Near-infrared light-enhanced enzymatic activity of laccase-platinum nanoparticles as a biosensor for colorimetric and visible detection of ascorbic acid

Enzymes, as green catalysts with high activity and substrate specificity, have attracted extensive interest in contrast to chemical catalysts with non-selectivity. However, the enzymes' activities are sensitive to external environments. Therefore, highly efficient strategies are encouraged to modulate the enzymatic activity and stability at the molecular level. Compared with conventional magnetic field, temperature, and pH-responsive enzymatic activities, the near-infrared (NIR) light-controlled activities have noninvasive and convenient controllability advantages, which remains a significant challenge. Besides, NIR light also possesses intense penetration and low phototoxicity compared with UV and blue lights. Herein, the supersmall platinum nanoparticles (Pt-NPs) were for the first time deposited on the laccase body (labelled as laccase-Pt), with the reduction of chloroplatinic acid hexahydrate by sodium borohydride. Fortunately, the synergetic catalysis between laccase and Pt-NPs was demonstrated. Moreover, with and without NIR light irradiation, laccase-Pt activities are 2.439 and 2.258 times of free laccase, respectively. NIR laser could also manipulate the reversible enzyme activity of laccase-Pt. Notably, the laccase-Pt displays a significant advance in three-dimensional structure compared with conventional immobilized and encapsulated enzymes. Then, the high-performance laccase-Pt was used as a sensitive biosensor to detect ascorbic acid, with a detection limit of 3.7 μM obtained by colorimetric approach and smartphone. Briefly, this work provides a novel and feasible idea for manipulating laccase activity by NIR laser, inspiring more scholars to control other natural enzyme activities. Simultaneously, it also gives clear proof for a better understanding of the component-activity relationship of the enzymes-metal nano-bio hybrid catalysts.