Penetration and disruption of Salmonella typhimurium biofilm using synthesized citric acid doped zein nanocomposites

In the current global scenario, antimicrobial resistance poses a major challenge and significantly contributes to increasing human mortality. Among resistant pathogens, the Salmonella genus, particularly Salmonella enterica serovar Typhimurium (S. Typhimurium), plays a prominent role, with resistance further intensified under mature biofilm conditions. To address this challenge and mitigate the pathogenicity of this Gram-negative bacterium, various strategies have been explored, among which nanodrug delivery using nanocomposites (NCs) has emerged as a promising approach. In the present study, NCs were developed by incorporating citric acid (CA) into zein nanoparticles (NPs) at defined concentrations. X-ray diffraction analysis confirmed the successful formation of CA@Zein NCs, while field-emission scanning electron microscopy (FE-SEM) verified the effective loading of CA onto the surface of zein NPs. Particle size, zeta potential, and polydispersity index analyses indicated optimal physicochemical properties for stable nanocomposite formation. The synthesised NCs were evaluated against both planktonic and biofilm forms of S. Typhimurium. The minimum inhibitory concentration and minimum biofilm inhibitory concentration of CA@Zein NCs were determined to be 64 µg/mL and 128 µg/mL, respectively. These results demonstrate the superior antibiofilm efficacy of CA@Zein NCs compared with CA and zein NPs alone. Furthermore, FE-SEM analysis provided direct evidence of EPS penetration and bacterial cell disruption by CA@Zein NCs. Overall, CA@Zein NCs exhibits strong potential as an effective antibiofilm agent against S. Typhimurium.