Environmental Science: Nano Blog

Nanoceria (nanoparticle form of CeO₂, cerium(IV) oxide) is quickly becoming a trending topic in Environmental Science. After recently discussing its health effects, today we present a fascinating paper regarding its biodistribution and retention in rats.

Currently, the main use for nanoceria is as an abrasive catalyst, especially important for the industry in silicon integrated circuit fabrication. In addition to that, and thanks to its autocatalytic behaviour, encouraging results have been presented in the past regarding its use as an antineoplastic agent. Nevertheless, there is concern on the topic of its toxicity in organisms.

Dr Robert A. Yokel and colleagues from the University of Kentucky have conducted an extensive investigation on the distribution and retention of several nanocerias after their systemic administration to rats.

The aim of their study was to determine if and how the biodistribution and persistence of nanocerias are modified according to the doses administered.

Additionally, interesting discussions regarding nanoceria shape and its influence on its toxicity, retention and disposition have been presented.

Moving forward, it will be exceptionally exciting to learn more about nanoceria’s clinical properties and effects on animals. In any case, this work is a big step forward in its research, helping us to clarify and consolidate our knowledge of the behaviour of nanocerias in mammalian organisms.

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

Nanoceria biodistribution and retention in the rat after its intravenous administration are not greatly influenced by dosing schedule, dose, or particle shape
Robert A. Yokel, Jason M. Unrine, Peng Wu, Binghui Wang and Eric A. Grulke
Environ. Sci.: Nano, 2014, Advance Article
DOI: 10.1039/C4EN00035H

The paper mentioned today is part of our Nanoceria Research themed collection, which is the most comprehensive and current source of information on the chemistry, biology, and beneficial and untoward effects of nanocerias.

*Access is free through a registered RSC account – click here to register

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.

Liked this blog? Find out more about Laurel in her first Environmental Science: Nano blog on rare earth elements.

*Access is free through a registered RSC account – click here to register

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.

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

* Access is free through a registered RSC account – click here to register

Groundwater contamination is becoming a bigger problem than in the past as a result of ever increasing industries and agricultural practices. Furthermore, a significant percentage of drinking water supply relies on clean ground water such that its efficient and effective remediation is a timely need. Specifically chlorinated solvents and nitroaromatic compounds are oxidized organics, which are frequently found as persistent contaminants in groundwater. As a result of their stability in oxic environments these contaminants can act as transporters to a variety of other pollutants between soil and ground waters phases in addition to endangering humans and wildlife.

The oxidized functional groups in these contaminants can be reduced by Fe(II) associated with iron minerals thus providing means for their degradation that can be incorporated into engineered remediation schemes. Ferrihydrite, goethite, magnetite, hematite and lepidocrocite are examples of some ubiquitous iron containing minerals. In these degradation reactions the number of reactive sites on the minerals are directly related to the specific surface area and thereforethe nanoparticles of these minerals, which inherently has large surface areas hold the greatest potential towards degrading these contaminants. Nevertheless, nanoparticles are highly susceptible to aggregation, which can significantly hinder the efficiency of the reduction process. Therefore, Amanda M. Stemig and co-workers from the University of Minnesota, have conducted an extensive investigation using 4-Chloronitrobenzene (4-ClNB) as a model compound to elucidate the link between the aggregation state of iron oxide nanoparticles and their reactivity.

The study was conducted by using well-characterized goethite nanoparticles  as the iron containing minerals. The results revealed that the size of the goethite nanoparticles are significantly reduced upon the adsorption of transition metals. This is, of course no surprise as the adsorption of transition metals introduces additional surface charge. Furthermore, a comparison between the pseudo first order rate constants of 4-ClNB degradation in a variety of buffers indicated that the buffer type affected the reaction kinetics by controlling the aggregation state and thereby changing the available surface area. It was clearly demonstrated that zwitterionic buffers with spatial charge separations are better at preventing aggregation, giving better degradation rates. In addition buffer concentration also affected the degradation kinetics as higher buffer concentrations resulted in more densely packed aggregates with lowered surface area.

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

Goethite nanoparticle aggregation: effects of buffers, metal ions, and 4-chloronitrobenzene reduction

Amanda M. Stemig, Tram Anh Do, Virany M. Yuwono, William A. Arnold and R. Lee Penn

DOI: 10.1039/c3en00063j

*Access is free through a registered RSC account – click here to register

Nanotechnology may be a relatively new field of research, but nanosized materials have been present naturally in our environment since long before scientists started engineering them in the lab. As synthetic nanoparticles find their way into a greater variety of consumer items, however, public concern about their potential health effects has increased. Researchers trying to monitor the spread of engineered nanomaterials now face a challenge: how to distinguish their creations from the background nanomaterials already present in the environment.

A new paper recently published in Environmental Science: Nano, addresses this concern by using rare earth elements (REEs) to label synthetic nanoparticles and trace their path through the environment.

So-called REEs are actually fairly abundant in the earth’s crust, but are typically widely dispersed and are largely absent from background nanomaterials. In this paper, researchers at the University of Zaragoza, Spain, tagged titanium dioxide (TiO₂) nanoparticles with two different REEs: lanthanum (La) and cerium (Ce). REEs were added to the nanoparticles during the synthesis stage so that they would be integrated into the particles’ structure. The incorporation of REEs induced a slight color shift, but did not cause significant structural changes—the labeled nanoparticles looked and behaved much like the non-labeled ones, though small differences in surface area and particle sized were observed at higher concentrations of REEs. However, because REEs are present in in the background in such low concentrations, the labeling technique is very sensitive—only a small amount of the element must be added in order for a signal to be picked up.

Then, the researchers tested whether their labeled nanoparticles were detectable in the environment. To simulate the type of contamination that might result from basic handling, they poured the nanoparticles between two beakers, a common laboratory procedure that has the potential to release particles into the air and deposit them onto the surrounding work surface.

They analyzed their work surface by systematically wiping the testing area and dissolving the wipe along with any particulate matter that it had picked up. Using optical spectrometry, they were able to quantify the amount of nanoparticle

s found near their beakers. The simple transfer procedure had spread nanoparticles across their work surface—a hint that failing to clean up the workspace between experiments could confound future results through cross-contamination!

Although this study found that even simple laboratory techniques can introduce nanoparticle contamination into the environment, it did not assess the potential health effects of these particles. Rather, the labeling technique described here provides an easy and sensitive method to trace engineered nanomaterials in the environment that will facilitate future studies attempting to answer this question.

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

Identification of TiO₂ nanoparticles using La and Ce as labels: application to the evaluation of surface contamination during the handling of nanosized matter.
DOI: 10.1039/c4en00060a
V. Gomez et al

About the webwriter

Laurel Hamers is a recent graduate of Williams College and an aspiring science journalist. She has written for the Marine Biological Laboratory, Inside Science News Service, and the Materials Research Society. You can find her on her blog (sciencescope.wordpress.com) or on Twitter (@arboreal_laurel.)

* Access is free through a registered RSC account – click here to register

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.

* Access is free through a registered RSC account – click here to register