Effects of Size and Asymmetry on Catalase‐Powered Silica Micro/nanomotors

Abstract

AbstractEnzyme‐powered micro/nanomotors that can autonomously move in biological environment are attractive in the fields of biology and biomedicine. The fabrication of enzyme‐powered micro/nanomotors normally focuses on constructing Janus structures of micro/nanomaterials, based on the intuition that the Janus coating of enzymes can generate driving force from asymmetric catalytic reactions. Here, in the fabrication of catalase‐powered silica micro/nanomotors (C‐MNMs), an archetypical model of enzyme‐powered micro/nanomotors, we find the silica size rather than asymmetric coating of catalase determines the motion ability of C‐MNMs. The effects of size and asymmetry have been investigated by a series of C‐MNMs at various sizes (0.5, 2, 5 and 10 μm) and asymmetric levels (full‐, half‐ and most‐coated with catalase). The motion performance indicates that 500 nm and 2 μm C‐MNMs show obvious increases (varying from 134% to 618%) of diffusion coefficient, but C‐MNMs bigger than 5 μm have no self‐propulsion behaviour at all, regardless of asymmetric levels. In addition, although asymmetry facilitates enhanced diffusion of C‐MNMs, only 2 μm C‐MNMs are sensitive to asymmetric level. This work elucidates the primary and secondary roles of size and asymmetry in the preparation of C‐MNMs, paving the way to fabricate enzyme‐powered micro/nanomotors with high motion performance in future.