Water-powered self-propelled magnetic nanobot for rapid and highly efficient capture of circulating tumor cells

Nanosized robots with self-propelling and navigating capabilities have become an exciting field of research, attributable to their autonomous motion and specific biomolecular interaction ability for bio-analysis and diagnosis. Here, we report magnesium–Fe3O4-based magneto-fluorescent Janus nanorobots (MFNs) that self-propel in blood without any external additives and selectively and rapidly isolate cancer cells. The MFNs (Mg-Fe3O4-GSH-G4-Cy5-Tf and Mg-Fe3O4-GSH-Cy5-Ab) were designed via simple surface modifications and conjugation chemistry to assemble: (i) EpCAM antibody or transferrin, (ii) Cy5 dye, (iii) fourth-generation (G4) PAMAM dendrimers for multivalent conjugation, and (iv) glutathione (GSH), onto one side of Mg nanoparticles covered hemispherically by Fe3O4 for magnetic guidance. The nanobots propelled efficiently in simulated biological media and blood. With continuous motion powered by the Mg–water reaction and magnetic steering by the Fe3O4 shell, MFNs greatly enhanced cancer cell capture sensitivity, efficiency, and speed, achieving nearly 100% capture in serum and whole blood, notably for MCF7 breast cancer cells.