Ultrasmall enzyme/light-powered nanomotor facilitates cholesterol detection

Enzymes that can convert chemical energy into mechanical force through biocatalysis have been used as engines for artificial micro/nanomotors. However, most nanomotors are powered by only one engine and have a microscale size range, which greatly limits their application scenarios. Herein, an ultrasmall enzyme/light-powered nanomotor (71.1 ± 8.2 nm) is prepared by directly coupling ultrasmall histidine-modified Fe₃O₄ nanoparticles (UHFe₃O₄ NPs, 2.71 ± 0.54 nm) with cholesterol oxidase (ChOx) for cholesterol detection. The chemical engine, ChOx, catalyzes the oxidation of cholesterol to actuate UHFe₃O₄@ChOx and produce H₂O₂. Meanwhile, UHFe₃O₄ NPs that possess peroxidase-mimicking property and photothermal effect act as a nanozyme to catalyze the subsequent chromogenic reaction between H₂O₂ and 3,3',5,5'-tetramethylbenzidine for cholesterol detection and simultaneously serve as a photothermal engine power by near-infrared (NIR) irradiation. The nanomotor behavior of UHFe₃O₄@ChOx results in an enhancement (55%) of ChOx catalytic efficiency. Moreover, due to the outstanding peroxidase-mimicking activity and cascade reaction, UHFe₃O₄@ChOx works as a cholesterol sensor with improved sensitivity and shortened analysis time; as low as 0.178 μM of cholesterol is detected with a linear response range of 2 to 100 μM. Taken together, the new conceptual synthetic strategy of enzymatic hybrid nanomotor is proven promising for sensing and biocatalytic applications.