Category Archives: health and safety

Reliable findings on the presence of synthetic (engineered) nanoparticles in bodies of water

An Aug. 29, 2016 news item on Nanowerk announces research into determining the presence of engineered (synthetic) nanoparticles in bodies of water,

For a number of years now, an increasing number of synthetic nanoparticles have been manufactured and incorporated into various products, such as cosmetics. For the first time, a research project at the Technical University of Munich and the Bavarian Ministry of the Environment provides reliable findings on their presence in water bodies.

An Aug. 29, 2016 Technical University of Munich (TUM) press release, which originated the news item, provides more information,

Nanoparticles can improve the properties of materials and products. That is the reason why an increasing number of nanoparticles have been manufactured over the past several years. The worldwide consumption of silver nanoparticles is currently estimated at over 300 metric tons. These nanoparticles have the positive effect of killing bacteria and viruses. Products that are coated with these particles include refrigerators and surgical instruments. Silver nanoparticles can even be found in sportswear. This is because the silver particles can prevent the smell of sweat by killing the bacteria that cause it.

Previously, it was unknown whether and in what concentration these nanoparticles enter the environment and e.g. enter bodies of water. If they do, this poses a problem. That is because the silver nanoparticles are toxic to numerous aquatic organisms, and can upset sensitive ecological balances.

Analytical challenge

In the past, however, nanoparticles have not been easy to detect. That is because they measure only 1 to 100 nanometers across [nanoparticles may be larger than 100nm or smaller than 1nm but the official definitions usually specify up to 100nm although some definitions go up to 1000nm] – a nanometer is a millionth of a millimeter. “In order to know if a toxicological hazard exists, we need to know how many of these particles enter the environment, and in particular bodies of water”, explains Michael Schuster, Professor for Analytical Chemistry at the TU Munich.

This was an analytical challenge for the researchers charged with solving the problem on behalf of the Bavarian Ministry of the Environment. In order to overcome this issue, they used a well-known principle that utilizes the effect of surfactants to separate and concentrate the particles. “Surfactants are also found in washing and cleaning detergents”, explains Schuster. “Basically, what they do is envelop grease and dirt particles in what are called micelles, making it possible for them to float in water.” One side of the surfactant is water-soluble, the other fat-soluble. The fat-soluble ends collect around non-polar, non-water soluble compounds such as grease or around particles, and “trap” them in a micelle. The water-soluble, polar ends of the surfactants, on the other hand, point towards the water molecules, allowing the microscopically small micelle to float in water.

A box of sugar cubes in the Walchensee lake

The researchers applied this principle to the nanoparticles. “When the micelles surrounding the particles are warmed slightly, they start to clump”, explains Schuster. This turns the water cloudy. Using a centrifuge, the surfactants and the nanoparticles trapped in them can then be separated from the water. This procedure is called cloud point extraction. The researchers then use the surfactants that have been separated out in this manner – which contain the particles in an unmodified, but highly concentrated form – to measure how many silver nanoparticles are present. To do this, they use a highly sensitive atomic spectrometer configured to only detect silver. In this manner, concentrations in a range of less than one nanogram per liter can be detected. To put this in perspective, this would be like detecting a box of sugar cubes that had dissolved in the Walchensee lake.

With the help of this analysis procedure, it is possible to gain new insight into the concentration of nanoparticles in drinking and waste water, sewage sludge, rivers, and lakes. In Bavaria, the measurements yielded good news: The concentrations measured in the water bodies were extremely low. In was only in four of the 13 Upper Bavarian lakes examined that the concentration even exceeded the minimum detection limit of 0.2 nanograms per liter. No measured value exceeded 1.3 nanograms per liter. So far, no permissible values have been established for silver nanoparticles.

Representative for watercourses, the Isar river was examined from its source to its mouth at around 30 locations. The concentration of silver nanoparticles was also measured in the inflow and outflow of sewage treatment plants. The findings showed that at least 94 percent of silver nanoparticles are filtered out by the sewage treatment plants.

Unfortunately, the researchers have not published their results.

Harvard University announced new Center on Nano-safety Research

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.

Canada’s consultation on nanoscale forms of substances on the Domestic Substances List (DSL)

Yes, there’s a redundancy in the head but there doesn’t seem to be a way around it. Ah well, it seems about seven weeks after Peter Julian (Member of Parliament) introduced his bill in the Canadian House of Commons to regulate nanotechnology (Aug. 29, 2016 posting), Environment and Climate Change Canada (ECCC) and Health Canada (HC) have announced a consultation on nanoscale materials. From an Aug. 4, 2016 posting by Lynn L. Bergeson on Nanotechnology Now (Note: Links have been removed),

On July 27, 2016, Environment and Climate Change Canada (ECCC) and Health Canada (HC) began a consultation on a proposed prioritization approach for nanoscale forms of substances on the Domestic Substances List (DSL). See Canada will use the proposed approach to: (1) establish a list of existing nanomaterials in Canada for prioritization; (2) identify how the information available will be used to inform prioritization of nanomaterials for risk assessment; and (3) outline the proposed outcomes of the prioritization process. In 2015, Canada conducted a mandatory survey under Section 71 of the Canadian Environmental Protection Act, 1999 (CEPA). The survey applied to persons who manufactured or imported any of 206 nanomaterials at a quantity greater than 100 kilograms (kg) during the 2014 calendar year. See Based on the results of the survey, ECCC and HC will prepare a final list of confirmed existing nanomaterials in Canada and will use the list for subsequent prioritization. ECCC and HC propose that, where possible, the substances identified via the survey be “rolled up into” their broader parent nanomaterial groups for the purposes of prioritization. According to ECCC and HC, this will allow, when possible, a more robust look at the hazard, volume, and use data as appropriate, rather than considering an individual substance-by-substance approach. ECCC and HC state that further consideration for sub-grouping (such as by use, unique property, or functionalization) may need to be considered for prioritization and/or risk assessment. …

You can find the Government of Canada’s 2015 Consultation Document: Proposed Approach to Address Nanoscale Forms of Substances on the Domestic Substances List page here, which set the stage for this prioritization exercise.

You can also find the Proposed prioritization approach for nanoscale forms of substances on the Domestic substances list page here where you’ll find information such as this,

Possible nanomaterial groupings, based on parent substance

Aluminum oxide
Iron (II)/(II/III) oxide
Modified silica
Bismuth oxide
Magnesium oxide
Silicon oxide
Calcium carbonate
Manganese (II & III) oxide
Cerium oxide
Titanium dioxide
Cobalt (II) oxide
Yttrium oxide
Copper (II) oxide
Nickel (II) oxide
Zinc oxide
Quantum dots
Zirconium oxide

You can also find information on how to submit comments,

Stakeholders are invited to submit comments on the content of this consultation document and provide other information that would help inform decision making. Please submit comments to one of the addresses provided below by September 25, 2016 [emphasis mine]. ECCC and HC will respond to comments and adapt the proposed approach based on the feedback received on this document, as described in Section 1.2.

Comments on this consultation document can be submitted to one of the following addresses:

By Mail:
Environment and Climate Change Canada
Substances Management Information Line
Chemicals Management Plan
351 St. Joseph Boulevard
Gatineau, Québec
K1A 0H3

By Email:
Please type “Consultation on Prioritization Approach for Nanomaterials” in the subject line of your message.

By Fax:

Suddenly, there’s lots (relative to the last few years) of action on nanotechnology regulation in Canada.

Everything old is new again: Canadian Parliament holds first reading of another bill to regulate nanotechnlogy

Back in March 2010, Canadian New Democratic Party (NDP) Member of Parliament (MP) Peter Julian introduced a bill to regulate nanotechnology (Bill C-494) in Canada. The Conservative government was in power at the time. I can’t remember how many readings it received but it never did get passed into legislation. Now, Mr. Julian is trying again and, coincidentally or not, the Liberals are in power this time. A July 26, 2016 post by Lynn L. Bergeson and Carla N. Hutton for the National Law Review (Note: Links have been removed),

On June 8, 2016, the Canadian House of Commons held its first reading of an Act to amend the Canadian Environmental Protection Act, 1999 (CEPA) (nanotechnology) (C-287).  The bill would add Part 6.1 to CEPA primarily to implement procedures for the investigation and assessment of nanomaterials. …

The bill would define nanomaterial as any manufactured substance or product or any component material, ingredient, device or structure that:  (a) is within the nanoscale (one nanometer (nm) up to and including 100 nm), in at least one external dimension; or (b) if it is not within the nanoscale, exhibits one or more properties that are attributable to the size of a substance and size effects.  The bill mandates a risk assessment process to identify the potential benefits and possible risks of nanotechnologies before nanoproducts enter the market.  It would also create a national inventory regarding nanotechnology, including nanomaterials and nanoparticles, using information collected under CEPA Sections 46 and 71 and “any other information to which the Ministers have access.” On July 25, 2015, Canada published a notice announcing a mandatory survey under CEPA Section 71(1)(b) with respect to certain nanomaterials in Canadian commerce.  …

I do have a few observations about the proposed bill. First, it’s more specific than what we have in place now. As I understand current CEPA regulations, they do not cover materials at the nanoscale which are already imported and/or produced at the macroscale and are considered safe, e.g. titanium dioxide. It is assumed that if they’re safe at the macroscale, they will be safe at the nanoscale. I gather this bill is designed to change that status.

Second, there is no mention in Julian’s press release (text to follow) of the joint Canada-United States Regulatory Cooperation Council (RCC) Nanotechnology Initiative which was designed to harmonize US and Canadian regulatory approaches to nanotechnology. Would bill C-287 introduce less harmony or was it designed to harmonize our approaches?

Third, I don’t see a big problem with the idea of an inventory, the issue is always implementation.

Finally, it appears that this bill means more bureaucrats or computerized systems and I’m not sure it addresses the problem that I believe it is trying to address: how to deal with uncertainty about the risks and hazards of an emerging technology while meeting demands for economic progress.

Very finally, here’s Peter Julian’s June 8, 2016 press release,

Julian’s bill to include Nanotechnology under Environmental Protection Act

You can watch the video here:…

OTTAWA – Today [June 8, 2016], Peter Julian, MP (New Westminster-Burnaby) re-introduced Bill C-287 in the House of Commons, which aims to include a framework that would regulate nanotechnology in the Canadian Environmental Protection Act.

“I first introduced this Bill in 2010. I am pleased to see that some of the aspects of this Bill are being considered by Health Canada and Environment Canada, such as the development of a registry for nanomaterials in commerce and use in Canada. However, there is much more that needs to be done to ensure the responsible use of nanotechnologies in Canada”, said Julian.

Nanotechnology is the application of science and technology to manipulate matter at the atomic or molecular level. Nanomaterials are any ingredient, device, or structure that is between 1 and 100 nm. These materials are present in more than 1000 consumer products, including food and cosmetics. The increasing proliferation of nanoproducts has not been met with an adequate regulatory framework.

Julian’s Bill C-287 would establish a balanced approach ensuring the responsible development of nanotechnology and the safe use off nanomaterials in Canada. The Bill mandates a risk assessment process to identify the potential benefits and possible risks of nanotechnologies before nanoproducts enter the market. It would also require a comprehensive, publicly accessible database that lists existing nanomaterials identified by the Government of Canada.

“While nanotechnology can be very beneficial to people, there are certain risks to it as well. We must identify and mitigate possible risks to better protect the environment and human health before they become an issue. Canada must ensure our regulatory processes ensure nanomaterial safety before the introduction of these substances in Canada”, said Julian.

I’m including links to my 2010 email interview with Peter Julian (published in three parts),

March 24, 2010 (Part one)

March 25, 2010 (Part two)

March 26, 2010 (Part three)

I also covered a hearing on nanomaterials and safety held by the Canadian House of Commons Standing Committee on Health on June 10, 2010 in a June 23, 2010 posting.

Two nano workshops precede OpenTox Euro conference

The main conference OpenTox Euro is focused on novel materials and it’s being preceded by two nano workshops. All of of these events will be taking place in Germany in Oct. 2016. From an Aug. 11, 2016 posting by Lynn L. Bergeson on Nanotechnology Now,

The OpenTox Euro Conference, “Integrating Scientific Evidence Supporting Risk Assessment and Safer Design of Novel Substances,” will be held October 26-28, 2016. … The current topics for the Conference include: (1) computational modeling of mechanisms at the nanoscale; (2) translational bioinformatics applied to safety assessment; (3) advances in cheminformatics; (4) interoperability in action; (5) development and application of adverse outcome pathways; (6) open science applications showcase; (7) toxicokinetics and extrapolation; and (8) risk assessment.

On Oct. 24, 2016, two days before OpenTox Euro, the EU-US Nano EHS [Environmental Health and Safety] 2016 workshop will be held in Germany. The theme is: ‘Enabling a Sustainable Harmonised Knowledge Infrastructure supporting Nano Environmental and Health Safety Assessment’ and the objectives are,

The objective of the workshop is to facilitate networking, knowledge sharing and idea development on the requirements and implementation of a sustainable knowledge infrastructure for Nano Environmental and Health Safety Assessment and Communications. The infrastructure should support the needs required by different stakeholders including scientific researchers, industry, regulators, workers and consumers.

The workshop will also identify funding opportunities and financial models within and beyond current international and national programs. Specifically, the workshop will facilitate active discussions but also identify potential partners for future EU-US cooperation on the development of knowledge infrastructure in the NanoEHS field. Advances in the Nano Safety harmonisation process, including developing an ongoing working consensus on data management and ontology, will be discussed:

– Information needs of stakeholders and applications
– Data collection and management in the area of NanoEHS
– Developments in ontologies supporting NanoEHS goals
– Harmonisation efforts between EU and US programs
– Identify practice and infrastructure gaps and possible solutions
– Identify needs and solutions for different stakeholders
– Propose an overarching sustainable solution for the market and society

The presentations will be focused on the current efforts and concrete achievements within EU and US initiatives and their potential elaboration and extension.

The second workshop is being held by the eNanoMapper (ENM) project on Oct. 25, 2016 and concerns Nano Modelling. The objectives and workshop sessions are:

1. Give the opportunity to research groups working on computational nanotoxicology to disseminate their modelling tools based on hands-on examples and exercises
2. Present a collection of modelling tools that can span the entire lifecycle of nanotox research, starting from the design of experiments until use of models for risk assessment in biological and environmental systems.
3. Engage the workshop participants in using different modelling tools and motivate them to contribute and share their knowledge.

Indicative workshop sessions

• Preparation of datasets to be used for modelling and risk assessment
• Ontologies and databases
• Computation of theoretical descriptors
• NanoQSAR Modelling
• Ab-initio modelling
• Mechanistic modelling
• Modelling based on Omics data
• Filling data gaps-Read Across
• Risk assessment
• Experimental design

We would encourage research teams that have developed tools in the areas of computational nanotoxicology and risk assessment to demonstrate their tools in this workshop.

That’s going to be a very full week in Germany.

You can register for OpenTox Euro and more here.

Enzyme-based sustainable sensing devices

This story about a sustainable sensing device involves sweat. A July 28, 2016 news item on ScienceDaily describes the sweaty situation,

It may be clammy and inconvenient, but human sweat has at least one positive characteristic — it can give insight to what’s happening inside your body. A new study published in the ECS [Electrochemical Society] Journal of Solid State Science and Technology aims to take advantage of sweat’s trove of medical information through the development of a sustainable, wearable sensor to detect lactate levels in your perspiration.

Caption: Depiction of patch sensor via CFDRC. Credit: Sergio Omar Garcia/CFDRC

Caption: Depiction of patch sensor via CFDRC. Credit: Sergio Omar Garcia/CFDRC

The patch in that image doesn’t seem all that wearable but presumably there will be some changes made. A July 28, 2016 Electrochemical Society news release on EurekAlert, which originated the news item, provides more detail about the technology,

“When the human body undergoes strenuous exercise, there’s a point at which aerobic muscle function becomes anaerobic muscle function,” says Jenny Ulyanova, CFD Research Corporation (CFDRC) researcher and co-author of the paper. “At that point, lactate is produce at a faster rate than it is being consumed. When that happens, knowing what those levels are can be an indicator of potentially problematic conditions like muscle fatigue, stress, and dehydration.”

Utilizing green technology

Using sweat to track changes in the body is not a new concept. While there have been many developments in recent years to sense changes in the concentrations of the components of sweat, no purely biological green technology has been used for these devices. The team of CFDRC researchers, in collaboration with the University of New Mexico, developed an enzyme-based sensor powered by a biofuel cell – providing a safe, renewable power source.

Biofuel cells have become a promising technology in the field of energy storage, but still face many issues related to short active lifetimes, low power densities, and low efficiency levels. However, they have several attractive points, including their ability to use renewable fuels like glucose and implement affordable, renewable catalysts.

“The biofuel cell works in this particular case because the sensor is a low-power device,” Ulyanova says. “They’re very good at having high energy densities, but power densities are still a work in progress. But for low-power applications like this particular sensor, it works very well.”

In their research, entitled “Wearable Sensor System Powered by a Biofuel Cell for Detection of Lactate Levels in Sweat,” the team powered the biofuel cells with a fuel based on glucose. This same enzymatic technology, where the enzymes oxidize the fuel and generate energy, is used at the working electrode of the sensor which allows for the detection of lactate in your sweat.

Targeting lactate

While the use of the biofuel cell is a novel aspect of this work, what sets it apart from similar developments in the field is the use of electrochemical processes to very accurately detect a specific compound in a very complex medium like sweat.

“We’re doing it electrochemically, so we’re looking at applying a constant load to the sensor and generating a current response,” Ulyanova says, “which is directly proportional to the concentration of our target analyte.”

Practical applications

Originally, the sensor was developed to help detect and predict conditions related to lactate levels (i.e. fatigue and dehydration) for military personnel.

“The sensor was designed for a soldier in training at boot camp,” says Sergio Omar Garcia, CFDRC researcher and co-author of the paper, “but it could be applied to people that are active and anyone participating in strenuous activity.”

As for commercial applications, the researchers believe the device could be used as a training aid to monitor lactate changes in the same way that athletes use heart rate monitors to see how their heart rate changes during exercise.

On-body testing

The team is currently working to redesign the physical appearance of the patch to move from laboratory research to on-body tests. Once the scientists optimize how the sensor adheres to the skin, its sweat sample delivery/removal, and the systems electronic components, volunteers will test its capabilities while exercising.

“We had actually talked about this idea to some local high school football coaches,” Ulyanova says, “and they seem to really like it and are willing to put forth the use of their players to beta test the idea.”

After initial data is gathered, the team will be able to work with other groups to interpret the data and relate it to the physical condition of the person. With this, predictive models could be built to potentially help prevent conditions related to individual overexertion.

Future plans for the device include implementing wireless transmission of results and the development of a suite of sensors (a hybrid sensor) that can detect various other biomolecules, indicative of physical or physiological stressors.

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

Wearable Sensor System Powered by a Biofuel Cell for Detection of Lactate Levels in Sweat by S. O. Garcia, Y. V. Ulyanova, R. Figueroa-Teran, K. H. Bhatt, S. Singhal and P. Atanassov. ECS J. Solid State Sci. Technol. 2016 volume 5, issue 8, M3075-M3081 doi: 10.1149/2.0131608jss

This paper is behind a paywall.

Nanoparticles for breaking up plaque and preventing cavities

There may be iron in your tooth care future if a team of researchers at the University of Pennsylvania have their way. From a July 26, 2016 news item on ScienceDaily,

The bacteria that live in dental plaque and contribute to tooth decay often resist traditional antimicrobial treatment, as they can “hide” within a sticky biofilm matrix, a glue-like polymer scaffold.

A new strategy conceived by University of Pennsylvania researchers took a more sophisticated approach. Instead of simply applying an antibiotic to the teeth, they took advantage of the pH-sensitive and enzyme-like properties of iron-containing nanoparticles to catalyze the activity of hydrogen peroxide, a commonly used natural antiseptic. The activated hydrogen peroxide produced free radicals that were able to simultaneously degrade the biofilm matrix and kill the bacteria within, significantly reducing plaque and preventing the tooth decay, or cavities, in an animal model.

“Even using a very low concentration of hydrogen peroxide, the process was incredibly effective at disrupting the biofilm,” said Hyun (Michel) Koo, a professor in the Penn School of Dental Medicine’s Department of Orthodontics and divisions of Pediatric Dentistry and Community and Oral Health and the senior author of the study, which was published in the journal Biomaterials. “Adding nanoparticles increased the efficiency of bacterial killing more than 5,000-fold.”

A July 25, 2016 University of Pennsylvania news release, which originated the news item, describes the genesis of the work and provides more details about the current research (Note: A link has been removed),

The work built off a seminal finding by Gao [Lizeng Gao, a postdoctoral researcher in Koo’s lab] and colleagues, published in 2007 in Nature Nanotechnology, showing that nanoparticles, long believed to be biologically and chemically inert, could in fact possess enzyme-like properties. In that study, Gao showed that an iron oxide nanoparticle behaved similarly to a peroxidase, an enzyme found naturally that catalyzes oxidative reactions, often using hydrogen peroxide.

When Gao joined Koo’s lab in 2013, he proposed using these nanoparticles in an oral setting, as the oxidation of hydrogen peroxide produces free radicals that can kill bacteria.

“When he first presented it to me, I was very skeptical,” Koo said, “because these free radicals can also damage healthy tissue. But then he refuted that and told me this is different because the nanoparticles’ activity is dependent on pH.”

Gao had found that the nanoparticles had no catalytic activity at neutral or near-neutral pH of 6.5 or 7, physiological values typically found in blood or in a healthy mouth. But when pH was acidic, closer to 5, they become highly active and can rapidly produce free radicals.

The scenario was ideal for targeting plaque, which can produce an acidic microenvironment when exposed to sugars.

Gao and Koo reached out to Cormode [David Cormode, an assistant professor of radiology and bioengineering], who had experience working with iron oxide nanoparticles in a radiological imaging context, to help them synthesize, characterize and test the effectiveness of the nanoparticles, several forms of which are already FDA-approved for imaging in humans.

Beginning with in vitro studies, which involved growing a biofilm containing the cavity-causing bacteria Streptococcus mutans on a tooth-enamel-like surface and then exposing it to sugar, the researchers confirmed that the nanoparticles adhered to the biofilm, were retained even after treatment stopped and could effectively catalyze hydrogen peroxide in acidic conditions.

They also showed that the nanoparticles’ reaction with a 1 percent or less hydrogen peroxide solution was remarkably effective at killing bacteria, wiping out more than 99.9 percent of the S. mutans in the biofilm within five minutes, an efficacy more than 5,000 times greater than using hydrogen peroxide alone. Even more promising, they demonstrated that the treatment regimen, involving a 30-second topical treatment of the nanoparticles followed by a 30-second treatment with hydrogen peroxide, could break down the biofilm matrix components, essentially removing the protective sticky scaffold.

Moving to an animal model, they applied the nanoparticles and hydrogen peroxide topically to the teeth of rats, which can develop tooth decay when infected with S. mutans just as humans do. Twice-a-day, one-minute treatments for three weeks significantly reduced the onset and severity of carious lesions, the clinical term for tooth decay, compared to the control or treatment with hydrogen peroxide alone. The researchers observed no adverse effects on the gum or oral soft tissues from the treatment.

“It’s very promising,” said Koo. “The efficacy and toxicity need to be validated in clinical studies, but I think the potential is there.”

Among the attractive features of the platform is the fact that the components are relatively inexpensive.

“If you look at the amount you would need for a dose, you’re looking at something like 5 milligrams,” Cormode said. “It’s a tiny amount of material, and the nanoparticles are fairly easily synthesize, so we’re talking about a cost of cents per dose.”

In addition, the platform uses a concentration of hydrogen peroxide, 1 percent, which is lower than many currently available tooth-whitening systems that use 3 to 10 percent concentrations, minimizing the chance of negative side effects.

Looking ahead, Gao, Koo, Cormode and colleagues hope to continue refining and improving upon the effectiveness of the nanoparticle platform to fight biofilms.

“We’re studying the role of nanoparticle coatings, composition, size and so forth so we can engineer the particles for even better performance,” Cormode said.

The funding agencies provide a note of interest (Note: Links have been removed),

The study was funded by the International Association for Dental Research/GlaxoSmithKline Innovation in Oral Health Award, National Science Foundation and University of Pennsylvania Research Foundation.

Presumably the industry as represented by the GlaxoSmithKline Innovation in Oral Health Award is keeping a close eye on this work.

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

Nanocatalysts promote Streptococcus mutans biofilm matrix degradation and enhance bacterial killing to suppress dental caries in vivo by Lizeng Gao, Yuan Liu, Dongyeop Kim, Yong Li, Geelsu Hwang, Pratap C. Naha, David P. Cormode, & Hyun Koo. Biomaterials Volume 101, September 2016, Pages 272–284 doi:10.1016/j.biomaterials.2016.05.051

This paper is behind a paywall.

DNA as a sensor

McMaster University (Ontario, Canada) researchers have developed a technique for using DNA (deoxyribonucleic acid) as a sensor according to a July 7, 2016 news item on ScienceDaily,

Researchers at McMaster University have established a way to harness DNA as the engine of a microscopic “machine” they can turn on to detect trace amounts of substances that range from viruses and bacteria to cocaine and metals.

“It’s a completely new platform that can be adapted to many kinds of uses,” says John Brennan, director of McMaster’s Biointerfaces Insitute and co-author of a paper in the journal Nature Communications that describes the technology. “These DNA nano-architectures are adaptable, so that any target should be detectable.”

A July 7, 2016 McMaster University news release (also on EurekAlert), which originated the news item, expands on the theme,

DNA is best known as a genetic material, but is also a very programmable molecule that lends itself to engineering for synthetic applications.

The new method shapes separately programmed pieces of DNA material into pairs of interlocking circles.

The first remains inactive until it is released by the second, like a bicycle wheel in a lock. When the second circle, acting as the lock, is exposed to even a trace of the target substance, it opens, freeing the first circle of DNA, which replicates quickly and creates a signal, such as a colour change.

“The key is that it’s selectively triggered by whatever we want to detect,” says Brennan, who holds the Canada Research Chair in Bioanalytical Chemistry and Biointerfaces. “We have essentially taken a piece of DNA and forced it to do something it was never designed to do. We can design the lock to be specific to a certain key. All the parts are made of DNA, and ultimately that key is defined by how we build it.”

The idea for the “DNA nanomachine” comes from nature itself, explains co-author Yingfu Li, who holds the Canada Research Chair in Nucleic Acids Research.

“Biology uses all kinds of nanoscale molecular machines to achieve important functions in cells,” Li says. “For the first time, we have designed a DNA-based nano-machine that is capable of achieving ultra-sensitive detection of a bacterial pathogen.”

The DNA-based nanomachine is being further developed into a user-friendly detection kit that will enable rapid testing of a variety of substances, and could move to clinical testing within a year.

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

Programming a topologically constrained DNA nanostructure into a sensor by Meng Liu, Qiang Zhang, Zhongping Li, Jimmy Gu, John D. Brennan, & Yingfu Li. Nature Communications 7, Article number: 12074  doi:10.1038/ncomms12074 Published 23 June 2016

This paper is open access.

Wireless, wearable carbon nanotube-based gas sensors for soldiers

Researchers at MIT (Massachusetts Institute of Technology) are hoping to make wireless, toxic gas detectors the size of badges. From a June 30, 2016 news item on Nanowerk,

MIT researchers have developed low-cost chemical sensors, made from chemically altered carbon nanotubes, that enable smartphones or other wireless devices to detect trace amounts of toxic gases.

Using the sensors, the researchers hope to design lightweight, inexpensive radio-frequency identification (RFID) badges to be used for personal safety and security. Such badges could be worn by soldiers on the battlefield to rapidly detect the presence of chemical weapons — such as nerve gas or choking agents — and by people who work around hazardous chemicals prone to leakage.

A June 30, 2016 MIT news release (also on EurekAlert), which originated the news item, describes the technology further,

“Soldiers have all this extra equipment that ends up weighing way too much and they can’t sustain it,” says Timothy Swager, the John D. MacArthur Professor of Chemistry and lead author on a paper describing the sensors that was published in the Journal of the American Chemical Society. “We have something that would weigh less than a credit card. And [soldiers] already have wireless technologies with them, so it’s something that can be readily integrated into a soldier’s uniform that can give them a protective capacity.”

The sensor is a circuit loaded with carbon nanotubes, which are normally highly conductive but have been wrapped in an insulating material that keeps them in a highly resistive state. When exposed to certain toxic gases, the insulating material breaks apart, and the nanotubes become significantly more conductive. This sends a signal that’s readable by a smartphone with near-field communication (NFC) technology, which allows devices to transmit data over short distances.

The sensors are sensitive enough to detect less than 10 parts per million of target toxic gases in about five seconds. “We are matching what you could do with benchtop laboratory equipment, such as gas chromatographs and spectrometers, that is far more expensive and requires skilled operators to use,” Swager says.

Moreover, the sensors each cost about a nickel to make; roughly 4 million can be made from about 1 gram of the carbon nanotube materials. “You really can’t make anything cheaper,” Swager says. “That’s a way of getting distributed sensing into many people’s hands.”

The paper’s other co-authors are from Swager’s lab: Shinsuke Ishihara, a postdoc who is also a member of the International Center for Materials Nanoarchitectonics at the National Institute for Materials Science, in Japan; and PhD students Joseph Azzarelli and Markrete Krikorian.

Wrapping nanotubes

In recent years, Swager’s lab has developed other inexpensive, wireless sensors, called chemiresistors, that have detected spoiled meat and the ripeness of fruit, among other things [go to the end of this post for links to previous posts about Swager’s work]. All are designed similarly, with carbon nanotubes that are chemically modified, so their ability to carry an electric current changes when exposed to a target chemical.

This time, the researchers designed sensors highly sensitive to “electrophilic,” or electron-loving, chemical substances, which are often toxic and used for chemical weapons.

To do so, they created a new type of metallo-supramolecular polymer, a material made of metals binding to polymer chains. The polymer acts as an insulation, wrapping around each of the sensor’s tens of thousands of single-walled carbon nanotubes, separating them and keeping them highly resistant to electricity. But electrophilic substances trigger the polymer to disassemble, allowing the carbon nanotubes to once again come together, which leads to an increase in conductivity.

In their study, the researchers drop-cast the nanotube/polymer material onto gold electrodes, and exposed the electrodes to diethyl chlorophosphate, a skin irritant and reactive simulant of nerve gas. Using a device that measures electric current, they observed a 2,000 percent increase in electrical conductivity after five seconds of exposure. Similar conductivity increases were observed for trace amounts of numerous other electrophilic substances, such as thionyl chloride (SOCl2), a reactive simulant in choking agents. Conductivity was significantly lower in response to common volatile organic compounds, and exposure to most nontarget chemicals actually increased resistivity.

Creating the polymer was a delicate balancing act but critical to the design, Swager says. As a polymer, the material needs to hold the carbon nanotubes apart. But as it disassembles, its individual monomers need to interact more weakly, letting the nanotubes regroup. “We hit this sweet spot where it only works when it’s all hooked together,” Swager says.

Resistance is readable

To build their wireless system, the researchers created an NFC tag that turns on when its electrical resistance dips below a certain threshold.

Smartphones send out short pulses of electromagnetic fields that resonate with an NFC tag at radio frequency, inducing an electric current, which relays information to the phone. But smartphones can’t resonate with tags that have a resistance higher than 1 ohm.

The researchers applied their nanotube/polymer material to the NFC tag’s antenna. When exposed to 10 parts per million of SOCl2 for five seconds, the material’s resistance dropped to the point that the smartphone could ping the tag. Basically, it’s an “on/off indicator” to determine if toxic gas is present, Swager says.

According to the researchers, such a wireless system could be used to detect leaks in Li-SOCl2 (lithium thionyl chloride) batteries, which are used in medical instruments, fire alarms, and military systems.

The next step, Swager says, is to test the sensors on live chemical agents, outside of the lab, which are more dispersed and harder to detect, especially at trace levels. In the future, there’s also hope for developing a mobile app that could make more sophisticated measurements of the signal strength of an NFC tag: Differences in the signal will mean higher or lower concentrations of a toxic gas. “But creating new cell phone apps is a little beyond us right now,” Swager says. “We’re chemists.”

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

Ultratrace Detection of Toxic Chemicals: Triggered Disassembly of Supramolecular Nanotube Wrappers by Shinsuke Ishihara, Joseph M. Azzarelli, Markrete Krikorian, and Timothy M. Swager. J. Am. Chem. Soc., Article ASAP DOI: 10.1021/jacs.6b03869 Publication Date (Web): June 23, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

Here are links to other posts about Swager’s work featured here previously:

Carbon nanotubes sense spoiled food (April 23, 2015 post)

Smart suits for US soldiers—an update of sorts from the Lawrence Livermore National Laboratory (Feb. 25, 2014 post)

Come, see my etchings … they detect poison gases (Oct. 9, 2012 post)

Soldiers sniff overripe fruit (May 1, 2012 post)