Selective Capture, Separation, and Photothermal Inactivation of Methicillin-Resistant Staphylococcus aureus (MRSA) Using Functional Magnetic Nanoparticles.

Antibiotic-free antimicrobial strategies are urgently needed to address the rapid evolution of antimicrobial resistance and transmission of multidrug-resistance bacterial infections. Herein, we fabricated polydopamine-coated porous magnetic nanoparticles (pMNPs@PDA) for effective separation and photothermal killing of methicillin-resistant Staphylococcus aureus (MRSA). Taking advantage of the excellent bacteria-affinitive property of polydopamine, the nanoparticles were anchored on the surface of bacteria, permitting rapid and efficient MRSA capture and separation with over 99% removal via the application of a magnetic field in 30 min. It was found, for the first time, that polydopamine-coated magnetic nanoparticles displayed a selective capture of Gram-positive bacteria when compared with Gram-negative bacteria. The selectivity was attributed to the preferable binding capability of pMNPs@PDA to peptidoglycan (PGN) of Gram-positive bacteria, compared to the lipopolysaccharide (LPS) of Gram-negative bacteria. With the magnetic separation and photothermal properties, pMNPs@PDA exhibited efficient killing of the captured MRSA under the irradiation of near-infrared (NIR) light. Cell cytotoxicity testing demonstrated good biocompatibility of the nanoparticles. These antibiotic-free nanoparticles capable of fast capture, separation, and inactivation of MRSA may be potentially used for water disinfection, blood purification, and treatment of bacterial infections.