Development of a whole-cell-based biosensor for detecting histamine as a model toxin.

A novel whole-cell potentiometric biosensor for screening of toxins has been developed. The constructed biosensor consists of a confluent monolayer of human umbilical vein endothelial cells (HUVECs) attached to an ion-selective cellulose triacetate (CTA) membrane modified with a covalently attached RGD (arginine-glycine-aspartic acid) peptide sequence. When the HUVECs form a confluent monolayer, ion transport is almost completely inhibited, thereby reducing the response of the ion-selective electrode (ISE). When the monolayer is exposed to agents that increase its permeability (e.g., toxins), ions can diffuse through the membrane, and a potential response from the ISE is achieved. Histamine, a model toxin that increases the permeability of HUVEC monolayers, was used in this study. When the cell-based membranes are exposed to varying concentrations of histamine, the overall response increases with increasing histamine concentration. Thus, the measured potential is an indirect measurement of the histamine concentration. Further experiments were performed for a similar molecule, l-histidine, to test for selectivity. The cell permeability was unaffected by l-histidine, and the sensor response remained unchanged. This type of sensor should find multiple applications in medical, food, and environmental fields and in homeland security.