Bacterial metabolite-directed synthesis of biogenic TiO2–Zn nanocomposites: characterization and multifunctional biomedical evaluation

Abstract

This study synthesized TiO₂–Zn nanocomposites using metabolites from Red Sea-isolated Bacillus tequilensis MYG163 and evaluated their multifunctional therapeutic potential. Chronic diseases such as diabetes, infections, and inflammation share overlapping pathological mechanisms that single-target therapies cannot adequately manage. XRD analysis confirmed the presence of anatase TiO₂ and wurtzite ZnO phases with crystallite sizes of 23.1 and 23.7 nm, respectively, in the TiO₂–Zn nanocomposite. TEM analysis revealed spherical particles with sizes ranging from 8 to 15 nm, while DLS analysis indicated a hydrodynamic diameter of 87.3 nm and a polydispersity index of 0.232. EDX analysis indicated the presence of Ti (32.1 wt%), Zn (29.2 wt%), and O (33.8 wt%) and a zeta potential of −34.5 mV, confirming colloidal stability. Hemolysis remained below 0.7% across all concentrations tested (50–1000 µg mL⁻¹), confirming blood compatibility, essential for biomedical applications. DPPH and ABTS radical scavenging assays yielded IC₅₀ values of 11.97 and 7.65 µg mL⁻¹, respectively. Anti-inflammatory testing demonstrated preferential COX-2 inhibition (IC₅₀ = 14.13 µg mL⁻¹) over COX-1 (IC₅₀ = 25.91 µg mL⁻¹), representing a therapeutically favorable selectivity profile that minimizes gastrointestinal side effects associated with nonselective inhibition as well as prevents BSA denaturation (IC₅₀ = 2.78 µg mL⁻¹). Antimicrobial assays showed inhibition zones of 35 ± 0.4 mm (B. subtilis), 33 ± 0.5 mm (C. albicans), 26 ± 0.3 mm (S. typhi), 25 ± 1.0 mm (K. pneumoniae), 25 ± 0.6 mm (F. oxysporum), and 22 ± 0.4 mm (MRSA), with activities matching or exceeding those of reference antibiotics and antifungals against several tested organisms. Antidiabetic screening revealed the inhibition of α-amylase and α-glucosidase with IC₅₀ values of 12.98 and 9.34 µg mL⁻¹, respectively. Marine bacterial metabolites functioned as reducing and stabilizing agents, yielding nanocomposites with multitarget therapeutic properties spanning oxidative, inflammatory, microbial, and metabolic pathways.