Nanomaterial-Enabled Fiber-Optic SPR Biosensor for Continuous and Noninvasive Body Fluid Monitoring:Progress and Prospects.

Continuous and noninvasive body fluid monitoring has attracted increasing attention in personalized healthcare, chronic disease management, and wearable point-of-care testing. Fiber-optic surface plasmon resonance (SPR) biosensors are particularly promising for this purpose because they combine label-free and real-time with miniaturization and low sample volume requirements. However, current body fluid sensing technologies and conventional bare metal SPR interfaces still face critical challenges, including insufficient analytical accuracy in complex biofluids, broad resonance linewidths, weak signal readability for trace biomarkers, and mechanical perturbations during wearable operation. These limitations highlight the need for nanomaterial-engineered fiber-optic SPR platforms that can convert interfacial molecular events into stable and sensitive signals. The review summarizes recent progress in nanomaterial-enabled fiber-optic SPR biosensors for continuous body fluid monitoring. Emphasis is first placed on nanomaterial mediated local electromagnetic field enhancement and plasmonic mode regulation. Subsequent discussion focuses on their functions in interfacial recognition, analyte enrichment, rapid mass transport, antifouling protection, and flexible integration for continuous operation. On this basis, representative sensing targets, material strategies, and device architectures for tears, urine, exhaled breath condensate, saliva and sweat are systematically analyzed. Finally, current challenges and future opportunities are discussed from the perspective of sensing reliability, wearable integration, and real sample validation.