Because of their magnetic properties, magnetic nanoparticles (MNPs) have numerous diverse biomedical applications. In addition, because of their ability to penetrate bacteria and biofilms, nanoantimicrobial agents have become increasingly popular for the control of infectious diseases. Here, MNPs were prepared through an iron salt coprecipitation method in an alkaline medium, followed by a chitosan coating step (CS-coated MNPs); finally, the MNPs were loaded with ampicillin (amp) to form an amp-CS-MNP nanocomposite. Both the MNPs and amp-CS-MNPs were subsequently characterized and evaluated for their antibacterial activity. X-ray diffraction results showed that the MNPs and nanocomposites were composed of pure magnetite. Fourier transform infrared spectra and thermogravimetric data for the MNPs, CS-coated MNPs, and amp-CS-MNP nanocomposite were compared, which confirmed the CS coating on the MNPs and the amp-loaded nanocomposite. Magnetization curves showed that both the MNPs and the amp-CS-MNP nanocomposites were superparamagnetic, with saturation magnetizations at 80.1 and 26.6 emu g(-1), respectively. Amp was loaded at 8.3%. Drug release was also studied, and the total release equilibrium for amp from the amp-CS-MNPs was 100% over 400 minutes. In addition, the antimicrobial activity of the amp-CS-MNP nanocomposite was determined using agar diffusion and growth inhibition assays against Gram-positive bacteria and Gram-negative bacteria, as well as Candida albicans. The minimum inhibitory concentration of the amp-CS-MNP nanocomposite was determined against bacteria including Mycobacterium tuberculosis. The synthesized nanocomposites exhibited antibacterial and antifungal properties, as well as antimycobacterial effects. Thus, this study introduces a novel β-lactam antibacterial-based nanocomposite that can decrease fungus activity on demand for numerous medical applications.
Previously, a hypothetical protein (HP) termed Bleg1_2437 (currently named Bleg1_2478) from Bacillus lehensis G1 was discovered to be an evolutionary divergent B3 subclass metallo-β-lactamase (MBL). Due to the scarcity of clinical inhibitors for B3 MBLs and the divergent nature of Bleg1_2478, this study aimed to design and characterise peptides as inhibitors against Bleg1_2478. Through in silico docking, RSWPWH and SSWWDR peptides with comparable binding energy to ampicillin were obtained. In vitro assay results showed RSWPWH and SSWWDR inhibited the activity of Bleg1_2478 by 50% at concentrations as low as 0.90 µM and 0.50 µM, respectively. At 10 µM of RSWPWH and 20 µM of SSWWDR, the activity of Bleg1_2478 was almost completely inhibited. Isothermal titration calorimetry (ITC) analyses showed slightly improved binding properties of the peptides compared to ampicillin. Docked peptide-protein complexes revealed that RSWPWH bound near the vicinity of the Bleg1_2478 active site while SSWWDR bound at the center of the active site itself. We postulate that the peptides caused the inhibition of Bleg1_2478 by reducing or blocking the accessibility of its active site from ampicillin, thus hampering its catalytic function.