Abstract-Selenium is well known as an essential trace element since the 20th century, but it can be overdosed easily because of its toxicity. According to the present regulations [1] only the potentially most harmful, inorganic selenium salts can be added to any comestibles. Elemental selenium is considered as the least toxical of all selenium forms and in the same time supplementation with its nano-size particles has the same or better bioavailability compared to its salts. In our experiments we managed to produce nano-size (100-500nm) elemental selenium by using probiotic yogurt bacteria in a fermentation procedure. We developed the laboratory technology of product purification and recovery from bacteria.

The uptake, accumulation and biological effects of red nano-sized elemental selenium (nanoSe) in comparison to selenate were investigated in plant system at the first time. The data clearly indicated that red nanoSe was taken up by tobacco callus cultures and rooted tobacco plantlets. The roots of regenerated plantlets accumulated selenium in very high concentrations, 2,947 ± 99 mg/kg DW, from the medium containing 530 lM nanoSe. The biological effects of nanoSe were different from the selenate ion in plant tissue culture. NanoSe (265-530 lM concentration range) stimulated the organogenesis and the growth of root system significantly (*40 %) while selenate did not show these effects at any concentration moreover inhibited both callus growth and root regeneration totally in 265-530 lM concentrations.

BackgroundAs an essential trace element selenium plays a significant role in many physiological functions of the organs. It is found within muscles as selenocystein in selenoprotein N, which is involved in redox-modulated calcium homeostasis and in protection against oxidative stress.MethodsThe effects of two different selenium compounds (selenate and NanoSe in 0.5 and 5 ppm concentration for two weeks) on muscle properties of mice were examined by measuring in vivo muscle performance, in vitro force in soleus (SOL) and extensor digitorum longus (EDL) muscles and changes in intracellular Ca2+ concentration in single fibers from flexor digitorum brevis (FDB) muscle.. Western-blot analysis on muscle lysates of EDL and SOL were used to measure the selenoprotein N expression. Control mice received 0.3 ppm Se.ResultsWhile the grip force did not change, 5 ppm selenium diets significantly increased the speed of voluntary running and the daily distance covered. Both forms of selenium increased significantly the amplitude of single twitches in EDL and SOL muscle in a concentration dependent manner. Selenate increased fatigue resistance in SOL. The amplitude of the calcium transients evoked by KCl depolarization increased significantly from the control of 343 ± 44 nM to 671 ± 51 nM in the presence of 0.5 ppm selenate in FDB fibers. In parallel, the rate of calcium release during short depolarizations increased significantly from 28.4 ± 2.2 to 45.5 ± 3.8 and 52.1 ± 1.9 μM/ms in the presence of 0.5 ppm NanoSe and selenate, respectively. In 0.5 ppm concentration both selenium compounds increased significantly the selenoprotein N expression only in EDL muscle.ConclusionsSelenium supplementation augments calcium release from the sarcoplasmic reticulum thus improves skeletal muscle performance. These effects are accompanied by the increased selenoprotein N expression in the muscles which could result in increased oxidative stress tolerance in case of long lasting contraction.Electronic supplementary materialThe online version of this article (doi:10.1186/s12986-016-0134-6) contains supplementary material, which is available to authorized users.

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