Synergism in isoconazole-loaded nano-bismuth oxide formulation: exploration of structural characterization, enhanced antimicrobial performance and kinetics

Drug-loaded nanoformulations exert numerous beneficial synergistic effects such as minimised toxicity and maximised bioavailability to combat drug resistance and achieve enhanced drug delivery. The current study explores the synthesis and enhanced antimicrobial behaviour of nano-Bi₂O₃ loaded with Isoconazole. Bi₂O₃ nanoparticles-Isoconazole formulation was characterised using XRD, FTIR in the range 500–4000 cm⁻¹, SEM, EDX and UV analysis. The association of Bi₂O₃ nanoparticles (Bi₂O₃ NPs) with Isoconazole was revealed by XRD through peaks that match with tetragonal structure of β-Bi₂O₃ for pure Bi₂O₃ nanoparticles and altered dominant peaks after loading. Similarly, scanning electron microscopy conveyed detectable morphological changes along with average particle size elevating from 47.11 to 70.79 nm upon loading. Brunauer–Emmett–Teller curves indicated a reduced quantity of adsorbed nitrogen with surface area, pore volume and pore diameter of Bi₂O₃ NPs decreasing from 7.23 m²/g, 6.98 × 10⁻³ cm³/g and 22 nm to 4.11 m²/g, 4.94 × 10⁻³ cm³/g and 18.011 nm, respectively. Also, significant changes in the signals of ¹H NMR upon loading Bi₂O₃ NPs with Isoconazole were observed. UV analysis showed a bandgap of 2.6 eV, and the peak underwent red shift upon loading Isoconazole. An appreciable loading efficiency and loading capacity is reported along with release kinetics pattern following Higuchi plot based on Fickian diffusion. Enhanced planktonic antibacterial activity of Bi₂O₃-Isoconazole formulation as compared to pure Bi₂O₃ and Isoconazole was found using zone inhibition. Also, antibiofilm activity by crystal violet assay was examined for minimum inhibitory concentration and minimum bactericidal concentration. Antifungal activity of 7.4–9.9 mm inhibition for concentrations of 5–75 μL with % growth inhibition of 98.3 and 95, respectively, was obtained by zone inhibition method and poison food technique. The antimicrobial studies based on the experimental evidences provide an insight into the behaviour of the new formulation that offers a cost-effective technique against new infections and works in a fairly suitable time frame.