Synthesis of MIL-Modified BiFeO₃ Nanocrystals for Enhancement of the Photoinduced Antibacterial Activity Under Visible Sunlight Irradiation

Antibiotic resistance is a critical challenge for modern medicine, although several approaches have been developed to address this serious global problem. Among these, one of the most promising systems involves the use of light-activated antibacterial agents, which, to be effective, must be irradiated with very intense visible light sources or UV radiation. However, this condition is not always easy to recreate.<br/>Against this background, we research discusses a nanometer hybrid material consisting of nanoparticles of bismuth multiferroic ferrite (BFO) modified through the growth of Metal-organic frameworks of the MIL (Materials Institute Lavoisier), which can be activated by natural sunlight irradiation. The obtained system retains both nanometric dimensions and the intrinsic photo degradative properties of BFO that are increased by the presence of Fe-based MIL.<br/>In our paper we argue that the chemical characterization conducted through various complementary techniques (X-ray-diffraction, thermogravimetric analysis, FT-IR and X-ray photoelectron spectroscopies) confirmed the anchorage of the organic component.<br/>The antibacterial activity was carried out on both Gram-positive and Gram-negative species with the method of the microdilutions in liquid medium, setting up serial dilutions to the doubling of each nanocompound in the range of [100 - 0,20 µg/ml]. Our experiments demonstrate that when incubated in the dark or after pre-illumination with UV-C, the nanoparticles did not exhibit any bacteriostatic or bactericidal activity even at the highest concentration tested (100µg/ml). The antibacterial activity of the BFO@MIL against the Gram-positive species shows a significant increase in MIC (Minimum Inhibitory Concentration) and MBC (Minimum Bactericidal Concentration) values compared to BFO, confirming the photoactivating efficacy of this material following exposure to natural sunlight.<br/>In particular, the BFO@MIL shows a reduction in MBC value (&gt;100 to 0.39 µg/ml and &gt;100 to 0.20 µg/ml) on two tested strains of Staphylococcus (<i>S. Haemolyticus </i>ATCC 29970 and <i>S. Aureus </i>ATCC 25923 respectively). Therefore, BFO@MIL tested on another strain of Staphylococcus (<i>S. Haemolyticus </i>ATCC 31874) shows different MIC and MBC values (0,39 to 0,20 and &gt;100 to 0,39 µg/ml respectively)<br/>In addition, the most relevant aspect for this material is the ability to inhibit the growth of four <i>E. Coli</i> strains (more resistant), although at the maximum concentration tested (100 µg/ml).<br/>These results suggest that the new nanocomposite BFO@MIL has been successfully developed and has been an effective antibacterial agent against a wide range of microorganisms.