A fluorescent biosensor based on glucose oxidase-DNAzyme/substrate complex synergy for salivary glucose monitoring

Non-invasive glucose sensing technology exhibits significant clinical potential for continuous diabetes monitoring and early screening in high-risk populations. Herein, we developed a modular fluorescent biosensor for salivary glucose monitoring through synergistic integration of a detection module (glucose oxidase) and a signal transduction module (PL DNAzyme-substrate complex). The sensing system employs a fluorophore/quencher pair-modified PL DNAzyme-substrate complex as a fluorescence switching element. Experimental results showed a linear detection range from 40 nM to 1.0 mM with a detection limit of 4.3 nM, demonstrating a 1163-fold improvement in sensitivity compared with the previous version. The biosensor exhibited excellent specificity and stability. It was used to detect 2-h postprandial saliva samples from 15 participants (mean glucose concentration: 53.7 ± 19.5 μM), and its extended functionality was demonstrated through continuous daily monitoring of three participants and 14-day consecutive tracking tests, which successfully captured temporal glucose fluctuations. This work presents a fluorescence-based platform for non-invasive salivary glucose monitoring, while its modular architecture provides a versatile framework for future performance optimization through component substitution.