Despite the fact that great advances have been made during the last two decades to quantify physiological activities in cultured cells using optical microscopes, quantification has been difficult. Electrical cell-substrate impedance sensing, ECIS, is a method which detects morphological changes and movements in cultured cells. However, direct observation of the cell-substrate interface is not possible in this technique. In addition, attachment and interaction of any other biological materials can affect the results. Most importantly the system cannot distinguish different biological interactions and cell behaviours, such as motion, spreading and attaching. Direct observation of the dynamic processes in the cell membrane in real time in a natural aqueous environment can provide a new tool for studying cell behaviour on substrates, the bio-surface interaction and the reaction of the cells to different agents and drugs. We introduced ‘waveguide evanescent field fluorescence (WEFF) microscopy. It was utilized for visualizing and quantifying cell-substrate distances and solid thin films. Recently, we used WEFF microscopy to investigate the cell-substrate interactions in vitro and in real time in the presence of toxic chemical substances. The images of single cell-substrate contact regions and the induced change at the focal and close contact regions by an external toxic and lethal agent in real time in an aqueous medium were monitored and captured. This method can be a new and powerful way to investigate and quantify the dynamics of biological interface phenomena in vitro and has potential as an alternative to animal testing for toxicology studies.
