Erythrocyte based achiral micromotors for localized therapeutic delivery

Bio-hybrid micromotors, active structures composed of both biological and synthetic components, are promising for use in several biomedical applications including targeted drug delivery, tissue engineering, and biosensing. Among biological candidates, erythrocytes are well suited for use as the biological component of bio-hybrid micromotors due to their biocompatibility, mechanical deformability, and long circulation time. However, their symmetric shape and small size make controlled actuation of these devices particularly challenging. Here, we present a novel strategy to overcome these limitations by fabricating achiral erythrocyte micromotors with enhanced propulsion efficiency. Inspired by recent work on synthetic achiral microswimmers, we report two and three-cell micromotors fabricated through biotin-streptavidin binding. These self-assembled red blood cell (RBC) structures are then interfaced with magnetic beads enabling them to swim and roll under the propulsion of a single homogenous rotating magnetic field at a much greater velocity compared to single cell micromotors in both Newtonian and viscoelastic fluids. Further, to demonstrate biomedical application of these self-assembled micromotors, the chemotherapeutic agent doxorubicin is loaded into RBC achiral micromotors, which are magnetically directed to cancer cells within a microfluidic chamber, successfully delivering their anticancer payload. The fabrication and propulsion method reported here will aid in the development of future erythrocyte-based micromotors for drug delivery and cancer therapy.