Functionalized Magnetic Nanoparticles with BODIPYs for Bioimaging and Antimicrobial Therapy Applications

The antimicrobial capability and recyclability of two conjugates that combines the versatility of iron oxide magnetic nanoparticles (MNPs) with the high photosensitizing proficiency of boron-dipyrromethene (BODIPY) dyes are assessed. By a relatively simple synthetic pathway, two conjugates were obtained. The first one, MNP-B1, contains a highly fluorescent dye for bioimaging and suitable inactivating properties. The other one, MNP-B2, is optimized to improve the production of cytotoxic reactive oxygen species (ROS) by incorporating heavy atoms in the BODIPY core. In vitro experiments in bacterial cell suspensions and at the single bacterium level reveal that both conjugates can inactivate either Gram-positive (methicillin-resistant Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. By means of fluorescence microscopy, not only cellular uptake of the conjugates but also recyclability and sustained performance over the cycles of photodynamic inactivation (PDI) are demonstrated. This is the first time that MNPs functionalized with BODIPY dyes are utilized to obtain fluorescent images of bacterial cells and photoinactivate pathogens.