Hairy nano-cellulose provides green anti-scaling solution – More applications including drug delivery, antimicrobial agents, and fluorescent dyes for medical imaging – McGill University


hairynanotecCredit: McGill University

A new type of cellulose nanoparticle, invented by McGill University researchers, is at the heart of a more effective and less environmentally damaging solution to one of the biggest challenges facing water-based industries: preventing the buildup of scale.

Formed by the accumulation of sparingly soluble minerals, scale can seriously impair the operation of just about any equipment that conducts or stores water – from household appliances to industrial installations. Most of the anti-scaling agents currently in use are high in phosphorus derivatives, environmental pollutants that can have catastrophic consequences for aquatic ecosystems.

In a series of papers published in the Royal Society of Chemistry’s Materials Horizons and the American Chemical Society’s Applied Materials & Interfaces, a team of McGill chemists and chemical engineers describe how they have developed a phosphorus-free anti-scaling solution based on a nanotechnology breakthrough with an unusual name: hairy nanocellulose.

An unlikely candidate

Lead author Amir Sheikhi, now a postdoctoral fellow in the Department of Bioengineering at the University of California, Los Angeles, says despite its green credentials  was not an obvious place to look for a way to fight scale.

“Cellulose is the most abundant biopolymer in the world. It’s renewable and biodegradable. But it’s probably one of the least attractive options for an anti-scaling agent because it’s neutral, it has no charged functional groups,” he says.

While working as a postdoctoral fellow with McGill chemistry professor Ashok Kakkar, Sheikhi developed a number of macromolecular antiscalants that were more effective than products widely used in industry – but all of his discoveries were phosphonate-based. His desire to push his research further and find a phosphorus-free alternative led him to take a closer look at cellulose.

“Nanoengineered hairy cellulose turned out to work even better than the phosphonated molecules,” he says.

The breakthrough came when the research team succeeded in nanoengineering negatively charged carboxyl groups onto cellulose nanoparticles. The result was a particle that was no longer neutral, but instead carried charged functional groups capable of controlling the tendency of positively charged calcium ions to form scale.

Hirsute wonder particle a chance discovery

Previous attempts to functionalize cellulose in this way focused on two earlier forms of nanoparticle – cellulose nanofibrils and . But these efforts produced only a minimal amount of useful product. The difference this time was that the McGill team worked with hairy nanocellulose – a new nanoparticle first discovered in the laboratory of McGill chemistry professor Theo van de Ven.

Van de Ven, who also participated in the anti-scaling research, recalls the moment in 2011 when Han Yang, then a doctoral student in his lab, stumbled upon the new form of nanocellulose.

“He came into my office with a test tube that looked like it had water in it and he said, ‘Sir! My suspension has disappeared!'” van de Ven says with a grin.

“He had a white suspension of kraft fibres and it had turned transparent. When something is transparent, you know immediately it has either dissolved or turned nano. We performed a number of characterizations and we realized he had made a new form of nanocellulose.”

Extreme versatility

The secret to making hairy nanocellulose lies in cutting cellulose nanofibrils – which are made up of an alternating series of crystalline and amorphous regions – at precise locations to produce nanoparticles with amorphous regions sprouting from either end like so many unruly strands of hair.

“By breaking the nanofibrils up the way we do, you get all these cellulose chains sticking out which are accessible to chemicals,” van de Ven explains. “That’s why our nanocellulose can be functionalized to a far greater extent than other kinds.”

Given the chemical versatility of hairy nanocellulose, the research team sees strong potential for applications beyond anti-scaling, including drug delivery, antimicrobial agents, and fluorescent dyes for medical imaging.

“We can link just about any molecule you can think of to hairy ,” van de Ven says.

 Explore further: Ready-to-use recipe for turning plant waste into gasoline

More information: Amir Sheikhi et al. Overcoming Interfacial Scaling Using Engineered Nanocelluloses: A QCM-D Study, ACS Applied Materials & Interfaces (2018). DOI: 10.1021/acsami.8b07435

Amir Sheikhi et al. Nanoengineering colloidal and polymeric celluloses for threshold scale inhibition: towards universal biomass-based crystal modification, Materials Horizons (2018). DOI: 10.1039/C7MH00823F

 

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Targeted drug delivery could help fight tumors and local infections


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Some drug regimens, such as those designed to eliminate tumors, are notorious for nasty side effects. Unwanted symptoms are often the result of medicine going where it’s not needed and harming healthy cells. To minimize this risk, researchers in Quebec have developed nanoparticles that only release a drug when exposed to near-infrared light, which doctors could beam onto a specific site. Their report appears in the Journal of the American Chemical Society.

For years, scientists have been striving to develop localized treatments to reduce side effects of therapeutic drugs. They have designed drug-delivery systems that respond to light, temperature, ultrasound and pH changes. One promising approach involved drug-carrying materials that are sensitive to ultraviolet (UV) light. Shining a beam in this part of the light spectrum causes the materials to release their therapeutic cargo at a designated location. But UV light has major limitations. It can’t penetrate body tissues, and it is carcinogenic. Near-infrared (NIR) light can go through 1 to 2 centimeters of tissue and would be a safer alternative, but photosensitive drug-carriers don’t react to it. McGill University engineering professor Marta Cerruti and colleagues sought a way to bring the two kinds of light together in one possible solution.

The researchers started with nanoparticles that convert NIR light into UV light and coated them in a UV-sensitive hydrogel shell infused with a fluorescent protein, a stand-in for drug molecules. When exposed to NIR light, the nanoparticles instantaneously converted it to UV, which induced the shell to release the protein payload. The researchers note that their on-demand delivery system could not only supply drug molecules but also agents for imaging and diagnostics.


Story Source:

The above post is reprinted from materials provided by McGill University. Note: Materials may be edited for content and length.


Journal Reference:

  1. Ghulam Jalani, Rafik Naccache, Derek H. Rosenzweig, Lisbet Haglund, Fiorenzo Vetrone, Marta Cerruti.Photocleavable Hydrogel-Coated Upconverting Nanoparticles: A Multifunctional Theranostic Platform for NIR Imaging and On-Demand Macromolecular Delivery. Journal of the American Chemical Society, 2016; DOI: 10.1021/jacs.5b12357

Chemists work to desalt the ocean for drinking water, 1 nanoliter at a time


QDOTS imagesCAKXSY1K 8(Nanowerk News) By creating a small electrical field  that removes salts from seawater, chemists at The University of Texas at Austin  and the University of Marburg in Germany have introduced a new method for the  desalination of seawater that consumes less energy and is dramatically simpler  than conventional techniques. The new method requires so little energy that it  can run on a store-bought battery.
The process evades the problems confronting current desalination  methods by eliminating the need for a membrane and by separating salt from water  at a microscale.
The technique, called electrochemically mediated seawater  desalination, was described last week in the journal Angewandte Chemie (“Electrochemically Mediated Seawater  Desalination”). The research team was led by Richard Crooks of The  University of Texas at Austin and Ulrich Tallarek of the University of Marburg.  It’s patent-pending and is in commercial development by startup company Okeanos  Technologies.
Desalination Microchannel
The  left panel shows the salt (which is tagged with a fluorescent tracer) flowing  upward after a voltage is applied by an electrode (the dark rectangle) jutting  into the channel at just the point where it branches. In the right panel no  voltage is being applied. (Image: Kyle Knust)
“The availability of water for drinking and crop irrigation is  one of the most basic requirements for maintaining and improving human health,”  said Crooks, the Robert A. Welch Chair in Chemistry in the College of Natural  Sciences. “Seawater desalination is one way to address this need, but most  current methods for desalinating water rely on expensive and easily contaminated  membranes. The membrane-free method we’ve developed still needs to be refined  and scaled up, but if we can succeed at that, then one day it might be possible  to provide fresh water on a massive scale using a simple, even portable,  system.”
This new method holds particular promise for the water-stressed  areas in which about a third of the planet’s inhabitants live. Many of these  regions have access to abundant seawater but not to the energy infrastructure or  money necessary to desalt water using conventional technology. As a result,  millions of deaths per year in these regions are attributed to water-related  causes.
“People are dying because of a lack of freshwater,” said Tony  Frudakis, founder and CEO of Okeanos Technologies. “And they’ll continue to do  so until there is some kind of breakthrough, and that is what we are hoping our  technology will represent.”
To achieve desalination, the researchers apply a small voltage  (3.0 volts) to a plastic chip filled with seawater. The chip contains a  microchannel with two branches. At the junction of the channel an embedded  electrode neutralizes some of the chloride ions in seawater to create an “ion  depletion zone” that increases the local electric field compared with the rest  of the channel. This change in the electric field is sufficient to redirect  salts into one branch, allowing desalinated water to pass through the other  branch.
“The neutralization reaction occurring at the electrode is key  to removing the salts in seawater,” said Kyle Knust, a graduate student in  Crooks’ lab and first author on the paper.
Like a troll at the foot of the bridge, the ion depletion zone  prevents salt from passing through, resulting in the production of freshwater.
Thus far Crooks and his colleagues have achieved 25 percent  desalination. Although drinking water requires 99 percent desalination, they are  confident that goal can be achieved.
“This was a proof of principle,” said Knust. “We’ve made  comparable performance improvements while developing other applications based on  the formation of an ion depletion zone. That suggests that 99 percent  desalination is not beyond our reach.”
The other major challenge is to scale up the process. Right now  the microchannels, about the size of a human hair, produce about 40 nanoliters  of desalted water per minute. To make this technique practical for individual or  communal use, a device would have to produce liters of water per day. The  authors are confident that this can be achieved as well.
If these engineering challenges are surmounted, they foresee a  future in which the technology is deployed at different scales to meet different  needs.
“You could build a disaster relief array or a municipal-scale  unit,” said Frudakis. “Okeanos has even contemplated building a small system  that would look like a Coke machine and would operate in a standalone fashion to  produce enough water for a small village.”
Source: McGill University

Read more: http://www.nanowerk.com/news2/newsid=31072.php#ixzz2XZnuQSxT

A Magic Formula to Predict Fracture in Steel


22.11.12 – EPFL researchers have elucidated a century-old mystery: how hydrogen destroys steels. A new mathematical model predicts this failure in the presence of the destructive atoms.

A veritable gangrene for steels and other structural metals, hydrogen is one of the most important causes of ruptures in industrial parts, such as pipelines. At the slightest defect in a material, these atoms introduce themselves in the crack and weaken the structure dramatically, making it brittle. The material need only be in contact with aggressive substances or placed in an aqueous environment from which for the dangerous hydrogen atoms enter the material. This phenomenon of “hydrogen embrittlement” has been known for many years, but so far no one managed to capture the physical process or predict when hydrogen embrittlement will occur. Bill Curtin of the Laboratory of Multiscale Mechanical Modeling at EPFL and his collaborator Prof. Jun Song at McGill, tackled this problem and developed a mathematical model to understand the behavior of hydrogen atoms in iron-based steels and thus to predict steel fracture. This is revolutionary in the world of materials, and serves as the subject of an article in the journal Nature Materials.

Hydrogen Attracted by Fractures To establish their equation, the researchers studied the behavior of iron at the atomic level. They showed that the reason hydrogen weakens the materials comes from the tendency of hydrogen atoms to cluster at the tip of a crack. “In the absence of hydrogen, dislocation defects form around a crack, allowing it to relax the stress in the material and preventing the crack from growing, making the material more resilient or tougher, explained Bill Curtin. By grouping around the crack, the hydrogen atoms prevent the creation of these dislocations, and prevent the stress relaxation, allowing the crack to grow and the material becomes extremely brittle.”

A mathematical model that predicts the fracture Using their simulations, the scientists were able to establish a complex mathematical model that calculates when a material in contact with hydrogen will start to break. Several factors are taken into account, such as the concentration of hydrogen in the environment, the speed at which the hydrogen molecules move toward the crack, type of steel, and the load on the structure. If a combination of these parameters attains a critical value, computed from the simulations, then the material will break. Using the model, they predicted the breaking point for a various steels under various conditions. “Our predictions coincided with the experiments in 9 out of 10 cases, rejoiced Bill Curtin. And the 10th case was right on the border”.

This knowledge should allow scientists to tackle the problem armed with new weapons. It will become easier to identify adverse operating modes and to construct materials that are more resistant to this type of deterioration.

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How does hydrogen come into contact with a material?

•When welding in damp conditions (presence of H2O). •When steels are used in the presence of hydrogen or hydrogenated gas mixtures (hydrocarbons in pipelines, for example) •Hydrogen can originate from corrosion in an aqueous environment, for example.

Additional information: Atomic mechanism and prediction of hydrogen embrittlement in iron