Chitosan is an amino polysaccharide with possible biomedical applications, for example, in bandage materials or as an antibacterial agent or a cytotoxic agent for tumor and cancer cells. In this study, the cytotoxic effect of chitosan (CTSN-P) on MCF-7 breast cancer cells was monitored in a nondestructive and real-time manner by electrical cell-substrate impedance sensing with a fabricated multidisc indium tin oxide electrode array. The electrical impedance characteristics of cell growth on the multidisc electrode were analyzed by equivalent electric circuit modeling. Application of CTSN-P caused deterioration of viability of cells on the electrode substrate and yielded a CTSN-P concentration-dependent decrease in impedance. The 50% cytotoxicity concentrations in a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and impedimetric assay were 1266.60 and 543.17 mu g/mL, respectively. Thus, impedance measurement is suitable for detecting low-dose effects of CTSN-P on the behavior or morphology of live cells. (C) 2018 The Electrochemical Society.