Beyond conventional glucose assays: a dual smartphone-Arduino point-of-care diagnostic platform based on Fe-Zn bimetallic nanozymes.

The increasing demand for decentralized healthcare has accelerated the development of portable point-of-care (POC) diagnostic systems capable of providing rapid, accurate, and user-friendly glucose monitoring. Herein, we report an Fe-Zn bimetallic nanozyme-based colorimetric sensing platform that integrates smartphone-assisted digital image analysis and Arduino-based signal acquisition for portable glucose determination. The Fe-Zn bimetallic nanoparticles (Fe-Zn BNPs) were synthesized through a simple aqueous route and exhibited excellent intrinsic peroxidase-like activity toward the hydrogen peroxide-mediated oxidation of 3,3',5,5'-tetramethylbenzidine (TMB). Coupling the nanozyme with a glucose oxidase (GOx)-mediated cascade reaction enabled sensitive and selective glucose detection through catalytic signal amplification. The synthesized Fe-Zn BNPs exhibited excellent peroxidase-like catalytic activity toward hydrogen peroxide with a broad linear range of 10-700 µM and an excellent correlation coefficient (R2 = 0.9996). Steady-state kinetic analysis revealed a low apparent Km of 0.0647 mM and a Vmax of 1.75 × 10-9 M s-1 confirming the high substrate affinity and catalytic efficiency of the developed nanozyme. The proposed glucose sensing platform displayed a wide linear range of 10-500 µM with excellent analytical performance using UV-Vis spectrophotometry (R2 = 0.9980), Arduino-assisted detection (R2 = 0.9975), and smartphone-based digital image analysis (R2 = 0.9967). The platform demonstrated high selectivity toward glucose over common biological interferents and was successfully validated in human serum providing a glucose concentration of 5.07 ± 0.15 mM which was in excellent agreement with that of the reference clinical method (4.93 ± 0.14 mM). The environmental sustainability of the developed platform was comprehensively assessed using the Nanomaterial Assessment Tool (NAT), Blue Applicability Grade Index (BAGI), Red Analytical Performance Index (RAPI), and Environmental Performance-Practicality Index (EPPI) achieving scores of 78, 75, 70, and 84.8, respectively, demonstrating excellent compliance with the principles of green and white analytical chemistry. By integrating efficient Fe-Zn nanozyme catalysis with dual smartphone-Arduino portable detection, the proposed platform provides a sensitive, sustainable, and practical strategy for next-generation point-of-care glucose diagnostics.