“Affairs of the Heart” – Texas Heart Institute & Rice University – Damaged hearts are rewired with Nanotube Fibers


Rice Nano Tube Hearts 7eae23_46bb535810c64757b54ee0fe3f4d8c8c_mv2
Researchers at Texas Heart Institute and Rice University have confirmed that flexible, conductive fibers made of carbon nanotubes can bridge damaged tissue to deliver electrical signals and keep hearts beating despite congestive heart failure or dilated cardiomyopathy or after a heart attack. @ Texas Heart Institute Thin, flexible fibers made of carbon nanotubes have now proven able to bridge damaged heart tissues and deliver the electrical signals needed to keep those hearts beating.

Scientists at Texas Heart Institute (THI) report they have used biocompatible fibers invented at Rice University in studies that showed sewing them directly into damaged tissue can restore electrical function to hearts.

“Instead of shocking and defibrillating, we are actually correcting diseased conduction of the largest major pumping chamber of the heart by creating a bridge to bypass and conduct over a scarred area of a damaged heart,” said Dr. Mehdi Razavi, a cardiologist and director of Electrophysiology Clinical Research and Innovations at THI, who co-led the study with Rice chemical and biomolecular engineer Matteo Pasquali.

“Today there is no technology that treats the underlying cause of the No. 1 cause of sudden death, ventricular arrhythmias,” Razavi said. “These arrhythmias are caused by the disorganized firing of impulses from the heart’s lower chambers and are challenging to treat in patients after a heart attack or with scarred heart tissue due to such other conditions as congestive heart failure or dilated cardiomyopathy.”

Results of the studies on preclinical models appear as an open-access Editor’s Pick in the American Heart Association’s Circulation: Arrhythmia and Electrophysiology. The association helped fund the research with a 2015 grant.

The research springs from the pioneering 2013 invention by Pasquali’s lab of a method to make conductive fibers out of carbon nanotubes. The lab’s first threadlike fibers were a quarter of the width of a human hair, but contained tens of millions of microscopic nanotubes. The fibers are also being studied for electrical interfaces with the brain, for use in cochlear implants, as flexible antennas and for automotive and aerospace applications.

The experiments showed the nontoxic, polymer-coated fibers, with their ends stripped to serve as electrodes, were effective in restoring function during month-long tests in large preclinical models as well as rodents, whether the initial conduction was slowed, severed or blocked, according to the researchers. The fibers served their purpose with or without the presence of a pacemaker, they found.

In the rodents, they wrote, conduction disappeared when the fibers were removed.

“The reestablishment of cardiac conduction with carbon nanotube fibers has the potential to revolutionize therapy for cardiac electrical disturbances, one of the most common causes of death in the United States,” said co-lead author Mark McCauley, who carried out many of the experiments as a postdoctoral fellow at THI. He is now an assistant professor of clinical medicine at the University of Illinois College of Medicine.

“Our experiments provided the first scientific support for using a synthetic material-based treatment rather than a drug to treat the leading cause of sudden death in the U.S. and many developing countries around the world,” Razavi added.

Many questions remain before the procedure can move toward human testing, Pasquali said. The researchers must establish a way to sew the fibers in place using a minimally invasive catheter, and make sure the fibers are strong and flexible enough to serve a constantly beating heart over the long term. He said they must also determine how long and wide fibers should be, precisely how much electricity they need to carry and how they would perform in the growing hearts of young patients.

“Flexibility is important because the heart is continuously pulsating and moving, so anything that’s attached to the heart’s surface is going to be deformed and flexed,” said Pasquali, who has appointments at Rice’s Brown School of Engineering and Wiess School of Natural Sciences.

“Good interfacial contact is also critical to pick up and deliver the electrical signal,” he said. “In the past, multiple materials had to be combined to attain both electrical conductivity and effective contacts. These fibers have both properties built in by design, which greatly simplifies device construction and lowers risks of long-term failure due to delamination of multiple layers or coatings.”

Razavi noted that while there are many effective antiarrhythmic drugs available, they are often contraindicated in patients after a heart attack. “What is really needed therapeutically is to increase conduction,” he said. “Carbon nanotube fibers have the conductive properties of metal but are flexible enough to allow us to navigate and deliver energy to a very specific area of a delicate, damaged heart.”

In Vivo Restoration of Myocardial Conduction With Carbon Nanotube Fibers

Mark D. McCauley, Flavia Vitale, J. Stephen Yan, Colin C. Young, Brian Greet, Marco Orecchioni, Srikanth Perike, Abdelmotagaly Elgalad, Julia A. Coco, Mathews John, Doris A. Taylor, Luiz C. Sampaio, Lucia G. Delogu, Mehdi Razavi, Matteo Pasquali

Circulation: Arrhythmia and Electrophysiology Vol. 12, No. 8

DOI: 10.1161/CIRCEP.119.007256

Contact information:

Matteo Pasquali

Professor of Chemical and Biomolecular Engineering at Rice University

mp@rice.edu

Phone: 713-348-5830

Pasquali Research Group

Mehdi Razavi

Cardiologist, Associate Professor of Medicine-Cardiology at Baylor College of Medicine and Director of Electrophysiology Clinical Research and Innovations at THI

razavi@bcm.edu

Rice University

Scientists develop Lithium Metal batteries that charge faster, last longer with 10X times more energy by volume than Li-Ion Batteries – BIG potential for Our EV / AV Future


 

October 25, 2018

Rice University scientists are counting on films of carbon nanotubes to make high-powered, fast-charging lithium metal batteries a logical replacement for common lithium-ion batteries.

The Rice lab of chemist James Tour showed thin nanotube films effectively stop dendrites that grow naturally from unprotected lithium metal anodes in batteries. Over time, these tentacle-like dendrites can pierce the battery’s electrolyte core and reach the cathode, causing the battery to fail.

That problem has both dampened the use of lithium metal in commercial applications and encouraged researchers worldwide to solve it.

img_0837-1Rice University graduate student Gladys López-Silva holds a lithium metal anode with a film of carbon nanotubes. Once the film is attached, it becomes infiltrated by lithium ions and turns red. Photo by Jeff Fitlow

Lithium metal charges much faster and holds about 10 times more energy by volume than the lithium-ion electrodes found in just about every electronic device, including cellphones and electric cars.

 

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MIT NEWS: Read More About Lithium Metal Batteries

“One of the ways to slow dendrites in lithium-ion batteries is to limit how fast they charge,” Tour said. “People don’t like that. They want to be able to charge their batteries quickly.”

The Rice team’s answer, detailed in Advanced Materials, is simple, inexpensive and highly effective at stopping dendrite growth, Tour said.

“What we’ve done turns out to be really easy,” he said. “You just coat a lithium metal foil with a multiwalled carbon nanotube film. The lithium dopes the nanotube film, which turns from black to red, and the film in turn diffuses the lithium ions.”

“Physical contact with lithium metal reduces the nanotube film, but balances it by adding lithium ions,” said Rice postdoctoral researcher Rodrigo Salvatierra, co-lead author of the paper with graduate student Gladys López-Silva. “The ions distribute themselves throughout the nanotube film.”

img_0835An illustration shows how lithium metal anodes developed at Rice University are protected from dendrite growth by a film of carbon nanotubes. Courtesy of the Tour Group

When the battery is in use, the film discharges stored ions and the underlying lithium anode refills it, maintaining the film’s ability to stop dendrite growth.

The tangled-nanotube film effectively quenched dendrites over 580 charge/discharge cycles of a test battery with a sulfurized-carbon cathode the lab developed in previous experiments.

The researchers reported the full lithium metal cells retained 99.8 percent of their coulombic efficiency, the measure of how well electrons move within an electrochemical system.

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Rice University scientists have discovered that a film of multiwalled carbon nanotubes quenches the growth of dendrites in lithium metal-based batteries. Courtesy of the Tour Group

Co-authors of the paper are Rice alumni Almaz Jalilov of the King Fahd University of Petroleum and Minerals, Saudi Arabia; Jongwon Yoon, a senior researcher at the Korea Basic Science Institute; and Gang Wu, an instructor, and Ah-Lim Tsai, a professor of hematology, both at the McGovern Medical School at the University of Texas Health Science Center at Houston.

Tour is the T.T. and W.F. Chao Chair in Chemistry as well as a professor of computer science and of materials science and nanoengineering at Rice.

The research was supported by the Air Force Office of Scientific Research, the National Institutes of Health, the National Council of Science and Technology, Mexico; the National Council for Scientific and Technological Development, Ministry of Science, Technology and Innovation and Coordination for the Improvement of Higher Education Personnel, Brazil; and Celgard, LLC.

1028_DENDRITE-5-rn-18fsg2wRice University chemist James Tour, left, graduate student Gladys López-Silva and postdoctoral researcher Rodrigo Salvatierra use a film of carbon nanotubes to prevent dendrite growth in lithium metal batteries, which charge faster and hold more power than current lithium-ion batteries. Photo by Jeff Fitlow.

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Using PEG Nanotubes as Drug Delivery Systems


This article is based around a talk given by Ben Newland from Cardiff University, UK, at the NANOMED conference hosted by the NANOSMAT Society in Manchester on the 26-28th June 2018. In his talk, Ben talks about how he uses soft and flexible poly(ethylene glycol) (PEG) nanotubes to provide a sustained and localized delivery of therapeutic drugs.

Link to Original AZ Nano Article

Dr. Newland, a lecturer at Cardiff University, has been dealing with PEG nanotubes for approximately ten years after they came about as a side project to his other research. It should be noted that these nanotubes are not like carbon nanotubes, in that they are not electronically confined in 2 dimensions (i.e., a 1D material), nor are they carbon nanotubes functionalized with PEG at the surface. They are strictly hollow cylinders that are made entirely of PEG, and only bear the name nanotube because that is what they most closely resemble (without the capped end).

The research came about after previously working on carbon nanopipes, where a porous template was used to create hollow carbon nanostructures; in conjunction with another area of Ben’s research, which looks at using cyclized knotted polymers as drug delivery agents. To combine these areas, Ben poured a polymer solution (with a photo-initiator) into a porous template and shone UV light on it, which in turn cross-linked the polymers and created tube-like structures. This was the starting point of this research.

Since starting the research, Ben has incrementally polished the process and now produces polymer nanotubes which are 200 nm in diameter and up to 60 micrometers in length. Cyclized knot polymers are required to construct these nanotubes and can be made with commercially available PEG materials that contain di-vinyl groups. Different polymers have been trialed, and the PEG nanotubes were found to be the softest.

The possibility of using these for drug delivery applications came about after they were found to uptake rhodamine (a tracer dye). On the process side, Ben’s research team discovered that when the templates are dissolved (with sodium hydroxide) to leave just the nanotubes, the process breaks some of the ester bonds and creates an abundance of negative charges on the surface of the nanotubes.

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The anti-cancer drug, doxorubicin, was also found to be actively uptaken out of solution by the negatively charged nanotubes, and it is a straightforward procedure to determine the uptake and release of doxorubicin as it is intrinsically fluorescent and has a colored appearance. Ben’s work has led him to look at the release of doxorubicin from the nanotubes and found that they release most of the drug payload within the first five days, but there is a sustained delivery of 2-3 micrograms over 35 to 40 days. Some of the doxorubicin was found to stay in the nanotube, so while it is not perfect at the moment regarding the release, these nanotubes do show a lot of promise as new material as drug delivery agents.

One aspect of any delivery agent is that it needs to be biocompatible and low in cytotoxicity. In-vitro cell viability tests have been performed for these nanotubes at varying concentrations, and up to the point where the nanotubes are completely covering the cell. The results showed that even at the end (fully covered cells) the nanotubes did not kill the cell. Other cell viability studies on drug-loaded nanotubes found that the release of the drugs was killing the cells, and thus confirmed its position as a potential drug delivery agent.

The research has been taken further and has been tested on metastatic breast cancer cells in mice in conjunction with researchers from the University of Strathclyde. These studies have shown that the doxorubicin-loaded nanotubes reduced the tumor growth and reduced metastasis (the creation of secondary tumors away from the primary tumor site) in the mice.

Future studies will look at the cytotoxicity of the polymer nanotubes in-vivo and will look at how the drug release profile can be improved. Other areas will look at varying the size of the nanotubes, changing the chain length to alter the stiffness and entanglement of the nanotubes and looking at the effects of functionalizing the nanotubes with different nanoparticles.

Sources:

• NANOMED 2018: http://www.nanomed.uk.com/

• Ben Newland: http://www.newlandresearch.net/

Rice University: Nanotubes change the shape of water


nanotubeschange water Rice UMolecular models of nanotube ice produced by engineers at Rice University show how forces inside a carbon nanotube at left and a boron nitride nanotube at right pressure water molecules into taking on the shape of a square tube. The …more

First, according to Rice University engineers, get a nanotube hole. Then insert water. If the nanotube is just the right width, the water molecules will align into a square rod.

Rice materials scientist Rouzbeh Shahsavari and his team used molecular models to demonstrate their theory that weak van der Waals forces between the inner surface of the nanotube and the  are strong enough to snap the oxygen and hydrogen atoms into place.

Shahsavari referred to the contents as two-dimensional “ice,” because the  freeze regardless of the temperature. He said the research provides valuable insight on ways to leverage atomic interactions between nanotubes and  molecules to fabricate nanochannels and energy-storing nanocapacitors.

A paper on the research appears in the American Chemical Society journal Langmuir.

Shahsavari and his colleagues built molecular models of carbon and  with adjustable widths. They discovered boron nitride is best at constraining the shape of water when the nanotubes are 10.5 angstroms wide. (One angstrom is one hundred-millionth of a centimeter.)

The researchers already knew that  in tightly confined water take on interesting structural properties. Recent experiments by other labs showed strong evidence for the formation of nanotube ice and prompted the researchers to build density functional theory models to analyze the forces responsible.

Shahsavari’s team modeled water molecules, which are about 3 angstroms wide, inside carbon and boron nitride nanotubes of various chiralities (the angles of their atomic lattices) and between 8 and 12 angstroms in diameter. They discovered that nanotubes in the middle diameters had the most impact on the balance between molecular interactions and van der Waals pressure that prompted the transition from a square water tube to ice.

“If the nanotube is too small and you can only fit one water molecule, you can’t judge much,” Shahsavari said. “If it’s too large, the water keeps its amorphous shape. But at about 8 angstroms, the nanotubes’ van der Waals force starts to push water molecules into organized square shapes.”

He said the strongest interactions were found in boron nitride  due to the particular polarization of their atoms.

Shahsavari said nanotube ice could find use in molecular machines or as nanoscale capillaries, or foster ways to deliver a few molecules of water or sequestered drugs to targeted cells, like a nanoscale syringe.

 Explore further: Scientists say boron nitride-graphene hybrid may be right for next-gen green cars

More information: Farzaneh Shayeganfar et al, First Principles Study of Water Nanotubes Captured Inside Carbon/Boron Nitride Nanotubes, Langmuir (2018). DOI: 10.1021/acs.langmuir.8b00856

Rice U: New Lithium metal battery prototype boasts 3X the capacity of current lithium-ions ~ Dendrite Problem Solved?


graphene-nanotube-lithium-battery-4

Could a new material involving a carbon nanotube and graphene hybrid put an end to the dendrite problem in lithium batteries? (Credit: Tour Group/Rice University)

The high energy capacity of lithium-ion batteries has led to them powering everything from tiny mobile devices to huge trucks. But current lithium-ion battery technology is nearing its limits and the search is on for a better lithium battery. But one thing stands in the way: dendrites. If a new technology by Rice University scientists lives up to its potential, it could solve this problem and enable lithium-metal batteries that can hold three times the energy of lithium-ion ones.

Dendrites are microscopic lithium fibers that form on the anodes during the charging process, spreading like a rash till they reach the other electrode and causing the battery to short circuit. As companies such as Samsung know only too well, this can cause the battery to catch fire or even explode.

“Lithium-ion batteries have changed the world, no doubt,” says chemist Dr. James Tour, who led the study. “But they’re about as good as they’re going to get. Your cellphone’s battery won’t last any longer until new technology comes along.”

Rice logo_rice3So until scientists can figure out a way to solve the problem of dendrites, we’ll have to put our hopes for a higher capacity, faster-charging battery that can quell range anxiety on hold. This explains why there’s been no shortage of attempts to solve this problem, from using Kevlar to slow down dendrite growth to creating a new electrolyte that could lead to the development of an anode-free cell. So how does this new technology from Rice University compare?

For a start, it’s able to stop dendrite growth in its tracks. Key to it is a unique anode made from a material that was first created at the university five years ago. By using a covalent bond structure, it combines a two-dimensional graphene sheet and carbon nanotubes to form a seamless three-dimensional structure. As Tour explained back when the material was first unveiled:

“By growing graphene on metal (in this case copper) and then growing nanotubes from the graphene, the electrical contact between the nanotubes and the metal electrode is ohmic. That means electrons see no difference, because it’s all one seamless material.”

Close-up of the lithium metal coating the graphene-nanotube anode (Credit: Tour Group/Rice University)

 

Envisioned for use in energy storage and electronics applications such as supercapacitors, it wasn’t until 2014, when co-lead author Abdul-Rahman Raji was experimenting with lithium metal and the graphene-nanotube hybrid, that the researchers discovered its potential as a dendrite inhibitor.

“I reasoned that lithium metal must have plated on the electrode while analyzing results of experiments carried out to store lithium ions in the anode material combined with a lithium cobalt oxide cathode in a full cell,” says Raji. “We were excited because the voltage profile of the full cell was very flat. At that moment, we knew we had found something special.”

Closer analysis revealed no dendrites had grown when the lithium metal was deposited into a standalone hybrid anode – but would it work in a proper battery?

To test the anode, the researchers built full battery prototypes with sulfur-based cathodes that retained 80 percent capacity after more than 500 charge-discharge cycles (i.e. the rough equivalent of what a cellphone goes through in a two-year period). No signs of dendrites were observed on the anodes.

How it works

The low density and high surface area of the nanotube forest allow the lithium metal to coat the carbon hybrid material evenly when the battery is charged. And since there is plenty of space for the particles to slip in and out during the charge and discharge cycle, they end up being evenly distributed and this stops the growth of dendrites altogether.

According to the study, the anode material is capable of a lithium storage capacity of 3,351 milliamp hours per gram, which is close to pure lithium’s theoretical maximum of 3,860 milliamp hours per gram, and 10 times that of lithium-ion batteries. And since the nanotube carpet has a low density, this means it’s able to coat all the way down to substrate and maximize use of the available volume.

“Many people doing battery research only make the anode, because to do the whole package is much harder,” says Tour. “We had to develop a commensurate cathode technology based upon sulfur to accommodate these ultrahigh-capacity lithium anodes in first-generation systems. We’re producing these full batteries, cathode plus anode, on a pilot scale, and they’re being tested.”

The study was published in ACS Nano.

Source: Rice University

 

Creating a Life-Saving, Blood-Repellent Super Material – Revolutionizing Medical Implants: Colorado State University


blood-repellent-titanium-1-1

Briefly

  • Biomedical engineers and materials scientists have developed a “superhemophobic” surface treatment for titanium that repels liquids including blood, plasma, and water.
  • The result is a surface that completely repels any liquid with which it would come in contact – a material that could revolutionize medical implants.

GOODBYE REJECTION

Implanted medical devices like stents, catheters, and titanium rods are essential, life-saving tools for patients around the world. Still, having a foreign object in the human body does pose its own risks – chiefly, having the body reject the object or increasing the risk of dangerous blood clots. A new collaboration between two distinct scientific disciplines is working toward making those risks a concern of the past.

Biomedical engineers and materials scientists from Colorado State University (CSU) have developed a “superhemophobic” surface treatment for titanium that repels liquids including blood, plasma, and water. The titanium is essentially studded with nanoscale tubes treated with a non-stick chemical. The result is a surface that completely repels any liquid with which it would come in contact. The team’s findings are published in Advanced Healthcare Materials.

1-bloodrepelle
Fluorinated nanotubes provided the best superhemophobic surfaces in the CSU researchers’ experiments. Credit: Kota lab/Colorado State University

AN END TO CLOTTING

In cases where a body does reject a medical implant, the patient’s immune system detects the foreign object and mounts a defense against it, which can lead to serious inflammation and other complications. The real trick to the team’s surface is that the body doesn’t even recognize that it’s there. According to Arun Kota, assistant professor of mechanical engineering and biomedical engineering at CSU, “We are taking a material that blood hates to come in contact with, in order to make it compatible with blood.”

Regarding clotting, patients with medical implants often need to stay on a regimen of blood-thinning drugs to decrease the risk. However, blood thinners are not guaranteed to work, and they also carry the risk of leading to excessive bleeding due to the prevention of even beneficial clotting near wounds. As Ketul Popat, associate professor of mechanical engineering and biomedical engineering at CSU explains, “The reason blood clots is because it finds cells in the blood to go to and attach.” He continues, “if we can design materials where blood barely contacts the surface, there is virtually no chance of clotting.”

This material is only in its earliest stages of development. Should the team’s findings hold up to further scrutinization, these life-saving medical devices could be given an unprecedented boost in safety.

An electric car battery that could charge in just five minutes ~ Where is the Israeli Start-Up “+StoreDot” One Year Later? +Video


An Israeli startup is setting its sights on creating a battery for electric carsthat charges in just five minutes. If they meet their goal, the battery would be able to power a car for hundreds of miles in a single charge. StoreDot, founded in 2012, has already developed the FlashBattery for Smartphones that can fully charge in less than a minute. The startup has raised $66 million which it plans to use to get their FlashBattery technology into electric cars.

The relatively slow growth of the electric car market is often blamed upon the inconvenience of recharging. The best batteries currently available can last up to 250 miles, but take several hours to fully charge using a standard charger. Tesla’s high-speed charger takes 30 minutes to give their batteries about 170 miles of range, while Toyota’s Rav4, which takes longer to charge, can only go around 100 miles per charge. A fast-charging, affordable battery with long range, like the one StoreDot has proposed, could be the key to making electric cars more popular than their gas-powered competitors.

Related: The world’s fastest charging electric bus powers up in 10 seconds flat

 

StoreDot describes their battery as a sponge, which soaks up electricity like a sponge soaks up water. The technology is based on peptides that have been turned into energy-storing nanotubes. The nanotubes, affectionately named Nanodots by the company, can soak up huge amounts of electricity all at once. Using around 7,000 of these Nanodots, they have promised to create an EV battery that goes the distance.

EV batteries, electric cars, electric car batteries, fast-charging batteries, StoreDot, Israel technology, lithium-ion, green technology, green cars

“This fast-charging technology shortens the amount of time drivers will have to wait in line to charge their cars, while also reducing the number of charging posts in each station,” Dr. Doron Myersdorf, StoreDot’s CEO told crowds at the 2014 ThinkNext event. It will result in “considerably cutting the overall cost of owning an electric car.”

For the Latest News About +StoreDot Go to: +StoreDot

University of California – San Diego:”Teeny-Tiny” Nanotubes Enhance and Upgrade Implant Technology


Operator in factory use microscope

Operator in factory use microscope

Nanotube Surface Technology

The nanotube surface treatment evolved from solar panel research by various groups and biomaterials research by Sungho Jin, PhD at the University of California San Diego (UCSD). Others, including Amit Bandyopadhyay, PhD and collaborating researchers at Washington State University (WSU), and Masa Ishigami, PhD’s team at the University of Central Florida (UCF), have helped to enhance the technology. Established companies specializing in medical implant surface treatments have helped to scale and commercialize the technology.

It is hard to imagine just how tiny nanotubes are compared to traditional implant surface structures. They are thousands of times smaller than traditional porous structures on implants or even cells. Millions of nanotubes form a surface texture and energy that interacts with the outer membrane of a cell wall. These arrays of millions of nanotubes per square millimeter can be formed onto flat or porous structures.

Nanotubes are not an additive coating. They are formed into the existing metal oxide tissue-contacting surface of implants. Titanium, tantalum, and zirconium metals and alloy implants are directly treated with an anodization process to form the nanotubes. Implants made from other materials such as PEEK, medical polymers, ceramics and CoCrMo are indirectly treated by first applying a thin layer of titanium that is then processed by a similar patented anodization technique to form nanotubes on its surface.

Any implant surface that requires stable fixation against bone such as a hip, knee, ankle, shoulder, hand, or spinal implant can be enhanced by nanotubes.

How does it work?

  • It mimics the stem cells around the implant into thinking that the surface of the implant is actually another cell.
  • The super-absorbent, ultra-hydrophilic surface enhances tissue cell attachment.
  • The cell then spreads and branches out on the implant surface.
  • The stem cell differentiates to match the cells that are around the nanotube surface.
  • If around bone cells, Osteoblasts form and the mineralization process begins.
  • If near cartilage, chondrocyte cells form starting cartilage regeneration

Testing

“In Vivo studies have shown that titanium implants that have nanotubes on them have a nine times greater osseointegration bond strength as compared to implants that don’t. We also see faster cell differentiation—the bonding happens weeks faster than it would without nanotubes. We’re interested in allowing patients to walk on or fully use their implants faster. We’re trying to speed that up not by days, but by weeks and perhaps months”

Sungho Jin, PhD

Berkeley: Nature-Inspired Nanotubes That Assemble Themselves, With Precision


Berleley nanotube 050316

When it comes to the various nanowidgets scientists are developing, nanotubes are especially intriguing. That’s because hollow tubes that have diameters of only a few billionths of a meter have the potential to be incredibly useful, from delivering cancer-fighting drugs inside cells to desalinating seawater.

But building nanostructures is difficult. And creating a large quantity of nanostructures with the same trait, such as millions of nanotubes with identical diameters, is even more difficult. This kind of precision manufacturing is needed to create the nanotechnologies of tomorrow.

Help could be on the way. As reported online this week in the journal Proceedings of the National Academy of Sciences, researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have discovered a family of nature-inspired polymers that, when placed in water, spontaneously assemble into hollow crystalline nanotubes. What’s more, the nanotubes can be tuned to all have the same diameter of between five and ten nanometers, depending on the length of the polymer chain.

The polymers have two chemically distinct blocks that are the same size and shape. The scientists learned these blocks act like molecular tiles that form rings, which stack together to form nanotubes up to 100 nanometers long, all with the same diameter.

“This points to a new way we can use synthetic polymers to create complex nanostructures in a very precise way,” says Ron Zuckermann, who directs the Biological Nanostructures Facility in Berkeley Lab’s Molecular Foundry, where much of this research was conducted.

Several other Berkeley Lab scientists contributed to this research, including Nitash Balsara of the Materials Sciences Division and Ken Downing of the Molecular Biophysics and Integrated Bioimaging Division.

“Creating uniform structures in high yield is a goal in nanotechnology,” adds Zuckermann. “For example, if you can control the diameter of nanotubes, and the chemical groups exposed in their interior, then you can control what goes through—which could lead to new filtration and desalination technologies, to name a few examples.”

The research is the latest in the effort to build nanostructures that approach the complexity and function of nature’s proteins, but are made of durable materials. In this work, the Berkeley Lab scientists studied a polymer that is a member of the peptoid family. Peptoids are rugged synthetic polymers that mimic peptides, which nature uses to form proteins. They can be tuned at the atomic scale to carry out specific functions.

For the past several years, the scientists have studied a particular type of peptoid, called a diblock copolypeptoid, because it binds with lithium ions and could be used as a battery electrolyte. Along the way, they serendipitously found the compounds form nanotubes in water. How exactly these nanotubes form has yet to be determined, but this latest research sheds light on their structure, and hints at a new design principle that could be used to build nanotubes and other complex nanostructures.

This cryo-electron microscopy image shows the self-assembling nanotubes have the same diameter. The circles are head-on views of nanotubes. The dark-striped features likely result from crystallized peptoid blocks. (Credit: Berkeley Lab)

Diblock copolypeptoids are composed of two peptoid blocks, one that’s hydrophobic one that’s hydrophilic. The scientists discovered both blocks crystallize when they meet in water, and form rings consisting of two to three individual peptoids. The rings then form hollow nanotubes.

Cryo-electron microscopy imaging of 50 of the nanotubes showed the diameter of each tube is highly uniform along its length, as well as from tube to tube. This analysis also revealed a striped pattern across the width of the nanotubes, which indicates the rings stack together to form tubes, and rules out other packing arrangements. In addition, the peptoids are thought to arrange themselves in a brick-like pattern, with hydrophobic blocks lining up with other hydrophobic blocks, and the same for hydrophilic blocks.

“Images of the tubes captured by electron microscopy were essential for establishing the presence of this unusual structure,” says Balsara. “The formation of tubular structures with a hydrophobic core is common for synthetic polymers dispersed in water, so we were quite surprised to see the formation of hollow tubes without a hydrophobic core.”

X-ray scattering analyses conducted at beamline 7.3.3 of the Advanced Light Source revealed even more about the nanotubes’ structure. For example, it showed that one of the peptoid blocks, which is usually amorphous, is actually crystalline.

Remarkably, the nanotubes assemble themselves without the usual nano-construction aids, such as electrostatic interactions or hydrogen bond networks.

“You wouldn’t expect something as intricate as this could be created without these crutches,” says Zuckermann. “But it turns out the chemical interactions that hold the nanotubes together are very simple. What’s special here is that the two peptoid blocks are chemically distinct, yet almost exactly the same size, which allows the chains to pack together in a very regular way. These insights could help us design useful nanotubes and other structures that are rugged and tunable—and which have uniform structures.”

The Advanced Light Source and the Molecular Foundry are DOE Office of Science User Facilities located at Berkeley Lab.

The research was supported by the Department of Energy’s Office of Science.

Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit www.lbl.gov.

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‘On-Demand ‘ Nanotube Forests’ for Electronics Fabrication


Nanotube Forrests 042116 id43200A system that uses a laser and electrical current to precisely position and align carbon nanotubes represents a potential new tool for creating electronic devices out of the tiny fibers.
 

Because carbon nanotubes have unique thermal and electrical properties, they may have future applications in electronic cooling and as devices in microchips, sensors and circuits. Being able to orient the carbon nanotubes in the same direction and precisely position them could allow these nanostructures to be used in such applications.

However, it is difficult to manipulate something so small that thousands of them would fit within the diameter of a single strand of hair, said Steven T. Wereley, a professor of mechanical engineering at Purdue University.
“One of the things we can do with this technique is assemble carbon nanotubes, put them where we want and make them into complicated structures,” he said.

 

This graphic illustrates a system that uses a laser and electrical field to precisely position and align carbon nanotube
This graphic illustrates a system that uses a laser and electrical field to precisely position and align carbon nanotubes, representing a potential new tool for assembling sensors and devices out of the tiny nanotubes and nanowires. The two microscope images at the bottom show the nanotubes aligned (left) and returning to their random orientation after the electric field and laser were turned off. (Image: Avanish Mishra and Steven Wereley)
New findings from research led by Purdue doctoral student Avanish Mishra are detailed in a paper that has appeared online March 24 in the journal Microsystems and Nanoengineering (“Dynamic optoelectric trapping and deposition of multiwalled carbon nanotubes”).
The technique, called rapid electrokinetic patterning (REP), uses two parallel electrodes made of indium tin oxide, a transparent and electrically conductive material. The nanotubes are arranged randomly while suspended in deionized water. Applying an electric field causes them to orient vertically. Then an infrared laser heats the fluid, producing a doughnut-shaped vortex of circulating liquid between the two electrodes. This vortex enables the researchers to move the nanotubes and reposition them.
“When we apply the electric field, they are immediately oriented vertically, and then when we apply the laser, it starts a vortex, that sweeps them into little nanotube forests,” Wereley said.
The research paper was authored by Mishra; Purdue graduate student Katherine Clayton; University of Louisville student Vanessa Velasco; Stuart J. Williams, an assistant professor of mechanical engineering at the University of Louisville and director of the Integrated Microfluidic Systems Laboratory; and Wereley. Williams is a former doctoral student at Purdue.
The technique overcomes limitations of other methods for manipulating particles measured on the scale of nanometers, or billionths of a meter. In this study, the procedure was used for multiwalled carbon nanotubes, which are rolled-up ultrathin sheets of carbon called graphene. However, according to the researchers, using this technique other nanoparticles such as nanowires and nanorods can be similarly positioned and fixed in vertical orientation.
The researchers have received a U.S. patent on the system.
The experimental work was performed at the Birck Nanotechnology Center in Purdue’s Discovery Park. Future research will explore using the technique to create devices.
Source: By Emil Venere, Purdue University

 

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