Sprecher
Beschreibung
In the field of micro- and nanomotors, uncovering the principles that govern their motion is essential not only for developing active materials for diverse applications, but for deepening our understanding of the fundamental mechanisms underlying motion at the nanoscale. Active motion arises from the conversion of energy into mechanical work; however, effective propulsion requires a degree of structural anisotropy. In enzymatically powered systems, this asymmetry creates an out-of-equilibrium state where localized product gradients induce entropically driven fluid flows that propel the particle forward. Asymmetry can be introduced via particle shape or the anisotropic placement of catalytic units, as seen in functionalized DNA fibers or stochastically enzyme-coated spheres. While these systems have revealed key aspects of active motion, their inherent heterogeneity in enzyme number, spatial distribution, and particle geometry, limits the ability to dissect the individual contributions of each parameter to motile behaviour.
To overcome these limitations, we employ DNA origami as a programmable platform for nanomotor design, enabling precise control over enzyme number and spatial arrangement. This approach allows systematic investigation of how catalytic loading and structural anisotropy together dictate nanoscale motion. Specifically, we designed DNA nanorods (18-helix bundles) with increasing numbers of radially distributed urease enzymes (Fig. 1). Following assembly, urease-oligo conjugates were hybridized to the origami scaffolds, and structural and functional validation was performed via gel electrophoresis, atomic force microscopy (AFM), and enzyme kinetic assays. The motion behaviour of fluorescently labelled nanomotors was analysed using single-particle tracking (SPT). Trajectory analysis yielded key motility parameters, including mean-squared displacement (MSD), speed and diffusion coefficients. Strikingly, enhanced motility was observed only at intermediate enzyme densities, revealing a non-linear relationship between catalytic loading and propulsion efficiency. These findings highlight the existence of a critical balance between catalytic activity and structural asymmetry in driving effective motion.
