A smartphone-integrated electrochemical biosensor based on engineered laccase-mimicking nanozymes for epinephrine detection in metabolic stress.

A highly sensitive and selective electrochemical biosensor was developed based on Cu- and O-vacancy-engineered, laccase-mimicking mesoporous carbon (MC) nanozymes for epinephrine (EP) detection. N-doped MC was synthesized via a hydrothermal method, followed by immobilization of CuZn bimetallic nanoparticles through wet impregnation, and the resulting Cu-Zn-MC composite was drop-cast onto a disposable electrode strip. The N functionalities, dispersed Cu and Zn atoms, and Cu and O vacancies emulated the Cu active sites and CuN coordination environment of laccase enzyme. The porous Cu-Zn-MC nanozymes facilitate adsorption, electron transfer, and oxidation of EP to adrenochrome, which is measurable by differential pulse voltammetry. The biosensor exhibited a well-defined oxidation peak at +0.195 V (vs. Ag/AgCl), with the detection limit of 10 nM, and rapid detection capability when interfaced with a smartphone-operated miniaturized potentiostat. The enhanced electrochemical performance was attributed to accelerated electron hopping mediated by Cu centers and dual semiconducting pathways, involving p-type CuO behavior induced by Cu vacancies and n-type ZnO conductivity associated with O vacancies. Practical feasibility was confirmed through EP analysis in ex-vivo tissues from a metabolic stress-induced mouse model, yielding satisfactory recoveries (91.9-102.2 %) and high precision (RSD < 5.6 %).