In this PhD project, biological sensors based on yeasts and enzymes will be investigated by electrochemical impedance spectroscopy methods. The biological sensor will be created and used for the investigation of toxicity. Electrochemical impedance spectroscopy will be used to determine cells or enzymes electrochemical activity dependent on toxic material concentration. These characteristics are very important in cell damage diagnosis, which can be related to toxic material influence on cell’s viability. For the single cell researches two methods will be used for experimental research: scanning electrochemical microscopy (SECM) and atomic force microscopy. Both of them can work in the cell’s natural environment, and evaluate single cells locally. Since SECM is equipped with ultramicroelectrode, it will be possible to detect the effect of low concentrations toxic materials. Additionally, SECM will be applied in order to register local electrochemical impedance spectroscopy and register changes in cell viability immediately. Atomic force microscopy can be used to evaluate cell’s morphological changes according to damage.