A comparison of fate and toxicity of selenite, biogenically and chemically synthesized selenium nanoparticles to zebrafish (Danio rerio) embryogenesis
Research output: Contribution to journal › Article › Scientific › peer-review
|Number of pages||34|
|Early online date||23 Dec 2016|
|Publication status||Published - 2017|
|Publication type||A1 Journal article-refereed|
Microbial reduction of selenium (Se) oxyanions to elemental Se is a promising technology for bioremediation and treatment of Se wastewaters. But a fraction of biogenic nano-Selenium (nano-Se(b)) formed in bioreactors remains suspended in the treated waters, thus entering the aquatic environment. The present study investigated the toxicity of nano-Se(b) formed by anaerobic granular sludge biofilms on zebrafish embryos in comparison with selenite and chemogenic nano-Se (nano-Se(c)). The nano-Se(b) formed by granular sludge biofilms showed a LC50 value of 1.77 mg/L, which was 3.2-fold less toxic to zebrafish embryos than selenite (LC50 = 0.55 mg/L) and 10-fold less toxic than bovine serum albumin stabilized nano-Se(c) (LC50 = 0.16 mg/L). Smaller (nano-Se(cs); particle diameter range: 25-80 nm) and larger (nano-Se(cl); particle diameter range: 50-250 nm) sized chemically synthesized nano-Se(c) particles showed comparable toxicity on zebrafish embryos. The lower toxicity of nano-Se(b) in comparison to nano-Se(c) was analyzed in terms of the stabilizing organic layer. The results confirmed that the organic layer extracted from the nano-Se(b) consisted of components of the extracellular polymeric substances (EPS) matrix, which govern the physiochemical stability and surface properties like ζ-potential of nano-Se(b). Based on the data, it is contented that the presence of humic acid like substances of EPS on the surface of nano-Se(b) plays a major role in lowering the bioavailability (uptake) and toxicity of nano-Se(b) by decreasing the interactions between nanoparticles and embryos.