Radicals generated by nanoparticles in contact with liquid water using spin trapping and mass spectrometry

Konferenceabstrakt til konference - 2018

Resume

Introduction
Inhalation of particles may cause airway inflammation induced by reactive oxygen species (ROS) generated by the particles. ROS are often measured by non-specific methods e.g. using 2’,7’-dichlorodihydro-fluorescein (DCFH2) and comprises both radicals (hydroxyl, superoxide) and non-radicals (hydrogen peroxide) which both contribute to the response of DCFH2. The aim of the study [1] was to measure specific radicals formed by nanoparticles in contact with water.

Methods
The method is based on spin trapping using diethoxyphosphoryl-5-methyl-1-pyrroline (DEPMPO) that traps radicals right after their formation. In short, nanoparticles (NPs) were dispersed in pure water with added spin trap, incubated over-night, and centrifuged. The supernatant was analysed with LC-MS and the “pellet” consisting of the NPs was analysed with MALDI-TOF-MS to directly measure the spin trap radical products adsorbed to the surface of the NPs.

Results
It turned out that the major part of the spin trap radical products was adsorbed to the particle surfaces. Carbon black (Printex 90) showed by far the strongest radical generation as compared to silica NP (NM-200), with carbon nanotubes (NM-400) in between. The preliminary results showed that the Printex 90 produced mainly the hydroxyl radical (·OH) but also the hydroperoxyl radical (·OOH). NM-400 produced only ·OH and NM-203 produced no radicals. The total radical formation potential (sum of·OH and ·OOH from both supernatant and “pellet”) of Printex 90 was 13-46 nmol/mg NP and 8-20 nmol/mg NP of NM-400 depending on the amount of NP dispersed in the water.

Conclusions
When studying the specific radical formation of NPs using spin traps and MS techniques it is necessary to be aware, that a substantial part of the spin trap radical products may be adsorbed to the surface of the NPs and has to be measured independently. The preliminary results show that radical formation by different types of NP may range from no radical formation of silica NP and up to about 50 nmol/mg NP of carbon black. All mechanisms behind ROS production are not known.

Novel Aspect
Quantitation of radicals formed by nanoparticles in their dispersion media and on their surface using spin trapping and MS has to our knowledge not been reported previously.

Reference

Radicals generated by nanoparticles in contact with liquid water using spin trapping and mass spectrometry. 2018.

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