Exploring the landscape of FRET-based molecular sensors: Design strategies and recent advances in emerging applications

Probing biological processes in living organisms that could provide one-of-a-kind insights into real-time alterations of significant physiological parameters is a formidable task that calls for specialized analytic devices. Classical biochemical methods have significantly aided our understanding of the mechanisms that regulate essential biological processes. These methods, however, are typically insufficient for investigating transient molecular events since they focus primarily on the end outcome. Fluorescence resonance energy transfer (FRET) microscopy is a potent tool used for exploring non-invasively real-time dynamic interactions between proteins and a variety of biochemical signaling events using sensors that have been meticulously constructed. Due to their versatility, FRET-based sensors have enabled the rapid and standardized assessment of a large array of biological variables, facilitating both high-throughput research and precise subcellular measurements with exceptional temporal and spatial resolution. This review commences with a brief introduction to FRET theory and a discussion of the fluorescent molecules that can serve as tags in different sensing modalities for studies in chemical biology, followed by an outlining of the imaging techniques currently utilized to quantify FRET highlighting their strengths and shortcomings. The article also discusses the various donor-acceptor combinations that can be utilized to construct FRET scaffolds. Specifically, the review provides insights into the latest real-time bioimaging applications of FRET-based sensors and discusses the common architectures of such devices. There has also been discussion of FRET systems with multiplexing capabilities and multi-step FRET protocols for use in dual/multi-analyte detections. Future research directions in this exciting field are also mentioned, along with the obstacles and opportunities that lie ahead.