Tag Archives: Benjamin J. Wiley

Lab-made cartilage gel for stiff, achy knees

Researchers claim their lab-made cartilage is better than the real thing in an August 11, 2022 news item on phys.org, Note: Links have been removed,

Over-the-counter pain relievers, physical therapy, steroid injections—some people have tried it all and are still dealing with knee pain.

Often knee pain comes from the progressive wear and tear of cartilage known as osteoarthritis, which affects nearly one in six adults—867 million people—worldwide. For those who want to avoid replacing the entire knee joint, there may soon be another option that could help patients get back on their feet fast, pain-free, and stay that way.

Writing in the journal Advanced Functional Materials, a Duke University-led team says they have created the first gel-based cartilage substitute that is even stronger and more durable than the real thing.

Caption: Duke researchers have developed a gel-based cartilage substitute to relieve achy knees that’s even stronger and more durable than the real thing. Clinical trials to start next year. Credit: Canva Credit: Benjamin Wiley, Duke University

Here’s the August 11, 2022 Duke University news release (also on EurekAlert), which originated the news item, where you’ll find more details about the research, Note: Links have been removed,

Mechanical testing reveals that the Duke team’s hydrogel — a material made of water-absorbing polymers — can be pressed and pulled with more force than natural cartilage, and is three times more resistant to wear and tear.

Implants made of the material are currently being developed by Sparta Biomedical and tested in sheep. Researchers are gearing up to begin clinical trials in humans next year.

“If everything goes according to plan, the clinical trial should start as soon as April 2023,” said Duke chemistry professor Benjamin Wiley, who led the research along with Duke mechanical engineering and materials science professor Ken Gall.

To make this material, the Duke team took thin sheets of cellulose fibers and infused them with a polymer called polyvinyl alcohol — a viscous goo consisting of stringy chains of repeating molecules — to form a gel.

The cellulose fibers act like the collagen fibers in natural cartilage, Wiley said — they give the gel strength when stretched. The polyvinyl alcohol helps it return to its original shape. The result is a Jello-like material, 60% water, which is supple yet surprisingly strong.

Natural cartilage can withstand a whopping 5,800 to 8,500 pounds per inch of tugging and squishing, respectively, before reaching its breaking point. Their lab-made version is the first hydrogel that can handle even more. It is 26% stronger than natural cartilage in tension, something like suspending seven grand pianos from a key ring, and 66% stronger in compression — which would be like parking a car on a postage stamp.

“It’s really off the charts in terms of hydrogel strength,” Wiley said.

The team has already made hydrogels with remarkable properties. In 2020, they reported that they had created the first hydrogel strong enough for knees, which feel the force of two to three times body weight with each step.

Putting the gel to practical use as a cartilage replacement, however, presented additional design challenges. One was achieving the upper limits of cartilage’s strength. Activities like hopping, lunging, or climbing stairs put some 10 Megapascals of pressure on the cartilage in the knee, or about 1,400 pounds per square inch. But the tissue can take up to four times that before it breaks.

“We knew there was room for improvement,” Wiley said.

In the past, researchers attempting to create stronger hydrogels used a freeze-thaw process to produce crystals within the gel, which drive out water and help hold the polymer chains together. In the new study, instead of freezing and thawing the hydrogel, the researchers used a heat treatment called annealing to coax even more crystals to form within the polymer network.

By increasing the crystal content, the researchers were able to produce a gel that can withstand five times as much stress from pulling and nearly twice as much squeezing relative to freeze-thaw methods.

The improved strength of the annealed gel also helped solve a second design challenge: securing it to the joint and getting it to stay put.

Cartilage forms a thin layer that covers the ends of bones so they don’t grind against one another. Previous studies haven’t been able to attach hydrogels directly to bone or cartilage with sufficient strength to keep them from breaking loose or sliding off. So the Duke team came up with a different approach.

Their method of attachment involves cementing and clamping the hydrogel to a titanium base. This is then pressed and anchored into a hole where the damaged cartilage used to be. Tests show the design stays fastened 68% more firmly than natural cartilage on bone.

“Another concern for knee implants is wear over time, both of the implant itself and the opposing cartilage,” Wiley said.

Other researchers have tried replacing damaged cartilage with knee implants made of metal or polyethylene, but because these materials are stiffer than cartilage they can chafe against other parts of the knee.

In wear tests, the researchers took artificial cartilage and natural cartilage and spun them against each other a million times, with a pressure similar to what the knee experiences during walking. Using a high-resolution X-ray scanning technique called micro-computed tomography (micro-CT), the scientists found that the surface of their lab-made version held up three times better than the real thing. Yet because the hydrogel mimics the smooth, slippery, cushiony nature of real cartilage, it protects other joint surfaces from friction as they slide against the implant.

Natural cartilage is remarkably durable stuff. But once damaged, it has limited ability to heal because it doesn’t have any blood vessels, Wiley said.

In the United States, osteoarthritis is twice as common today than it was a century ago. Surgery is an option when conservative treatments fail. Over the decades surgeons have developed a number of minimally invasive approaches, such as removing loose cartilage, or making holes to stimulate new growth, or transplanting healthy cartilage from a donor. But all of these methods require months of rehab, and some percentage of them fail over time.

Generally considered a last resort, total knee replacement is a proven way to relieve pain. But artificial joints don’t last forever, either. Particularly for younger patients who want to avoid major surgery for a device that will only need to be replaced again down the line, Wiley said, “there’s just not very good options out there.”

“I think this will be a dramatic change in treatment for people at this stage,” Wiley said.

This work was supported in part by Sparta Biomedical and by the Shared Materials Instrumentation Facility at Duke University. Wiley and Gall are shareholders in Sparta Biomedical.

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

A Synthetic Hydrogel Composite with a Strength and Wear Resistance Greater than Cartilage by Jiacheng Zhao, Huayu Tong, Alina Kirillova, William J. Koshut, Andrew Malek, Natasha C. Brigham, Matthew L. Becker, Ken Gall, Benjamin J. Wiley. Advanced Functional Materials DOI: https://doi.org/10.1002/adfm.202205662 First published: 04 August 2022

This paper is behind a paywall.

You can find Sparta Biomedical here.

‘Brewing up’ conductive inks for printable electronics

Scientists from Duke University aren’t exactly ‘brewing’ or ‘cooking up’ the inks but they do come close according to a Jan. 3, 2017 news item on ScienceDaily,

By suspending tiny metal nanoparticles in liquids, Duke University scientists are brewing up conductive ink-jet printer “inks” to print inexpensive, customizable circuit patterns on just about any surface.

A Jan. 3, 2017 Duke University news release (also on EurekAlert), which originated the news item, explains why this technique could lead to more accessible printed electronics,

Printed electronics, which are already being used on a wide scale in devices such as the anti-theft radio frequency identification (RFID) tags you might find on the back of new DVDs, currently have one major drawback: for the circuits to work, they first have to be heated to melt all the nanoparticles together into a single conductive wire, making it impossible to print circuits on inexpensive plastics or paper.

A new study by Duke researchers shows that tweaking the shape of the nanoparticles in the ink might just eliminate the need for heat.

By comparing the conductivity of films made from different shapes of silver nanostructures, the researchers found that electrons zip through films made of silver nanowires much easier than films made from other shapes, like nanospheres or microflakes. In fact, electrons flowed so easily through the nanowire films that they could function in printed circuits without the need to melt them all together.

“The nanowires had a 4,000 times higher conductivity than the more commonly used silver nanoparticles that you would find in printed antennas for RFID tags,” said Benjamin Wiley, assistant professor of chemistry at Duke. “So if you use nanowires, then you don’t have to heat the printed circuits up to such high temperature and you can use cheaper plastics or paper.”

“There is really nothing else I can think of besides these silver nanowires that you can just print and it’s simply conductive, without any post-processing,” Wiley added.

These types of printed electronics could have applications far beyond smart packaging; researchers envision using the technology to make solar cells, printed displays, LEDS, touchscreens, amplifiers, batteries and even some implantable bio-electronic devices. The results appeared online Dec. 16 [2016] in ACS Applied Materials and Interfaces.

Silver has become a go-to material for making printed electronics, Wiley said, and a number of studies have recently appeared measuring the conductivity of films with different shapes of silver nanostructures. However, experimental variations make direct comparisons between the shapes difficult, and few reports have linked the conductivity of the films to the total mass of silver used, an important factor when working with a costly material.

“We wanted to eliminate any extra materials from the inks and simply hone in on the amount of silver in the films and the contacts between the nanostructures as the only source of variability,” said Ian Stewart, a recent graduate student in Wiley’s lab and first author on the ACS paper.

Stewart used known recipes to cook up silver nanostructures with different shapes, including nanoparticles, microflakes, and short and long nanowires, and mixed these nanostructures with distilled water to make simple “inks.” He then invented a quick and easy way to make thin films using equipment available in just about any lab — glass slides and double-sided tape.

“We used a hole punch to cut out wells from double-sided tape and stuck these to glass slides,” Stewart said. By adding a precise volume of ink into each tape “well” and then heating the wells — either to relatively low temperature to simply evaporate the water or to higher temperatures to begin melting the structures together — he created a variety of films to test.

The team say they weren’t surprised that the long nanowire films had the highest conductivity. Electrons usually flow easily through individual nanostructures but get stuck when they have to jump from one structure to the next, Wiley explained, and long nanowires greatly reduce the number of times the electrons have to make this “jump”.

But they were surprised at just how drastic the change was. “The resistivity of the long silver nanowire films is several orders of magnitude lower than silver nanoparticles and only 10 times greater than pure silver,” Stewart said.

The team is now experimenting with using aerosol jets to print silver nanowire inks in usable circuits. Wiley says they also want to explore whether silver-coated copper nanowires, which are significantly cheaper to produce than pure silver nanowires, will give the same effect.

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

Effect of Morphology on the Electrical Resistivity of Silver Nanostructure Films by Ian E. Stewart, Myung Jun Kim, and Benjamin J. Wiley. ACS Appl. Mater. Interfaces, Article ASAP
DOI: 10.1021/acsami.6b12289 Publication Date (Web): December 16, 2016

Copyright © 2016 American Chemical Society

This paper is behind a paywall but there is an image of the silver nanowires, which is not exactly compensation but is interesting,

Caption: Duke University chemists have found that silver nanowire films like these conduct electricity well enough to form functioning circuits without applying high temperatures, enabling printable electronics on heat-sensitive materials like paper or plastic.
Credit: Ian Stewart and Benjamin Wiley