Biomineralization-inspired copper-cystine nanoleaves capable of laccase-like catalysis for the colorimetric detection of epinephrine

Abstract

Recently, many efforts have been dedicated to creating enzyme-mimicking catalysts to replace natural enzymes in practical fields. Inspired by the pathological biomineralization behaviour of l-cystine, in this study, we constructed a laccase-like catalyst through the co-assembly of l-cystine with Cu ions. Structural analysis revealed that the formed catalytic Cu-cystine nanoleaves (Cu-Cys NLs) possess a Cu(I)-Cu(II) electron transfer system similar to that in natural laccase. Reaction kinetic studies demonstrated that the catalyst follows the typical Michaelis-Menten model. Compared with natural laccase, the Cu-Cys NLs exhibit superior stability during long-term incubation under extreme pH, high-temperature or high-salt conditions. Remarkably, the Cu-Cys NLs could be easily recovered and still maintained 76% of their activity after 8 cycles. Finally, this laccase mimic was employed to develop a colorimetric method for epinephrine detection, which achieved a wider linear range (9–455 µmol·L−1) and lower limit of detection (2.7 µmol·L−1). The Cu-Cys NLs also displayed excellent specificity and sensitivity towards epinephrine in a test based on urine samples.