Abstract
Genetically engineered whole cells as biosensing systems in biosensors have been employed, in the past two decades, for the detection of a variety of analytes. In addition to being rapid, specific/selective, and sensitive, these whole-cell-based sensing systems provide information pertaining to the analyte bioavailability. This information is particularly important to study the effect of harmful/toxic chemicals on living systems. The whole cells used for designing and developing cell-based sensing systems can be either prokaryotic or eukaryotic in nature. These intact prokaryotic or eukaryotic cells can be genetically engineered to recognize the analytes of interest and respond with the production of a measurable signal in a dose-dependent manner. Generally, prokaryotic bacterial whole-cell sensing systems are developed by introducing a plasmid construct with a reporter gene fused to a promoter, which is induced by a target analyte through a regulatory protein. Similarly, a receptor, which is activated by a target analyte, is coupled with a reporter gene for the development of genetically modified eukaryotic cell-based biosensing systems. The most commonly used reporter proteins in whole-cell biosensing include luminescent proteins, such as bacterial and firefly luciferases; green fluorescent protein along with its variants; and β-galactosidase. The analytes that can be detected using genetically manipulated whole-cell sensing systems range from general toxicants and cell stress factors to specific analytes, such as metals, metalloids, organic pollutants, sugars, drugs, and bacterial signaling molecules. In order to develop self-contained sensing devices based on recombinant whole-cell sensing systems, preservation, miniaturization, and portability are important issues that need to be addressed.
