Development of pH-Dependent Magnetically Actuated Millirobot for Colon-Targeted Delivery of Diverse Drug Types

Oral administration is an ideal route for colon-targeted drug delivery; however, precise delivery to the colon remains a challenge. This work presents a magnetically actuated millirobot combined with a traditional pH-dependent strategy. It aims to combine the advantages of the two methods: under normal physiological conditions, it enables autonomous targeted drug delivery, effectively reducing manipulation costs; in abnormal physiological environments, precise targeted delivery can be achieved via external magnetic intervention. The millirobot uses a magnetic composite shell and a pH-dependent film to encapsulate drug carriers. The pH-dependent film ensures an appropriate delay in drug release under different simulated pH conditions. The magnetic composite shell exhibits satisfactory magnetic responsiveness and can perform stable tumbling motion on the surface of the ex vivo intestinal tract, demonstrating good controllability and motility. Furthermore, the millirobot can carry different types of drug carriers to achieve tunable drug-release rates, thereby improving its versatility. These experimental results demonstrate that this pH-dependent magnetically actuated millirobot is a promising platform for reducing manipulation costs and enhancing the reliability of colon-targeted drug delivery.