posted on 2023-10-30, 15:34authored byJessica
Ann O’Callaghan, Daeyeon Lee, Daniel A. Hammer
Autonomous
motion of enzyme-powered motors has important implications
for drug delivery, cell–cell communication, and protocell engineering.
Although many of these systems are inspired by the motion of biological
cells, most of them lack key structural features, like micrometer-sized
boundaries and aqueous compartments, and rely on bubble propulsion
to generation motion. In this study, we use droplet microfluidics
to generate large populations of cell-sized microcapsules with poly(lactic-co-glycolic acid) shells and functionalize their surfaces
with the enzyme urease to drive their motion. We adjust the number
of surface functional groups for urease conjugation by preparing microcapsules
with two different surfactants, poly(vinyl alcohol) (PVA) and poly(ethylene-alt-maleic anhydride) (PEMA). We also tune the surface roughness
of the microcapsules by varying the concentration of silica nanoparticles
in the droplet middle phase. We find that PEMA plays a crucial role
in increasing the grafting density of urease on the surface of smooth
microcapsules, leading to active motion in the presence of urea. In
addition, rough microcapsules prepared with PEMA and loaded with comparable
amounts of urease move up to three times faster than their smooth
counterparts, which we believe is due to an asymmetric distribution
of urease on the surface, giving rise to a preferred direction of
motion. Taken together, these results provide new insights into the
role that various stabilizing agents play in the induction of motion
by enzymatic motors prepared from microfluidics, which is a potentially
powerful tool for future preparation of motile protocells in biomedicine.