Enhanced Propulsion of Urease-Powered Micromotors by Multilayered Assembly of Ureases on Janus Magnetic Microparticles.

Enzyme-powered micro/nanomotors propelled by biocompatible fuels generally show a weak propulsive force, which greatly limits their applications in complex biological environments. Herein, we have developed a novel and versatile approach to significantly enhance the propulsion of enzyme-powered micromotors by multilayered assembly of enzymes. As an example, multilayers of biotinylated ureases (BU) were asymmetrically immobilized on biotinylated Janus Au/magnetic microparticles (MMPs) with the assistance of streptavidin (SA). When the mass ratio of BU into SA and the amount of BU used in the assembly process are increased, the amount of urease immobilized on the biotinylated Janus Au/MMPs increased monotonously while the migration speed of the micromotor was augmented gradually until a saturated value. The as-optimized micromotors can be self-propelled with an average speed up to about 21.5 ± 0.8 μm/s at physiological urea concentrations (10 mM), which is five times faster than that of the monolayered counterparts and two times faster than that of the previously reported values. Owing to the enhanced thrust, the micromotors can move in liquids with viscosities similar to that of blood. In addition, with the inherent magnetic property of MMPs, the micromotors can exhibit fast magnetic separation and controllable motion direction by external magnetic fields. Our results provide a new pathway for designing high-efficient enzyme-powered micro/nanomotors and thereby promote their biomedical applications.