Multifunctional magnetic hairbot for untethered osteogenesis, ultrasound contrast imaging and drug delivery.

To explore novel materials graded for biological functions is one of the grand challenges and ambitions of robotics. In this study, the design, development, and external guidance of micron-sized hair-derived robots (hairbots) are shown as autologous cargo carriers for guided drug delivery, untethered osteogenesis, and sonographic contrast agents. Having biogenic origin, the hairbots show excellent biocompatibility, as demonstrated with cell adhesion, spreading and proliferation. External magnetic fields are used to enhance differentiation of mesenchymal stem cells (MSCs) into bone like cells, which can be used as magnetic therapy for bone healing. Effect of external magnetic forces was simulated by COMSOL Multiphysics® modelling software. The action of hairbots as osteoconductive material triggering osteogenic differentiations of MSCs is studied via calcium signaling by fluorescence microscopy. Further, by exploiting the hollow medullary region, the proposed hairbots are designed to perform theranostic dual functions (therapy + diagnostic) - as Doxorubicin drug delivery vehicle, and for Ultrasound contrast imaging. Harnessing sensing and actuation due to magnetic capabilities of hairbots, for enhanced biological functionality shown herein, provides a novel material in the search of new multifunctional microrobots.