Age-dependent assessment of selenium nanoparticles: biodistribution and toxicity study in young and adult rats supplementary data

<b>Aim: </b>To study the biodistribution and toxicology of selenium nanoparticles (SeNPs) versus their bulk counterpart in young and adult male rats in a 28-day study. <b>Methods: </b>SeNPs were synthesized and conjugated with indocyanine green to assess comparative biodistribution by <i>in vivo </i>imaging and further characterized by transmission electron microscopy, Fourier transform infrared, scanning electron microscopy <b>/ </b>energy dispersive x-ray spectroscopy, UV and <b>ζ</b>-analysis. The toxicity of bulk selenium was evaluated relative to its nano form by hematology indices, redox, inflammatory markers and histopathology. <b>Results: </b>Indocyanine green-conjugated nanoparticles showed preferential accumulation in the liver, followed by testis and kidney. The protective effect of SeNPs was more significantly observed in young livers than in adults compared with the bulk counterpart. <b>Conclusion: </b>Age-dependent monitoring and diagnosis of toxicity may need different biomarkers of selenium and may also provide better understanding of SeNPs as therapeutics.<b>Plain language summary: </b>Selenium is an essential element in the body. Its bioactive properties can protect against neurological conditions, diabetes, cancer and other chronic disorders. However, selenium in various biological forms (bulk) can be toxic. Selenium nanoparticles (SeNPs) have unique properties which might prevent this toxicity, providing a potential alternative for selenium supplementation and therapy. However, more studies are needed to see where SeNPs localize in the body, as well as comparing their toxicology with conventional forms of selenium in different age groups. We synthesized and characterized SeNPs of 70–90 nm, then injected them into young and adult rats to see where they distributed in the body. This was compared with rats injected with bulk selenium. SeNPs showed preferential accumulation in the liver, followed by the testes and kidneys. Next, the toxicity profiles of SeNPs and bulk selenium were established by measuring a series of health markers in the liver. It was found that the protection against toxicity provided by SeNPs was more significant in younger rats. Our results demonstrate that the same dose may behave differently in different age groups and that bulk selenium induces different toxicities in young and adult rats compared with SeNPs, highlighting the importance of different indicators of health for the monitoring of selenium-related toxicity when designing selenium-based therapeutics.