ABSTRACT An integrated opto-electric biosensor is developed that uses an optically transparent and electrically conductive indium tin oxide (ITO) thin film coated on a slide glass substrate. This biosensor can simultaneously acquire the micro-impedance response and microscopic images of live cells in vitro under various toxic agent stimuli. The dynamic response of live porcine pulmonary artery endothelial cells (PPAECs) exposed to various doses of cytochalasin D are comprehensively examined by monitoring the micro-impedance characteristics at a specified frequency and DICM images using the opto-electric biosensor. The change in PPAEC morphology and motility caused by cytochalasin D clearly illustrates the dosedependent actin filament disruption where optical images are correlated with the changes in the micro-electric impedance. INTRODUCTION Micro-impedance sensing has a great deal of potential in quantifying cell physiology by monitoring cells cultured on small gold electrodes [1] Micro-impedance measurements however, are a sensitive and complex function of both cell-cell and cell-substrate interactions. Cellsubstrate interactions, for example, are mediated by integrin receptors that are functionally linked to the actin cytoskeleton. Biophysical cellsubstrate measurements have, therefore, been correlated with widely accepted biochemically established assays for cytotoxicity [2]. Although micro-impedance measurements have proven to be a valuable tool in examining the response of a large group of cells to various dose of cytochalasin D [3], this technique alone cannot completely evaluate inter cellular interactions. In order to properly examine cell-cell, and cell-substrate adhesion, visual techniques are required. Differential interference contrast microscopy (DICM) provides an excellent method for examining these interactions. Both electrically conductive and optically transparent ITO bioelectrodes [4] are combined with an integrated dynamic live cell imaging system. This system can therefore acquire optical and electrical measurements simultaneously, allowing the observation of cytochalasin D effects on live endothelial cells. Of specific interest is the morphological changes caused by the disruption of actin filaments in the cytoskeleton. This biosensor is able to electrically and optically monitor the real-time and label free drug effect on PPEACs with high temporal and spatial resolutions. The actual effect of three actin-affecting drugs (Cytochalasin D, Latrunculin A, and Jasplakinolide) on cell motility has been quantitatively investigated using video-microscopy of cancer cells [5]. The complicated phenomena of cell-substrate interactions and/or cellcell interaction also represent attractive indicators for studying cell signaling and tumor cell inhibition. In tumor cells, for example, it is a major challenge to inhibit the spreading from primary tumor sites to particular organs, which most likely create metastases killing approximately 90% of cancer patients. The present paper presents a new study of morphology and motility of PPAECs caused by cytochalasin D, which inhibits actin polymerization, by using opto-electric biosensors allowing simultaneous dynamic optical and electrical measurements. EXPERIMENT A. Microscopy DICM Senso
