Tag Archives: Philip Demokritou

Cellulose nanocrystals (CNC), protein, and starch eletrospun to develop ‘smart’ food packaging

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A December 29, 2021 news item on ScienceDaily announces research into ;smart’ sustainable packaging from a joint Nanyang Technical University and Harvard University,

A team of scientists from Nanyang Technological University, Singapore (NTU Singapore) and Harvard T.H. Chan School of Public Health, US, has developed a ‘smart’ food packaging material that is biodegradable, sustainable and kills microbes that are harmful to humans. It could also extend the shelf-life of fresh fruit by two to three days.

The waterproof food packaging is made from a type of corn protein called zein, starch and other naturally derived biopolymers, infused with a cocktail of natural antimicrobial compounds. These include oil from thyme, a common herb used in cooking, and citric acid, which is commonly found in citrus fruits.

…

A December 28, 2021 Nanyang Technological University press release (PDF), also on EurekAlert but published December 27, 2021, which originated the news item, offers a few more details about the research (Note 1: Links have been removed; Note 2: I had to dig into the abstract to find the cellulose nanocrystals),

In lab experiments, when exposed to an increase in humidity or enzymes from harmful bacteria, the fibres in the packaging have been shown to release the natural antimicrobial compounds, killing common dangerous bacteria that contaminate food, such as E. Coli and Listeria, as well as fungi.

The packaging is designed to release the necessary miniscule amounts of antimicrobial compounds only in response to the presence of additional humidity or bacteria. This ensures that the packaging can endure several exposures, and last for months.

As the compounds combat any bacteria that grow on the surface of the packaging as well as on the food product itself, it has the potential to be used for a large variety of products, including ready-to-eat foods, raw meat, fruits, and vegetables.

In an experiment, strawberries that were wrapped in the packaging stayed fresh for seven days before developing mould, compared to counterparts that were kept in mainstream fruit plastic boxes, which only stayed fresh for four days.

The invention is the result of the collaboration by scientists from the NTU-Harvard T. H. Chan School of Public Health Initiative for Sustainable Nanotechnology (NTU-Harvard SusNano), which brings together NTU and Harvard Chan School researchers to work on cutting edge applications in agriculture and food, with an emphasis on developing non-toxic and environmentally safe nanomaterials.

The development of this advanced food packaging material is part of the University’s efforts to promote sustainable food tech solutions, that is aligned with the NTU 2025 strategic plan, which aims to develop sustainable solutions to address some of humanity’s pressing grand challenges.

Professor Mary Chan, Director of NTU’s Centre of Antimicrobial Bioengineering, who co-led the project, said: “This invention would serve as a better option for packaging in the food industry, as it has demonstrated superior antimicrobial qualities in combatting a myriad of food-related bacteria and fungi that could be harmful to humans. The packaging can be applied to various produces such as fish, meat, vegetables, and fruits. The smart release of antimicrobials only when bacteria or high humidity is present, provides protection only when needed thus minimising the use of chemicals and preserving the natural composition of foods packaged.”

Professor Philip Demokritou, Adjunct Professor of Environmental Health at Harvard Chan School, who is also Director of Nanotechnology and Nanotoxicology Center and Co-director of NTU-Harvard Initiative on Sustainable Nanotechnology, who co-led the study, said: “Food safety and waste have become a major societal challenge of our times with immense public health and economic impact which compromises food security. One of the most efficient ways to enhance food safety and reduce spoilage and waste is to develop efficient biodegradable non-toxic food packaging materials. In this study, we used nature-derived compounds including biopolymers, non-toxic solvents, and nature-inspired antimicrobials and develop scalable systems to synthesise smart antimicrobial materials which can be used not only to enhance food safety and quality but also to eliminate the harm to the environment and health and reduce the use of non-biodegradable plastics at global level and promote sustainable agri-food systems.” 

Providing an independent assessment of the work done by the NTU research team, Mr Peter Barber, CEO of ComCrop, a Singapore company that pioneered urban rooftop farming, said: “The NTU-Harvard Chan School food packaging material would serve as a sustainable solution for companies like us who want to cut down on the usage of plastic and embrace greener alternatives. As ComCrop looks to ramp up product to boost Singapore’s food production capabilities, the volume of packaging we need will increase in sync, and switching to a material such as this would help us have double the impact. The wrapping’s antimicrobial properties, which could potentially extend the shelf life of our vegetables, would serve us well. The packaging material holds promise to the industry, and we look forward to learning more about the wrapping and possibly adopting it for our usage someday.”

The results of the study were published in the peer-reviewed academic journal ACS Applied Materials & Interfacesin October [2021].

Cutting down on packaging waste

The packaging industry is the largest and growing consumer of synthetic plastics derived from fossil fuels, with food packaging plastics accounting for the bulk of plastic waste that are polluting the environment.

In Singapore, packaging is a major source of trash, with data from Singapore’s National Environment Agency showing that out of the 1.76 million tonnes of waste disposed of by domestic sources in 2018, one third of it was packaging waste, and over half of it (55 per cent) was plastic.

The smart food package material, when scaled up, could serve as an alternative to cut down on the amount of plastic waste, as it is biodegradable. Its main ingredient, zein, is also produced from corn gluten meal, which is a waste by-product from using corn starch or oils in order to produce ethanol.

The food packaging material is produced by electrospinning[1] the zein, the antimicrobial compounds with cellulose, a natural polymer starch that makes up plant cell walls, and acetic acid, which is commonly found in vinegar.

Prof Mary Chan added: “The sustainable and biodegradable active food packaging, which has inbuilt technology to keep bacteria and fungus at bay, is of great importance to the food industry. It could serve as an environmentally friendly alternative to petroleum-based polymers used in commercial food packaging, such as plastic, which have a significant negative environmental impact.”

Prof Demokritou added: “Due to the globalisation of food supply and attitude shift towards a healthier lifestyle and environmentally friendly food packaging, there is a need to develop biodegradable, non-toxic and smart/responsive materials to enhance food safety and quality. Development of scalable synthesis platforms for developing food packaging materials that are composed of nature derived, biodegradable biopolymers and nature inspired antimicrobials, coupled with stimuli triggered approaches will meet the emerging societal needs to reduce food waste and enhance food safety and quality.”

The team of NTU and Harvard Chan School researchers hope to scale up their technology with an industrial partner, with the aim of commercialisation within the next few years.

They are also currently working on developing other technologies to develop biopolymer-based smart food package materials to enhance food safety and quality.

Here’s a link to and a citation for the paper, followed by the key (nanocellulose crystal mention) sentences in the abstract,

Enzyme- and Relative Humidity-Responsive Antimicrobial Fibers for Active Food Packaging by Zeynep Aytac, Jie Xu, Suresh Kumar Raman Pillai, Brian D. Eitzer, Tao Xu, Nachiket Vaze, Kee Woei Ng, Jason C. White, Mary B. Chan-Park, Yaguang Luo, and Philip Demokritou. ACS Appl. Mater. Interfaces 2021, 13, 42, 50298–50308 I: https://doi.org/10.1021/acsami.1c12319 Publication Date: October 14, 2021 Copyright © 2021 American Chemical Society

This paper is behind a paywall.

Excerpt from abstract,

Active food packaging materials that are sustainable, biodegradable, and capable of precise delivery of antimicrobial active ingredients (AIs) are in high demand. Here, we report the development of novel enzyme- and relative humidity (RH)-responsive antimicrobial fibers with an average diameter of 225 ± 50 nm, which can be deposited as a functional layer for packaging materials. Cellulose nanocrystals (CNCs) [emphasis mine], zein (protein), and starch were electrospun to form multistimuli-responsive fibers that incorporated a cocktail of both free nature-derived antimicrobials such as thyme oil, citric acid, and nisin and cyclodextrin-inclusion complexes (CD-ICs) of thyme oil, sorbic acid, and nisin. …

I have been following the CNC story for some time. If you’re curious, just use ‘cellulose nanocrystal(s)’ as your search term. You can find out more about ComCrop here.

Harvard University announced new Center on Nano-safety Research

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The nano safety center at Harvard University (Massachusetts, US) is a joint center with the US National Institute of Environmental Health  Sciences according to an Aug. 29, 2016 news item on Nanowerk,

Engineered nanomaterials (ENMs)—which are less than 100 nanometers (one millionth of a millimeter) in diameter—can make the colors in digital printer inks pop and help sunscreens better protect against radiation, among many other applications in industry and science. They may even help prevent infectious diseases. But as the technology becomes more widespread, questions remain about the potential risks that ENMs may pose to health and the environment.

Researchers at the new Harvard-NIEHS [US National Institute of Environmental Health Sciences] Nanosafety Research Center at Harvard T.H. Chan School of Public Health are working to understand the unique properties of ENMs—both beneficial and harmful—and to ultimately establish safety standards for the field.

An Aug. 16, 2016 Harvard University press release, which originated the news item, provides more detail (Note: Links have been removed),

“We want to help nanotechnology develop as a scientific and economic force while maintaining safeguards for public health,” said Center Director Philip Demokritou, associate professor of aerosol physics at Harvard Chan School. “If you understand the rules of nanobiology, you can design safer nanomaterials.”

ENMs can enter the body through inhalation, ingestion, and skin contact, and toxicological studies have shown that some can penetrate cells and tissues and potentially cause biochemical damage. Because the field of nanoparticle science is relatively new, no standards currently exist for assessing the health risks of exposure to ENMs—or even for how studies of nano-biological interactions should be conducted.

Much of the work of the new Center will focus on building a fundamental understanding of why some ENMs are potentially more harmful than others. The team will also establish a “reference library” of ENMs, each with slightly varied properties, which will be utilized in nanotoxicology research across the country to assess safety. This will allow researchers to pinpoint exactly what aspect of an ENM’s properties may impact health. The researchers will also work to develop standardized methods for nanotoxicology studies evaluating the safety of nanomaterials.

The Center was established with a $4 million dollar grant from the National Institute of Environmental Health Science (NIEHS) last month, and is the only nanosafety research center to receive NIEHS funding for the next five years. It will also play a coordinating role with existing and future NIEHS nanotoxicology research projects nantionwide. Scientists from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), MIT, University of Maine, and University of Florida will collaborate on the new effort.

The Center builds on the existing Center for Nanotechnology and Nanotoxicology at Harvard Chan School, established by Demokritou and Joseph Brain, Cecil K. and Philip Drinker Professor of Environmental Physiology, in the School’s Department of Environmental Health in 2010.

A July 5, 2016 Harvard University press release announcing the $4M grant provides more information about which ENMs are to be studied,

The main focus of the new HSPH-NIEHS Center is to bring together  scientists from across disciplines- material science, chemistry, exposure assessment, risk assessment, nanotoxicology and nanobiology- to assess the potential  environmental Health and safety (EHS) implications of engineered nanomaterials (ENMs).

The $4 million dollar HSPH based Center  which is the only Nanosafety Research  Center to be funded by NIEHS this funding cycle, … The new HSPH-NIEHS Nanosafety Center builds upon the nano-related infrastructure in [the] collaborating Universities, developed over the past 10 years, which includes an inter-disciplinary research group of faculty, research staff and students, as well as state-of-the-art platforms for high throughput synthesis of ENMs, including metal and metal oxides, cutting edge 2D/3D ENMs such as CNTs [carbon nanotubes] and graphene, nanocellulose, and advanced nanocomposites, [emphasis mine] coupled with innovative tools to assess the fate and transport of ENMs in biological systems, statistical and exposure assessment tools, and novel in vitro and in vivo platforms for nanotoxicology research.

“Our mission is to integrate material/exposure/chemical sciences and nanotoxicology-nanobiology   to facilitate assessment of potential risks from emerging nanomaterials.  In doing so, we are bringing together the material synthesis/applications and nanotoxicology communities and other stakeholders including industry,   policy makers and the general public to maximize innovation and growth and minimize environmental and public health risks from nanotechnology”, quoted by  Dr Philip Demokritou, …

This effort certainly falls in line with the current emphasis on interdisciplinary research and creating standards and protocols for researching the toxicology of engineered nanomaterials.

Harvard University’s Engineered Water Nanostructures (EWNS)

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I last wrote about this research in a March 19, 2015 posting, which focused on work proving that a water-engineered nanostructure platform had microbial properties useful for decontaminating food and allowing manufacturers to avoid using chemicals for the task. This latest research focuses on finetuning the platform’s ability. Here’s more from the latest research paper’s abstract,

A chemical free, nanotechnology-based, antimicrobial platform using Engineered Water Nanostructures (EWNS) was recently developed. EWNS have high surface charge, are loaded with reactive oxygen species (ROS), and can interact-with, and inactivate an array of microorganisms, including foodborne pathogens. Here, it was demonstrated that their properties during synthesis can be fine tuned and optimized to further enhance their antimicrobial potential. A lab based EWNS platform was developed to enable fine-tuning of EWNS properties by modifying synthesis parameters. Characterization of EWNS properties (charge, size and ROS content) was performed using state-of-the art analytical methods. Further their microbial inactivation potential was evaluated with food related microorganisms such as Escherichia coli, Salmonella enterica, Listeria innocua, Mycobacterium parafortuitum, and Saccharomyces cerevisiae inoculated onto the surface of organic grape tomatoes. The results presented here indicate that EWNS properties can be fine-tuned during synthesis resulting in a multifold increase of the inactivation efficacy. More specifically, the surface charge quadrupled and the ROS content increased. Microbial removal rates were microorganism dependent and ranged between 1.0 to 3.8 logs after 45 mins of exposure to an EWNS aerosol dose of 40,000 #/cm3.

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

Optimization of a nanotechnology based antimicrobial platform for food safety applications using Engineered Water Nanostructures (EWNS) by Georgios Pyrgiotakis, Pallavi Vedantam, Caroline Cirenza, James McDevitt, Mary Eleftheriadou, Stephen S. Leonard, & Philip Demokritou. Scientific Reports 6, Article number: 21073 (2016) doi:10.1038/srep21073 Published online: 15 February 2016

This is an open access paper.

Disinfectants without chemicals for the food industry

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Michael Berger in his March 16, 2015 Nanowerk Spotlight article profiles some very interesting research into replacing chemicals with water nanostructures,

The burden of foodborne diseases worldwide is huge, with serious economic and public health consequences. The CDC [US Centers for Disease Control] estimates that each year in the USA approximately 48 million people get sick, 128,000 get hospitalized and 3,000 die from the consumption of food contaminated with pathogenic microorganisms. The food industry is in search of effective intervention methods that can be applied from ‘farm to fork’ to ensure the safety of the food chain and be consumer and environment friendly at the same time.

In the food industry, chemicals are routinely used to clean and disinfect product contact surfaces as well as the outer surface of the food itself. These chemicals provide a necessary and required step to ensure that the foods produced and consumed are as free as possible from microorganisms that can cause foodborne illness.

Food activists are concerned that some of the chemicals used by the food industry for disinfection can cause health issues for consumers. A prime example is the current discussion in Europe about ‘American chlorine chicken’. …

Berger goes on to highlight the research being conducted at the Harvard T. Chan School of Public Health (Harvard University). The team announced a new technique called Engineered Water Nanostructures (EWNS), which is generated by electrospraying water. The team published this paper in 2014,

A chemical free, nanotechnology-based method for airborne bacterial inactivation using engineered water nanostructures by Georgios Pyrgiotakis, James McDevitt, Andre Bordini, Edgar Diaz, Ramon Molina, Christa Watson, Glen Deloid, Steve Lenard, Natalie Fix, Yosuke Mizuyama, Toshiyuki Yamauchi, Joseph Brain and Philip Demokritou. Environ. Sci.: Nano, 2014,1, 15-26 DOI: 10.1039/C3EN00007A

First published online 28 Nov 2013

This paper is open access.

More recently, the team has proved the efficacy of this technique on stainless steel surfaces and tomatoes. A Feb. 25, 2015 Harvard T. Chan School of Public Health news release provides information about the costs of foodborne diseases and goes on to describe the technique and the latest experiments,

The burden of foodborne diseases worldwide is huge, with serious economic and public health consequences. The U.S. Department of Agriculture’s (USDA’s) Economic Research Service reported in 2014 that foodborne illnesses are costing the economy more than $15.6 billion and about 53,245 Americans visit the hospital annually due to foodborne illnesses. The food industry is in search of effective intervention methods that can be applied form “farm to fork” to ensure the safety of the food chain and be consumer and environment friendly at the same time.

Researchers at the Center for Nanotechnology and Nanotoxicology of the Harvard T. Chan School of Public Health are currently exploring the effectiveness of a nanotechnology based, chemical free, intervention method for the inactivation of foodborne and spoilage microorganisms on fresh produce and on food production surfaces. This method utilizes Engineered Water Nanostructures (EWNS) generated by electrospraying of water. EWNS possess unique properties; they are 25 nm in diameter, remain airborne in indoor conditions for hours, contain Reactive Oxygen Species (ROS), have very strong surface charge (on average 10e/structure) and have the ability to interact and inactivate pathogens by destroying their membrane.

In a study funded by the USDA and just published this week in the premier Environmental Science and Technology journal, the efficacy of these tiny water nanodroplets, in inactivating representative foodborne pathogens such as Escherichia coli, Salmonella enterica and Listeria innocua, on stainless steel surfaces and on tomatoes, was assessed showing significant log reductions in inactivation of select food pathogens. These promising results could open up the gateway for further exploration into the dynamics of this method in the battle against foodborne disease. More importantly this novel, chemical-free, cost effective and environmentally friendly intervention method holds great potential for development and application in the food industry, as a ‘green’ alternative to existing inactivation methods.

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

Inactivation of Foodborne Microorganisms Using Engineered Water Nanostructures (EWNS) by Georgios Pyrgiotakis, Archana Vasanthakumar, Ya Gao, Mary Eleftheriadou, Eduardo Toledo, Alice DeAraujo, James McDevitt, Taewon Han, Gediminas Mainelis, Ralph Mitchell, and Philip Demokritou. Environ. Sci. Technol., Article ASAP DOI: 10.1021/es505868a Publication Date (Web): February 19, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall. The researchers have made this image illustrating a ‘water shell’s’ effect on a bacterium located on a tomato,

Courtesy: Researchers and the American Chemical Society

Courtesy: Researchers and the American Chemical Society

I’m not sure how chemical companies are going to feel but this is very exciting news. Still, one has to wonder just how much water this technique would require for full scale adoption and would it be reusable?

DNA damage from engineered nanoparticles (zinc oxide, silver, silicon dioxide, cerium oxide and iron oxide)

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Before launching into this research, there are a few provisos. This work was done in a laboratory, a highly specialized environment that does not mimic real-life conditions, and performed on animal cells (a hamster’s). As well, naturally occurring nanoparticles were not included (my Nov. 24, 2011 post has some information about naturally occurring nanomaterials including nanosilver which we have been ingesting for centuries).

That said, the studies from the Massachusetts Institute of Techology (MIT) and the Harvard School of Public Health (HSPH; last mentioned here in an April 2, 2014 post) are concerning (from an April 9, 2014 news item on Azonano).

A new study from MIT and the Harvard School of Public Health (HSPH) suggests that certain nanoparticles can also harm DNA. This research was led by Bevin Engelward, a professor of biological engineering at MIT, and associate professor Philip Demokritou, director of HSPH’s Center for Nanotechnology and Nanotoxicology.

The researchers found that zinc oxide nanoparticles, often used in sunscreen to block ultraviolet rays, significantly damage DNA. Nanoscale silver, which has been added to toys, toothpaste, clothing, and other products for its antimicrobial properties, also produces substantial DNA damage, they found.

The findings, published in a recent issue of the journal ACS Nano, relied on a high-speed screening technology to analyze DNA damage. This approach makes it possible to study nanoparticles’ potential hazards at a much faster rate and larger scale than previously possible.

More details about current testing requirements and the specific nanoparticles studied can be found in the April 8, 2014 MIT news release, which originated the news item,

The Food and Drug Administration does not require manufacturers to test nanoscale additives for a given material if the bulk material has already been shown to be safe. However, there is evidence that the nanoparticle form of some of these materials may be unsafe: Due to their immensely small size, these materials may exhibit different physical, chemical, and biological properties, and penetrate cells more easily.

“The problem is that if a nanoparticle is made out of something that’s deemed a safe material, it’s typically considered safe. There are people out there who are concerned, but it’s a tough battle because once these things go into production, it’s very hard to undo,” Engelward says.

The researchers focused on five types of engineered nanoparticles — silver, zinc oxide, iron oxide, cerium oxide, and silicon dioxide (also known as amorphous silica) — that are used industrially. Some of these nanomaterials can produce free radicals called reactive oxygen species, which can alter DNA. Once these particles get into the body, they may accumulate in tissues, causing more damage.

“It’s essential to monitor and evaluate the toxicity or the hazards that these materials may possess. There are so many variations of these materials, in different sizes and shapes, and they’re being incorporated into so many products,” says Christa Watson, a postdoc at HSPH and the paper’s lead author. “This toxicological screening platform gives us a standardized method to assess the engineered nanomaterials that are being developed and used at present.”

The researchers hope that this screening technology could also be used to help design safer forms of nanoparticles; they are already working with partners in industry to engineer safer UV-blocking nanoparticles. Demokritou’s lab recently showed that coating zinc oxide particles with a nanothin layer of amorphous silica can reduce the particles’ ability to damage DNA.

Given that Demokritou was part of a team that recently announced a new testing platform (Volumetric Centrifugation Method [VCM]) for nanoparticles as mentioned in my April 2, 2014 post, I was a little curious about the  platform for this project ( the CometChip) and, as always, curious about the results for all the tested engineered nanoparticles (Note: A link has been removed), from the news release,

Until now, most studies of nanoparticle toxicity have focused on cell survival after exposure. Very few have examined genotoxicity, or the ability to damage DNA — a phenomenon that may not necessarily kill a cell, but one that can lead to cancerous mutations if the damage is not repaired.

A common way to study DNA damage in cells is the so-called “comet assay,” named for the comet-shaped smear that damaged DNA forms during the test. The procedure is based on gel electrophoresis, a test in which an electric field is applied to DNA placed in a matrix, forcing the DNA to move across the gel. During electrophoresis, damaged DNA travels farther than undamaged DNA, producing a comet-tail shape.

Measuring how far the DNA can travel reveals how much DNA damage has occurred. This procedure is very sensitive, but also very tedious.

In 2010, Engelward and MIT professor Sangeeta Bhatia developed a much more rapid version of the comet assay, known as the CometChip. Using microfabrication technology, single cells can be trapped in tiny microwells within the matrix. This approach makes it possible to process as many as 1,000 samples in the time that it used to take to process just 30 samples — allowing researchers to test dozens of experimental conditions at a time, which can be analyzed using imaging software.

Wolfgang Kreyling, an epidemiologist at the German Research Center for Environmental Health who was not involved in the study, says this technology should help toxicologists catch up to the rapid rate of deployment of engineered nanoparticles (ENPs).

“High-throughput screening platforms are desperately needed,” Kreyling says. “The proposed approach will be not only an important tool for nanotoxicologists developing high-throughput screening strategies for the assessment of possible adverse health effects associated with ENPs, but also of great importance for material scientists working on the development of novel ENPs and safer-by-design approaches.”

Using the CometChip, the MIT and HSPH researchers tested the nanoparticles’ effects on two types of cells that are commonly used for toxicity studies: a type of human blood cells called lymphoblastoids, and an immortalized line of Chinese hamster ovary cells.

Zinc oxide and silver produced the greatest DNA damage in both cell lines. At a concentration of 10 micrograms per milliliter — a dose not high enough to kill all of the cells — these generated a large number of single-stranded DNA breaks.

Silicon dioxide, which is commonly added during food and drug production, generated very low levels of DNA damage. Iron oxide and cerium oxide also showed low genotoxicity.

Happily the researchers are taking a pragmatic approach to the results (from the news release),

More studies are needed to determine how much exposure to metal oxide nanoparticles could be unsafe for humans, the researchers say.

“The biggest challenge we have as people concerned with exposure biology is deciding when is something dangerous and when is it not, based on the dose level. At low levels, probably these things are fine,” Engelward says. “The question is: At what level does it become problematic, and how long will it take for us to notice?”

One of the areas of greatest concern is occupational exposure to nanoparticles, the researchers say. Children and fetuses are also potentially at greater risk because their cells divide more often, making them more vulnerable to DNA damage.

The most common routes that engineered nanoparticles follow into the body are through the skin, lungs, and stomach, so the researchers are now investigating nanoparticle genotoxicity on those cell types. They are also studying the effects of other engineered nanoparticles, including metal oxides used in printer and photocopier toner, which can become airborne and enter the lungs.

Kudos to the writer for the clarity and care shown here (I think it’s Anne Trafton but MIT is not including bylines as it did previously, so I’m uncertain).

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

High-Throughput Screening Platform for Engineered Nanoparticle-Mediated Genotoxicity Using CometChip Technology by Christa Watson, Jing Ge, Joel Cohen, Georgios Pyrgiotakis, Bevin P. Engelward, and Philip Demokritou. ACS Nano, 2014, 8 (3), pp 2118–2133 DOI: 10.1021/nn404871p Publication Date (Web): March 11, 2014
Copyright © 2014 American Chemical Society

This article is behind a paywall.

New method for measuring risks and quantities of engineered nanomaterials delivered to cells

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Despite all the talk about testing engineered nanoparticles and their possible effects on cells, there are problems with the testing process which researchers at the Harvard School of Public Health (HSPH) claim to have addressed (h/t Nanowerk, March 28, 2014).

A March 28, 2014 HSPH press release explains the interest in testing the effects of engineered nanomaterials/nanoparticles on health and describes some of the problems associated with testing their interaction with cells,

Thousands of consumer products containing engineered nanoparticles — microscopic particles found in everyday items from cosmetics and clothing to building materials — enter the market every year. Concerns about possible environmental health and safety issues of these nano-enabled products continue to grow with scientists struggling to come up with fast, cheap, and easy-to-use cellular screening systems to determine possible hazards of vast libraries of engineered nanomaterials. However, determining how much exposure to engineered nanoparticles could be unsafe for humans requires precise knowledge of the amount (dose) of nanomaterials interacting with cells and tissues such as lungs and skin.

With chemicals, this is easy to do but when it comes to nanoparticles suspended in physiological media, this is not trivial. Engineered nanoparticles in biological media interact with serum proteins and form larger agglomerates which alter both their so called effective density and active surface area and ultimately define their delivery to cell dose and bio-interactions. This behavior has tremendous implications not only in measuring the exact amount of nanomaterials interacting with cells and tissue but also in defining hazard rankings of various engineered nanomaterials (ENMs). As a result, thousands of published cellular screening assays are difficult to interpret and use for risk assessment purposes.

The press release goes on to describe the new technique (Note: Links have been removed),

Scientists at the Center for Nanotechnology and Nanotoxicology at Harvard School of Public Health (HSPH) have discovered a fast, simple, and inexpensive method to measure the effective density of engineered nanoparticles in physiological fluids, thereby making it possible to accurately determine the amount of nanomaterials that come into contact with cells and tissue in culture.

The method, referred to as the Volumetric Centrifugation Method (VCM), was published in the March 28, 2014 Nature Communications.

The new discovery will have a major impact on the hazard assessment of engineered nanoparticles, enabling risk assessors to perform accurate hazard rankings of nanomaterials using cellular systems. Furthermore, by measuring the composition of nanomaterial agglomerates in physiologic fluids, it will allow scientists to design more effective nano-based drug delivery systems for nanomedicine applications.

“The biggest challenge we have in assessing possible health effects associated with nano exposures is deciding when something is hazardous and when it is not, based on the dose level. At low levels, the risks are probably miniscule,” said senior author Philip Demokritou, associate professor of aerosol physics in the Department of Environmental Health at HSPH. “The question is: At what dose level does nano-exposure become problematic? The same question applies to nano-based drugs when we test their efficiency using cellular systems. How much of the administered nano-drug will come in contact with cells and tissue? This will determine the effective dose needed for a given cellular response,” Demokritou said.

Federal regulatory agencies do not require manufacturers to test engineered nanoparticles, if the original form of the bulk material has already been shown to be safe. However, there is evidence that some of these materials could be more harmful in the nanoscale — a scale at which materials may penetrate cells and bypass biological barriers more easily and exhibit unique physical, chemical, and biological properties compared to larger size particles. Nanotoxicologists are struggling to develop fast and cheap toxicological screening cellular assays to cope with the influx of vast forms of engineered nanomaterials and avoid laborious and expensive animal testing. However, this effort has been held back due to the lack of a simple-to-use, fast, method to measure the dose-response relationships and possible toxicological implications. While biological responses are fairly easy to measure, scientists are struggling to develop a fast method to assess the exact amount or dose of nanomaterials coming in contact with cells in biological media.

“Dosimetric considerations are too complicated to consider in nano-bio assessments, but too important to ignore,” Demokritou said. “Comparisons of biological responses to nano-exposures usually rely on guesstimates based on properties measured in the dry powder form (e.g., mass, surface area, and density), without taking into account particle-particle and particle-fluid interactions in biological media. When suspended in fluids, nanoparticles typically form agglomerates that include large amounts of the suspending fluid, and that therefore have effective densities much lower than that of dry material. This greatly influences the particle delivery to cells, and reduces the surface area available for interactions with cells,” said Glen DeLoid, research associate in the Department of Environmental Health, one of the two lead authors of the study. “The VCM method will help nanobiologists and regulators to resolve conflicting in vitro cellular toxicity data that have been reported in the literature for various nanomaterials. These disparities likely result from lack of or inaccurate dosimetric considerations in nano-bio interactions in a cellular screening system,” said Joel Cohen, doctoral student at HSPH and one of the two lead authors of the study.

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

Estimating the effective density of engineered nanomaterials for in vitro dosimetry by Glen DeLoid, Joel M. Cohen, Tom Darrah, Raymond Derk, Liying Rojanasakul, Georgios Pyrgiotakis, Wendel Wohlleben, & Philip Demokritou. Nature Communications 5, Article number: 3514 doi:10.1038/ncomms4514 Published 28 March 2014

This paper is behind a paywall but a free preview is available via ReadCube Access.