Prooxidant and antimicrobic effects of iron and titanium oxide nanoparticles and thalicarpine

The aim is to evaluate the prooxidant and antimicrobial effects of Fe₃O₄ and TiO₂ nanoparticles and thalicarpine by luminescent and standard microbiological assays. Their effect on the kinetics of free-radical oxidation reactions (at pH 7.4 and pH 8.5) is studied in the following model systems, using activated chemiluminescence: chemical, with Fenton's reagent (H₂O₂-FeSO₄)-for the generation of hydroxyl radicals (^.OH); chemical, with oxidant hydrogen peroxide (H₂O₂); chemical (NAD.H-PhMS), for the generation of superoxide radicals (O₂^.-). Fe₃O₄ nanoparticles exhibit highly pronounced antioxidant properties; TiO₂ nanoparticles exhibit mild to moderate prooxidant properties at neutral and alkaline conditions. Those properties are tested by the chemiluminescent method for the first time. Thalicarpine and its combination with TiO₂ nanoparticles exhibit pronounced antioxidant activities at pH 8.5 which are lost and transformed into well-presented prooxidant effects at pH 7.4. That is a result-supported proof on the observed typical properties of thalicarpine and TiO₂, namely antibacterial, organic-preserving and anti-pathogenic activities. The antimicrobial effect is tested on Gram-positive and Gram-negative bacteria: two strains of Escherichia coli, Bacillus cereus 1095 and Staphylococcus aureus. All bacteria are destroyed after the application of TiO₂, but not Fe₃O₄ nanoparticles, showing their antibacterial effect. Thalicarpine, in combination with TiO₂, showed even synergetic antibacterial effect.