Development of efficient and sensitive whole-cell biosensors

Abstract

Biosensors are analytical devices that incorporate biological entities, i.e., enzymes, antibodies, nucleic acids (DNA, RNA), and whole cells, such as the sensing moiety. Biosensors have facilitated the detection and quantification of analytes without relying on sophisticated, expensive, and labor-intensive analytical techniques like GC and HPLC. Among the different types of biosensors, whole-cell biosensors (WCBs) stand out as a unique and versatile category. Unlike other biosensors that rely on isolated biomolecules such as enzymes or antibodies, WCBs utilize entire living cells as the sensing element. When microorganisms are used as a whole for biosensing, they are termed microbial whole-cell biosensors (MWCBs). MWCBs utilize the regulatory pathways of microbes, where the DNA sequence elements and regulatory proteins (transcription factors) work in tandem to regulate the expression of genes in the microbial genome. Therefore, the transcription factor, activator or repressor, is pivotal in generating specific and sensitive responses. Although the MWCBs have succeeded in laboratory settings, they have failed to reach the commercial front. However, with the advent of synthetic biology, MWCBs have gained more success by optimizing the sensitivity and specificity of the biosensor. It has opened a plethora of avenues for optimizing the biosensor response, like promoter modifications, reporter protein variation, transcription factor engineering, and changing the RBS of the gene. Also, the chassis for housing the biosensing module can be altered to enhance biosensing attributes like sensitivity, specificity, detection time, etc. MWCBs are widely used in various fields, including medical diagnostics, environmental monitoring, and food safety.