A non-enzymatic nickel-citrate-rhodamine B fluorescent platform for glucose determination in serum

A novel non-enzymatic fluorescent nanosensing platform is developed based on citric acid-stabilized nickel nanoparticles (Ni-Cit) integrated with Rhodamine B isothiocyanate (RhB) for sensitive glucose detection in aqueous and biological media. Unlike conventional fluorescence sensors that rely on dye displacement or enzymatic catalysis, the proposed system operates through an association-driven photophysical modulation mechanism, in which fluorescence quenching of RhB upon interfacial interaction with Ni-Cit is reversibly restored via glucose-induced surface reorganization. The formation and functionality of the Ni-Cit-RhB hybrid system were systematically elucidated using UV-visible absorption, fluorescence spectroscopy, FTIR, and zeta potential analyses, providing direct spectroscopic evidence of non-covalent interfacial interactions governing the sensing response. The nanosensor exhibits a well-defined linear fluorescence enhancement at 582 nm (λ_ex = 550 nm) over a low micromolar glucose range (0.1-3.1 μM) with a high correlation coefficient (R² = 0.984), along with a detection limit of 52 nM, demonstrating excellent sensitivity toward glucose. The sensor shows rapid response behavior and high reproducibility, with relative standard deviation (RSD) values below 1%. Its practical applicability was validated in real human serum samples, yielding recovery values between 98.99% and 101.19% using the standard addition method. Statistical comparison with the conventional glucose oxidase (GOD) assay confirmed no significant difference at the 95% confidence level. This work introduces a mechanistically distinct, enzyme-free sensing strategy based on interfacial photophysical reorganization, offering a simple, stable, and cost-effective alternative to conventional glucose detection methods. The findings highlight the potential of Ni-based nanostructures as versatile platforms for fluorescence sensing in complex biological environments.