Whole cell biosensors--electrochemical and optical approaches to ecotoxicity testing.

Two different approaches to the interrogation of prokaryotic and eukaryotic cells have been explored, with the objective of developing biosensor based rapid ecotoxicity test protocols for use in a wide range of applications. Prokaryotic cells and some eukaryotic cell types lend themselves to interrogation by mediated amperometry, a technique that allows metabolic activity of the cell to be monitored by accessing cellular redox events with a chemical mediator. Reduction of the mediator by the cell is followed by re-oxidation at an electrode surface poised at a fixed potential. The resulting current flow is proportional to the metabolic status of the cell. A commercial ecotoxicity test, CellSense, employing such whole cell biosensors has now been developed. An alternative approach to interrogation of vertebrate cells has been the use of luminescent reporter genes to determine changes in the metabolic status of the cells following environmental challenge. Several clones have been established of epithelial cells from the bluegill sunfish (BF-2), transfected with the pCIneoLuc plasmid, that express luciferase constitutively. Protocols using these transformed cells are being developed to provide an alternative to the standard neutral red retention test.