Radical polymerization reactions for amplified biodetection signals

Chemical reactions that provide amplified biodetection signals are essential in point-of-care diagnostics, a category of portable biosensors that should detect nanomolar to attomolar concentrations of clinically actionable biomarkers in bodily fluids without using advanced lab equipment. As an alternative to common signal amplification methods that use enzymes or nanoparticles, radical polymerization has been explored as an approach to sensitive biodetection because of the inherent amplification in the chain-growth process. Polymerization-based biodetection benefits from different types of initiation reactions and a wide variety of monomer choices, making it adaptable to diverse sensing conditions and detection methods. This review presents the many radical polymerization chemistries that have been implemented in biodetection platforms and evaluates their utility. First, we describe the principle of each polymerization-based biodetection and discuss its advantages and current limitations for practical use in the field. Then, we compare all of the methods in terms of performance, equipment-dependence, user-friendliness, and amplification time. Finally, we highlight exciting future directions and opportunities for developing practical biosensors that use radical polymerization reactions to generate signals.