Intelligent micro/nanorobots for improved tumor therapy

A major bottleneck underlying nanomaterial-based tumor therapy lies in complex biological environment and physiological barriers. Micro/nanorobots with the features of self-propulsion and controllable navigation have gradually become a research hotspot in the tumor therapeutic community, exhibiting their advantages in efficient cargo loading, controllable cargo delivery, stimuli-triggered cargo release, deeper tumor tissue penetration, and enhanced cargo accumulation in tumor tissue. In this review, the self-propulsion and controllable navigation are introduced as two major properties of micro/nanorobots, in which micro/nanorobots are propelled by chemical reactions, physical fields, and biological systems and could be navigated by chemotaxis, remote magnetic guidance, and light. Then, the recent advances of micro/nanorobots for chemotherapy, immunotherapy, photothermal therapy, photodynamic therapy, chemodynamic therapy, and multimodal tumor therapy would be discussed. Finally, the perspective and challenges are also mentioned. It is expected that this review gives an insight into intelligent micro/nanorobots for improved tumor therapy, aiming for more extensive and in-depth investigations, and final applications in the clinic.