Dual-responsive micromotor pill for targeted retention in the intestines <i>in vivo</i>

There has been considerable interest in the recent advances in synthetic micro/nanomotors in diverse biofluids due to their potential biomedical applications. However, the propulsion of existing micro/nanomotor platforms for delivery in the gastrointestinal (GI) tract is inefficient. Herein, we present a magnetically and chemically actuated micromotor-tableted pill that can be actively retained in the GI tract <i>in vivo</i>. A drug-loaded and water-powered magnesium Janus micromotor enveloped in an enteric polymer-protected magnetic pill was stable in the stomach. The movement of the micromotor pill (MP) was promoted using an external gradient alternating magnetic field with low frequency toward the targeted regions in the intestines. An alternating magnetic field with high frequency induces intensive water-powered propulsion of the micromotors though a magnetocaloric effect, and thus effectively prolongs retention in the intestines. The integration of the newly developed MP system enables active retention of micromotors <i>in vivo</i> and promises active drug delivery for GI therapy.