The increasing use of platinum in different forms including engineered nanoparticles (PtNPs) in a wide range of industrial applications and in particular in automotive catalysts is leading to a rising concern about their release and fate in the environment. This study investigates for the first time the uptake and fate of PtNPs by plants. Two model organisms Lepidium sativum and Sinapis alba were exposed to 70 nm PtNPs. An enzymatic digestion method was developed in order to extract intact PtNPs from the different plant tissues, optimizing different parameters in order to obtain the highest number of nanoparticles. Single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) was developed to provide information about nanoparticle size, nanoparticle number concentration and the presence of dissolved platinum in the samples. The enzymatic treatment allowed the extraction of PtNPs from the different tissues without changing their oxidation or aggregation state. The presence of PtNPs at the nominal size in all tissues from both plants was observed. PtNPs with higher sizes than the nominal one were observed as well, suggesting the occurrence of an aggregation process. The presence of platinum in the dissolved form was not detected.

Selenium (Se) was found to inhibit the growth of the yeast Candida utilis ATCC 9950. Cells cultured in 30 mg selenite/L supplemented medium could bind 1368 µg Se/g of dry weight in their structures. Increased accumulation of trehalose and glycogen was observed, which indicated cell response to stress conditions. The activity of antioxidative enzymes (glutathione peroxidase, glutathione reductase, thioredoxin reductase, and glutathione S-transferase) was significantly higher than that of the control without Se addition. Most Se was bound to water-insoluble protein fraction; in addition, the yeast produced 20–30 nm Se nanoparticles (SeNPs). Part of Se was metabolized to selenomethionine (10%) and selenocysteine (20%). The HPLC-ESI-Orbitrap MS analysis showed the presence of five Se compounds combined with glutathione in the yeast. The obtained results form the basis for further research on the mechanisms of Se metabolism in yeast cells.

A method based on single particle inductively coupled plasma mass spectrometry (SP-ICPMS) was developed for the analysis of commercial Se-rich yeasts, to confirm the occurrence of selenium nanoparticles in these food supplements. A considerable reduction of background levels was achieved by combining data acquisition at microsecond dwell times and the use of a H₂ reaction cell, improving by a factor of 10 the current state-of-the-art methodology, and bringing size detection limits down to 18 nm for selenium nanoparticles. The presence of nanoparticulate selenium was revealed by size-exclusion chromatography ICPMS, with detection of a selenium peak at the exclusion volume of the column showing absorption at a wavelength corresponding to selenium nanoparticles. SP-ICPMS allowed us to confirm the presence of Se-nanoparticles, as well as to calculate the nanoparticle size distribution, from information about the shape and elemental composition of the nanoparticles obtained by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS), respectively. These results reveal the significance of nanoparticles in the speciation of metals and metalloids in biological samples and the capability of SP-ICPMS in combination with TEM-EDS to carry out these analyses.