Environmental Science: Nano Blog

Nanomaterials have shown such great potential to advance science and engineering that sometimes research on their applications can skip ahead of safety tests.

Nanoceria, a commonly used nanomaterial, is one such substance. These fine grains of cerium oxide have been proposed for use in fuels, sunscreens, and even pharmaceutical treatments, but the effects of long-term exposure have not been comprehensively investigated. Now, in a critical review published in Environmental Science: Nano’s themed issue, a team of pharmacists and environmental chemists have compiled and analyzed the available research on nanoceria’s health effects.

Nanoceria appears to have minimal effects when applied to the skin, and is not absorbed into the body through the digestive tract. However, once it makes its way into the bloodstream, whether through inhalation or direct injection, it can travel throughout the body.

Nanoceria is biopersistent, meaning that it does not dissolve or break down in the body, but instead builds up. When it finds its way into certain organs—such as the lungs or the liver—it can take months to completely leave, and can lead to inflammation and abnormal tissue growth. As with many hazardous materials, the risks are greater with higher doses or longer-term exposure.

The researchers propose that nanoceria’s toxic effects occur through inducing oxidative stress, an imbalance between oxidizing molecules and antioxidants that can disrupt biochemical pathways in the body. Because the surface properties of nanomaterials are believed to have the greatest influence on their potential toxicity, the authors suggest that coating the particles with a biologically inert material or altering their surface structure could reduce their impacts.

Nanoceria should not be indiscriminately avoided based on these findings—and some research has found positive biological applications for the substance, and even essential chemicals like water can be toxic in high enough doses. Rather, scientists working with these particles should understand their potential risks and work to minimize them.

To access the full article, download a copy for free* by clicking the link below.

The yin: an adverse health perspective of nanoceria: uptake, distribution, accumulation, and mechanisms of its toxicity
DOI: 10.1039/c4en00039k
R. Yokel et al.

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You may have heard of a material called asbestos. Asbestos was used as a construction material in the 19^th and 20^th centuries until it became the pivot of a widely-spread health concern in the 1980s and 1990s. The fibers’ long aspect ratio and crystalline makeup can cause serious respiratory illnesses, including lung cancer. This health hazard drove a ban on asbestos products.

Carbon nanotubes (CNTs) also have a high aspect ratio—they are very long and thin, and their atoms are also very neatly arranged in a crystal structure. So it is fair to assume that, if inhaled, CNTs may deposit on the respiratory system and cause a health risk similar to that of asbestos.

Currently there are multiple research efforts aiming at understanding the potential inhalation toxicity of CNTs. One complicated issue of this type of research is being able to discern the toxic effect caused by the CNT and the metal catalysts that are usually present. These metal catalysis are used to help synthesize CNTs and left at the tips of the tubes. The recently published work of Cerasela Zoica Dinu and colleagues examines the toxicity of CNTs that had been stripped clean of their metal catalysts.

Another very complicating factor of examining the inhalation toxicity to nanomaterials in general—but especially fibers—is  exposing lung cell cultures to nanomaterials in the same way that our lung cells would be exposed to these very nanomaterials, in air. While this work didn’t use the air route to expose the lung cells to CNTs, they were able to find interesting results. Their research takes us one step closer to understanding how CNTs interact with human cells, cause changes in multiple cellular processes to result in various degrees of toxicity.

To access the full article, download a copy for free* by clicking the link below.

Towards Elucidating the Effects of Purified MWCNTs on Human Lung Epithelial cells
DOI: 10.1039/C4EN00102H
Chenbo Dong et al.

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Silver nanoparticles (AgNPs) are becoming increasingly popular due to their antimicrobial properties. In fact, silver compounds have been used to treat or prevent infections since before penicillin was ever discovered. The ability of AgNPs to kill microorganisms brings great potential for treating drinking water in situations when traditional water treatment is not possible.

Roughly 10% of the world’s population does not have access to safe, clean drinking water because basic sanitation is lacking. In some cases, a point-of-use (aka in-your-home) water treatment method that is easy and affordable might make a great difference in preventing or reducing the incidence of diseases caused by water-borne microbes, such as cholera and poliomyelitis. A water filter that is embedded with a small amount of AgNPs is a great example of a point-of-use treatment method that can be easily distributed to homes in developing countries and used with minimal training.

In this paper, T. Dankovich, from the University of Virginia, presents us an elegant method for creating paper filters that are embedded with silver nanoparticles. Her method can be considered more environmentally friendly than usual silver nanoparticle synthesis techniques because the reducing agent is glucose (that’s right, sugar!) and the heating technique involved nothing more than a domestic microwave oven (that’s right, a kitchen microwave!). In this technique, silver nanoparticles were synthesized directly on the paper filters, as opposed to being synthesized in a liquid suspension and then applied onto the filter. This method avoids the potential pitfall of nanoparticle aggregation during application onto the filter.

The paper filters were successful treating water containing two different types of bacteria (E. coli, and E. faecalis). Moving forward, it will be interesting to know the efficiency of this type of filter in treating real surface water samples and the filtering capacity, or how many liters of water each filter is capable of treating before it needs to be replaced.

To access the full article, download a copy for free* by clicking the link below.

Microwave-assisted incorporation of silver nanoparticles in paper for point-of-use water purification
DOI: 10.1039/c4en00067f
Theresa A. Dankovich

Liked this blog? Find out more about Marina in her first Environmental Science Nano blog on carbon nanotubes.

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Nanocellulose (NC) provides a readily available and biodegradable substrate that can act as a novel template or carrier for a range of different nanomaterials (NMs) including carbonaceous, mineral and metal particles. NC is an ideal platform for inorganic NMs due to its high specific surface area, highly porous structure and high mechanical strength. The resulting NC combines the characteristics of both constituents therefore displaying synergistic properties useful for a variety of uses.

Peter Vikesland and colleagues from Virginia Tech and Duke University, USA provide a tutorial review discussing recent advances in the preparation of NC-based nanocomposites and their potential uses in addressing current and future environmental challenges. This is the first review of its kind to discuss the use of these novel nanocomposites in the context of environmental sciences and engineering applications.

You can download the full review for free* on our publishing platform

The authors describe:

• different forms in which NC is produced,
• how the NC can be derived both from plant materials and bacterial processes,
• how NC can be modified into a number of useful forms.

Furthermore, in-depth discussion of the different methods used in the preparation of NC and different types of composites is provided. This includes a discussion of how the guest NM can be incorporated in/on to the NC structure, guidance regarding the challenges faced in these processes and how researchers have address these problems, and instructions on the best available methods currently known for these procedures.

The review also details the uses of NC-based nanocomposities in key environmental science/engineering applications and summarises the practical considerations and advantages these provide over more conventional NMs. This focuses on four principal areas:

1) The better incorporation of antimicrobial materials such as Ag NMs into NC-based filters for air and drinking water purification.

2) The use of NC as a support for photocatalysts and metal catalysts used in the degradation of organic pollutants in water remediation.

3) The use of Au NP/NC biosensors for monitoring of water-borne pathogens and organic contaminants.

4) The use of NC-based nanocomposites in the design of superior energy conversion devices such as fuel cells, solar cells and Li-ion battery manufacturing.

Finally, potential directions of further research in the field of NC nanocomposites are highlighted. Specifically, researching methods to better control the size and distribution of NMs on or within the NC substrate, investigating how the loading of NMs influence the potential applications, and ways to prolong the lifetime and/or regenerate NMs to ensure their sustainability.

Cellulose is an abundant, cheap and renewable resource. Nanocellulose is shown to form useful nanocomposites with inorganic nanomaterials, which display valuable optical, catalytic, electrical properties. This review provides guidance to researchers in the field of environmental sciences and engineering on the production and uses for this type of nanocomposites to address current and emerging environmental challenges.

Environmental science and engineering applications of nanocellulose-based nanocomposites
Haoran Wei, Katia Rodriguez, Scott Renneckar and Peter J. Vikesland
Environ. Sci.: Nano, 2014,1, 302
DOI: 10.1039/c4en00059e

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