Synthesis, Characterization, and Anti-Listerial Activity of Chitosan-Stabilized Selenium Nanoparticles

The antibacterial efficacy of chitosan (C) stabilized selenium nanoparticles (C-SeNPs) against Listeria monocytogenes (LM) was assessed. In addition, the physicochemical properties of C-SeNPs, including particle size, morphology, surface charge, optical behavior, elemental composition, and crystallinity were systematically characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), dynamic light scattering (DLS), zeta potential analysis, X-ray diffraction (XRD), inductively coupled plasma–optical emission spectroscopy (ICP-OES), energy-dispersive X-ray spectroscopy (EDX), UV–visible spectroscopy, and fluorescence spectroscopy. Based on ICP-OES analysis, elemental selenium (Se⁰) content in the C-SeNPs was 29.80 ± 0.35 mg/L. DLS analysis revealed a mean hydrodynamic diameter of 173.4 nm, primary particles sizes of 70–120 nm (TEM) and 50–90 nm (SEM), and a positive zeta potential (+35.35 mV). The nanoparticles (NPs) were primarily spherical and showed good colloidal stability. Agglomerated clusters (18.84 ± 0.6 µm) with a crystallinity index of 75.43% were found by XRD assessment. C-SeNPs demonstrated potent antibacterial action against multidrug resistant LM with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 130 and 260 µg/ml, respectively. Ion leakage (K⁺ 1158.00 ± 13.22 mg/L, Mg²⁺ 5.95 ± 0.02 mg/L) enhanced conductivity (14.4 ± 0.1µS/cm), indicating disruption of bacterial membrane integrity. Time-kill kinetic analysis demonstrated complete bacterial inactivation within 24 h at 2×MIC. C-SeNPs performed more effectively than potassium sorbate in suppressing LM growth in the inoculated shrimp. C-SeNPs showed low cytotoxicity (85% BJ cell viability at ≤ 7.81 µg/ml), highlighting their potential for food preservation. This is the first study demonstrating that C-SeNPs can be used to inactivate LM in seafoods.