Motility of Enzyme-Powered Vesicles

Abstract

Autonomous nanovehicles powered by energy derived from chemical catalysis have potential applications as active delivery agents. For in vivo applications, it is necessary that the engine and its fuel, as well as the chassis itself, be biocompatible. Enzyme molecules have been shown to generate mechanical force through substrate turnover and are attractive candidates as engines; phospholipid vesicles are biocompatible and can serve as cargo containers.Herein, we describe the autonomous movement of vesicles with membrane-bound enzymes in the presence of the substrate. We find that the motility of the vesicles increases with increasing enzymatic turnover rate. The enhanced diffusion of these enzyme-powered systems was further substantiated in real time by tracking the motion of the vesicles using optical microscopy. The membrane-bound protocells that move by transducing chemical energy into mechanical motion serve as models for motile living cells and are key to the elucidation of the fundamental mechanisms governing active membrane dynamics and cellular movement.

Single-molecule diffusometry reveals no catalysis-induced diffusion enhancement of alkaline phosphatase as proposed by FCS experiments

“…Catalysis-fueled propulsion of biomolecules at the nanoscale is no doubt a fascinating concept and has potential applications in the field of nanoscience and medicine ( 42 – 49 ). However, mounting experimental and theoretical evidence argue against the mechanism, scale, and even the existence of such phenomenon ( 1 , 2 , 14 , 16 , 38 , 50 ).…”

Engineering transient dynamics of artificial cells by stochastic distribution of enzymes

“…Marangoni flow has also been employed as a propulsion force, e.g., to drive autonomous motion of surfactant-stabilized droplets [16][17][18][19][20] , to induce collective motion 21 , or to navigate in complex environment 22 . Recently, a random surface distribution of enzymes has been shown to propel micromotors in the presence of fuel 4,5 . This inspired us to construct a system, in which asymmetry (i.e., heterogeneous distribution of enzymes) is transient and dynamic, enabled by the inherently fluidic polymer membrane (Fig.…”

“…For example, in the field of nanomotor and micromotor research, the stochastic positioning of propulsive units has been used as an explanation for the observed motility. Specific examples include the stochastic attachment in a fixed position of enzymes to the surface of nanoparticles by Sanchez et al 4 and the conjugation of enzymes to the fluid membrane of liposomes by Sen et al 5 . However, in contrast to nature, stochasticity has never been used in motor systems, or any other synthetic systems, as a purposely introduced component to control the system's features.…”

Recent Advances in Motion Control of Micro/Nanomotors

“…Extensively, directional motility of the enzyme-powered micro/nanomotors could also be obtained by tuning the external environment or surrounding solute. Sen and co-workers reported a series of vesicles and liposomal protocells coated with different enzymes including catalase, urease, [137] and ATPase, [138,139] and they found that the autonomous movement of these micro/ nanomotors could be regulated by externally imposing a substrate with proper gradient and by adjusting the enzymatic turnover rate. Also different enzymes resulted in distinct positive and negative chemotactic movement, which could be further governed by their interactions with the surrounding solute gradients.…”