Annealing Temperature Influences the Cytocompatibility, Bactericidal and Bioactive Properties of Green Synthesised TiO2 Nanocomposites from Calotropis Gigantea

Annealing is a crucial functional parameter relevant to the green synthesis and bactericidal properties of TiO2 nanocomposites (TiO2-NPs). In this work, the effect of the annealing temperature on the physicochemical and bactericidal properties of TiO2-NPs obtained from Calotropis gigantea was comprehensively studied. The synthesised TiO2-NPs were characterised using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, UV–Vis spectrophotometer and FTIR spectroscopy. The bactericidal properties were determined via the minimum inhibitory concentration (MIC) and Kirby–Bauer disc diffusion methods. The cytocompatibility of green TiO2 was further investigated using fibroblast cells lines model. Results indicated that amorphous-phase TiO2-NPs were transformed into the anatase phase at 500 °C with a crystallite size of 40.9 nm and MIC of 100 mg/mL towards S. aureus (colony count reduction from 4.3 log10 to 1.01 log10). Whereas TiO2-NPs annealed at 400 °C demonstrated no bacterial reduction, TiO2-NPs annealed at 500 °C showed a moderate zone of inhibition of 6.33–6.83 mm towards Escherichia coli and Pseudomonas aeruginosa. Findings from this study found that TiO-500C nanocomposites concentration at 100 mg/mL is cytocompatible to the fibroblast cells lines with proliferation rate/activity higher than 116% after 24 h treatment. The plant-mediated nano-sized cubic and spherical anatase TiO2-NPs encapsulated bioactive green elements, such as carbon, sodium, magnesium, chlorine, potassium, calcium and sulphur, from the C. gigantea extract, ultimately leading to versatile and eco-friendly bactericidal agents with wound-healing properties. Further studies are necessary to support the findings of this work.