Facile Fabrication of Magnetic Microrobots Based on Spirulina Templates for Targeted Delivery and Synergistic Chemo-Photothermal Therapy

Magnetic microrobots can be actuated in fuel-free conditions and are envisioned for biomedical applications related to targeted delivery and therapy in a minimally invasive manner. However, mass fabrication of microrobots with precise propulsion performance and excellent therapeutic efficacy is still challenging, especially in a predictable and controllable manner. Herein, we propose a facile technique for mass production of magnetic microrobots with multiple functions using Spirulina (Sp.) as biotemplate. Coreshell-structured Pd@Au nanoparticles (NPs) were synthesized in Sp. cells by electroless deposition, working as photothermal conversion agents. Subsequently, the Fe3O4 NPs were deposited onto the surface of the obtained (Pd@Au)@Sp. particles via a sol-gel process, enabling them to be magnetically actuated. Moreover, the anticancer drug doxorubicin (DOX) was loaded on the (Pd@Au)/Fe3O4@Sp. microrobots, which endows them with additional chemotherapeutic efficacy. The as-prepared biohybrid (Pd@Au)/Fe3O4@Sp.-DOX microrobots not only possess efficient propulsion performance with the highest speed of 526.2 mu m/s under a rotating magnetic field but also have enhanced synergistic chemo-photothermal therapeutic efficacy. Furthermore, they can be structurally disassembled into individual particles under near-infrared (NIR) laser irradiation and exhibit pH- and NIR-triggered drug release. These intriguing properties enable the microrobots to be a very promising and efficient platform for drug loading, targeted delivery, and chemo-photothermal therapy.