Self-Generated Chemical Gradients for Controlling the Locomotion of Artificial Nanomotors

Chemical gradient-steered directed transportation is crucial for biological systems. Inspired by nature, self-propelled artificial nanomotors capable of spontaneously creating chemical gradients via catalytic reactions have been developed for application in physiological environments. Herein, we demonstrate the autonomous movement of lipase-activated acylated dextran-fueled nanomotors driven by self-generated chemical gradients of different compositions in an ion-enriched aqueous medium. Interfacial hydrolysis degrades the acylated dextran and releases water-soluble carboxylates into the surrounding media. The motilities of nanomotors containing different acylates exhibit an anti-carboxylate concentration series, in which fast enzymatic hydrolysis leads to slow self-propulsion. The study demonstrates that the nature of the product quantitatively governs the dynamic retention of partial carboxylates at the interface. This occurs via interfacial interactions with nanomotors, resulting in interfacial concentration gradients of carboxylates that drive autonomous movement rather than concentration gradients of the produced whole carboxylates. Regulating the compositions of this interfacial chemical field enables the convenient manipulation and modulation of self-propulsion. This is also applied to widely used urease-powered nanomotors that generate interfacial chemical gradients with different compositions in response to various pH. Precisely controlling self-generated interfacial chemical gradients holds considerable potential for developing smart nanobots that can reconfigure self-propulsion with good adaptability to the surrounding environment.