Environmental Science: Nano Blog

As nanotechnology continues to develop at a fast growing speed, more research efforts should focus on the assessment of nanotoxicity in order to better understand whether engineered nanoparticles (ENPs) pose hazards upon exposure. ENPs have been used in a large variety of products (from toothpaste, soap, sunscreen lotion to plastic ware, electronics, cement, paint, etc.) and therefore the likelihood for ecological exposure to these nanoproducts in relation to their leachable by-products is inevitable.

Dubey and co-workers highlight the importance of assessing the interaction of ENPs with naturally occurring colloids in relation to environmental factors. Upon entering the aquatic system, these factors could modify their colloidal stability and ultimately affect their toxicity. Their studies focused on silver nanoparticles (AgNP) which have been widely used for their broad spectrum of antimicrobial and plasmonic properties. In particular, Dubey et al investigated the potential effects of multiple water chemistry on the colloidal stability, dissolution rate and antibacterial activity of citrate-coated silver nanoparticles (Citrate-AgNPs) against Escherichia coli. Concomitantly, toxicity studies of Citrate–AgNPs and AgNO₃ were also performed in the river water samples collected across three seasons.

The work carried out by Dubey and co-workes underlines the importance of evaluating aquatic toxicity of ENPs in order to understand the potential implications on the ecosystem’s health and functions.

Read the full article for free!

Natural Water Chemistry (Dissolved Organic Carbon, pH, and Hardness) Modulates Colloidal Stability, Dissolution, and Antimicrobial Activity of Citrate Functionalized Silver Nanoparticles
Lok R. Pokhrel, Brajesh Dubey and Phillip R. Scheuerman
Environ. Sci.: Nano, 2014, Advance Article
DOI: 10.1039/C3EN00017F

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Scientists at Clarkson University, USA, have investigated the effect of nanoparticles (NPs) on intestinal development of embryonic zebrafish (Danio rerio). They saw that levels of serotonin, a developmental marker, change according to exposure time and concentration.

NP use in commercial goods and food is ever increasing. Previously, studies have shown that NPs can alter skeletal development¹ and tissue formation,² but there is a need to find out more about what NPs might be doing to our bodies. The gastrointestinal (GI) tract has been identified as a hanging out point for ingested NPs that get trapped within our numerous intestinal folds; Özel and colleagues built on this observation and tested nickel (Ni) and copper oxide (CuO) NP exposure in the intestines of zebrafish embryos.

A zebrafish embryo

In their newly published paper³, Özel et al measured serotonin (5HT) levels to investigate intestinal development. 5HT, which is secreted by cells in the GI tract, is known to act as a growth factor during embryogenesis; it is particularly involved in brain development, with disruption of serotonin-related cellular processes leading to CNS (central nervous system) disorders.⁴ Intestinal levels of 5HT were measured as an indication of developmental physiology. 5HT concentration was determined via carbon filter microelectrodes, inserted directly into the embryo, and differential pulse voltammetry.

Immunohistochemistry (using rabbit anti-serotonin antibody) of 50ppm NP-exposed zebrafish embryos showed a decrease in fluorescence intensity of 5HT in Ni-exposed embryos, compared to the control. In contrast, CuO exposure was associated with an increase in 5HT fluorescence intensity (Fig 1).

Fig 1. Zebrafish embryos showing 5HT levels after NP exposure using anti-5HT immunohistochemistry

These findings were supported by in vivo electrochemical measurements, which showed significantly decreased 5HT for concentrations of 20ppm and higher Ni, and a general increase in 5HT for CuO exposure (Fig 2).

Özel and colleagues suggest that the different effects seen between Ni and CuO NP exposure demonstrate the complexity of the toxicity induced by NPs. As well as measuring 5HT levels, the team also showed that rates of embryo hatching from the chorion (an acellular membrane surrounding fish eggs) were generally decreased by increasing NP concentrations. At 50 to 100ppm CuO, more than 98% of embryos failed to hatch, whilst Ni produced a 70% failure rate.

Fig 2. Changes of in vivo intestinal 5HT concentrations after NP exposure

The findings of this paper indicate that environmental exposure to NPs may affect the physiology of developing organs, as well as the triggering of developmentally-timed events, such as hatching. In future, there is a need to extend these studies in order to fully understand how NPs in the environment may affect development, from fish to humans and everything in between. We are all exposed.

This paper is one of the first to be published in Environmental Science: Nano. We must say a big thank you to the authors, and the Nano Editorial Team, who worked hard to publish it. Environmental Science: Nano is providing free access upon registration* to all content published during 2014 and 2015. To get your free download of this paper, follow the links below:

R. E. Özel, K. N. Wallace and S. Andreescu, Alterations of intestinal serotonin following nanoparticle exposure in embryonic zebrafish, DOI: 10.1039/C3EN00001J

References:

1. C. Ispas et al, Environmental Science & Technology, 2009, 43, 6349-6356
2. D. Xiong et al, Science of The Total Environment, 2011, 409, 1444-1452
3. R. E Özel et al, Environmental Science Nano, 2014, DOI: 10.1039/C3EN00001J
4. M.S. Sodhi & E. Sanders-Bush, Int. Rev. Neurobiol., 2004, 59, 111-174

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