Recently a whole cell based biosensor has been developed in our laboratory that consists of a monolayer of human umbilical vein endothelial cells (HUVECs) on the asymmetric cellulose triacetate (CTA) membrane of an ion selective electrode (ISE). When a confluent cell monolayer is formed across the membrane, response from the sensor is inhibited due to inhibited ion transport across the membrane. When the cell based biosensor is exposed to permeability modifying agents, the permeability across the cell monolayer is altered facilitating more ion transport and as a result the response from the sensor increases. This sensor response can be related to the concentration of these agents. One objective of this research was to investigate the ability of the sensor to detect a physiological toxin, alpha toxin from Staphylococcus aureus. Studies demonstrated that the biosensor can detect 0.1ng/ml alpha toxin. Considering the fact that the concentration of this toxin is 100-250 ng/ml in whole blood in humans, this biosensor has the ability to act as the diagnostic tool for staphylococcal diseases. Another part of this research was to investigate the ability of the biosensor to measure angiogenesis by measuring the changes in permeability induced by cytokines such as vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF) and tumor necrosis factor andamp;aacute; (TNF- andamp;aacute;) individually and in combination. The sensor response was then compared with the common in vitro assays for angiogenesis. The study demonstrated that at the concentrations studied the sensor response in the presence of cytokines was much higher than that observed for other angiogenesis assays, thereby bolstering the potential of the biosensor to act as a quick screening tool for angiogenesis. Furthermore, epithelial cell based sensor responses to the same cytokines were compared with the responses from endothelial cell based sensor and the mechanisms behind the increased sensor response were elucidated. Finally, to investigate the ability of the sensor to screen cancer, the biosensor was exposed to the serum from healthy individuals and cancer patients. The results showed that the sensor can distinguish between healthy individuals and cancer patients and the results correlate with the stages of cancer.