Integrated smartphone-assisted dual-mode glucose biosensor based on GOx-loaded MOF-derived recyclable Nanozymes for portable diabetes monitoring

The development of portable and highly sensitive sensing platforms is essential for point-of-care diabetes monitoring. The synergistic combination of nanocatalysts with natural enzymes offers a promising strategy for high-performance biomarker detection. Herein, we present a novel dual-mode biosensor for glucose detection that integrates colorimetric and fluorometric readouts into a smartphone-assisted analytical platform. This hybrid design overcomes the inherent instability of natural enzymes and the limited catalytic efficiency of conventional nanozymes through a rationally engineered hybrid nanozyme. The sensing platform was constructed by encapsulating natural glucose oxidase (GOx) within a stable metal-organic framework (MOF) grown on Fe 3 O 4 nanoparticle cores, yielding the composite designated as Fe 3 O 4 @MOF@GOx nanoparticles (FM@GOx NPs). The resulting nanocomposite exhibits enhanced catalytic performance through a synergistic cascade reaction mechanism. The cascade reaction product, oxidized TMB (oxTMB), effectively quenches the fluorescence of Rhodamine B isothiocyanate. Together with the intrinsic color change of oxTMB, this leads to distinct colorimetric and fluorometric shifts, enabling dual-mode detection. The biosensor demonstrates high sensitivity, excellent selectivity, and low detection limits of 0.4 μM (colorimetric) and 2.3 μM (fluorometric). Furthermore, the colorimetric signal is integrated with smartphone-based imaging analysis, wherein captured images are analyzed for their grayscale intensity for real-time glucose quantification. The hybrid nanozyme also shows remarkable stability and can be efficiently recycled multiple times without significant activity loss. The practical applicability was validated by accurately detecting glucose in serum samples from diabetic patients. This integrated and portable sensing platform represents a reliable and user-friendly strategy for diabetes monitoring outside conventional laboratory settings.