Electrochemical detection of creatinine in artificial saliva using nanostructured CuZn bimetallic materials

In this study, Zn was incorporated as a protective and sacrificial co-metal alongside Cu, the electroactive metal, to form electrodeposited CuZn materials for creatinine detection. Four Cu-to-Zn ratios (1:2, 1:4, 1:8 and 1:12) were prepared using ethylenediamine-tetraacetic acid (EDTA) as an additive. Physicochemical characterization revealed Zn atomic contests of 43 %, and 30 % for the 1:2 and 1:12 ratios, respectively, while the 1:4 and 1:8 ratios yielded lower Zn contents of 13 % and 3 %. Electrochemical evaluation demonstrated improved creatinine detection performance (in activity and repeatability) at the lower Zn concentrations, with the 1:4 CuZn composition (87 % Cu, 13 % Zn) showing the best results. This optimal composition exhibited a linear response for creatinine detection in the range of 0–500 μM in a 0.1 M phosphate buffer solution (PBS) containing 20 mM NaCl and 2 mM KCl, with a correlation coefficient (R²) of 0.99. Linearity was maintained in artificial saliva diluted 1:5 in PBS (R² = 0.98), although repeatability was reduced. To address this, a micro-environment was established using screen-printed electrodes (SPEs), enhancing repeatability while preserving linearity (R² = 0.98) within a 0–200 μM range. These findings highlight that low dilution rates (1:5) can be effectively used for creatinine detection when Zn is employed as a co-metal. Zn not only protects Cu but also facilitates the formation of Cu⁺ species, supporting a dual detection mechanism involving both Cu⁺– and Cu²⁺–creatinine complexes.