Recent Advances in Heterosilica-Based Micro/Nanomotors: Designs, Biomedical Applications, and Future Perspectives

The development of self-propelled micro/nanomotors (MNMs) has presented a variety of opportunities in the biomedical field because of their surprisingly high performance. However, the biosafety and feasibility of MNMs is still far from satisfactory for disease treatment in clinical application. Silica is one of the most extensively used material for the construction of versatile MNMs and has been intensively applied in the biomedical field due to their excellent biocompatibility, negligible cytotoxicity, and tailorable physiochemical properties such as stimuli-responsive behavior, controllable particle size, surface topology, shape, and mesostructure as well as conjugating targeting molecules and/or gatekeepers to endow enhanced cellular internalization, improved cell selectivity, and on-demand release. Heterosilica-based MNMs, a class of silica-based structures incorporated with diverse functional units and materials, exhibit new burgeoning possibilities for practical biomedical applications. These functional units and compositions substantially created an enormous impact on improving the motion performances and morphological features of MNMs. In this review, we present a systematic overview of the development of the heterosilica-based MNM systems. The discussion is mainly focused on the design and construction of diverse heterosilica-based engines. Meanwhile, we also highlight the effects of key parameters on their performance such as surface properties. Then, we summarize their biomedical applications. We further provide an outlook toward future developments of the heterosilica-based MNMs. This review is expected to inspire further development in future biomedical applications.