MALDI mass spectrometry for probing the anti- staphylococcal capability of TiO2 nanoparticles via near-UV and laser irradiation

Abstract

We report the use of MALDI-MS as an effective tool in investigating the anti-staphylococcal property of TiO₂ nanoparticles under near-UV and for the first time also under laser irradiation. Since near-UV based photocatalytic activity is toxic to biological cells, it is not feasible for biological studies and hence we propose a more biologically friendly system such as laser irradiation for inhibition of the clinical pathogen S. aureus. In-house prepared anatase phase TiO₂ nanoparticles were incubated with the bacterial pathogen and irradiated using near-UV and laser. The anti-staphylococcal effect was studied using MALDI-MS as an analytical technique in addition to the conventional plate counting method and high resolution TEM. The results showed that the anatase TiO₂ nanoparticles at the concentrations of 0.5 μg mL⁻¹ and 1.5 μg mL⁻¹ showed anti-staphylococcal activity under laser irradiation (one order reduction in bacterial counts) and near-UV irradiation (five order inhibition) compared to the control (no TiO₂ NPs) (10⁷ cfu per mL). The application of laser light offers a new prospective for the replacement of near-UV light for sensitive experiments involving biological applications to avoid damage to normal cells. In this study, the ability of TiO₂ nanoparticles (NPs) under laser and near UV irradiation leading to the anti-staphylococcal activity was demonstrated using MALDI-MS as the analytical probing tool.