Photocatalytic and antibacterial performance of β-cyclodextrin-TiO2 nanoparticles loading sorbic and benzoic acids

TiO₂ nanoparticles (NPs) have been modified with β-cyclodextrin (βCD)-food preservative complexes to be applied in food packaging. The susceptibility of Escherichia coli and Staphylococcus aureus to TiO₂ NPs, sorbic acid (SA), benzoic acid (BA), and β-Cyclodextrin-TiO₂ NPs including SA or BA, was studied. At 0.5 mg mL⁻¹, TiO₂ NPs were more effective in the inhibition of bacterial growth than modified-TiO₂ NPs, achieving 71% inhibition rate. At the higher concentration of 3 mg mL⁻¹ there were no significant differences between treatments, being all of them highly effective reaching 90% inhibition. Higher treatment-doses were related to slower growth rates. Flow cytometry findings suggested efficient NPs interaction with bacteria, being more noticeable in the case of TiO₂ NPs. Regarding the photocatalytic activity, under 0.600 mW cm⁻² irradiation, TiO₂ NPs reached 95% methylene-blue dye degradation after 150 min, while βCD-TiO₂ NPs showed 3-times lower kinetic constant. Overall results suggest potential application of the new systems in active packages to protect food from microbial spoilage.

Higher doses of treatment resulted in greater inhibition of bacterial growth, slower growth kinetics, larger structure cell damages and lower metabolic activity of bacteria. TiO₂ NPs were highly effective against E. coli and S. aureus, whereas relatively high concentrations of βCD-food preservative-TiO₂ NPs were required to inhibit bacterial growth. The βCD coverage on TiO₂ NPs surface may hindrance their interaction with bacteria, and thus their antibacterial activity. However, the main interest of NPs modification is found in the sustained release of the food preservatives from the cavity of the βCD, that allows to extend the antimicrobial effect over time. The overall results showed a correlation between the photocatalytic activity of the NPs, and their antibacterial capacity; high photocatalytic activities induced high antibacterial behaviour. 

Leire Goñi-Ciaurriz, Pablo Rosas-Val, Carlos Gamazo, Itziar Vélaz, Photocatalytic and antibacterial performance of β-cyclodextrin-TiO2 nanoparticles loading sorbic and benzoic acids. Colloid and Interface Science Communications 57, 2023, 100747. https://doi.org/10.1016/j.colcom.2023.100747