A comparative study on the mode of interaction of different nanoparticles during MALDI-MS of bacterial cells

摘要

We propose the benefits of preincubation during nanoparticle-assisted bacterial analysis, where the bacteria are grown along with the nanoparticles. We were able to obtain a two to ten fold enhancement of bacterial signals in 3 h compared to the generally used methodology followed in previous literature. The previous literature method required a long time (18 h) to obtain such an enhancement. We probe the interactions of two bacteria, Staphylococcus aureus and Pseudomonas aeruginosa, with Ag, NiO, Pt TiO_2 and ZnO nanoparticles via transmission electron microscopy, ultraviolet spectroscopy and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). Based on these results, we propose a mechanism for interaction of these five nanoparticles with bacteria. Two mechanisms were observed for the interactions: (1) Mechanism A is proposed for the Pt and NiO NPs which functioned based on affinity for bacterial cells. (2) Mechanism B was proposed for the bactericidal NPs such as TiO_2, ZnO and Ag NPs. The results indicate that the success of the unmodified NPs in MALDI-MS bacterial studies lies in following the ideal protocol for incubation at the ideal concentrations.