Spirulina-templated porous hollow carbon@magnetite core-shell microswimmers

Magnetic helical micro/nanoswimmers, one swimming micro/nanorobots inspired by the E. coli bacterium, have attracted much attention of the community. Using low-strength rotating magnetic fields, they can be effectively actuated and perform controlled locomotion in various fluids, and are therefore envisioned for advanced biomedicine, precise micromanipulation and efficient environmental purification. In this study, we demonstrate a core-shell-structured hollow helical microswimmer that possesses an inner core of porous carbon and an outer shell aggregated by mesoporous spindle-like magnetite nanoparticles (NPs). The fabrication of it is achieved via a straightforward Spirulina-based biotemplating process, featuring high yield and low cost. The obtained microswimmers integrate desirable photothermal attributes and specific surface areas (SSA) from their magnetite-carbon composition and porous hollow architectures. Here these two functions are harnessed for bacterial killing and heavy metal ion collection (or cargo loading). Furthermore, such swimmers exhibit high magnetic saturation, advantageous superparamagnetic characteristics and robust swimming performance. The results of this study suggest a multifunctional helical microswimmer suitable for photothermal antibacterial therapy, biological detoxification and targeted delivery in the gastrointestinal (GI) tract.