Title: Oxidative and antimicrobic effects of iron, titanium oxide nanoparticles and thalicarpine

Abstract

The aim is to evaluate the oxidant and antimicrobial effects of Fe3O4, TiO2 nanoparticles and thalicarpine by luminescent and standard microbiological assays. Their effect is studied on the kinetics of free-radical oxidation reactions (at pH 7.4 and pH 8.5) in 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.