Selenium/Zinc nanocomposite (Se/Zn NC) bioengineered by Bacillus rugosus metabolites: physicochemical characterization, anti-inflammatory, and antidiabetic activities.

Abstract

This study reports the biosynthesis of a Selenium/Zinc nanocomposite (Se/Zn NC) using a marine bacterial extract from Bacillus rugosus SYG20. FT-IR detected Zn-O stretching vibrations at 614.81, 500.71, and 463.61 cm⁻¹, together with shifts in biomolecule peaks. XRD revealed a hexagonal wurtzite structure with an average crystallite size of 14.9 nm, and UV-Vis spectroscopy gave an optical band gap of 3.46 eV. TEM showed spherical particles of 10-80 nm, while HRTEM lattice fringes and a polycrystalline diffraction pattern matching cubic ZnSe planes confirmed strong interfacial Se-Zn coordination. DLS indicated a hydrodynamic diameter of 87 nm with a polydispersity index of 0.28. EDX confirmed Se incorporation at 7.0 wt% (Zn:Se atomic ratio ≈ 1.6:1). XPS showed Zn in the divalent state and Se bound to the metal centers rather than as elemental selenium, with a Zn 2p binding-energy shift indicating interfacial coordination rather than a native oxide layer. Hemolysis remained below 1.5% even at 1000 μg/mL, and cytotoxicity against WI-38 normal fibroblasts showed a wide safety margin (IC₅₀ = 392.64 ± 4 μg/mL). The nanocomposite exhibited strong antioxidant activity, with IC₅₀ values of 11.85 ± 0.11 μg/mL (DPPH) and 11.46 ± 0.05 μg/mL (ABTS⁺^•), reaching 94.4% and 93.9% inhibition, respectively. Anti-inflammatory assays gave IC₅₀ values of 6.67 ± 0.5 μg/mL for COX-1 and 14.12 ± 0.1 μg/mL for COX-2. Protein denaturation was inhibited with an IC₅₀ of 2.04 ± 0.05 μg/mL, nearly matching diclofenac sodium (2.01 ± 0.04 μg/mL). Antidiabetic screening showed α-amylase and α-glucosidase inhibition with IC₅₀ values of 5.24 and 7.84 μg/mL, and 95.4% and 95.7% blockade at 1000 μg/mL. These in vitro findings support the potential of B. rugosus-derived Se/Zn NC against oxidative stress-related metabolic disorders.