Synergistic photocatalytic and biomedical applications of Ag₂O-immobilized Bacillus subtilis-hyaluronic acid

This study reports the synthesis of hyaluronic acid-coated silver oxide (Ag₂O) nano-adsorbents using Bacillus subtilis PV154141.1 for dual environmental and biomedical applications. Multiple parameters were optimized for the formation and constancy of HA-Ag₂O nano-adsorbents, including silver nitrate (AgNO₃) concentration and reaction time. Several characterization techniques including X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy were employed to determine the structural properties, morphology, and elemental composition of the synthesized HA-Ag₂O nano-adsorbents. XRD pattern confirmed the presence of Ag₂O nano-adsorbents by showing peaks having hkl values of 110, 111, 200, 220, 311, and 222, located at 2θ values of roughly 26.46°, 32.55°, 37.76°, 54.48°, 64.92° and 68.19°, respectively. SEM analysis indicated a mean particle size of 193.93 ± 0.23 nm for the nano-adsorbents, while EDX confirmed their elemental composition. The optimized nano-adsorbents were subjected to various applications, including the antibacterial activity, antioxidant activity, and photocatalytic dye degradation efficiency. The antibacterial activity of HA-Ag₂O nano-adsorbents was evaluated against gram-negative (E. coli) and gram-positive (S. aureus, Lactobacillus spp.) pathogens, demonstrating broad-spectrum efficacy. The highest activity was observed against S. aureus (8 ± 0.4 mm inhibition zone), underscoring their potential to treat drug-resistent infections. Additionally, the antioxidant capacity, evaluated using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, exhibited a radical scavenging activity of 84.36 ± 0.44%. Under UV irradiation (λ = 365 nm), the HA-Ag₂O nano-adsorbents achieved 82.28% degradation of methylene blue (MB) dye within 120 min, demonstrating robust photocatalytic activity. Unlike conventional Ag₂O systems, these biohybrid nano-adsorbents combine the photocatalytic efficiency of Ag₂O with the biocompatibility and biofilm-inhibiting properties of microbially-derived HA, enabling dual functionality not achieved in single-component systems.