Ultrathin polyaniline film coated on an indium–tin oxide cell-based chip for study of anticancer effect Waleed Ahmed El-Said b , Cheol-Heon Yea a , Jeong-Woo Choi a,b, ⁎, Il-Keun Kwon c a Department of Chemical & Biomolecular Engineering, Sogang University, #1 Shinsu-dong, Mapo-gu, Seoul 121-742, Republic of Korea b Interdisciplinary Program of Integrated Biotechnology, Sogang University, #1 Shinsu-dong, Mapo-gu, Seoul 121-742, Republic of Korea c Division of Oral Biology School of Dentistry, Kyung Hee University, Seoul 130-701, Republic of Korea abstract article info Available online 12 July 2009 Keywords: PANI Cell-based chip HeLa cell Cyclic voltammetry Anticancer drugs Polyaniline emeraldine base (EB) coated indium–tin oxide (ITO) electrode was prepared for the construction of a cell-based chip. Ultrathin polyaniline PANI film on an ITO was electroactive at neutral pH without co- deposition of an acidic counterion. HeLa cells were cultured on a PANI/ITO substrate and utilized to assess the biological toxicity of anticancer drugs. Cell growth, cell viability and drug-related cell toxicity were evaluated by a cyclic voltammetry (CV) method under a neutral pH. We demonstrated the functionality of a PANI coated ITO electrode for use as a cell chip and found that PANI was a good surface for the HeLa cells to grow without any significant morphological changes. © 2009 Elsevier B.V. All rights reserved. 1. Introduction The factors that play an essential role in cell adhesion mechan- isms are: specific surface chemistry, surface hydrophobicity, topog- raphy, surface charge, and protein interactions [1]. Conductive polymers are found to have widespread use in the development of new biosensing technologies. Enzymes, antibodies and whole living cells [2] have been incorporated as biorecognition elements into inherently conductive polymers. Amongst conductive polymers, PANI is regarded as one of the most technologically promising polymer due to its ease of synthesis, low cost and environmental stability [3,4]. Its chemical, electrical and optical properties can be used to convert chemical information or biointeractions into electrical or optical signals, which can easily be detected by modern techniques [5,6]. Unfortunately, PANI shows electrochemical activity only in acidic conditions. This restricts its applications especially in bioelectrochemistry, since most biocatalytic and immunological reactions occur optimally at neutral pH (pH 7). Many efforts have been focused on adapting PANI to be active at neutral solution pH. This has been done by the introduction of acidic groups into the PANI chains [7], or doping PANI with negatively charged polyelectrolytes [8]. However, all of these approaches cannot obtain polymers with higher degrees of homogeneity. Ultrathin films of PANI have received great interest due to their potential applications in chemical and biological sensors [9]. The Langmuir–Blodgett (LB) technique, electropolymerization, and layer-by-layer self-assembly have been used to deposit PANI thin films onto a variety of electrode materials [10]. It is difficult to prepare homogenous ultrathin (b10 nm) poly- mer films by electropolymerization. Relative to LB deposition self- assembly is advantageous due to both of its technical simplicity and inherent flexibility. A living cell can be properly described as an electrochemically dynamic system; many important processes in living cells have electrochemical characteristics. For example, redox reactions and changes in ionic composition derived from various cellular processes lead to electron generation and electron transfer at the interface of living cells [11,12]. Cell-based sensors are poten- tially useful for studying the effects of drugs and cell–external stimuli interactions [13]. In vitro immobilization of living cells is an important process in the fabrication of a cell-based chip [14], and the interaction between cells and the adhesion of cells to the chip surface can be a reliable candidate for cellular attachment without loss of viability. In the present study, we used ultrathin PANI film deposited on ITO [15]. Unlike metal electrodes such as platinum or gold, PANI deposited on ITO electrode is electroactive at neutral pH without co-deposition of an acidic counterion. Immobilized HeLa cells were used to study the ability of this system to determine the cell viability electrochemically. This method was used to determine the effectiveness of anti-cancer drugs on cancer cell viability. The prepared ultrathin PANI film deposited on ITO surface was demon- strated to be very effective for the immobilization of cancer cells and provide a simple, low-cost and easy method for electrochemical study of cell adhesion, proliferation and the effect of anticancer drugs on cells. Thin Solid Films 518 (2009) 661–667 ⁎ Corresponding author. Department of Chemical and Biomolecular Engineering, Sogang University, Seoul, Republic of Korea. Tel.: +82 2 705 8480; fax: +82 2 3273 0331. E-mail address: jwchoi@sogang.ac.kr (J.-W. Choi). 0040-6090/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.tsf.2009.07.062 Contents lists available at ScienceDirect Thin Solid Films journal homepage: www.elsevier.com/locate/tsf