A mucoadhesive magnetic millimeter-scale robot with two motion modes for drug delivery to the colon

The small-scale robots for targeted drug delivery are gradually attracting great interest, and increasing the residence time of robots in targeted areas is conducive to increasing bioavailability. A drug-loaded magnetic millimetre-scale robot that can bond to colonic mucosa has been developed. The main body of the robot is composed of two approximately rectangular Poly (lactic acid) (PLA) sheets perpendicular to each other. The magnetic disk and the drug-loaded adhesive film are symmetrically distributed at the tail sheet. The robot has two ways to move: swimming and rolling. A high-frequency-rotating magnetic field can drive it to swim in liquid environments, or a low-frequency-rotating magnetic field can drive it to roll in an air environment. The drugloaded adhesion patch can attach to both PLA and mucosa, ensuring the bond to the robot during movement and maintaining mucoadhesion to the intestinal mucosa during drug release. The initial contact force applied by a magnet between the robot and the intestinal surface was calculated and measured. The adhesion functionality of the robot to porcine colon was proved in the vitro simulated adhesion experiment.