Hollow-Structured Nanorobot with Excellent Magnetic Propulsion for Catalytic Pollutant Degradation, Anti-Bacterial and Biofilm Removal.

Chemical pollution, pathogenic bacteria, and bacterial biofilms pose significant threats to public health. Although various nanoplatforms with both catalytic and antibacterial activities have been developed, creating a remotely controllable nanorobot with precise targeting and propulsion capabilities remains a challenge. This study presents the fabrication of a hollow-structured Fe3O4@AgAu@polydopamine (PDA) nanosphere, which demonstrated controllable catalytic activity and superior magnetically enhanced antibacterial and biofilm removal properties. The AgAu bimetallic nanorods are assembled between the Fe3O4 core and the biocompatible PDA, resulting in a magnetic nanorobot with high photothermal conversion efficiency (54%) and excellent catalytic activity. Importantly, due to the efficient propulsion behavior originating from the magnetic Fe3O4, organic pollutants such as 4-nitrophenol and methylene blue can be accurately degraded by the catalytic Fe3O4@AgAu@PDA magnetic nanorobots in a simulated wastewater pool. By incorporating the zinc phthalocyanine (ZnPc) photosensitizer, the Fe3O4@AgAu@PDA-ZnPc nanosphere exhibits a synergistic "photothermal-photodynamic-Ag+" antibacterial effect against Escherichia coli and Staphylococcus aureus. Remarkably, the antibacterial rate can be enhanced to 99.99% by applying magnetic propulsion via a rotating magnetic field (RMF). Furthermore, this unique magnetic propulsion endows the nanorobot with effective biofilm removal capabilities in both flat surfaces and tubular structures, highlighting its advantages over traditional antibacterial agents in dynamic removal applications.