Category Archives: biomimcry

Inhibiting viruses with nanocrystalline cellulose (NCC) in Finland

Research and interest in cellulose nanomaterials of one kind or another seems to be reaching new heights. That’s my experience since this is my third posting on the topic in one week.

The latest research features NCC (nanocrystalline cellulose [NCC] or, as it’s sometimes known, cellulose nanocrystals [CNC]) ,as a ‘viral inhibitor’ and is described in an April 15, 2014 news item on Nanowerk,

Researchers from Aalto University [Finland] and and the University of Eastern Finland have succeeded in creating a surface on nano-sized cellulose crystals that imitates a biological structure. The surface adsorbs viruses and disables them. The results can prove useful in the development of antiviral ointments and surfaces, for instance.

There are many viral diseases in the world for which no pharmaceutical treatment exists. These include, among others, dengue fever, which is spread by mosquitoes in the tropics, as well as a type of diarrhea, which is more familiar in Finland and is easily spread by the hands and can be dangerous especially for small children and the elderly.

An April 15, 2014 Aalto University news release, which originated the news item, provides more detail,

Researchers at Aalto University and the University of Eastern Finland have now succeeded in preliminary tests to prevent the spread of one type of virus into cells with the help of a new type of nanocrystalline cellulose. Nano-sized cellulose crystals were manufactured out of cotton fibre or filter paper with the help of sulphuric acid, causing sulphate ions with negative charges to attach to their surfaces. The ions then attached to alphaviruses used in the test and neutralised them. When the researchers replaced the sulphate ions with cellulose derivatives that imitate tyrosine sulphates, the activity of the viruses was further reduced. The experiments succeeded in preventing viral infection in 88-100 percent of the time with no noticeable effect on the viability of the cells by the nanoparticles. The research findings were published in the journal Biomacromolecules.

Here’s a diagram illustrating how the new type of NCC works,

Courtesy of Aalto University

Courtesy of Aalto University

The news release includes perspectives from the researchers,

’Certain cellulose derivatives had been seen to have an impact on viruses before. The nano scale increases the proportion of the surface area to that of the number of grams to a very high level, which is an advantage, because viruses specifically attach themselves to surfaces. Making the cellulose crystals biomimetic, which means that they mimic biological structures, was an important step, as we know that in nature viruses often interact specifically with tyrosine structures,’ he [Jukka Seppälä, Professor of Polymer Technology at Aalto University] says.

Both Jukka Seppälä and Ari Hinkkanen, Professor of Gene Transfer Technology at the University of Eastern Finland, emphasise that the research is still in the early stages.

‘Now we know that the attachment of a certain alphavirus can be effectively prevented when we use large amounts of nanocrystalline cellulose.  Next we need to experiment with other alpha viruses and learn to better understand the mechanisms that prevent viral infection. In addition, it is necessary to ascertain if cellulose can also block other viruses and in what conditions, and to investigate whether or not the sulphates have a deleterious effects on an organism,’ Ari Hinkkanen explains.

According to Kristiina Järvinen, Professor of Pharmaceutical Technology at the University of Eastern Finland, there are many routes that can be taken in the commercialisation of the results. The development of an antiviral medicine is the most distant of these; the idea could be sooner applied in disinfectant ointments and coatings, for instance.

‘It would be possible to provide protection against viruses, spread by mosquitoes, by applying ointment containing nanocrystalline cellulose onto the skin. Nanocrystalline cellulose applied on hospital door handles could kill viruses and prevent them from spreading.  However, we first need to ascertain if the compounds will remain effective in a non-liquid form and how they work in animal tests,’ she ponders.

For the curious, here’s a link to and a citation for the paper,

Synthesis of Cellulose Nanocrystals Carrying Tyrosine Sulfate Mimetic Ligands and Inhibition of Alphavirus Infection by Justin O. Zoppe, Ville Ruottinen, Janne Ruotsalainen, Seppo Rönkkö, Leena-Sisko Johansson, Ari Hinkkanen, Kristiina Järvinen, and Jukka Seppälä. Biomacromolecules, 2014, 15 (4), pp 1534–1542 DOI: 10.1021/bm500229d Publication Date (Web): March 14, 2014

Copyright © 2014 American Chemical Society

This paper is behind a paywall.

As for my other recent postings on cellulose nanomaterials, there’s this April 14, 2014 piece titled: Preparing nanocellulose for eventual use in dressings for wounds and this from April 10, 2014 titled: US Dept. of Agriculture wants to commercialize cellulose nanomaterials.

ATMs (automated teller machines) fend off attackers with biomimicry and nanoparticles

Attack an ATM (automated teller machine) and you will be in peril one day soon, if Swiss researchers at ETH Zurich (Swiss Federal Institute of Technology in Zurich) have their way. An April 11, 2014 news item on Nanowerk describes the inspiration,

Hot foam may soon send criminals running if they damage [an] ATM. ETH researchers have developed a special film that triggers an intense reaction when destroyed. The idea originates from a beetle that uses a gas explosion to fend off attackers.

An April 11, 2014 ETH Zurich news release (also on EurekAlert), which originated the news, item, provides more details about the insect inspiring this new approach to protecting ATMs and information about the increase of ATM attacks,

Its head and pronotum are usually rusty red, and its abdomen blue or shiny green: the bombardier beetle is approximately one centimetre long and common to Central Europe. At first glance, it appears harmless, but it possesses what is surely the most aggressive chemical defence system in nature. When threatened, the bombardier beetle releases a caustic spray, accompanied by a popping sound. This spray can kill ants or scare off frogs. The beetle produces the explosive agent itself when needed. Two separately stored chemicals are mixed in a reaction chamber in the beetle’s abdomen. An explosion is triggered with the help of catalytic enzymes.

“When you see how elegantly nature solves problems, you realise how deadlocked the world of technology often is,” says Wendelin Jan Stark, a professor from the ETH Department of Chemistry and Applied Biosciences. He and his team therefore looked to the bombardier beetle for inspiration and developed a chemical defence mechanism designed to prevent vandalism – a self-defending surface composed of several sandwich-like layers of plastic. If the surface is damaged, hot foam is sprayed in the face of the attacker. This technology could be used to prevent vandalism or protect valuable goods. “This could be used anywhere you find things that shouldn’t be touched,” said Stark. In agriculture and forestry, for example, it could be used to keep animals from gnawing on trees.

The newly developed film may be particularly well suited to protecting ATMs or cash transports, write the researchers in their paper published in the Journal of Materials Chemistry A. In ATMs, banknotes are kept in cash boxes, which are exchanged regularly. The Edinburgh-based European ATM Security Team reports that the number of attacks on ATMs has increased in recent years. During the first half of 2013, more than 1,000 attacks on ATMs took place in Europe, resulting in losses of EUR 10 million.

While protective devices that can spray robbers and banknotes already exist, these are mechanical systems, explains Stark. “A small motor is set in motion when triggered by a signal from a sensor. This requires electricity, is prone to malfunctions and is expensive.” The objective of his research group is to replace complicated control systems with cleverly designed materials.

More technical information about the films and about an earlier project applying a similar technology to seeds is offered in the news release,

The researchers use plastic films with a honeycomb structure for their self-defending surface. The hollow spaces are filled with one of two chemicals: hydrogen peroxide or manganese dioxide. The two separate films are then stuck on top of each another. A layer of clear lacquer separates the two films filled with the different chemicals. When subjected to an impact, the interlayer is destroyed, causing the hydrogen peroxide and manganese dioxide to mix. This triggers a violent reaction that produces water vapour, oxygen and heat. Whereas enzymes act as catalysts in the bombardier beetle, manganese dioxide has proven to be a less expensive alternative for performing this function in the lab.

The researchers report that the product of the reaction in the film is more of a foam than a spray when compared to the beetle, as can be seen in slow motion video footage. Infrared images show that the temperature of the foam reaches 80 degrees. Just as in nature, very little mechanical energy is required in the laboratory to release a much greater amount of chemical energy – quite similar to a fuse or an electrically ignited combustion cycle in an engine.

To protect the cash boxes, the researchers prepare the film by adding manganese dioxide. They then add a dye along with DNA enveloped in nanoparticles. If the film is destroyed, both the foam and the dye are released, thereby rendering the cash useless. The DNA nanoparticles that are also released mark the banknotes so that their path can be traced. Laboratory experiments with 5 euro banknotes have shown that the method is effective. The researchers write that the costs are also reasonable and expect one square meter of film to cost approximately USD 40.

In a similar earlier project, ETH researchers developed a multi-layer protective envelope for seed that normally undergoes complex chemical treatment. Researchers emulated the protective mechanism of peaches and other fruit, which releases toxic hydrogen cyanide to keep the kernels from being eaten. Wheat seeds are coated with substances that also form hydrocyanic acid when they react. However, the base substances are separated from each other in different layers and react only when the seeds are bitten by a herbivore. Stark describes the successful research method as “imitating nature and realising simple ideas with high-tech methods.”

Here are links to and citations for both research papers (ATM & seeds),

Self-defending anti-vandalism surfaces based on mechanically triggered mixing of reactants in polymer foils by Jonas G. Halter, Nicholas H. Cohrs, Nora Hild, Daniela Paunescu, Robert N. Grass, and Wendelin Jan Stark. J. Mater. Chem. A, 2014, DOI: 10.1039/C3TA15326F First published online 07 Mar 2014

Induced cyanogenesis from hydroxynitrile lyase and mandelonitrile on wheat with polylactic acid multilayer-coating produces self-defending seeds by Jonas G. Halter, Weida D. Chen, Nora Hild, Carlos A. Mora, Philipp R. Stoessel, Fabian M. Koehler, Robert N. Grass, and Wendelin J. Stark. J. Mater. Chem. A, 2014,2, 853-858 DOI: 10.1039/C3TA14249C
First published online 03 Dec 2013

The ‘anti-vandalism’ paper is open access but the ‘cyanogenesis’ paper is not. As for the beetle who inspired this work, here’s an image of one courtesy of ETH,

The bombardier beetle inspired the researchers of ETH Zurich. (Photo: jayvee18 – Fotolia)

The bombardier beetle inspired the researchers of ETH Zurich. (Photo: jayvee18 – Fotolia)

It looks rather pretty with its hard green (iridescent?) back shell.

Biomimicry book focusses on adhesive and non-adhesive properties

While I’m not familiar with Emiliano Lepore’s work, his co-author’s name, Nicola Pugno, rang a bell; he’s mentioned in my Feb. 3, 2012 posting about spiderwebs and strength and in my Nanotech Mysteries wiki entry, ‘Scientists read comics, watch tv, and more‘ about adhesive properties at the nanoscale. The two men have authored a book, ‘An Experimental Study on Adhesive or Anti-Adhesive, Bio-Inspired Experimental Nanomaterials‘ (print version) according to an April 2, 2014 news item on Nanowerk (Note: A link has been removed),

While recognising that bio-inspiration for technological development is already an established concept, “An Experimental Study on Adhesive or Anti-Adhesive, Bio-Inspired Experimental Nanomaterials” by Italian scientists Emiliano Lepore and Nicola Pugno, released in Open Access by De Gruyter Open, sets out to explore the potential of three categories of bio-inspired materials, namely, adhesives, anti-adhesives, and materials designed to offer exceptional characteristics – particularly in terms of their strength-to-weight ratio. In each of these areas, the technologies, which are currently at the forefront of scientific research, are described in relation to how they have been inspired by nature in an attempt to optimise their physical characteristics and performance in operation, with an aim to design and develop new innovative products.

Lepore and Pugno investigate a wide range of natural systems and employ original experimental procedures, the book additionally stands out for its rigorous and innovative approach to biomaterials. For example, the challenge of creating strong, reliable and affordable adhesives appears in numerous areas of engineering, such as the development of aircrafts, and all types of vehicles for transportation on land or water, where the need to save energy consumption by reducing weight is of paramount importance. There is also a specific interest in bonding dissimilar materials, which due to their physical properties prohibit the application of more conventional joining techniques. In this field, inspiration has been sought by investigating the adhesive abilities of insects, spiders, and reptiles.

The book published by De Gruyter is available in a free PDF format in addition to the print version which can be purchased through Amazon.

Bioceramic armour: tough and clear

This story about a mollusk and its armour eventually led me back to one of my favourite science writers, David L. Chandler at the Massachusetts Institute of Technology (MIT). First, here’s an excerpt from a March 30, 2014 news item on ScienceDaily,

The shells of a sea creature, the mollusk Placuna placenta, are not only exceptionally tough, but also clear enough to read through. Now, researchers at MIT have analyzed these shells to determine exactly why they are so resistant to penetration and damage — even though they are 99 percent calcite, a weak, brittle mineral.

The shells’ unique properties emerge from a specialized nanostructure that allows optical clarity, as well as efficient energy dissipation and the ability to localize deformation, the researchers found. The results are published this week in the journal Nature Materials, in a paper co-authored by MIT graduate student Ling Li and professor Christine Ortiz.

A March 30, 2014 MIT press release (I’m not positive Chandler wrote this but he is the press contact) describes both the engineered bioceramic armour and the mollusk’s naturally occurring armour,

Engineered ceramic-based armor, while designed to resist penetration, often lacks the ability to withstand multiple blows, due to large-scale deformation and fracture that can compromise its structural integrity, Ortiz says. In transparent armor systems, such deformation can also obscure visibility.

Creatures that have evolved natural exoskeletons — many of them ceramic-based — have developed ingenious designs that can withstand multiple penetrating attacks from predators. The shells of a few species, such as Placuna placenta, are also optically clear.

To test exactly how the shells — which combine calcite with about 1 percent organic material — respond to penetration, the researchers subjected samples to indentation tests, using a sharp diamond tip in an experimental setup that could measure loads precisely. They then used high-resolution analysis methods, such as electron microscopy and diffraction, to examine the resulting damage.

The material initially isolates damage through an atomic-level process called “twinning” within the individual ceramic building blocks: A crystal breaks up into a pair of mirror-image regions that share a common boundary, rather like a butterfly’s wings. This twinning process occurs all around the stressed region, helping to form a kind of boundary that keeps the damage from spreading outward.

The MIT researchers found that twinning then activates “a series of additional energy-dissipation mechanisms … which preserve the mechanical and optical integrity of the surrounding material,” Li says. This produces a material that is 10 times more efficient in dissipating energy than the pure mineral, Li adds.

The properties of this natural armor make it a promising template for the development of bio-inspired synthetic materials for both commercial and military applications — such as eye and face protection for soldiers, windows and windshields, and blast shields, Ortiz says.

Huajian Gao, a professor of engineering at Brown University who was not involved in this research, calls it “an excellent and elegant piece of work.” He says it “successfully demonstrates the effectiveness of nanoscale deformation twins in energy dissipation in bioceramics, and should be able to inspire and guide the development of manmade ceramic materials.” He adds, “As a first-of-its-kind [demonstration of] the effectiveness of deformation twins in natural materials, this work should have huge practical impact.”

The work was supported by the National Science Foundation; the U.S. Army Research Office through the MIT Institute for Soldier Nanotechnologies; the National Security Science and Engineering Faculty Fellowships Program; and the Office of the Assistant Secretary of Defense for Research and Engineering.

The researchers have produced an image showing how the mollusk shell reacts to being damaged,

A Scanning Electron Microscope (SEM) image of the region surrounding an indentation the researchers made in a piece of shell from Placuna placenta. The image shows the localization of damage to the area immediately surrounding the stress. Image: Ling Li and James C. Weaver. Courtesy: MIT

A Scanning Electron Microscope (SEM) image of the region surrounding an indentation the researchers made in a piece of shell from Placuna placenta. The image shows the localization of damage to the area immediately surrounding the stress.
Image: Ling Li and James C. Weaver. Courtesy: MIT

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

Pervasive nanoscale deformation twinning as a catalyst for efficient energy dissipation in a bioceramic armour by Ling Li & Christine Ortiz. Nature Materials (2014) doi:10.1038/nmat3920 Published online 30 March 2014

This paper is behind a paywall.

One tough mother, imitating mother-of-pearl for stronger ceramics

I love mother-of-pearl or nacre as it’s also known,

The iridescent nacre inside a Nautilus shell cut in half. The chambers are clearly visible and arranged in a logarithmic spiral. Photo taken by me -- Chris 73 | Talk 12:40, 5 May 2004 (UTC)

The iridescent nacre inside a Nautilus shell cut in half. The chambers are clearly visible and arranged in a logarithmic spiral.
Photo taken by me — Chris 73 | Talk 12:40, 5 May 2004 (UTC)

We had a mother-of-pearl-covered shell when I was a child one I loved to hold but ours had a blue-black sheen. Enough of this trip down memory lane, it turns out that nacre has inspired a new type of stronger ceramic material from scientists at the Centre national de la recherche scientifique (CNRS) as a March 24, 2014 news item on ScienceDaily notes,

Whether traditional or derived from high technology, ceramics all have the same flaw: they are fragile. Yet this characteristic may soon be a thing of the past: a team of researchers led by the Laboratoire de Synthèse et Fonctionnalisation des Céramiques (CNRS/Saint-Gobain), in collaboration with the Laboratoire de Géologie de Lyon: Terre, Planètes et Environnement (CNRS/ENS de Lyon/Université Claude Bernard Lyon 1) and the Laboratoire Matériaux: Ingénierie et Science (CNRS/INSA Lyon/Université Claude Bernard Lyon 1), has recently presented a new ceramic material inspired by mother-of-pearl from the small single-shelled marine mollusk abalone.

This material, almost ten times stronger than a conventional ceramic, is the result of an innovative manufacturing process that includes a freezing step. This method appears to be compatible with large-scale industrialization and should not be much more expensive than the techniques already in use.

The CNRS March 21,2014 press release, which originated the news item, describes the properties of nacre which excited the scientists and the way in which they mimicked those properties in a synthetic material,

Toughness, i.e. the ability of a material containing a crack to resist fracture, is considered to be the Achilles heel of ceramics. To compensate for their intrinsic fragilit y, these are sometimes combined with tougher materials such as metals or polymers — generally leading to varying degrees of limitations. For example, polymers cannot resist temperatures above 300°C, which restricts their use in motors or ovens.

A material similar to ceramic, although extremely tough, is found in nature. Mother-of-pearl, which covers the shells of abalone and some bivalves, is 95% composed of calcium carbonate (aragonite), an intrinsically fragile material that is nonetheless very tough. Mother-of-pearl can be seen as a stack of small bricks, welded together with mortar composed of proteins. Its toughness is due to its complex, hierarchical structure where cracks must follow a tortuous path to propagate. It is this structure that inspired the researchers.

As a base ingredient, the team from the Laboratoire de Synthèse et Fonctionnalisation des Céramiques (CNRS/Saint-Gobain) used a common ceramic powder, alumina, in the form of microscopic platelets. To obtain the layered mother-of-pearl structure, they suspended this powder in water. The colloidal suspension (1) was then cooled to obtain controlled ice crystal growth, caus ing alumina to self-assemble in the form of stacks of platelets. The final material was subsequently obtained from a high temperature densification step.

This artificial mother-of-pearl is ten times tougher than a conventional alumina ceramic. This is because a crack has to move round the alumina “bricks” one by one to propagate. This zigzag pathway prevents it from crossing the material easily.

One of the advantages of the process is that it is not exclusive to alumina. Any ceramic powder, as long as it is in the form of platelets, can self-assemble via the same process, which could easily be used on an industrial scale. This bio-inspired material’s toughness for equivalent density could make it possible to produce smaller, lighter parts with no significant increase in costs. This invention could become a material of choice for applications subjected to severe constraints in fields ranging from energy to armor plating.

For those who like their communiqué de presse en français,

Les céramiques, qu’elles soient traditionnelles ou de haute technologie, présentent toutes un défaut : leur fragilité. Ce côté cassant pourrait bientôt disparaître : une équipe de chercheurs, menée par le Laboratoire de synthèse et fonctionnalisation des céramiques (CNRS/Saint-Gobain), en collaboration avec le Laboratoire de géologie de Lyon : Terre, planètes et environnement (CNRS/ENS de Lyon/Université Claude Bernard Lyon 1) et le laboratoire Matériaux : ingénierie et science (CNRS/INSA Lyon/Université Claude Bernard Lyon 1) vient de présenter un nouveau matériau céramique inspiré de la nacre des ormeaux, petits mollusques marins à coquille unique. Ce matériau, près de dix fois plus tenace qu’une céramique classique, est issu d’un procédé de fabrication innovant qui passe par une étape de congélation. Cette méthode semble compatible avec une industrialisation à échelle plus importante, à priori sans surcoût notable par rapport à celles déjà employées. Conservant ses propriétés à des températures d’au moins 600°C, cette nacre artificielle pourrait trouver une foule d’applications dans l’industrie et permettre d’alléger ou de réduire en taille des éléments céramiques des moteurs ou des dispositifs de génération d’énergie. Ces travaux sont publiés le 23 mars 2014 sur le site internet de la revue Nature Materials.

La ténacité, capacité d’un matériau à résister à la rupture en présence d’une fissure, est considérée comme le talon d’Achille des céramiques. Pour pallier leur fragilité intrinsèque, celles-ci sont parfois combinées à d’autres matériaux plus tenaces, métalliques ou polymères. L’adjonction de tels matériaux s’accompagne généralement de limitations plus ou moins sévères. Par exemple, les polymères ne résistent pas à des températures supérieures à 300°C, ce qui limite leur utilisation dans les moteurs ou les fours.

Dans la nature, il existe un matériau proche de la céramique qui est extrêmement tenace : la nacre qui recouvre la coquille des ormeaux et autres bivalves. La nacre est composée à 95 % d’un matériau intrinsèquement fragile, le carbonate de calcium (l’aragonite). Pourtant, sa ténacité est forte. La nacre peut être vue comme un empilement de briques de petite taille, soudées entre elles par un mortier composé de protéines. Sa ténacité tient à sa structure complexe et hiérarchique. La propagation de fissures dans ce type d’architecture est rendue difficile par le chemin tortueux que celles-ci doivent parcourir pour se propager. C’est cette structure qui a inspiré les chercheurs.

Comme ingrédient de base, l’équipe du Laboratoire de synthèse et fonctionnalisation des céramiques (CNRS/Saint-Gobain) a pris une poudre céramique courante, l’alumine, qui se présente sous la forme de plaquettes microscopiques. Pour obtenir la structure lamellée de la nacre, ils ont mis cette poudre en suspension dans de l’eau. Cette suspension colloïdale (1) a été refroidie de manière à obtenir une croissance contrôlée de cristaux de glace. Ceci conduit à un auto-assemblage de l’alumine sous forme d’un empilement de plaquettes. Finalement, le matériau final a été obtenu grâce à une étape de densification à haute température.

Cette nacre artificielle est dix fois plus tenace qu’une céramique classique composée d’alumine. Ceci est dû au fait qu’une fissure, pour se propager, doit contourner une à une les « briques » d’alumine. Ce chemin en zigzag l’empêche de traverser facilement le volume du matériau.

L’un des avantages du procédé est qu’il n’est pas exclusif à l’alumine. N’importe quelle poudre céramique, pour peu qu’elle se présente sous la forme de plaquettes, peut subir le même processus d’auto-assemblage. De plus, l’industrialisation de ce procédé ne devrait pas présenter de difficultés. L’obtention de pièces composées avec ce matériau bio-inspiré ne devrait pas entraîner de grands surcoûts. Sa forte ténacité pour une densité équivalente pourrait permettre de fabriquer des pièces plus petites et légères. Il pourrait devenir un matériau de choix pour les applications soumises à des contraintes sévères dans des domaines allant de l’énergie au blindage.

Here’s a link to and a citation for the research paper which was published in English,

Strong, tough and stiff bioinspired ceramics from brittle constituents by Florian Bouville, Eric Maire, Sylvain Meille, Bertrand Van de Moortèle, Adam J. Stevenson, & Sylvain Deville. Nature Material (2014) doi:10.1038/nmat3915 Published online 23 March 2014

This paper is behind a paywall.

 

Caltech’s (California Institute of Technology) microbes improve ultrasound imaging

After last week’s (March 17 – 21, 2014) TED blogging marathon I’m finally catching up on my usual topics such as this California Institute of Technology (Caltech) item about micro-organisms being used to develop better ultrasound images. From a March 20, 2014 Caltech news release,

Ultrasounds – one of the most widely used imaging modalities in medicine – could be greatly improved using nanoscale microorganisms.

This transformative new nanotechnology could have a significant impact on ultrasound technology, and opens the door to a variety of potential imaging applications where the nanometer size is advantageous, e.g., in labeling targets outside the bloodstream; in detecting tumors in the body; and in diagnosing the health of the gastrointestinal system.

HERE’S HOW THEY DID IT

Caltech’s Dr. Mikhail Shapiro was interested in developing nanoscale imaging agents for ultrasound to enable non-invasive imaging of a much broader range of biological and biomedical events in the body.  Turning to nature for inspiration, he and his colleagues at Caltech and UC Berkeley, successfully created the first ultrasound imaging agent based on genetically encoded gas-containing structures.

Shapiro’s team utilized photosynthetic micro-organisms that form gas nanostructures called “gas vesicles,” that the researchers discovered were excellent imaging agents for ultrasound, with several unique properties making them especially useful in biomedical applications.

Previously, most ultrasound imaging agents were based on small gas bubbles, which ultrasound can detect because they have a different density than their surroundings and can resonate with sound waves. Unfortunately, these “microbubbles” could only be synthesized at sizes of several microns (or larger) because of their fundamental physics: the smaller you tried to make them, the less stable they became. As a result, they were always confined to the bloodstream and could only image a limited number of biological targets.

The researchers wanted to find another way of making gas-filled structures that could be nanoscale.  In particular, certain photosynthetic micro-organisms regulate their buoyancy by forming protein-shelled gas nanostructures called “gas vesicles” inside the cell body. These structures interact with gas in a way that is fundamentally different from microbubbles, allowing them to have nanometer size. In this study, they discovered that gas vesicles are excellent imaging agents for ultrasound.

The researchers showed that they were able to easily attach biomolecules to the gas vesicle surface to enable targeting. In addition, because these structures are encoded as genes, they now have a chance to modify these genes to optimize gas vesicles’ ultrasound properties.  Already the team has shown that gas vesicles from different species, which vary in genetic sequence, exhibit different properties that can be used to, for example, distinguish them from each other in an ultrasound image.

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

Biogenic gas nanostructures as ultrasonic molecular reporters by Mikhail G. Shapiro, Patrick W. Goodwill, Arkosnato Neogy, Melissa Yin, F. Stuart Foster, David V. Schaffer, & Steven M. Conolly. Nature Nanotechnology (2014) doi:10.1038/nnano.2014.32 Published online 16 March 2014

This paper is behind a paywall.

Kayaks, communication by bacteria, wind power, and biomimcry at TED 2014′s All Stars session 1: Planet Dearth

These are short talks (shorter than the 18 min. TED talk).  Wish I could cover everyone but I’m beginning to tire so I’ve started with George Dyson, historian of science, from his TED biography,

In telling stories of technologies and the individuals who created them, George Dyson takes a clear-eyed view of our scientific past — while illuminating what lies ahead.

Dyson described Vancouver of 16,000 years ago under an ice sheet and then 10,000 years ago people showed up. 5000 years ago the rainforest emerged and became the setting for a culture and society unique in the world. Most traces of that culture are gone.  Dyson then segued into a description of his love for kayaks and how he arrived in Vancouver at age 17 (19?). He now lives in Washington state. He wants to suggest that commercial sail will return or as they are saying in this session, become ‘de-extinct’.

Then there was Bonnie Bassler, molecular biologist, from her TED biography,

Bonnie Bassler studies how bacteria can communicate with one another, through chemical signals, to act as a unit. Her work could pave the way for new, more potent medicine.

She talked about quorum sensing (chemical communication), the means by which bacteria communicate with each other. They in Bassler’s lab can change the molecule which signals quorum sensing the means by which bacteria communicate to create biofilm, a precursor to toxin secretion and infection. (I forget which disease she mentioned) By changing the molecule they can stop the process in the laboratory. You can find out more about bacteria and quorum sensing here.

Next, there was Amory Lovins, physicist and energy guru, from his TED biography (Note: A link has been removed),

Amory Lovins was worried (and writing) about energy long before global warming was making the front — or even back — page of newspapers. Since studying at Harvard and Oxford in the 1960s, he’s written dozens of books, and initiated ambitious projects — cofounding the influential, environment-focused Rocky Mountain Institute; prototyping the ultra-efficient Hypercar — to focus the world’s attention on alternative approaches to energy and transportation.

He talked about wind and solar power and mass production of equipment to produce this energy. He debunked the notion that alternatives such as wind and solar power are not dependable sources by citing statistics from France showing that they can predict how energy is needed and can be produced in situations of uncertainty.

Finally, Robert Full, biologist, from his TED biography,

Robert Full studies cockroach legs and gecko feet. His research is helping build the perfect “distributed foot” for tomorrow’s robots, based on evolution’s ancient engineering.

Difference between human and nature’s design is robustness, i.e., able to adapt to changing terrain and use same structures for different tasks. He also mentions fault tolerance, i.e., change in a structure does not have to unduly affect the animal/insect, e.g., a  cockroach has an alternative means of achieving the same ends, e.g. walking without feet. Full’s conclusion is that you never know where curiosity-driven research will take you as he mentions the possibility of cockroach-inspired robots while showing scenes of disaster (building rubble) where a suit based on an insect exoskeleton which survives compression could be very handy.

Mesenchymal condensation (a process embryos use to begin forming a variety of organs, including teeth, cartilage, bone, muscle, tendon, and kidney) for complex 3D tissue engineering

It seems that there are three strategies for creating complex 3D tissues and until now scientists have used only two of the three. From a March 5, 2014 news item on ScienceDaily,

A bit of pressure from a new shrinking, sponge-like gel is all it takes to turn transplanted unspecialized cells into cells that lay down minerals and begin to form teeth.

The bioinspired gel material could one day help repair or replace damaged organs, such as teeth and bone, and possibly other organs as well, scientists from the Wyss Institute for Biologically Inspired Engineering at Harvard University, Harvard School of Engineering and Applied Sciences (SEAS), and Boston Children’s Hospital report recently in Advanced Materials.

“Tissue engineers have long raised the idea of using synthetic materials to mimic the inductive power of the embryo,” said Don Ingber, M.D., Ph.D., Founding Director of the Wyss Institute, …, Professor of Bioengineering at SEAS, and senior author of the study. “We’re excited about this work because it shows that it really is possible.”

The March 5, 2014 Wyss Institute news release, which originated the news item, delves into the nature of the research,

Embryonic tissues have the power to drive cells and tissues to specialize and form organs. To do that, they employ biomolecules called growth factors to stimulate growth; gene-activating chemicals that cause the cells to specialize, and mechanical forces that modulate cell responses to these other factors.

But so far tissue engineers who want to build organs in the laboratory have employed only two of the three strategies — growth factors and gene-activating chemicals. Perhaps as a result, they have not yet succeeded in producing complex three-dimensional tissues.

A few years ago, Ingber and Tadanori Mammoto, M.D., Ph.D., Instructor in Surgery at Boston Children’s Hospital and Harvard Medical School, investigated a process called mesenchymal condensation that embryos use to begin forming a variety of organs, including teeth, cartilage, bone, muscle, tendon, and kidney.

In mesenchymal condensation, two adjacent tissue layers — loosely packed connective-tissue cells called mesenchyme and sheet-like tissue called an epithelium that covers it — exchange biochemical signals. This exchange causes the mesenchymal cells to squeeze themselves tightly into a small knot directly below where the new organ will form.

Here’s a video from the Wyss Institute illustrating the squeezing process,

When the temperature rises to just below body temperature, this biocompatible gel shrinks dramatically within minutes, bringing tooth-precursor cells (green) closer together. Credit: Basma Hashmi

Getting back to the research (from the news release),

By examining tissues isolated from the jaws of embryonic mice, Mammoto and Ingber showed that when the compressed mesenchymal cells turn on genes that stimulate them to generate whole teeth composed of mineralized tissues, including dentin and enamel.

Inspired by this embryonic induction mechanism, Ingber and Basma Hashmi, a Ph.D. candidate at SEAS who is the lead author of the current paper, set out to develop a way to engineer artificial teeth by creating a tissue-friendly material that accomplishes the same goal. Specifically, they wanted a porous sponge-like gel that could be impregnated with mesenchymal cells, then, when implanted into the body, induced to shrink in 3D to physically compact the cells inside it.

To develop such a material, Ingber and Hashmi teamed up with researchers led by Joanna Aizenberg, Ph.D., a Wyss Institute Core Faculty member who leads the Institute’s Adaptive Materials Technologies platform. Aizenberg is the Amy Smith Berylson Professor of Materials Science at SEAS and Professor of Chemistry and Chemical Biology at Harvard University.

They chemically modified a special gel-forming polymer called PNIPAAm that scientists have used to deliver drugs to the body’s tissues. PNIPAAm gels have an unusual property: they contract abruptly when they warm.

But they do this at a lukewarm temperature, whereas the researchers wanted them to shrink specifically at 37°C — body temperature — so that they’d squeeze their contents as soon as they were injected into the body. Hashmi worked with Lauren Zarzar, Ph.D., a former SEAS graduate student who’s now a postdoctoral associate at Massachusetts Institute of Technology, for more than a year, modifying PNIPAAm and testing the resulting materials. Ultimately, they developed a polymer that forms a tissue-friendly gel with two key properties: cells stick to it, and it compresses abruptly when warmed to body temperature.

As an initial test, Hashmi implanted mesenchymal cells in the gel and warmed it in the lab. Sure enough, when the temperature reached 37°C, the gel shrank within 15 minutes, causing the cells inside the gel to round up, shrink, and pack tightly together.

“The reason that’s cool is that the cells are alive,” Hashmi said. “Usually when this happens, cells are dead or dying.”

Not only were they alive — they activated three genes that drive tooth formation.

To see if the shrinking gel also worked its magic in the body, Hashmi worked with Mammoto to load mesenchymal cells into the gel, then implant the gel beneath the mouse kidney capsule — a tissue that is well supplied with blood and often used for transplantation experiments.

The implanted cells not only expressed tooth-development genes — they laid down calcium and minerals, just as mesenchymal cells do in the body as they begin to form teeth.

“They were in full-throttle tooth-development mode,” Hashmi said.

The researchers have future plans (from the news release),

In the embryo, mesenchymal cells can’t build teeth alone — they need to be combined with cells that form the epithelium. In the future, the scientists plan to test whether the shrinking gel can stimulate both tissues to generate an entire functional tooth.

Here’s a link to and a citation for the paper about the successful attempt to stimulate mesenchymal cells into the beginnings of tooth formation,

Developmentally-Inspired Shrink-Wrap Polymers for Mechanical Induction of Tissue Differentiation by Basma Hashmi, Lauren D. Zarzar, Tadanori Mammoto, Akiko Mammoto, Amanda Jiang, Joanna Aizenberg, and Donald E. Ingber. Advanced Materials Article first published online: 18 FEB 2014 DOI: 10.1002/adma.201304995

© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

Glass as a sponge

A glass sponge which can be found at the bottom of either the Indian and Pacific oceans is inspiring a group of physicists at the Max Planck Institute of Colloids and Interfaces according to a Feb. 25, 2014 news item on Azonano,

… Recently, Igor Zlotnikov and Peter Fratzl, who study biomaterials at the Max Planck Institute of Colloids and Interfaces in collaboration with the team of Peter Werner from the Max Planck Institute of Microstructure Physics, Emil Zolotoyabko from the Israeli Institute of Technology and Yannicke Dauphin from the Université P. & M. Curie, have discovered a mesoporous material in nature, namely in the glass sponge Monorhaphis chuni. The sponge lives on the bottom of the Indian and Pacific Oceans, and forms an approximately one-centimetre-thick glass rod to attach itself to the ocean’s floor. Over the course of its life, the rod can grow up to three meters in length. The glass filament, passing through the centre of this rod, is perforated with pores having a diameter of about five nanometres. Each pore is occupied by an egg-shaped protein molecule, called silicatein, connected to the protein molecules in adjacent pores through holes in the glass.

The Feb. 24, 2014 Max Planck Institute of Colloids and Interfaces news release, which originated the news item, explains the importance of nanoporous or mesoporous materials, natural and manufactured,

The amount of surface area often plays an important role in materials used in medicine and technology and normally, it should be as large as possible. It can accommodate, for instance, large quantities of pharmaceutical agents and release them gradually in the body. In chemistry, the efficiency of numerous processes is dependent on catalysts exhibiting a large surface on which reactions can occur. In sensors, for example, the sensitivity is strongly dependent on the amount of surface to which the detected molecules can attach. Porous structures are a good example for such materials.

Materials having pores measuring between 2 to 50 nanometres are particularly well suited for such purposes. Scientists refer to these as mesoporous structures, to distinguish them from structures that are microporous, having smaller pores, or macroporous, with larger pores.

Having discovered the glass sponge’s Monorhaphis chuni, ability to create a mesoporous material (a glass filament), the researchers attempted further studies, from the news release,

“Mesoporous glass structures are among the most studied materials. This makes it even more exiting to find them in nature,” says Igor Zlotnikov. “Presumably, this structure is not limited to M. chuni, but can also occur in other glass sponges.” However, not only does M. chuni produces a mesoporous material that is technologically relevant; the sponge sets standards in terms of size distribution and arrangement of the pores. In the sample that Igor Zlotnikov and his colleagues studied, all pores have the size of the inhabiting protein molecule and they are completely regularly arranged. Metaphorically speaking, the structure resembles egg cartons that are stacked one on top of another like pallets.

The researchers used two characterization techniques to gain an accurate picture of the internal architecture of the filament. First, they employed X-ray analysis at the BESSY II synchrotron facility in Berlin. Experiments with X-ray diffraction usually serve to identify the atomic periodic structure of crystals. However, Igor Zlotnikov’s team used a variant of this technology to reveal structural periodicity on a larger scale, namely, on the scale of the pores size and their spatial arrangement. The results were confirmed in cooperation with the team working with Peter Werner from the Max Planck Institute of Microstructure Physics using high resolution transmission electron microscopy. In addition to structural details, this technique allows researchers to make assertions about local chemical composition.

But what surprised the researchers even more than the periodicity of the structure that was revealed is the way in which M. chuni produces it: “It’s absolutely astonishing that nature and mankind converged on a similar manufacturing method independently”, says Peter Fratzl, Director at the Max Planck Institute of Colloids and Interfaces. To continue with the image of the egg cartons, the glass sponge first stacks one or maybe even several layers of eggs – that is, protein molecules – and then fills the gaps with cardboard, or in this case glass.

Here’s an image the researchers have provided to illustrate their ‘egg carton’ analogy,

 Pore distribution in the glass filament resembles stacked, pallet-like egg cartons. Each cavity is occupied by one protein molecule, called silicatein, measuring approximately five nanometres in size. © Igor Zlotnikov / MPI of Colloids and Interfaces


Pore distribution in the glass filament resembles stacked, pallet-like egg cartons. Each cavity is occupied by one protein molecule, called silicatein, measuring approximately five nanometres in size. © Igor Zlotnikov / MPI of Colloids and Interfaces

Even though humans have managed a similar engineering feat, it appears Nature has more successfully controlled sizes and mechanical properties (from the news release),

Since the protein molecules, which serve as a kind of a model for the surrounding glass structure, are all in the same size, the pores in the obtained material also have the same diameter and form a completely uniform structure. Achieving this precision via synthetic methods is difficult, even though the mesoporous glass is created in a very similar manner. Here, organic droplets around which the glass is produced determine the pore shape. Subsequently, the droplets are dissolved out of the nanostructure using a detergent – in principle, nothing other than a dishwashing liquid. However, scientists can’t adjust the size of the droplets as precisely as the biochemical apparatus of a living organism that controls the size of the proteins. Thus, the pore size in synthetic mesoporous materials varies, and the cavities don’t arrange themselves into a perfectly regular pattern.

“With silicatein or other proteins, it would be possible to produce mesoporous materials having a completely uniform pore size and a perfectly periodic arrangement”, says Igor Zlotnikov. “That would be very expensive.” Mimicking regularly structured materials similar to those found in M. chuni, for the time being, is not the goal of Max Planck researchers. They are currently investigating whether the mesoporous structure is as uniform over large regions of the glass filament as it is in the 100 micrometer section they analysed for the current publication. “Besides that, we focus on the relationship between the structure and the mechanical properties of the entire glass rod”, says Peter Fratzl. Also there, M. chuni sets standards in terms of structural optimization to enhance its mechanical behaviour.

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

A Perfectly Periodic Three-Dimensional Protein/Silica Mesoporous Structure Produced by an Organism by Igor Zlotnikov, Peter Werner, Horst Blumtritt, Andreas Graff, Yannicke Dauphin, Emil Zolotoyabko, & Peter Fratzl. Advanced Materials. Article first published online: 12 DEC 2013 DOI: 10.1002/adma.201304696

© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

This paper is behind a paywall.

SLIPS (Slippery Liquid-Infused Porous Surfaces) lead the way to stain-free, self-cleaning clothes

Thanks to the researchers at Harvard University’s Wyss Institute for Biologically Inspired Engineering, I have discovered a new word, omniphobicity. Before getting to this new word, here’s a little more information about the project which spawned the word. According to a Jan. 14, 2014 news item on Nanowerk,

The researchers behind SLIPS (Slippery Liquid-Infused Porous Surfaces) have demonstrated a spate of sleek applications of the super-slick coating since unveiling it in a 2011 issue of Nature – and they just expanded its repertoire even more.

The Jan. ??, 2014 Harvard University Wyss Institute news release, which originated the news item, provides additional information about the SLIPS (Slippery Liquid-Infused Porous Surfaces) technology explaining the engineers have taken their inspiration from the pitcher plant rather the lotus, as is more common,

The team from Harvard’s Wyss Institute and the School of Engineering and Applied Sciences (SEAS) has demonstrated the uncanny ability of SLIPS – inspired by the pitcher plant – to repel nearly any material it contacts: water, ice, oil, saltwater, wax, blood, and more. They have demonstrated its versatility under extreme conditions of pH and temperature, and have successfully used SLIPS to coat everything from refrigeration coils to lenses, windows, and ceramics. What’s more, in 2012 they won an R&D 100 Award for the technology from R&D Magazine. This annual award honors the year’s 100 most significant products, the so-called game-changers of the technology scene.

Here’s what an image illustrating the pitcher plant and SLIPS,

Inspired by the Nepenthes pitcher plant... [Image credit: New Scientist; Bohn & Federie, PNAS 101, 14138-14143, 2004] Courtesy Wyss Institute

Inspired by the Nepenthes pitcher plant… [Image credit: New Scientist; Bohn & Federie, PNAS 101, 14138-14143, 2004] Courtesy Wyss Institute

The team’s latest work features cotton and polyster fabrics (from the news release),

And now, as reported January 10 [2014] in a special issue celebrating the 25th year of the journal Nanotechnology, the team has modified everyday cotton and polyester fabrics to exhibit traditional antifouling SLIPS behavior. The advance could meet the need for a robust, stain-resistant textile for a host of consumer and industrial applications.

“We took one page out of Nature’s book, and are finding that it has the potential to help us develop solutions to a variety of age-old challenges: ice we don’t want on refrigeration coils, bacteria that we don’t want on medical devices, and now stains we don’t want on clothes,” said Joanna Aizenberg, Ph.D., who leads the development of the technology. Aizenberg is a Core Faculty member of the Wyss Institute and the Amy Smith Berylson Professor of Materials Science at SEAS

Most currently available state-of-the-art, stain-resistant fabrics draw their inspiration and design from the lotus leaf. Tiny nanotextures on the surface of lotus leaves resist water, causing droplets of water to bead up on a cushion of air at the edge of the surface. Lotus-inspired textiles therefore use air-filled nanostructures to repel water. These are capable of repelling most aqueous liquids and dirt particles, but they suffer from a series of shortcomings, explained Cicely Shillingford, a Wyss Research Assistant and lead author of the Nanotechnology publication. They require a stable solid-air layer for the beading process to occur and thus fail easily under pressure – as in a heavy rainstorm – and do not withstand physical damage, such as twisting and abrasion, very well. They also stain more easily from organic or complex liquids, such as oil.

On the other hand, SLIPS is inspired by the carnivorous pitcher plant, which locks in a water layer to create a slick coating that causes insects that land on it to literally hydroplane and fall into the plant. The SLIPS coating anchors a slippery lubricated film infused to a nanoporous solid surface, creating a material that performs exceedingly well under pressure or physical damage, and can resist all kinds of liquids, including oil.
To create a fabric with SLIPS-type functionality, the team bought off-the-shelf cotton and polyester fabrics from stores near their lab in Cambridge, Massachusetts, and developed two ways to chemically treat them. One involved coating them with tiny particles of silica (SiM), and the other required a treatment with sol-gel based alumina (SgB). …

What happened after the team put the SLIPS-fabrics through a ringer of tests performed according to industrial standards – from twisting to rubbing and staining attempts?

“The SLIPS-fabric showed an unprecedented ability to repel a wide range of fluids and resist staining, and it handles physical stresses and strains just fine,” said Aizenberg.

While not every SLIPS-fabric was as breathable (yet) as the researchers hoped, it outperformed currently available stain-resistant fabrics on just about every other measure. As such, the most likely immediate applications could be fabrics needed in potentially extreme environments where breathability is not paramount but exposure to challenging contaminating liquids and biological hazards is involved, such as tactical suits for the military, lab coats, medical clothing, specialty garments for construction and manufacturing, and perhaps even tents and sports stadiums.

The scientists have also provided an image of a lab coat that was partially (sleeves) converted to SLIPS and than stained with a variety of foodstuffs,

Former Wyss Postdoctoral Fellow Tak-Sing Wong, Ph.D., who is now an assistant professor at The Pennsylvania State University, wears a labcoat in which the sleeves were converted to SLIPS, after sprayed with wine, tomato juice, eggs, and more. Courtesy Wyss Institute

Former Wyss Postdoctoral Fellow Tak-Sing Wong, Ph.D., who is now an assistant professor at The Pennsylvania State University, wears a labcoat in which the sleeves were converted to SLIPS, after sprayed with wine, tomato juice, eggs, and more. Courtesy Wyss Institute

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

Fabrics coated with lubricated nanostructures display robust omniphobicity by Cicely Shillingford, Noah MacCallum, Tak-Sing Wong, Philseok Kim and Joanna Aizenberg. Nanotechnology 25 01 4019 doi:10.1088/0957-4484/25/1/014019

This paper is behind a paywall. As for an explanation of the word omniphobicity this abstract is helpful,

The development of a stain-resistant and pressure-stable textile is desirable for consumer and industrial applications alike, yet it remains a challenge that current technologies have been unable to fully address. Traditional superhydrophobic surfaces, inspired by the lotus plant, are characterized by two main components: hydrophobic chemical functionalization and surface roughness. While this approach produces water-resistant surfaces, these materials have critical weaknesses that hinder their practical utility, in particular as robust stain-free fabrics. For example, traditional superhydrophobic surfaces fail (i.e., become stained) when exposed to low-surface-tension liquids, under pressure when impacted by a high-velocity stream of water (e.g., rain), and when exposed to physical forces such as abrasion and twisting. We have recently introduced slippery lubricant-infused porous surfaces (SLIPS), a self-healing, pressure-tolerant and omniphobic surface, to address these issues. [emphasis mine] Herein we present the rational design and optimization of nanostructured lubricant-infused fabrics and demonstrate markedly improved performance over traditional superhydrophobic textile treatments: SLIPS-functionalized cotton and polyester fabrics exhibit decreased contact angle hysteresis and sliding angles, omni-repellent properties against various fluids including polar and nonpolar liquids, pressure tolerance and mechanical robustness, all of which are not readily achievable with the state-of-the-art superhydrophobic coatings.

If I understand it rightly the researchers are using the word omniphobic (omni meaning ‘all’ or ‘everything’) to imply that this surface repels liquids in many more situations, e.g. high-velocity stream of water (rain) than the superhydrophobic materials.