A versatile strategy for constructing background fluorescence-free and dual-mode hydrogel nanosensor for sensitive...

The portable sensing platform based on fluorescent test strips has garnered considerable attention due to its advantages of portability, rapid response, and visual analysis. There still have challenges such as probe immobilization during the strip printing process, background fluorescence, and single-mode response. On this basis, a proof-of-concept background-free and dual-mode response hydrogel nanosensor is developed for colorimetric and luminescent detection of amikacin (AMK). The hydrogel nanosensor is prepared based on polyacrylamide (PAM) hydrogel, embedded with upconversion nanoparticles (UCNPs) and congo red (CR). The ion-association reaction between CR and AMK leads to color fading and the restoration of green emission of UCNPs. Compared to traditional paper-based sensors, this hydrogel nanosensor provides a stable liquid-phase detection environment, maintains sensitivity, and avoids background fluorescence through near-infrared excited UCNPs, thereby improving detection accuracy. Furthermore, a portable sensing platform is developed to realize point-of-care, real-time quantitative detection of AMK, with a limit of detection of 1.3 nM. The designed hydrogel nanosensor, featuring dual-signal response and no background interference, offers a versatile sensing strategy for portable, visual, and highly sensitive detection of drug safety and food contaminants.