Enhanced Antibacterial Activity through the Synergistic Interaction of Magnetic Nanospheres with Conventional Antibiotics

Abstract

The rise of multidrug-resistant bacteria has highlighted the critical need for innovative antimicrobial methods that can supplement the efficiency of current medicines. This study used a solvothermal approach to synthesise Fe₃O₄ magnetic nanospheres from precursors such as FeCl₃•6H₂O, ethylene glycol, and sodium acetate. The nanospheres had a homogeneous spherical morphology with an average particle size of 35–50 nm, as validated by scanning electron microscopy (SEM). X-ray diffraction (XRD) revealed separate peaks at 2θ values of 30.1°, representing the (220) and (311) planes of crystalline magnetite. The FTIR spectrum showed classic Fe‒O stretching vibrations at approximately 580 cm⁻¹, indicating the synthesis of pure Fe₃O₄. The antibacterial activity was assessed against both gram-positive and gram-negative microorganisms via the Kirby–Bauer disc diffusion method. The Fe₃O₄ nanospheres alone produced inhibition zones ranging from 10 to 13 mm, whereas their combination with standard antibiotics yielded enhanced inhibition zones of 20--26 mm, indicating a pronounced synergistic effect. The observed synergy is attributed to increased cell membrane permeability, reactive oxygen species (ROS) generation, and localised magnetic interactions that facilitate antibiotic penetration and bacterial cell disruption.

Keywords: Magnetic nanospheres, Fe₃O₄, antibacterial synergy, solvothermal synthesis, antibiotic resistance.