Category Archives: nanotechnology

Making rubber more rubbery for better condoms

A May 20, 2016 news item on Nanowerk announces some research on rubber from the University of Manchester (Note: A link has been removed),

In an article published in Carbon (“Graphene and water-based elastomers thin-film composites by dip-moulding”), Dr Aravind Vijayaraghavan and Dr Maria Iliut from Manchester have shown that adding a very small amount of graphene, the world’s thinnest and strongest material, to rubber films can increase both their strength and the elasticity by up to 50%. Thin rubber films are ubiquitous in daily life, used in everything from gloves to condoms.

A May 20, 2016 University of Manchester press release (also on EurekAlert), which originated the news item, provides more detail,

In their experiments, the scientists tested two kinds of rubbery materials – natural rubber, comprised of a material called polyisoprene, and a man-made rubber called polyurethane. To these, they added graphene of different kinds, amounts and size.

In most cases, it they observed that the resulting composite material could be stretched to a greater degree and with greater force before it broke. Indeed, adding just one tenth of one percent of graphene was all it took to make the rubber 50% stronger.

Dr Vijayaraghavan, who leads the Nano-functional Materials Group, explains “A composite is a material which contains two parts, a matrix which is soft and light and a filler which is strong. Taken together, you get something which is both light and strong. This is the principle behind carbon fibre composites used in sports cars, or Kevlar composites used in body armour.

“In this case, we have made a composite of rubber, which is soft and stretchy but fragile, with graphene and the resulting material is both stronger and stretchier.”

Dr Maria Iliut, a research associate in Dr Vijayaraghavan’s group, describes how this material is produced: “We use a form of graphene called graphene oxide, which unlike graphene is stable as a dispersion in water. The rubber materials are also in a form that is stable in water, allowing us to combine them before forming thin films with a process called dip moulding.”

“The important thing here is that because these films are so thin, we need a strengthening filler which is also very thin. Fortunately, graphene is both the thinnest and strongest material we know of.”

The project emerged from a call by the Bill & Melinda Gates Foundation, to develop a more desirable condom. [my Nov. 22, 2013 post features the grant announcement and Dr. Vijayaraghavan’s research plans] According to Dr Vijayaraghavan, this composite material has tremendous implications in daily life.

He adds “Our thinking was that if we could make the rubber used in condoms stronger and stretchier, then you could use that to make even thinner condoms which would feel better without breaking.

“Similar arguments can be made for using this material to make better gloves, sportswear, medical devices and so on. We are seeing considerable industrial interest in this area and we hope more companies will want to get involved in the commercial opportunities this research could create.”

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

Graphene and water-based elastomers thin-film composites by dip-moulding by Maria Iliut, Claudio Silva, Scott Herrick, Mark McGlothlin, Aravind Vijayaraghavan. Carbon doi:10.1016/j.carbon.2016.05.032 Available online 14 May 2016

This paper is open access.

 

Update on the International NanoCar race coming up in Autumn 2016

First off, the race seems to be adjusting its brand (it was billed as the International NanoCar Race in my Dec. 21, 2015 posting), from a May 20, 2016 news item on Nanowerk,

The first-ever international race of molecule-cars (Nanocar Race) will take place at the CEMES laboratory in Toulouse this fall [2016].

A May 9, 2016 notice on France’s Centre national de la recherce scientifique’s (CNRS) news website, which originated the news item, fills in a few more details,

Five teams are fine-tuning their cars—each made up of around a hundred atoms and measuring a few nanometers in length. They will be propelled by an electric current on a gold atom “race track.” We take you behind the scenes to see how these researcher-racers are preparing for the NanoCar Race.

About this video

Original title: The NanoCar Race

Production year: 2016

Length: 6 min 23

Director: Pierre de Parscau

Producer: CNRS Images

Speaker(s) :

Christian Joachim
Centre d’Elaboration des Matériaux et d’Etudes Structurales

Gwénaël Rapenne
(CEMES/CNRS)

Corentin Durand
(CEMES/CNRS)

Pierre Abeilhou
(CEMES/CNRS)

Frank Eisenhut
Technical University of Dresden

You can find the video which is embedded in both the Nanowerk news item and here with the CNRS notice.

Device detects molecules associated with neurodegenerative diseases

It’s nice to get notice of research in South America, an area for which I rarely stumble across any news releases. Brazilian researchers have developed a device that could help diagnose neurodegenerative diseases such as Alzheimer’s and and Parkinson’s as well as some cancers according to a May 20, 2016 news item on Nanotechnology Now,

A biosensor developed by researchers at the National Nanotechnology Laboratory (LNNano) in Campinas, São Paulo State, Brazil, has been proven capable of detecting molecules associated with neurodegenerative diseases and some types of cancer.

The device is basically a single-layer organic nanometer-scale transistor on a glass slide. It contains the reduced form of the peptide glutathione (GSH), which reacts in a specific way when it comes into contact with the enzyme glutathione S-transferase (GST), linked to Parkinson’s, Alzheimer’s and breast cancer, among other diseases. The GSH-GST reaction is detected by the transistor, which can be used for diagnostic purposes.

The project focuses on the development of point-of-care devices by researchers in a range of knowledge areas, using functional materials to produce simple sensors and microfluidic systems for rapid diagnosis.

A May 19, 2016 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) press release, which originated the news item, provides more detail,

“Platforms like this one can be deployed to diagnose complex diseases quickly, safely and relatively cheaply, using nanometer-scale systems to identify molecules of interest in the material analyzed,” explained Carlos Cesar Bof Bufon, Head of LNNano’s Functional Devices & Systems Lab (DSF) and a member of the research team for the project, whose principal investigator is Lauro Kubota, a professor at the University of Campinas’s Chemistry Institute (IQ-UNICAMP).

In addition to portability and low cost, the advantages of the nanometric biosensor include its sensitivity in detecting molecules, according to Bufon.

“This is the first time organic transistor technology has been used in detecting the pair GSH-GST, which is important in diagnosing degenerative diseases, for example,” he explained. “The device can detect such molecules even when they’re present at very low levels in the examined material, thanks to its nanometric sensitivity.” A nanometer (nm) is one billionth of a meter (10-9 meter), or one millionth of a millimeter.

The system can be adapted to detect other substances, such as molecules linked to different diseases and elements present in contaminated material, among other applications. This requires replacing the molecules in the sensor with others that react with the chemicals targeted by the test, which are known as analytes.

The team is working on paper-based biosensors to lower the cost even further and to improve portability and facilitate fabrication as well as disposal.

The challenge is that paper is an insulator in its usual form. Bufon has developed a technique to make paper conductive and capable of transporting sensing data by impregnating cellulose fibers with polymers that have conductive properties.

The technique is based on in situ synthesis of conductive polymers. For the polymers not to remain trapped on the surface of the paper, they have to be synthesized inside and between the pores of the cellulose fibers. This is done by gas-phase chemical polymerization: a liquid oxidant is infiltrated into the paper, which is then exposed to monomers in the gas phase. A monomer is a molecule of low molecular weight capable of reacting with identical or different molecules of low molecular weight to form a polymer.

The monomers evaporate under the paper and penetrate the pores of the fibers at the submicrometer scale. Inside the pores, they blend with the oxidant and begin the polymerization process right there, impregnating the entire material.

The polymerized paper acquires the conductive properties of the polymers. This conductivity can be adjusted by manipulating the element embedded in the cellulose fibers, depending on the application for which the paper is designed. Thus, the device can be electrically conductive, allowing current to flow without significant losses, or semiconductive, interacting with specific molecules and functioning as a physical, chemical or electrochemical sensor.

There’s no mention of a published paper.

Injectable medicine made safer?

The lede for this May 19, 2016 news item on Nanowerk is great,

Bring the drugs, hold the suds.

The May 19, 2016 University of Buffalo news release (also on EurekAlert) by Cory Nealon, which originated the news item, quickly gets to the point,

That summarizes a promising new drug-making technique designed to reduce serious allergic reactions and other side effects from anti-cancer medicine, testosterone and other drugs that are administered with a needle.

Developed by University at Buffalo researchers, the breakthrough removes potentially harmful additives – primarily soapy substances known as surfactants – from common injectable drugs.

“We’re excited because this process can be scaled up, which could make existing injectable drugs safer and more effective for millions of people suffering from serious diseases and ailments,” says Jonathan F. Lovell, a biomedical engineer at UB and the study’s corresponding author.

Pharmaceutical companies use surfactants to dissolve medicine into a liquid solution, a process that makes medicine suitable for injection. While effective, the process is seldom efficient. Solutions loaded with surfactant and other nonessential ingredients can carry the risk of causing anaphylactic shock, blood clotting, hemolysis and other side effects.

Researchers have tried to address this problem in two ways, each with varying degrees of success.

Some have taken the so-called “top down” approach, in which they shrink drug particles to nanoscale sizes to eliminate excess additives. While promising, the method doesn’t work well in injectable medicine because the drug particles are still too large to safely inject.

Other researchers work from the “bottom up” using nanotechnology to build new drugs from scratch. This may yield tremendous results; however, developing new drug formulations takes years, and drugs are coupled with new additives that create new side effects.

The technique under development at UB differs because it improves existing injectable drug-making methods by taking the unusual step of stripping away all of the excess surfactant.

In laboratory experiments, researchers dissolved 12 drugs – cabazitaxel (anti-cancer), testosterone, cyclosporine (an immunosuppressant used during organ transplants) and others – one at a time into a surfactant called Pluronic. Then, by lowering the solution’s temperature to 4 degrees Celsius (most drugs are made at room temperature), they were able to remove the excess Pluronic via a membrane.

The end result are drugs that contain 100 to 1,000 times less excess additives.

“For the drugs we looked at, this is as close as anyone has gotten to introducing pure, injectable medicine into the body,” says Lovell, PhD, assistant professor in the Department of Biomedical Engineering in UB’s School of Engineering and Applied Sciences. “Essentially, it’s a new way to package drugs.”

The findings are significant, he says, because they show that many injectable drug formulations may be improved through an easy-to-adopt process. Future experiments are planned to further refine the method, he says.

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

Therapeutic surfactant-stripped frozen micelles by Yumiao Zhang, Wentao Song, Jumin Geng, Upendra Chitgupi, Hande Unsal, Jasmin Federizon, Javid Rzayev, Dinesh K. Sukumaran, Paschalis Alexandridis, & Jonathan F. Lovell. Nature Communications 7, Article number: 11649 doi:10.1038/ncomms11649 Published 19 May 2016

This is an open access paper.

A few years back, a friend got a flu shot and became ill (not the flu). Suspicions  (my friend is a doctor) centered on the additives in the shot as that particular year a number of people got sick from the shot.

Mimicking nature’s ‘anti-freeze’

Some frogs can survive being frozen for weeks and that’s the property scientists at the University of Leeds (UK) are trying to mimic according to a May 19, 2016 news item on Nanowerk (Note: A link has been removed),

The new research, published today [May 18, 2016] in the print edition of the Journal of Physical Chemistry B (“Low-Density Water Structure Observed in a Nanosegregated Cryoprotectant Solution at Low Temperatures from 285 to 238 K”), reveals how glycerol prevents ice crystals from forming in water as the solution is cooled to -35°C, with important implications for improving cryoprotectants used in fertility treatments and food storage.

A May 19, 2016 University of Leeds press release (also on EurekAlert), which originated the news item, provides more detail (Note: A link has been removed),

Dr Lorna Dougan from the University’s School of Physics and Astronomy, who leads the research group, said: “The experiments provide more insight into the fundamental properties of water. It raises questions about what cryoprotectants are doing in living organisms and could help us take steps to understanding how these organisms survive.

“If we understand what glycerol is doing we might be able to fine-tune some of these cryoprotectants that are used to find more effective combinations.”

Cryoprotectant molecules, including glycerol, play an important role in protecting cells and tissues from harmful ice crystals when they are cooled to sub-zero temperatures during freeze storage. Experts have adopted the use of cryoprotectants in fertility treatments and food storage, but not as effectively as in nature.

It is the ability of organisms that can survive in extreme cold environments – known as ‘psychrophiles’ – that inspired the team of physicists to unpick the biological rules that allow their survival.

In winter months, for example, the Eastern Wood frog in North America survives being frozen to temperatures as low as -8°C for weeks, and then in spring thaws out and continues to live perfectly healthily.

To understand how reptiles like the Eastern Wood frog can freeze and thaw, the team used a Science and Technology Facilities Council (STFC) instrument called SANDALS that was purpose-built for investigating the structure of liquids and amorphous materials.

They wanted to answer the fundamental question of how cryoprotectants alter the structure of water at low temperatures, as it is the water structure that is so important in leading to potential ice damage.

The SANDALS instrument allowed the team to see, at the molecular level, that the water and glycerol segregated into clusters. When they looked in more detail, they found the water looked similar to a low density form of itself, showing all the signs it was about to freeze but then it did not. Instead, the glycerol molecules encapsulated the water, preventing the formation of an icy network.

The team will now use these results as a platform for discovering the next generation of cryoprotectants.

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

Low-Density Water Structure Observed in a Nanosegregated Cryoprotectant Solution at Low Temperatures from 285 to 238 K by J. J. Towey, A. K. Soper, and L. Dougan. J. Phys. Chem. B, 2016, 120 (19), pp 4439–4448 DOI: 10.1021/acs.jpcb.6b01185 Publication Date (Web): March 18, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall.

I did search for images of Eastern Wood Frogs but they have to be paid for. These frogs must be a very much in demand as I’ve haven’t encountered this before. You can usually find what you want on Wikipedia or on a frog enthusiast site. It’s not an Eastern one but here’s a Wood Frog (from Wikipedia),

Lithobates sylvaticus (Woodfrog) Date: 3 July 2011, 19:31 Author:Brian Gratwicke This file is licensed under the Creative Commons Attribution 2.0 Generic license.

Lithobates sylvaticus (Woodfrog)
Date: 3 July 2011, 19:31
Author: Brian Gratwicke
This file is licensed under the Creative Commons Attribution 2.0 Generic license.

Removing viruses from water with a ‘mille-feuille’ filter

Mille-feuille is a pastry and it’s name translates to ‘a thousand leaves’, which hints at how a ‘mille-feuille’ nanofilter is constructed. From a May 18, 2016 news item on Nanowerk,

A simple paper sheet made by scientists at Uppsala University can improve the quality of life for millions of people by removing resistant viruses from water. The sheet, made of cellulose nanofibers, is called the mille-feuille filter as it has a unique layered internal architecture resembling that of the French puff pastry mille-feuille (Eng. thousand leaves).

Caption: The sheet made of cellulose nanofibers in the mille-feuille filter which can remove resistant viruses from water. Research led by Albert Mihranyan, Professor of Nanotechnology at Uppsala University, Image by Simon Gustafsson. Credit: Simon Gustafsson

Caption: The sheet made of cellulose nanofibers in the mille-feuille filter which can remove resistant viruses from water. Research led by Albert Mihranyan, Professor of Nanotechnology at Uppsala University, Image by Simon Gustafsson. Credit: Simon Gustafsson

A May 18, 2016 Uppsala University (Sweden) press release on EurekAlert, which originated the news item, expands on the theme,

With a filter material directly from nature, and by using simple production methods, we believe that our filter paper can become the affordable global water filtration solution and help save lives. Our goal is to develop a filter paper that can remove even the toughest viruses from water as easily as brewing coffee’, says Albert Mihranyan, Professor of Nanotechnology at Uppsala University, who heads the study.

Access to safe drinking water is among the UN’s Sustainable Development Goals. More than 748 million people lack access to safe drinking water and basic sanitation. Water-borne infections are among the global causes for mortality, especially in children under age of five, and viruses are among the most notorious water-borne infectious microorganisms. They can be both extremely resistant to disinfection and difficult to remove by filtration due to their small size.

Today we heavily rely on chemical disinfectants, such as chlorine, which may produce toxic by-products depending on water quality. Filtration is a very effective, robust, energy-efficient, and inert method of producing drinking water as it physically removes the microorganisms from water rather than inactivates them. But the high price of efficient filters is limiting their use today.

‘Safe drinking water is a problem not only in the low-income countries. Massive viral outbreaks have also occurred in Europe in the past, including Sweden, continues Mihranyan referring to the massive viral outbreak in Lilla Edet municipality in Sweden in 2008, when more than 2400 people or almost 20% of the local population got infected with Norovirus due to poor water. ‘ Cellulose is one of the most common filtering media used in daily life from tea-bags to vacuum cleaners. However, the general-purpose filter paper has too large pores to remove viruses. In 2014, the group has described for the first time a paper filter that can remove large size viruses, such as influenza virus.

Small size viruses have been much harder to get rid of, as they are extremely resistant to physical and chemical inactivation. A successful filter should not only remove viruses but also feature high flow, low fouling, and long life-time, which makes advanced filters very expensive to develop. Now, with the breakthrough achieved using the mille-feuille filter the long awaited shift to affordable advanced filtration solutions may at last become a reality. Another application of the filter includes production of therapeutic proteins and vaccines.

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

Mille-feuille paper: a novel type of filter architecture for advanced virus separation applications by Simon Gustafsson, Pascal Lordat, Tobias Hanrieder, Marcel Asper,  Oliver Schaeferb, and Albert Mihranyan, Mater. Horiz., 2016, Advance Article DOI: 10.1039/C6MH00090H First published online 18 May 2016

This paper is behind a paywall.

Extreme water repellency achieved by combining nanostructured surfaces with Leidenfrost effect

Apparently a new twist has been added to the water repellency story. From a May 17, 2016 news item on ScienceDaily,

What do you get if you combine nanotextured ‘Cassie’ surfaces with the Leidenfrost effect? Highly water-repellent surfaces that show potential for developing future self-cleaning windows, windshields, exterior paints and more [sic]

Combining superhydrophobic surfaces with Leidenfrost levitation–picture a water droplet hovering over a hot surface rather than making physical contact with it–has been explored extensively for the past decade by researchers hoping to uncover the holy grail of water-repellent surfaces.

A May 17, 2016 American Institute of Physics news release on EurekAlert, which originated the news item, provides more detail about the work,

In a new twist, a group of South Korean researchers from Seoul National University and Dankook University report an anomalous water droplet-bouncing phenomenon generated by Leidenfrost levitation on nanotextured surfaces in Applied Physics Letters, from AIP Publishing.

“Wettability plays a key role in determining the equilibrium contact angles, contact angle hysteresis, and adhesion between a solid surface and liquid, as well as the retraction process of a liquid droplet impinged on the surface,” explained Doo Jin Lee, lead author, and a postdoctoral researcher in the Department of Materials and Engineering at Seoul National University.

Nonwetting surfaces tend to be created by one of two methods. “First, textured surfaces enable nonwettability because a liquid can’t penetrate into the micro- or nano-features, thanks to air entrapment between asperities on the textured materials,” Lee said.

Or, second, the Leidenfrost effect “can help produce a liquid droplet dancing on a hot surface by floating it on a cushion of its own vapor,” he added. “The vapor film between the droplet and heated surface allows the droplet to bounce off the surface–also known as the ‘dynamic Leidenfrost phenomenon.'”

Lee and colleagues developed a special “nonwetting, nanotextured surface” so they could delve into the dynamic Leidenfrost effect’s impact on the material.

“Our nanotextured surface was verified to be ‘nonwetting’ via thermodynamic analysis,” Lee elaborated. “This analytical approach shows that the water droplet isn’t likely to penetrate into the surface’s nanoholes, which is advantageous for designing nonwetting, water-repellant systems. And the water droplet bouncing was powered by the synergetic combination of the nonwetting surface–often called a ‘Cassie surface’–and the Leidenfrost effect.”

By comparing the hydrophobic surface and nanotextured surface, the group discovered that enhanced water droplet bouncing was created by the combined impact of the Leidenfrost levitation and the nonwetting Cassie state.

“A thermodynamic approach predicts the nonwettability on the nanotextured surface, and a scaling law between the capillary and vapor pressure of the droplet explains the mechanism of the dynamic Leidenfrost phenomenon,” said Lee.

These findings should “be of value for a wide range of research areas, such as the study of nonwetting surfaces by the Leidenfrost effect and nanotextured features, enhanced liquid droplet bouncing, and film boiling of liquid droplets on heated Cassie surfaces,” he added.

Significantly, the group’s work furthers the fundamental understanding of the dynamic Leidenfrost droplet levitation and droplet-bouncing phenomena on hydrophobic and nanoengineered surfaces. This means that it will be useful for developing highly water-repellant surfaces for industrial applications such as self-cleaning windows, windshields, exterior paints, anti-fouling coatings, roof tiles, and textiles in the future.

“Our future work will focus on developing multiscale structures with microscale and nanoscale regularities, and explore the nonwetting characteristics of their surfaces with the dynamic Leidenfrost effect,” Lee noted.

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

Anomalous water drop bouncing on a nanotextured surface by the Leidenfrost levitation by Doo Jin Lee and Young Seok Song.  Appl. Phys. Lett. 108, 201604 (2016); http://dx.doi.org/10.1063/1.4948769

This paper appears to be open access.

Nanoparticles in baby formula

Needle-like particles of hydroxyapatite found in infant formula by ASU researchers. Westerhoff and Schoepf/ASU, CC BY-ND

Needle-like particles of hydroxyapatite found in infant formula by ASU [Arizona State University] researchers. Westerhoff and Schoepf/ASU, CC BY-ND

Nanowerk is featuring an essay about hydroxyapatite nanoparticles in baby formula written by Dr. Andrew Maynard in a May 17, 2016 news item (Note: A link has been removed),

There’s a lot of stuff you’d expect to find in baby formula: proteins, carbs, vitamins, essential minerals. But parents probably wouldn’t anticipate finding extremely small, needle-like particles. Yet this is exactly what a team of scientists here at Arizona State University [ASU] recently discovered.

The research, commissioned and published by Friends of the Earth (FoE) – an environmental advocacy group – analyzed six commonly available off-the-shelf baby formulas (liquid and powder) and found nanometer-scale needle-like particles in three of them. The particles were made of hydroxyapatite – a poorly soluble calcium-rich mineral. Manufacturers use it to regulate acidity in some foods, and it’s also available as a dietary supplement.

Andrew’s May 17, 2016 essay first appeared on The Conversation website,

Looking at these particles at super-high magnification, it’s hard not to feel a little anxious about feeding them to a baby. They appear sharp and dangerous – not the sort of thing that has any place around infants. …

… questions like “should infants be ingesting them?” make a lot of sense. However, as is so often the case, the answers are not quite so straightforward.

Andrew begins by explaining about calcium and hydroxyapatite (from The Conversation),

Calcium is an essential part of a growing infant’s diet, and is a legally required component in formula. But not necessarily in the form of hydroxyapatite nanoparticles.

Hydroxyapatite is a tough, durable mineral. It’s naturally made in our bodies as an essential part of bones and teeth – it’s what makes them so strong. So it’s tempting to assume the substance is safe to eat. But just because our bones and teeth are made of the mineral doesn’t automatically make it safe to ingest outright.

The issue here is what the hydroxyapatite in formula might do before it’s digested, dissolved and reconstituted inside babies’ bodies. The size and shape of the particles ingested has a lot to do with how they behave within a living system.

He then discusses size and shape, which are important at the nanoscale,

Size and shape can make a difference between safe and unsafe when it comes to particles in our food. Small particles aren’t necessarily bad. But they can potentially get to parts of our body that larger ones can’t reach. Think through the gut wall, into the bloodstream, and into organs and cells. Ingested nanoscale particles may be able to interfere with cells – even beneficial gut microbes – in ways that larger particles don’t.

These possibilities don’t necessarily make nanoparticles harmful. Our bodies are pretty well adapted to handling naturally occurring nanoscale particles – you probably ate some last time you had burnt toast (carbon nanoparticles), or poorly washed vegetables (clay nanoparticles from the soil). And of course, how much of a material we’re exposed to is at least as important as how potentially hazardous it is.

Yet there’s a lot we still don’t know about the safety of intentionally engineered nanoparticles in food. Toxicologists have started paying close attention to such particles, just in case their tiny size makes them more harmful than otherwise expected.

Currently, hydroxyapatite is considered safe at the macroscale by the US Food and Drug Administration (FDA). However, the agency has indicated that nanoscale versions of safe materials such as hydroxyapatite may not be safe food additives. From Andrew’s May 17, 2016 essay,

Hydroxyapatite is a tough, durable mineral. It’s naturally made in our bodies as an essential part of bones and teeth – it’s what makes them so strong. So it’s tempting to assume the substance is safe to eat. But just because our bones and teeth are made of the mineral doesn’t automatically make it safe to ingest outright.

The issue here is what the hydroxyapatite in formula might do before it’s digested, dissolved and reconstituted inside babies’ bodies. The size and shape of the particles ingested has a lot to do with how they behave within a living system. Size and shape can make a difference between safe and unsafe when it comes to particles in our food. Small particles aren’t necessarily bad. But they can potentially get to parts of our body that larger ones can’t reach. Think through the gut wall, into the bloodstream, and into organs and cells. Ingested nanoscale particles may be able to interfere with cells – even beneficial gut microbes – in ways that larger particles don’t.These possibilities don’t necessarily make nanoparticles harmful. Our bodies are pretty well adapted to handling naturally occurring nanoscale particles – you probably ate some last time you had burnt toast (carbon nanoparticles), or poorly washed vegetables (clay nanoparticles from the soil). And of course, how much of a material we’re exposed to is at least as important as how potentially hazardous it is.Yet there’s a lot we still don’t know about the safety of intentionally engineered nanoparticles in food. Toxicologists have started paying close attention to such particles, just in case their tiny size makes them more harmful than otherwise expected.

Putting particle size to one side for a moment, hydroxyapatite is classified by the US Food and Drug Administration (FDA) as “Generally Regarded As Safe.” That means it considers the material safe for use in food products – at least in a non-nano form. However, the agency has raised concerns that nanoscale versions of food ingredients may not be as safe as their larger counterparts.Some manufacturers may be interested in the potential benefits of “nanosizing” – such as increasing the uptake of vitamins and minerals, or altering the physical, textural and sensory properties of foods. But because decreasing particle size may also affect product safety, the FDA indicates that intentionally nanosizing already regulated food ingredients could require regulatory reevaluation.In other words, even though non-nanoscale hydroxyapatite is “Generally Regarded As Safe,” according to the FDA, the safety of any nanoscale form of the substance would need to be reevaluated before being added to food products.Despite this size-safety relationship, the FDA confirmed to me that the agency is unaware of any food substance intentionally engineered at the nanoscale that has enough generally available safety data to determine it should be “Generally Regarded As Safe.”Casting further uncertainty on the use of nanoscale hydroxyapatite in food, a 2015 report from the European Scientific Committee on Consumer Safety (SCCS) suggests there may be some cause for concern when it comes to this particular nanomaterial.Prompted by the use of nanoscale hydroxyapatite in dental products to strengthen teeth (which they consider “cosmetic products”), the SCCS reviewed published research on the material’s potential to cause harm. Their conclusion?

The available information indicates that nano-hydroxyapatite in needle-shaped form is of concern in relation to potential toxicity. Therefore, needle-shaped nano-hydroxyapatite should not be used in cosmetic products.

This recommendation was based on a handful of studies, none of which involved exposing people to the substance. Researchers injected hydroxyapatite needles directly into the bloodstream of rats. Others exposed cells outside the body to the material and observed the effects. In each case, there were tantalizing hints that the small particles interfered in some way with normal biological functions. But the results were insufficient to indicate whether the effects were meaningful in people.

As Andrew also notes in his essay, none of the studies examined by the SCCS OEuropean Scientific Committee on Consumer Safety) looked at what happens to nano-hydroxyapatite once it enters your gut and that is what the researchers at Arizona State University were considering (from the May 17, 2016 essay),

The good news is that, according to preliminary studies from ASU researchers, hydroxyapatite needles don’t last long in the digestive system.

This research is still being reviewed for publication. But early indications are that as soon as the needle-like nanoparticles hit the highly acidic fluid in the stomach, they begin to dissolve. So fast in fact, that by the time they leave the stomach – an exceedingly hostile environment – they are no longer the nanoparticles they started out as.

These findings make sense since we know hydroxyapatite dissolves in acids, and small particles typically dissolve faster than larger ones. So maybe nanoscale hydroxyapatite needles in food are safer than they sound.

This doesn’t mean that the nano-needles are completely off the hook, as some of them may get past the stomach intact and reach more vulnerable parts of the gut. But the findings do suggest these ultra-small needle-like particles could be an effective source of dietary calcium – possibly more so than larger or less needle-like particles that may not dissolve as quickly.

Intriguingly, recent research has indicated that calcium phosphate nanoparticles form naturally in our stomachs and go on to be an important part of our immune system. It’s possible that rapidly dissolving hydroxyapatite nano-needles are actually a boon, providing raw material for these natural and essential nanoparticles.

While it’s comforting to know that preliminary research suggests that the hydroxyapatite nanoparticles are likely safe for use in food products, Andrew points out that more needs to be done to insure safety (from the May 17, 2016 essay),

And yet, even if these needle-like hydroxyapatite nanoparticles in infant formula are ultimately a good thing, the FoE report raises a number of unresolved questions. Did the manufacturers knowingly add the nanoparticles to their products? How are they and the FDA ensuring the products’ safety? Do consumers have a right to know when they’re feeding their babies nanoparticles?

Whether the manufacturers knowingly added these particles to their formula is not clear. At this point, it’s not even clear why they might have been added, as hydroxyapatite does not appear to be a substantial source of calcium in most formula. …

And regardless of the benefits and risks of nanoparticles in infant formula, parents have a right to know what’s in the products they’re feeding their children. In Europe, food ingredients must be legally labeled if they are nanoscale. In the U.S., there is no such requirement, leaving American parents to feel somewhat left in the dark by producers, the FDA and policy makers.

As far as I’m aware, the Canadian situation is much the same as the US. If the material is considered safe at the macroscale, there is no requirement to indicate that a nanoscale version of the material is in the product.

I encourage you to read Andrew’s essay in its entirety. As for the FoE report (Nanoparticles in baby formula: Tiny new ingredients are a big concern), that is here.

Hologram with nanostructures could improve fraud protection

This research on holograms comes from Harvard University according to a May 13, 2016 news item on ScienceDaily,

Holograms are a ubiquitous part of our lives. They are in our wallets — protecting credit cards, cash and driver’s licenses from fraud — in grocery store scanners and biomedical devices.

Even though holographic technology has been around for decades, researchers still struggle to make compact holograms more efficient, complex and secure.

Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences have programmed polarization into compact holograms. These holograms use nanostructures that are sensitive to polarization (the direction in which light vibrates) to produce different images depending on the polarization of incident light. This advancement, which works across the spectrum of light, improves anti-fraud holograms as well as those used in entertainment displays.

A May 13, 2016 Harvard University press release (also on EurekAlert) by Leah Burrows, which originated the news item, provides more detail,

“The novelty in this research is that by using nanotechnology, we’ve made holograms that are highly efficient, meaning that very little light is lost to create the image,” said Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering and senior author of the paper. “By using incident polarized light, you can see far a crisper image and can store and retrieve more images. Polarization adds another dimension to holograms that can be used to protect against counterfeiting and in applications like displays.”

Harvard’s Office of Technology Development has filed patents on this and related technologies and is actively pursuing commercial opportunities.

Holograms, like digital photographs, capture a field of light around an object and encode it on a chip. However, photographs only record the intensity of light while holograms also capture the phase of light, which is why holograms appear three-dimensional.

“Our holograms work like any other but the image produced depends on the polarization state of the illuminating light, providing an extra degree of freedom in design for versatile applications,” said Mohammadreza Khorasaninejad, postdoctoral fellow in the Capasso Lab and first author of the paper.

There are several states of polarization. In linearly polarized light the direction of vibration remains constant while in circularly polarized light it rotates clockwise or counterclockwise. The direction of rotation is the chirality.

The team built silicon nanostructured patterns on a glass substrate, which act as superpixels. Each superpixel responds to a certain polarization state of the incident light. Even more information can be encoded in the hologram by designing and arranging the nanofins to respond differently to the chirality of the polarized incident light.

“Being able to encode chirality can have important applications in information security such as anti-counterfeiting,” said Antonio Ambrosio, a research scientist in the Capasso Lab and co-first author. “For example, chiral holograms can be made to display a sequence of certain images only when illuminated with light of specific polarization not known to the forger.”

“By using different nanofin designs in the future, one could store and retrieve far more images by employing light with many states of polarization,” said Capasso.

Because this system is compact, it has application in portable projectors, 3D movies and wearable optics.

“Modern polarization imaging systems require cascading several optical components such as beam splitters, polarizers and wave plates,” said Ambrosio. “Our metasurface can distinguish between incident polarization using a single layer dielectric surface.”

“We have also incorporated in some of the holograms a lens function that has allowed us to produce images at large angles,” said Khorasaninejad. “This functionality combined with the small footprint and lightweight, has significant potential for wearable optics applications.”

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

Broadband and chiral binary dielectric meta-holograms by Mohammadreza Khorasaninejad, Antonio Ambrosio, Pritpal Kanhaiya, and Federico Capasso. Science Advances  13 May 2016: Vol. 2, no. 5, e1501258 DOI: 10.1126/sciadv.1501258

This paper is open access.