Advances in portable fiber optic-based aptasensors for on-site detection: design, evolution, and application

The emergence of on-site detection using portable devices has transformed traditional analytical methods, which rely on precise but bulky laboratory instruments, into a promising technique for point-of-care testing. In this case, fiber optic (FO)-based aptasensors, featuring miniaturized devices, high sensitivity, and strong specificity, are candidates to meet the requirement of on-site detection. To enhance the interaction between light and the surrounding environment, numerous FO probes with novel micro/nano-structures have been designed, including tilted fiber Bragg grating (TFBG), long-period grating (LPG), bent, microfiber, D-shaped, and photonic bandgap fibers. Aptamers fold into unique tertiary structure to specifically and sensitively bind with their targets through a direct reaction or a binding-induced structural switch. Benefitting from advancements in FO probes and aptamers, multiple FO-based aptasensors have been constructed for sensitive detection, including evanescent wave-based, fluorescent-, localized surface plasmon resonance (LSPR)-based, and interferometer-based sensors. To date, FO-based aptasensors have been widely applied in clinical diagnosis, environmental monitoring, and food safety. This review focuses on design strategies, evolution, and applications of FO-based aptasensors. The opportunities and challenges of FO-based aptasensors for on-site detection are discussed in depth. This review aims to highlight the significance of FO-based aptasensors for on-site detection and promote their development from laboratory research to practical application.