Experiments of in vivo HgSe nanoparticle formation demonstrate the potential of multi-element single particle icpTOF analysis for complex biological samples.
Olga Borovinskaya1, Zuzana Gajdosechova2, Eva Krupp2, Jörg Feldmann2
1. TOFWERK, Thun, Switzerland 2. University of Aberdeen, Scotland
MeHg is toxic to humans and the mechanism of its detoxification is still not entirely understood. Selenium is believed to play the role of defender in the detoxification scheme, converting MeHg to less toxic species such as HgSe. HgSe nanoparticle formation, on the other hand, is believed to deplete the Se pool in the body, misbalancing the normal biological cycle and suppressing antioxidant activity of Se-proteins.
The mechanism of in vivo HgSe nanoparticle formation was recently studied in liver and brain specimens of stranded pilot whales, which can incorporate relatively high levels of Hg. HgSe clusters with size up to 5 μm and Hg/Se molar ratio close to 1 were found in adult animals using synchrotron μ-XRF imaging with 800 nm lateral resolution. Smaller aggregates surrounding large clusters had Hg/Se molar ratio <1, which suggests the growing of HgSe nanoparticles on Se-rich core center structures. Single particle quadrupole inductively coupled plasma mass spectrometry (ICP-MS) analysis revealed increases in particle size and concentration with increasing animal age.
To shed more light on the mechanism of HgSe nanoparticle formation we characterized Hg/Se molar ratios in individual particles extracted from whale liver using multi-element single particle analysis with the TOFWERK icpTOF.
HgSe particles from the liver extract had sizes in the range of 40-100 nm and a mean Hg/Se molar ratio of 0.7. A slight increase of Hg/Se with increase in particle size was observed, which is in agreement with the results of the synchrotron μ-XRF. In addition to Hg and Se, the icpTOF also detected Cd and Fe at significant levels, with molar ratios of Hg/Cd=1.1 and Hg/Fe=0.02.
Though it is still unclear whether the Cd and Fe observations can provide further insight into HgSe crystal formation and growth, this finding demonstrates the potential of multi-element single particle icpTOF analysis for complex biological samples.
 Z. Gajdosechova, M. M. Lawan, D. S. Urgast, A. Raab, K. G. Scheckel, E. Lombi, P. M. Kopittke, K. Loeschner, E. H. Larsen, G. Woods, A. Brownlow, F. L. Read, J. Feldmann, E. M. Krupp, Scientific Reports 2016, 6, 34361.