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

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.