Biofabrication of Pterocarpus marsupium extract-mediated CoFe2O4 and Ag-decorated CoFe2O4 nanoparticles for antioxidant and antibacterial applications: experimental and computational validation.

This study presents the green synthesis of cobalt ferrite (CoFe2O4) and extract-mediated (phytochemical-capped) CoFe2O4-Ag nanocomposites using aqueous bark extract of Pterocarpus marsupium Roxb. The silver nanoparticles (Ag NPs) are uniformly decorated on the surface of CoFe2O4. The characterisation results from X-ray diffraction (XRD) analysis indicated a cubic spinel structure, with a crystallite size of about 23.85 nm and Ag-induced lattice strain, yielding a lattice parameter of a 0 = 8.1662 Å. The surface plasmon resonance (SPR) peak at 368 nm in the UV-vis spectroscopy spectrum revealed the deposition of Ag NPs on the surface of CoFe2O4. The Fourier transform infrared (FTIR) spectrum analysis revealed the presence of phytochemical functional groups on the nanocomposite surface. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) micrographs showed the formation of spherical, polydisperse nanoparticles in the 10-40 nm size range, with reduced agglomeration and improved crystallinity in Ag-decorated CoFe2O4. The EDX-XPS analyses revealed elemental homogeneity and features corresponding to definite elemental oxidation states. The phytochemical-capped CoFe2O4-Ag nanocomposites exhibited dose-dependent scavenging activity (55.842 ± 1.210 at 60 µg mL-1) and also showed promising antibacterial activity against Salmonella typhi, Streptococcus mutans, and methicillin-resistant Staphylococcus aureus (MRSA) with a zone of inhibition (ZOI) up to 25 mm for S. typhi (80 µg mL-1, surpassing streptomycin's of 22 mm; p < 0.01). Additionally, in silico molecular docking of the identified compounds in P. marsupium was conducted against bacterial enzymes, including DNA gyrase, penicillin-binding proteins, and dihydropteroate synthase. The results revealed strong binding energies (ranging from 7.48 to -9.24 kcal mol-1) between the ligands and the target proteins. The stability of the docked complexes was further investigated using 200 ns of Molecular Dynamics (MD) simulation. Throughout the simulation, the system remained stable, with RMSD values <2.7 Å and a slight decrease in the radius of gyration from 14.8 to 14.7 Å. Limited structural fluctuations were observed, as indicated by RMSF values below 3 Å, while sustained formation of 2-4 hydrogen bonds confirmed stable intermolecular interactions. This work highlights the advantages of using P. marsupium extract for the sustainable synthesis of multifunctional nanocomposites with potential applications in combating oxidative stress and bacterial infections. Further in vivo studies are recommended to explore their biomedical translation.