Fabrication of Ag-La-based/Arabic gum nanocomposites via Nigella sativa : Structural, biological activity, and silver release assessment

Abstract

Ag-La hybrid and Arabic gum-stabilized Ag-La nanocomposites were prepared by a green chemistry method, where an aqueous solution of Nigella sativa seeds was used as a reducing and stabilizing agent. During the synthesis process, silver ions were reduced to Ag 0 , while a fraction precipitated as AgCl, coexisting with La(OH) 3 to form a hybrid nanocomposite material. Arabic gum further enhanced nanoparticle dispersion and stabilization. Arabic gum acted as a biopolymeric stabilizer, enhancing nanoparticle dispersion and colloidal stability through surface functionalization. The FTIR, ultraviolet-visible (UV-Vis), transmittance electron microscopy (TEM), scanning electron microscopy (SEM) with energy dispersive X-ray analysis (SEM-EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis of the nanocomposites suggested the presence of quasi-spherical nanoparticles (9-45 nm) with polycrystalline domains of La(OH) 3 , AgCl, and metallic Ag. Antioxidant analysis of Arabic gum-functionalized nanocomposites indicated enhanced activity, such as radical scavenging, ferric reducing power, and total antioxidant activity at IC 50 = 42 µg/mL, 96.3 µg AAE/mL, and 90.1 µg AAE/mL, respectively. The controlled release of Ag + ions (6.87–13.55%) and the high antibacterial activity, with inhibition zones between 13 and 18 mm for Gram-positive and Gram-negative bacteria, together with a minimum inhibitory concentration (MIC) of 0.25 mg/mL, suggest strong antibacterial performance at relatively low concentrations. Molecular docking indicated high binding affinity of oxidized quercetin and kaempferol toward DNA gyrase B, suggesting a possible interaction mechanism; however, experimental validation is required to confirm this activity. In conclusion, the results have suggest that the green synthesis method is an effective approach for the synthesis of Ag/La(OH) 3 /AgCl/Arabic gum nanocomposites with promising physicochemical and biological properties. However, further research is needed to investigate the long-term stability and mechanisms of the nanocomposites for their applicability.