Accumulation and biotransformation of chitosan-modified selenium nanoparticles in exposed radish (Raphanus sativus)

In this investigation, we evaluate the biotransformation of chitosan-modified SeNPs (CS-SeNPs) in radish plants (Raphanus sativus) by using an analytical methodology which combines high performance liquid chromatography (HPLC) and asymmetrical flow field flow fractionation (AF4) on line coupled to inductively coupled plasma mass spectrometry (ICP-MS), as well as transmission electron microscopy (TEM). CS-SeNPs were synthesized using a solution-phase approach based on the reduction of selenite with ascorbic acid in the presence of chitosan as a stabilizing agent. The average diameter of the resulting spherical CS-SeNPs was 26 ± 3 nm. Extracts of radish plants exposed to CS-SeNPs were analyzed by HPLC-ICPMS and the results showed that a percentage higher than 95% of the selenium accumulated biotransformed into MeSeCys and SeMet. We assume that CS-SeNPs are first adsorbed on the root system and then transformed into organic selenium compounds following a similar metabolic pathway to selenite. Characterization of CS-SeNP diameter size in the radish root system was performed by using both AF4-UV-ICPMS and TEM. The size distributions, determined by TEM, were in good agreement with that obtained from AF4-ICPMS. The results are of importance since the number of applications of AF4-ICPMS to diameter size estimation of nanoparticles in living systems is still scarce. To the best of our knowledge, this is the first report confirming the biotransformation of SeNPs in plants.