Magnetic Biohybrid Microrobot Multimers Based on Chlorella Cells for Enhanced Targeted Drug Delivery

Magnetic micro-/nanorobots have been regarded as a promising platform for targeted drug delivery, and tremendous strategies have been developed in recent years. However, realizing precise and efficient drug delivery in vivo still remains challenging, in which the versatile integration of good biocompatibility and reconfiguration is the main obstacle for micro-/nanorobots. Herein, we proposed a novel strategy of magnetic biohybrid microrobot multimers (BMMs) based on Chlorella (Ch.) and demonstrated their great potential for targeted drug delivery. The spherical Ch. cells around 3-5 μm were magnetized with Fe₃O₄ to fabricate biohybrid microrobots and then loaded with doxorubicin (DOX). Using magnetic dipolar interactions, the microrobot units could reconfigure into chain-like BMMs as tiny dimers, trimers, and so forth via attraction-induced self-assembly and disassemble reversibly via repulsion. The BMMs exhibited diverse swimming modes including rolling and tumbling with high maneuverability, and the rolling dimer's velocity could reach 107.6 μm/s (∼18 body length/s) under a 70 Gs precessing magnetic field. Furthermore, the BMMs exhibited low cell toxicity, high DOX loading capacity, and pH-triggered drug release, which were verified by chemotherapy experiments toward HeLa cancer cells. Due to the remarkable versatility and facile fabrication, the BMMs demonstrate great potential for targeted anticancer therapy.