 2-5 . A transparent conducting material, indium tin oxide (ITO)-deposited glass substrate, was utilized as a working electrode to replace the gold electrode for the integration of other optical techniques 6 . Unfortunately, the sensitivity of cell chip composed of ITO working electrode was found to be significantly decreased due to the low electrochemical activity of ITO surface that sacrificed huge advantage of electrochemical method. Besides the electrochemical activity and resistance of working electrode in cell chip, surface modification of electrode surface is another important issue for the enhancement of sensitivity of cell chip. Since the sensitivity of cell chip depends on the electron transfer between cell and electrode surface generated by the redox characteristics of cells, the surface modification of working electrode for establishing in vivo-like condition is very important step for the increase of cell adhesion, proliferation and spreading on electrode surface that directly affects the sensitivity of cell chip. ECM or its components are well-known biomaterials which have excellent ability for increasing cell adhesion on artificial surface via integrin receptor-based linking 7 . Consequently, a variety of ECM proteins or its components (e.g., fibronectin, collagen, PLL, RGD etc.) were modified on cell chip to attach living cells to electrode surface by chemical or physical adsorption that showed remarkable performance for cell adhesion 8-9 . However, the uncontrolled thickness of ECM proteins decreased the electrochemical sensitivity of working electrode and caused the decrease of sensitivity 10 . Hence, advanced technique which can enhance cell adhesion without decreasing the electrical sensitivity of electrode is needed. We have previously reported a cell chip modified with newly developed RGD peptide that entails the cysteine residues at the end of its sequence 11 . By using cysteine- containing RGD peptide, RGD peptide could be easily modified on the electrode surface by simple self-assembly technique that showed significant enhancement of the redox peaks from cells on electrode surface compared to the other NSTI-Nanotech 2011, www.nsti.org, ISBN 978-1-4398-7138-6 Vol. 3, 2011 60