Abstract
Selenium nanoparticles (SeNPs) present a promising alternative to toxic inorganic selenium salts, yet the differential bioactivity between their allotropic forms-amorphous red (RSeNPs) and crystalline grey (GSeNPs)-is not fully determined. This study investigated the allotropic status and concentration-dependent effects of RSeNPs and GSeNPs (0.5, 5, and 50 mg·L(-1)) on Saccharomyces cerevisiae growth, monitored via foam expansion distance, calculated growth rate, and the normal logarithm of the samples' optical densities at 600 nm. The results revealed that the allotropic form was the dominant factor influencing yeast performance. Specifically, RSeNPs exhibited superior biocompatibility; the 0.5 mg·L(-1) dose (RSe0.5) yielded the highest overall growth rate, suggesting a potential growth-promoting effect. Conversely, GSeNPs demonstrated concentration-dependent toxicity, with the 50 mg·L(-1) dose (GSe50) causing a statistically significant inhibition compared to the control. Moreover, optical density measurements confirmed that both red and grey SeNPs enhanced the maximum specific growth rate (µmax) compared to the control, demonstrating a stimulatory effect on yeast growth kinetics. These findings confirm that amorphous RSeNPs are less inhibitory and potentially more beneficial than their crystalline grey counterparts, underscoring the critical importance of nanoparticle morphology in determining biological outcomes.