Magnetic/pH-sensitive double-layer microrobots for drug delivery and sustained release

[Display omitted] •The TDMs are pH-sensitive and fulfill drug sustained release tasks in alkaline conditions.•The TDMs can be precisely delivered towards the predefined destinations under a vision-guided magnetic driving system.•The TDMs had excellent biological compatibility and sustained released drug without human intervention.•The TDMs will be competent for intestinal cancer targeted therapy after oral administration and bridge the gap between scientific research and market demand. Remarkable evolution of drug-loaded microrobots has aroused growing interest in targeted therapy. However, existing microrobots encounter a number of challenges including maneuverability, biodegradability, and drug sustained release capabilities in medical applications. Designed double-layer drug-loaded microrobots (TDMs) were made of outer layer calcium alginate hydrogel and inner layer magnetic chitosan microspheres (mCSs). TDMs precisely deliver drug-loaded mCSs following the expected route towards the predefined destinations under a vision-guided magnetic driving system. In acidic conditions the outer layer of TDMs can protect mCSs, while in alkaline conditions calcium alginate hydrogel dissolves at an appropriate rate to render mCSs be continuously released. The mCSs fulfill drug sustained release tasks in vitro. The new designed low-cost microrobots will be competent for intestinal cancer targeted therapy after oral administration and bridge the gap between scientific research and market demand.