Green synthesis and evaluation of doped silver nanoparticles using Ceratonia siliqua leaf extract: antibacterial and...

This study reports the low-cost, eco-friendly green synthesis of silver nanoparticles (AgNPs) using Ceratonia siliqua, which were subsequently co-doped with yttrium (Y), gadolinium (Gd), and chromium (Cr) to produce YGdCr@AgNPs. The structural, optical, and magnetic properties of YGdCr@AgNPs were characterized using X-ray Powder Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray technique (EDX), Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet-vis spectroscopy (UV-vis), Photoluminescence (PL), and Vibrating Sample Magnetometer (VSM). XRD analysis confirmed a well-defined face-centered cubic Ag lattice structure, validating successful dopant incorporation. XPS analysis verified silver in both ionic (Ag⁺) and metallic (Ag⁰) states, alongside detectable Y, Gd, and Cr levels. Biologically, the YGdCr@AgNPs demonstrated remarkable antibacterial efficacy against both Gram-positive and Gram-negative strains, with MICs ranging from 65 to 500 µg mL^-1. Furthermore, the nanoparticles displayed dose-dependent inhibition of biofilm formation and significantly eradicated preformed biofilm biomass. Molecular docking studies revealed strong binding affinities (ranging from -12.44 to -18.90 kcal mol^-1) toward four essential bacterial enzymes: DNA gyrase, PBPs, KPC-2 carbapenemase, and DHPS. These interactions, involving extensive hydrogen bonding and hydrophobic contacts, disrupt critical processes such as cell wall synthesis, DNA replication, and folate biosynthesis. The results suggest that YGdCr@AgNPs act as potent, multi-target antibacterial agents with significant potential to combat antibiotic-resistant pathogens.