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 Fe 3 O 4 nanoparticles (UHFe 3 O 4 NPs, 2.71 ± 0.54 nm) with cholesterol oxidase (ChOx) for cholesterol detection. The chemical engine, ChOx , catalyzes the oxidation of cholesterol to actuate UHFe 3 O 4 @ChOx and produce H 2 O 2 . Meanwhile, UHFe 3 O 4 NPs that possess peroxidase-mimicking property and photothermal effect act as a nanozyme to catalyze the subsequent chromogenic reaction between H 2 O 2 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 UHFe 3 O 4 @ChOx results in an enhancement (55%) of ChOx catalytic efficiency. Moreover, due to the outstanding peroxidase-mimicking activity and cascade reaction, UHFe 3 O 4 @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.