Tag Archives: zinc oxide nanoparticles

Inhibiting pathogens in meat with edible antimicrobial films

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Food poisoning is, at best, unpleasant and, at worst, lethal, so anything which helps people and other animals to avoid that condition is to be lauded, assuming there are no significant shortcomings with the solution to avoiding bad meat. According to a May 4, 2014 news item on Nanowerk a team at Penn (Pennsylvania) State University has developed an antimicrobial, edible film which may help solve the problem,

Antimicrobial agents incorporated into edible films applied to foods to seal in flavor, freshness and color can improve the microbiological safety of meats, according to researchers in Penn State’s College of Agricultural Sciences.

Using films made of pullulan — an edible, mostly tasteless, transparent polymer produced by the fungus Aureobasidium pulluns — researchers evaluated the effectiveness of films containing essential oils derived from rosemary, oregano and nanoparticles against foodborne pathogens associated with meat and poultry.

A May 1, 2014 Penn State University news release by Jeff Mulhollem, which originated the news item, describes the research in further detail,

In the study, which was published online in the April issue of the Journal of Food Science, researchers determined survivability of bacterial pathogens after treatment with 2 percent oregano essential oil, 2 percent rosemary essential oil, zinc oxide nanoparticles or silver nanoparticles.

The compounds then were incorporated into edible films made from pullulan, and the researchers determined the antimicrobial activity of these films against bacterial pathogens inoculated onto petri dishes.

Finally, the researchers experimentally inoculated fresh and ready-to-eat meat and poultry products with bacterial pathogens, treated them with the pullulan films containing the essential oils and nanoparticles, vacuum packaged, and then evaluated for bacterial growth following refrigerated storage for up to three weeks.

“The results from this study demonstrated that edible films made frompullulan and incorporated with essential oils or nanoparticles have the potential to improve the safety of refrigerated, fresh or further-processed meat and poultry products,” said Cutter. “The research shows that we can apply these food-grade films and have them do double duty — releasing antimicrobials and imparting characteristics to protect and improve food we eat.”

…

The edible films are a novelbut effective way to deliver antimicrobial agents to meats, Cutter explained, because the bacteria-killing action is longer lasting. Liquid applications run off the surface, are not absorbed and are less effective. The pullulan films adhere to the meat, allowing the incorporated antimicrobials to slowly dissolve, providing immediate and sustained kill of bacteria. In addition, the microorganisms do not have the opportunity to regrow.

There’s at least one problem with the pullulan films and its not, as far as the researcher is concerned, the silver or zinc oxide nanoparticles (from the news release),

Cutter conceded that pullulan films are not as oxygen-impermeable as plastic packaging now used to package meats, so the edible films are not likely to replace that material.

“The meat industry likes the properties of the polyethylene vacuum packaging materials that they are using now,” she said. “However, the one thing I really want to be able to do in the next few years is to figure out a way to co-extrude antimicrobial, edible films with the polyethylene so we have the true oxygen barrier properties of the plastic with the antimicrobial properties of the edible film.”

Knowing that edible films can release antimicrobials slowly over time and keep bacteria in meat at bay, further research will be aimed at creating what Cutter referred to as “active packaging” — polyethylene film with antimicrobial properties.

“Right now, we have two different packaging materials that are not necessarily compatible, leading to a two-step process. I keep thinking there’s a way to extrude edible, antimicrobial film in one layer with polyethylene, creating all-in-one packaging.

“The chemistry of binding the two together is the challenge, but we need to find a way to do it because marrying the two materials together in packaging would make foods — especially meat and poultry — safer to eat.”

Here’s a link to and a citation for the paper,

Incorporation of Essential Oils and Nanoparticles in Pullulan Films to Control Foodborne Pathogens on Meat and Poultry Products by Mohamed K. Morsy, Hassan H. Khalaf, Ashraf M. Sharoba, Hassan H. El-Tanahi and Catherine N. Cutter. Journal of Food Science, April 2014, Volume 79, Issue 4, pages M675–M684. DOI: 10.1111/1750-3841.12400 Article first published online: 12 MAR 2014

© 2014 Institute of Food Technologists®

This is behind a paywall.

Food and nanotechnology (as per Popular Mechanics) and zinc oxide nanoparticles in soil (as per North Dakota State University)

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I wouldn’t expect to find an article about food in a magazine titled Popular Mechanics but there it is, a Feb. 19,2014 article by Christina Ortiz (Note: A link has been removed),

For a little more than a decade, the food industry has been using nanotechnology to change the way we grow and maintain our food. The grocery chain Albertsons currently has a list of nanotech-touched foods in its home brand, ranging from cookies to cheese blends.

Nanotechnology use in food has real advantages: The technology gives producers the power to control how food looks, tastes, and even how long it lasts.

Looks Good and Good for You?

The most commonly used nanoparticle in foods is titanium dioxide. It’s used to make foods such as yogurt and coconut flakes look as white as possible, provide opacity to other food colorings, and prevent ingredients from caking up. Nanotech isn’t just about aesthetics, however. The biggest potential use for this method involves improving the nutritional value of foods.

Nano additives can enhance or prevent the absorption of certain nutrients. In an email interview with Popular Mechanics, Jonathan Brown, a research fellow at the University of Minnesota, says this method could be used to make mayonnaise less fattening by replacing fat molecules with water droplets.

…

I did check out US grocer, Albertson’s list of ‘nanofoods’, which they provide and discovered that it’s an undated listing on the Project of Emerging Nanotechnologies’ Consumer Products Inventory (CPI). The inventory has been revived recently after lying moribund for a few years (my Oct. 28, 2013 posting describes the fall and rise) and I believe that this 2013 CPI incarnation includes some oversight and analysis of the claims made, which the earlier version did not include. Given that the Albertson’s list is undated it’s difficult to assess the accuracy of the claims regarding the foodstuffs.

If you haven’t read about nanotechnology and food before, the Ortiz article provides a relatively even-handed primer although it does end on a cautionary note. In any event, it was interesting to get a bit of information about the process of ‘nanofood’ regulation in the US and other jurisdictions (from the Ortiz article),

Aside from requiring manufacturers to provide proof that nanotechnology foods are safe, the FDA has yet to implement specific testing of its own. But many countries are researching ways to balance innovation and regulation in this market. In 2012 the European Food Safety Authority (EFSA) released an annual risk assessment report outlining how the European Union is addressing the issue of nanotech in food. In Canada the Food Directorate “is taking a case-by-case approach to the safety assessment of food products containing or using nanomaterials.”

I featured the FDA’s efforts regarding regulation and ‘nanofood’ in an April 23, 2012 posting,

It looks to me like this [FDA’s draft guidance for ‘nanofoods’] is an attempt to develop a relationship where the industry players in the food industry to police their nanotechnology initiatives with the onus being on industry to communicate with the regulators in a continuous process, if not at the research stage certainly at the production stage.

At least one of the primary issues with any emerging technology revolves around the question of risk. Do we stop all manufacturing and development of nanotechnology-enabled food products until we’ve done the research? That question assumes that taking any risks is not worth the currently perceived benefits. The corresponding question, do we move forward and hope for the best? does get expressed perhaps not quite so baldly; I have seen material which suggests that research into risks needlessly hampers progress.

After reading on this topic for five or so years, my sense is that most people are prepared to combine the two approaches, i.e., move forward while researching possible risks. The actual conflicts seem to centre around these questions, how quickly do we move forward; how much research do we need; and what is an acceptable level of risk?

On the topic of researching the impact that nanoparticles might have on plants (food or otherwise), a January 24, 2013 North Dakota State University (NDSU) news release highlights a student researcher’s work on soil, plants, and zinc oxide nanoparticles,

NDSU senior Hannah Passolt is working on a project that is venturing into a very young field of research. The study about how crops’ roots absorb a microscopic nutrient might be described as being ahead of the cutting-edge.

In a laboratory of NDSU’s Wet Ecosystem Research Group, in collaboration with plant sciences, Passolt is exploring how two varieties of wheat take up extremely tiny pieces of zinc, called nanoparticles, from the soil.

As a point of reference, the particles Passolt is examining are measured at below 30 nanometers. A nanometer is 1 billionth of a meter.

“It’s the mystery of nanoparticles that is fascinating to me,” explained the zoology major from Fargo. “The behavior of nanoparticles in the environment is largely unknown as it is a very new, exciting science. This type of project has never been done before.”

In Passolt’s research project, plants supplied by NDSU wheat breeders are grown in a hydroponic solution, with different amounts of zinc oxide nanoparticles introduced into the solution.

Compared to naturally occurring zinc, engineered zinc nanoparticles can have very different properties. They can be highly reactive, meaning they can injure cells and tissues, and may cause genetic damage. The plants are carefully observed for any changes in growth rate and appearance. When the plants are harvested, researchers will analyze them for actual zinc content.

“Zinc is essential for a plant’s development. However, in excess, it can be harmful,” Passolt said. “In one of my experiments, we are using low and high levels of zinc, and the high concentrations are showing detrimental effects. However, we will have to analyze the plants for zinc concentrations to see if there have been any effects from the zinc nanoparticles.”

Passolt has conducted undergraduate research with the Wet Ecosystem Research Group for the past two years. She said working side-by-side with Donna Jacob, research assistant professor of biological sciences; Marinus Otte; professor of biological sciences; and Mohamed Mergoum, professor of plant sciences, has proven to be challenging, invigorating and rewarding.

“I’ve gained an incredible skill set – my research experience has built upon itself. I’ve gotten to the point where I have a pretty big role in an important study. To me, that is invaluable,” Passolt said. “To put effort into something that goes for the greater good of science is a very important lesson to learn.”

According to Jacob, Passolt volunteered two years ago, and she has since become an important member of the group. She has assisted graduate students and worked on her own small project, the results of which she presented at regional and international scientific conferences. “We offered her this large, complex experiment, and she’s really taken charge,” Jacob said, noting Passolt assisted with the project’s design, handled care of the plants and applied the treatments. When the project is completed, Passolt will publish a peer-reviewed scientific article.

“There is nothing like working on your own experiment to fully understand science,” Jacob said. “Since coming to NDSU in 2006, the Wet Ecosystem Research Group has worked with more than 50 undergraduates, possible only because of significant support from the North Dakota IDeA Networks of Biomedical Research Excellence program, known as INBRE, of the NIH National Center for Research Resources.”

Jacob said seven undergraduate students from the lab have worked on their own research projects and presented their work at conferences. Two articles, so far, have been published by undergraduate co-authors. “I believe the students gain valuable experience and an understanding of what scientists really do during fieldwork and in the laboratory,” Jacob said. “They see it is vastly different from book learning, and that scientists use creativity and ingenuity daily. I hope they come away from their experience with some excitement about research, in addition to a better resume.”

Passolt anticipates the results of her work could be used in a broader view of our ecosystem. She notes zinc nanoparticles are an often-used ingredient in such products as lotions, sunscreens and certain drug delivery systems. “Zinc nanoparticles are being introduced into the environment,” she said. “It gets to plants at some point, so we want to see if zinc nanoparticles have a positive or negative effect, or no effect at all.”

Researching nanoparticles the effects they might have on the environment and on health is a complex process as there are many types of nanoparticles some of which have been engineered and some of which occur naturally, silver nanoparticles being a prime example of both engineered and naturally occurring nanoparticles. (As well, the risks may lie more with interactions between nanomaterials.) For an example of research, which seems similar to the NDSU effort, there’s this open access research article,

Low Concentrations of Silver Nanoparticles in Biosolids Cause Adverse Ecosystem Responses under Realistic Field Scenario by Benjamin P. Colman, Christina L. Arnaout, Sarah Anciaux, Claudia K. Gunsch, Michael F. Hochella Jr, Bojeong Kim, Gregory V. Lowry,  Bonnie M. McGill, Brian C. Reinsch, Curtis J. Richardson, Jason M. Unrine, Justin P. Wright, Liyan Yin, and Emily S. Bernhardt. PLoS ONE 2013; 8 (2): e57189 DOI: 10.1371/journal.pone.0057189

One last comment, the Wet Ecosystem Research Group (WERG) mentioned in the news release about Passolt has an interesting history (from the homepage; Note: Links have been removed),

Marinus Otte and Donna Jacob brought WERG to the Department of Biological Sciences in the Fall of 2006.  Prior to that, the research group had been going strong at University College Dublin, Ireland, since 1992.

The aims for the research group are to train graduate and undergraduate students in scientific research, particularly wetlands, plants, biogeochemistry, watershed ecology and metals in the environment.  WERG research  covers a wide range of scales, from microscopic (e.g. biogeochemical processes in the rhizosphere of plants) to landscape (e.g. chemical and ecological connectivity between prairie potholes across North Dakota).  Regardless of the scale, the central theme is biogeochemistry and the interactions between multiple elements in wet environments.

The group works to collaborate with a variety of researchers, including soil scientists, geologists, environmental engineers, microbiologists, as well as with groups underpinning management of natural resources, such the Minnesota Department of Natural Resources, the Department of Natural Resources of Red Lake Indian Reservation, and the North Dakota Department of Health, Division of Water Quality.

Currently, WERG has several projects, mostly in North Dakota and Minnesota.  Otte and Jacob are also Co-directors of the North Dakota INBRE Metal Analysis Core, providing laboratory facilities and mentoring for researchers in undergraduate colleges throughout the state. Otte and Jacob are also members of the Upper Midwest Aerospace Consortium.

Green chemistry and zinc oxide nanoparticles from Iran (plus some unhappy scoop about Elsevier and access)

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It’s been a while since I’ve featured any research from Iran partly due to the fact that I find the information disappointingly scant. While the Dec. 22, 2013 news item on Nanowerk doesn’t provide quite as much detail as I’d like it does shine a light on an aspect of Iranian nanotechnology research that I haven’t previously encountered, green chemistry (Note: A link has been removed),

Researchers used a simple and eco-friendly method to produce homogenous zinc oxide (ZnO) nanoparticles with various applications in medical industries due to their photocatalytic and antibacterial properties (“Sol–gel synthesis, characterization, and neurotoxicity effect of zinc oxide nanoparticles using gum tragacanth”).

Zinc oxide nanoparticles have numerous applications, among which mention can be made of photocatalytic issues, piezoelectric devices, synthesis of pigments, chemical sensors, drug carriers in targeted drug delivery, and the production of cosmetics such as sunscreen lotions.

The Dec. 22, 2013 Iran Nanotechnology Initiative Council (INIC) news release, which originated the news item, provides a bit more detail (Note: Links have been removed),

By using natural materials found in the geography of Iran and through sol-gel technique, the researchers synthesized zinc oxide nanoparticles in various sizes. To this end, they used zinc nitrate hexahydrate and gum tragacanth obtained from the Northern parts of Khorassan Razavi Province as the zinc-providing source and the agent to control the size of particles in aqueous solution, respectively.

Among the most important characteristics of the synthesis method, mention can be made of its simplicity, the use of cost-effective materials, conservation of green chemistry principals to prevent the use of hazardous materials to human safety and environment, production of nanoparticles in homogeneous size and with high efficiency, and most important of all, the use of native materials that are only found in Iran and its introduction to the world.

Here’s a link to and a citation for the paper,

Sol–gel synthesis, characterization, and neurotoxicity effect of zinc oxide nanoparticles using gum tragacanth by Majid Darroudi, Zahra Sabouri, Reza Kazemi Oskuee, Ali Khorsand Zak, Hadi Kargar, and Mohamad Hasnul Naim Abd Hamidf. Ceramics International, Volume 39, Issue 8, December 2013, Pages 9195–9199

There’s a bit more technical information in the paper’s abstract,

The use of plant extract in the synthesis of nanomaterials can be a cost effective and eco-friendly approach. In this work we report the “green” and biosynthesis of zinc oxide nanoparticles (ZnO-NPs) using gum tragacanth. Spherical ZnO-NPs were synthesized at different calcination temperatures. Transmission electron microscopy (TEM) imaging showed the formation most of nanoparticles in the size range of below 50 nm. The powder X-ray diffraction (PXRD) analysis revealed wurtzite hexagonal ZnO with preferential orientation in (101) reflection plane. In vitro cytotoxicity studies on neuro2A cells showed a dose dependent toxicity with non-toxic effect of concentration below 2 µg/mL. The synthesized ZnO-NPs using gum tragacanth were found to be comparable to those obtained from conventional reduction methods using hazardous polymers or surfactants and this method can be an excellent alternative for the synthesis of ZnO-NPs using biomaterials.

I was not able to find the DOI (digital object identifier) and this paper is behind a paywall.

Elsevier and access

On a final note, Elsevier, the company that publishes Ceramics International and many other journals, is arousing some ire with what appears to be its latest policies concerning access according to a Dec. 20, 2013 posting by Mike Masnick for Techdirt Note: Links have been removed),

We just recently wrote about the terrible anti-science/anti-knowledge/anti-learning decision by publishing giant Elsevier to demand that Academia.edu take down copies of journal articles that were submitted directly by the authors, as Elsevier wished to lock all that knowledge (much of it taxpayer funded) in its ridiculously expensive journals. Mike Taylor now alerts us that Elsevier is actually going even further in its war on access to knowledge. Some might argue that Elsevier was okay in going after a “central repository” like Academia.edu, but at least it wasn’t going directly after academics who were posting pdfs of their own research on their own websites. While some more enlightened publishers explicitly allow this, many (including Elsevier) technically do not allow it, but have always looked the other way when authors post their own papers.

That’s now changed. As Taylor highlights, the University of Calgary sent a letter to its staff saying that a company “representing” Elsevier, was demanding that they take down all such articles on the University’s network.

While I do feature the topic of open access and other issues with intellectual property from time to time, you’ll find Masnick’s insights and those of his colleagues are those of people who are more intimately familiar (albeit firmly committed to open access) with the issues should you choose to read his Dec. 20, 2013 posting in its entirely.

Toxicity, nanoparticles, soil, and Europe’s NANO-ECOTOXICITY Project

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I have featured pieces on nanoparticles, toxicity, and soil in the past (this Aug. 15, 2011 posting about Duke University’s mesocosm project is probably the most relevant) but this study is the first one I’ve seen focusing on earthworms. From the Sept. 23, 2013 news item on Nanowerk (Note: A link has been removed),

From the clothes and make-up we wear to the electronic devices we use every day, nanotechnology is becoming ubiquitous. But while industry has mastered the production of such materials, little is known about their fate once their service life comes to an end. The NANO-ECOTOXICITY project looked into their impact on soil organisms.

The Sept. 23, 2013 CORDIS (European Commission Community Research and Development Information Service) news release, which originated the new item, offers a Q&A (Question and Answer) with the project research leader,

Dr Maria Diez-Ortiz, research leader of the NANO-ECOTOXICITY project, tells us about her research findings and how she expects them to help increase knowledge and shape tools allowing for standard environmental hazard and risk-assessment methodologies.

What is the background of the NANO-ECOTOXICITY project?

Nanotechnology is based on the idea that, by engineering the size and shape of materials at the scale of atoms, i.e. nanometres (nm), distinct optical, electronic, or magnetic properties can be tuned to produce novel properties of commercial value. However, there is an obvious concern that such novel properties may also lead to novel behaviour when interacting with biological organisms, and thus to potentially novel toxic effects.

Since nanoparticles (NPs) are similar in size to viruses, their uptake by and transport through tissues are based on mechanisms distinct from those of molecular uptake and transport. Therefore, there is concern that standard toxicological tests may not be applicable or reliable in relation to NPs, hence compromising current risk-assessment procedures.

The majority of research on nano-safety in the environment has so far focused on the aquatic environment. Current research on environmental fate, however, indicates that soils will become the biggest environmental sink for nanoparticles. Following their entry into liquid waste streams, nanoparticles will pass through wastewater-treatment. processes, ending up in waste sludge which may accumulate in the agricultural land where this sludge is often applied.

What are the main objectives of the project?

This project deals with the toxicokinetics – that is, the rate at which a chemical enters a body and affects it – of metal nanoparticles coming into contact with soil-dwelling organisms. The aim is to determine NPs’ fate and effects in terrestrial ecosystems by means of case studies with zinc oxide and silver NPs, which represent different fate kinetics.

The project’s main objectives are to assess the toxicity of metal nanoparticles in soils in the short and long term; the main route of exposure for earthworms and whether it differs from those of ionic metals; and, finally, the influence of the exposure media on metal nanoparticle toxicity.

What is new or innovative about the project and the way it is addressing these issues?

We have been running a long-term study where soils with AgNP [silver nanoparticles] were stored and left to age for up to a year; their toxicity was tested at the start and after three, seven and 12 months of ageing. The results showed that silver toxicity increased over time, meaning that short-term standard toxicity tests may underestimate the environmental risk of silver nanoparticles.

In parallel, we found that organisms exposed to silver nanoparticles in short-term studies accumulated higher silver concentrations than organisms that were exposed to the same mass concentration of ionic silver. However, these NP exposed organisms actually suffered lower toxic effects. This observation contradicts the prevailing assumption in toxicology that the internalised concentration is directly related to chemical concentration at the target site and hence to its toxicity. This observation creates a new paradigm for nano-ecotoxicology.

What is not yet known is whether the accumulated NP metal may in the longer-term ultimately become toxic (e.g. through dissolution and ion release) in cells and tissues where AgNPs may be stored. Should this occur, the high concentrations accumulated may ultimately result in greater long-term toxicity for NPs than for ionic forms. This may reveal these accumulated NPs as internalised ‘time bombs’ relevant to long-term effects and toxicity.

However, it has to be borne in mind that the redicted environmental concentrations resulting from current use of nanoparticles (e.g. results from EU projects like NANOFATE2) are many times smaller than those used in these studies, meaning that such accumulations of nanoparticle-related silver are unlikely to occur in the environment or, ultimately, in humans.

What difficulties did you encounter and how did you solve them?

The main problems encountered relate to the tracking of nanoparticles inside the tissues and soils, as both are complex matrices. The analysis of the particles is a challenge in itself, even when in water, but to get information about their state in these matrices often requires unrealistic exposure concentrations (due to low detection limits of the highly specialised techniques used for analysis) or extraction of the particles from the matrices, which could potentially change the state of the particles.

In this project, I travelled to University of Kentucky to work with Jason Unrine and used gentle water-based extractions of soil samples immediately before analysing them using ‘Field-flow fractionation’ and ‘Inductively coupled plasma mass spectrometry’ to identify the state of nanoparticles in my aged soils.

To look at what form (speciation) of silver and zinc from the nanoparticle exposures could be found inside worms I collaborated with NANOFATE researchers at Cardiff University who fixed and thinly sectioned the worm tissues. I was lucky to be given the time to use specialist facilities like the UK’s Diamond Light Source synchrotron to investigate where and in what form the metals and potential nanoparticles could be found in these tissues.

The main challenge is that as soon as you take nanoparticles out of the manufacturers’ bottle they start changing, particularly when put into environments likes natural soils and waters, or even organisms. Therefore a lot of characterisation is needed during exposure to establish the state of the nanoparticles the organisms have been exposed to and how fast they are changing from pristine particles to dissolved ions, or particles with completely different surfaces.

Technical solutions to characterisation have been found during this short project, but this will remain a logistical challenge for many years to come as the analysis equipment is still very specialised and expensive and therefore not generally available.

What are the concrete results from the research so far?

The project has helped us draw various conclusions regarding the impact of NPs on the environment and how to assess them. First, we now know that soil acidity, or pH, influences the dissolution and toxicity of ZnO nanoparticles [zinc oxide].

Then, we found that toxicity of silver nanoparticles’ increases over time and that the particles’ coating affects their toxicity to soil invertebrates.

As previously mentioned, earthworms exposed to silver nanoparticles for 28 days accumulated higher silver concentrations than earthworms exposed to silver ions, without the excess silver from the nanoparticles having a toxic effect. [emphasis mine] Moreover, soil ingestion was identified as the main route of exposure to AgNP and ZnONP in earthworms.

How can industry and decision-makers ensure that nanomaterials do not impact our environment?

We hope that this project, and the larger EU project NANOFATE to which it is linked, will provide knowledge and tools enabling standard environmental-hazard and risk-assessment methodologies to be applied to engineered nanoparticles (ENPs) with just a few judicious modifications. The current systems and protocols for chemical risk assessment have been developed over decades, and where no novel toxic mechanisms exist, our results tend to say that nano fits in as long as we measure the right things and characterise realistic exposures properly.

Our research aims to determine the minimum methodological tweaks needed. So far everything indicates that the potential benefits from nanotechnology can be realised and managed safely alongside other chemicals. While we are fairly confident at this stage that ENPs impose no greater acute effects on important biological parameters – like reproduction – than their ionic forms, the NANO-ECOTOXICITY results demonstrate that we have some way to go before we can state loud and clear that we do not believe there is any novel low-level or long-term effect.

As for all chemicals, proving such a negative is impossible using short-term tests. We think the final conclusions by industry and regulators on safe use of nanoparticles should and will have to be made according to a ‘weight of evidence’ approach – proving there is a gap between predicted likely exposure levels and those levels seen to cause any effects or accumulations within ecosystem species.

What are the next topics for your research?

This project has finished but the next step for any other funding opportunity would be to address increasingly environmentally relevant exposure scenarios by analysing how nanoparticles modify in the environment and interact with living tissues and organisms at different trophic levels. I would like to investigate nanoparticle transformation and interactions in living tissues. To date, the studies that have identified this ‘excess’ accumulation of non-toxic metal loads in nanoparticleexposed organisms have only been short term.

Apart from the obviously increased food-chain transfer potential, is also not known whether, over the longer term, the accumulated NP-derived metal ultimately becomes toxic when present in tissues and cells. Such transformation and release of metal ions within tissues may ultimately result in greater longterm toxicity for NPs than for ionic forms.

Furthermore, I want to test exposures in a functioning model ecosystem including interspecific interactions and trophic transfer. Since interactions between biota and nanoparticles are relevant in natural soil systems, caution is needed when attempting to predict the ecological consequences of nanoparticles based on laboratory assays conducted with only a single species. In the presence of the full complement of biological components of soil systems, complex NPs may follow a range of pathways in which coatings may be removed and replaced with exudate materials. Studies to quantify the nature of these interactions are therefore needed to identify the fate, bioavailability and toxicity of realistic ‘non-pristine’ forms of NPs present in real soil environments.

New to me was the material about ageing silver nanoparticles and their increased toxicity over time. While this is an interesting piece of information it’s not necessarily all that useful. It seems even with their increased uptake compared to silver ions, silver nanoparticles (Diez-Ortiz doesn’t indicate whether or not * they tested variously aged silver nanoparticles) did not have toxic effects on the earthworms tested.

The NANO-ECOTOXICITY website doesn’t appear to exist anymore but you can find the NANOFATE (Nanoparticle Fate Assessment and Toxicity in the Environment) website here.

* ‘not’ removed to clarify meaning, Oct. 9, 2013. (Note: I had on Oct. 8, 2013 removed ‘not’ in a second place from the sentence in an attempt t o clarify the meaning and ended up not making any sense at all.) Please read Maria Diez-Ortiz in the Comments, as she clarifies matters in a way I could never hope to.

Soybeans and nanoparticles

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They seem ubiquitous today but there was a time when hardly anyone living in Canada  knew much about soybeans.  There’s a good essay about soybeans and their cultivation in Canada by Erik Dorff for Statistics Canada, from Dorff’s soybean essay,

Until the mid-1970s, soybeans were restricted by climate primarily to southern Ontario. Intensive breeding programs have since opened up more widespread growing possibilities across Canada for this incredibly versatile crop: The 1.2 million hectares of soybeans reported on the Census of Agriculture in 2006 marked a near eightfold increase in area since 1976, the year the ground-breaking varieties that perform well in Canada’s shorter growing season were introduced.

Soybeans have earned their popularity, with the high-protein, high-oil beans finding use as food for human consumption, animal rations and edible oils as well as many industrial products. Moreover, soybeans, like all legumes, are able to “fix” the nitrogen the plants need from the air. This process of nitrogen fixation is a result of a symbiotic interaction between bacteria microbes that colonize the roots of the soy plant and are fed by the plant. In return, the microbes take nitrogen from the air and convert it into a form the plant can use to grow.

This means legumes require little in the way of purchased nitrogen fertilizers produced from expensive natural gas-a valuable property indeed.

Until reading Dorff’s essay, I hadn’t early soybeans had been introduced to the Canadian agricultural sector,

While soybeans arrived in Canada in the mid 1800s-with growing trials recorded in 1893 at the Ontario Agricultural College-they didn’t become a commercial oilseed crop in Canada until a crushing plant was built in southern Ontario in the 1920s, about the same time that the Department of Agriculture (now Agriculture and Agri-Food Canada) began evaluating soybean varieties suited for the region. For years, soybeans were being grown in Canada but it wasn’t until the Second World War that Statistics Canada began to collect data showing the significance of the soybean crop, with 4,400 hectares being reported in 1941. In fact, one year later the area had jumped nearly fourfold, to 17,000 hectares…

As fascinating as I find this history, this bit about soybeans and their international importance explain why research about soyboans and nanoparticles is of wide interest (from Dorff’s essay),

The soybean’s valuable characteristics have propelled it into the agricultural mix in many parts of the world. In 2004, soybeans accounted for approximately 35% of the total harvested area worldwide of annual and perennial oil crops according to the Food and Agriculture Organization of the United Nations (FAO) but only four countries accounted for nearly 90% of the production with Canada in seventh place at 1.3% (Table 2). Soymeal-the solid, high-protein material remaining after the oil has been extracted during crushing-accounts for over 60% of world vegetable and animal meal production, while soybean oil accounts for 20% of global vegetable oil production.

There’s been a recent study on the impact of nanoparticles on soybeans at the University of California at Santa Barbara (UC Santa Barbara) according to an Aug. 20, 2012 posting by Alan on the Science Business website, (h/t to Cientifica),

Researchers from University of California in Santa Barbara found manufactured nanoparticles disposed after manufacturing or customer use can end up in agricultural soil and eventually affect soybean crops. Findings of the team that includes academic, government, and corporate researchers from elsewhere in California, Texas, Iowa, New York, and Korea appear online today in the Proceedings of the National Academy of Sciences.

The research aimed to discover potential environmental implications of new industries that produce nanomaterials. Soybeans were chosen as test crops because their prominence in American agriculture — it is the second largest crop in the U.S. and the fifth largest crop worldwide — and its vulnerability to manufactured nanomaterials. The soybeans tested in this study were grown in greenhouses.

The Aug. 20, 2012 UC Santa Barbara press release has additional detail abut why the research was undertaken,

“Our society has become more environmentally aware in the last few decades, and that results in our government and scientists asking questions about the safety of new types of chemical ingredients,” said senior author Patricia Holden, a professor with the Bren School [UC Santa Barbara’s Bren School of Environmental Science & Management]. “That’s reflected by this type of research.”

Soybean was chosen for the study due to its importance as a food crop –– it is the fifth largest crop in global agricultural production and second in the U.S. –– and because it is vulnerable to MNMs [manufactured nanomaterials]. The findings showed that crop yield and quality are affected by the addition of MNMs to the soil.

The scientists studied the effects of two common nanoparticles, zinc oxide and cerium oxide, on soybeans grown in soil in greenhouses. Zinc oxide is used in cosmetics, lotions, and sunscreens. Cerium oxide is used as an ingredient in catalytic converters to minimize carbon monoxide production, and in fuel to increase fuel combustion. Cerium can enter soil through the atmosphere when fuel additives are released with diesel fuel combustion.

The zinc oxide nanoparticles may dissolve, or they may remain as a particle, or re-form as a particle, as they are processed through wastewater treatment. At the final stage of wastewater treatment there is a solid material, called biosolids, which is applied to soils in many parts of the U.S. This solid material fertilizes the soil, returning nitrogen and phosphorus that are captured during wastewater treatment. This is also a point at which zinc oxide and cerium oxide can enter the soil.

The scientists noted that the EPA requires pretreatment programs to limit direct industrial metal discharge into publicly owned wastewater treatment plants. However, the research team conveyed that “MNMs –– while measurable in the wastewater treatment plant systems –– are neither monitored nor regulated, have a high affinity for activated sludge bacteria, and thus concentrate in biosolids.”

The authors pointed out that soybean crops are farmed with equipment powered by fossil fuels, and thus MNMs can also be deposited into the soil through exhaust.

The study showed that soybean plants grown in soil that contained zinc oxide bioaccumulated zinc; they absorbed it into the stems, leaves, and beans. Food quality was affected, although it may not be harmful to humans to eat the soybeans if the zinc is in the form of ions or salts, in the plants, according to Holden.

In the case of cerium oxide, the nanoparticles did not bioaccumulate, but plant growth was stunted. Changes occurred in the root nodules, where symbiotic bacteria normally accumulate and convert atmospheric nitrogen into ammonium, which fertilizes the plant. The changes in the root nodules indicate that greater use of synthetic fertilizers might be necessary with the buildup of MNMs in the soil.

At this point, the researchers don’t know how zinc oxide nanoparticles and cerium oxide nanoparticles currently used in consumer products and elsewhere are likely to affect agricultural lands. The only certainty is that these nanoparticles are used in consumer goods and, according to Holden, they are entering agricultural soil.

The citation for the article,

Soybean susceptibility to manufactured nanomaterials with evidence for food quality and soil fertility interruption by John H. Priester, Yuan Ge, Randall E. Mielke, Allison M. Horst Shelly Cole Moritz, Katherine Espinosa, Jeff Gelb, Sharon L. Walker, Roger M. Nisbet, Youn-Joo An, Joshua P. Schimel, Reid G. Palmer, Jose A. Hernandez-Viezcas, Lijuan Zhao, Jorge L. Gardea-Torresdey, Patricia A. Holden. Published online [Proceedings of the National Academy of Sciences {PNAS}] before print August 20, 2012, doi: 10.1073/pnas.1205431109

The article is open access and available here.

 

Caution and nanoscale zinc oxide in sunscreens

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While I’ve had my reservations about the anti-nanoscreen campaigning, it is important to remember that safety research into the use of nanoparticles in sunscreens is ongoing. A new piece of research on nanoscale zinc oxide and sunscreens has been performed at the Missouri University of Science and Technology and this is something I would put under the category of interesting, possibly disturbing, and not at all definitive.

From the May 8, 2012 news item on Nanowerk,

… researchers at Missouri University of Science and Technology are discovering that sunscreen may not be so safe after all. Cell toxicity studies by Dr. Yinfa Ma, Curators’ Teaching Professor of chemistry at Missouri S&T, and his graduate student Qingbo Yang, suggest that when exposed to sunlight, zinc oxide, a common ingredient in sunscreens, undergoes a chemical reaction that may release unstable molecules known as free radicals. Free radicals seek to bond with other molecules, but in the process, they can damage cells or the DNA contained within those cells. This in turn could increase the risk of skin cancer.

…

“Zinc oxide may generate free radicals when exposed to UV (ultraviolet) sunlight,” May [sic] says, “and those free radicals can kill cells.”

Ma studied how human lung cells immersed in a solution containing nano-particles of zinc oxide react when exposed to different types of light over numerous time frames. Using a control group of cells that were not immersed in the zinc oxide solution, Ma compared the results of light exposure on the various groups of cells. He found that zinc oxide-exposed cells deteriorated more rapidly than those not immersed in the chemical compound. Even when exposed to visible light only, the lung cells suspended in zinc oxide deteriorated. But for cells exposed to ultraviolet rays, Ma found that “cell viability decreases dramatically.”

I categorized this research as mildly disturbing for a couple of reasons. (a) It’s never good to hear about lung cells deteriorating. (b) I never slather sunscreen on my lungs. (c) Why didn’t the researcher test skin cells? (d) The cells were immersed in a solution; what concentration of zinc oxide nanoparticles were present in the solution and is that the same concentration found in my sunscreen?

As the researcher notes this work is just part of a longer scientific inquiry (from the May 8, 2012 news item),

Ma’s research on zinc oxide’s effect on cells is still in the early stages, so he cautions people from drawing conclusions about the safety or dangers of sunscreen based on this preliminary research.

“More extensive study is still needed,” May says. “This is just the first step.”

For instance, Ma plans to conduct electron spin resonance tests to see whether zinc oxide truly does generate free radicals, as he suspects. In addition, clinical trials will be needed before any conclusive evidence may be drawn from his studies.

In the meantime, Ma advises sunbathers to use sunscreen and to limit their exposure to the sun.

“I still would advise people to wear sunscreen,” he says. “Sunscreen is better than no protection at all.”

I suspect that last comment is an indirect reference to a recent study (mentioned in my Feb. 9, 2012 posting) that found 13% of Australians said they weren’t using any sunscreens due to their fears about nanoparticles in those products.

At this point, nanosunscreens get a very cautious pass given the information at hand.

For anyone who’s interested in how stories about science and risk, specifically concerning nanosunscreens, can get reported, I’d advise a glance at the 2020 Science blog. (Andrew Maynard, Director of the Risk Science Center at the University of Michigan, has been writing on his 2020 blog for years and covered nanosunscreens on more than one occasion.) In his May 3, 2012 posting he recounts his experience trying to refine comments about nanosunscreens and safety as a reporter is getting his story, with quotes from Andrew, to press.

ETA Aug. 17, 2012: I’d forgotten but was recently reminded that lung cells and skin cells are the same base cell until they differentiate themselves at a later stage of development. (I’m sure scientists are silently screaming but that’s my best description of the process.) So, I better appreciate why the researchers used lung cells for their study but my comment remains, I don’t slather sunscreen on my lungs. While the results of the study are interesting, they don’t seem applicable to a real world experience.