Chapter 15: Cell-based Bioluminescent Biosensors

Cell-based biosensors are designed to take advantage of the unique selectivity afforded by biological recognition elements in combination with a protein reporter that generates a measurable signal, i.e., fluorescence, chemiluminescence, bioluminescence, colorimetric or electrochemical. These biosensors are constructed, in general, by transforming a living bacterial cell with an engineered plasmid on which the expression of a reporter protein is under the regulatory control of a promoter/regulatory protein which recognizes an analyte of interest. As a result of this design, the biosensors are capable of rapid, specific/selective, and sensitive measurement in standard as well as miniaturized, rugged, portable platforms. A further benefit of cell-based biosensors is that they provide information regarding the bioavailablility of the analyte in a sample. Cell-based biosensors have been developed using a number of genes for luminescent proteins such as prokaryotic and eukaryotic luciferases, green fluorescent protein (GFP) and its mutants, aequorin, and β-galactosidase. The spectrum of analytes for which cell-based biosensors have been constructed is constantly expanding. Currently, there are biosensors designed to detect general toxicants as well as stress factors and specific analytes or groups of analytes such as metals, inorganic molecules, organic pollutants, antibiotics, sugars, and quorum sensing molecules. Additionally, the development of rugged biosensors, like those based on spore-forming microbes, the miniaturization of cell-based assay formats, and their incorporation onto microfluidics platforms will further expand the applications in on-site environmental/clinical analysis.