Tag Archives: Il Woong Jung

Small, soft, and electrically functional: an injectable biomaterial

This development could be looked at as a form of synthetic biology without the genetic engineering. From a July 1, 2016 news item on ScienceDaily,

Ideally, injectable or implantable medical devices should not only be small and electrically functional, they should be soft, like the body tissues with which they interact. Scientists from two UChicago labs set out to see if they could design a material with all three of those properties.

The material they came up with, published online June 27, 2016, in Nature Materials, forms the basis of an ingenious light-activated injectable device that could eventually be used to stimulate nerve cells and manipulate the behavior of muscles and organs.

“Most traditional materials for implants are very rigid and bulky, especially if you want to do electrical stimulation,” said Bozhi Tian, an assistant professor in chemistry whose lab collaborated with that of neuroscientist Francisco Bezanilla on the research.

The new material, in contrast, is soft and tiny — particles just a few micrometers in diameter (far less than the width of a human hair) that disperse easily in a saline solution so they can be injected. The particles also degrade naturally inside the body after a few months, so no surgery would be needed to remove them.

A July 1, 2016 University of Chicago news release (also on EurekAlert) by , which originated the news item, provides more detail,

Each particle is built of two types of silicon that together form a structure full of nano-scale pores, like a tiny sponge. And like a sponge, it is squishy — a hundred to a thousand times less rigid than the familiar crystalline silicon used in transistors and solar cells. “It is comparable to the rigidity of the collagen fibers in our bodies,” said Yuanwen Jiang, Tian’s graduate student. “So we’re creating a material that matches the rigidity of real tissue.”

The material constitutes half of an electrical device that creates itself spontaneously when one of the silicon particles is injected into a cell culture, or, eventually, a human body. The particle attaches to a cell, making an interface with the cell’s plasma membrane. Those two elements together — cell membrane plus particle — form a unit that generates current when light is shined on the silicon particle.

“You don’t need to inject the entire device; you just need to inject one component,” João L. Carvalho-de-Souza , Bezanilla’s postdoc said. “This single particle connection with the cell membrane allows sufficient generation of current that could be used to stimulate the cell and change its activity. After you achieve your therapeutic goal, the material degrades naturally. And if you want to do therapy again, you do another injection.”

The scientists built the particles using a process they call nano-casting. They fabricate a silicon dioxide mold composed of tiny channels — “nano-wires” — about seven nanometers in diameter (less than 10,000 times smaller than the width of a human hair) connected by much smaller “micro-bridges.” Into the mold they inject silane gas, which fills the pores and channels and decomposes into silicon.

And this is where things get particularly cunning. The scientists exploit the fact the smaller an object is, the more the atoms on its surface dominate its reactions to what is around it. The micro-bridges are minute, so most of their atoms are on the surface. These interact with oxygen that is present in the silicon dioxide mold, creating micro-bridges made of oxidized silicon gleaned from materials at hand. The much larger nano-wires have proportionately fewer surface atoms, are much less interactive, and remain mostly pure silicon. [I have a note regarding ‘micro’ and ‘nano’ later in this posting.]

“This is the beauty of nanoscience,” Jiang said. “It allows you to engineer chemical compositions just by manipulating the size of things.”

Web-like nanostructure

Finally, the mold is dissolved. What remains is a web-like structure of silicon nano-wires connected by micro-bridges of oxidized silicon that can absorb water and help increase the structure’s softness. The pure silicon retains its ability to absorb light.

Transmission electron microscopy image shows an ordered nanowire array. The 100-nanometer scale bar is 1,000 times narrower than a hair. Courtesy of Tian Lab

Transmission electron microscopy image shows an ordered nanowire array. The 100-nanometer scale bar is 1,000 times narrower than a hair. Courtesy of
Tian Lab

The scientists have added the particles onto neurons in culture in the lab, shone light on the particles, and seen current flow into the neurons which activates the cells. The next step is to see what happens in living animals. They are particularly interested in stimulating nerves in the peripheral nervous system that connect to organs. These nerves are relatively close to the surface of the body, so near-infra-red wavelength light can reach them through the skin.

Tian imagines using the light-activated devices to engineer human tissue and create artificial organs to replace damaged ones. Currently, scientists can make engineered organs with the correct form but not the ideal function.

To get a lab-built organ to function properly, they will need to be able to manipulate individual cells in the engineered tissue. The injectable device would allow a scientist to do that, tweaking an individual cell using a tightly focused beam of light like a mechanic reaching into an engine and turning a single bolt. The possibility of doing this kind of synthetic biology without genetic engineering [emphasis mine] is enticing.

“No one wants their genetics to be altered,” Tian said. “It can be risky. There’s a need for a non-genetic system that can still manipulate cell behavior. This could be that kind of system.”

Tian’s graduate student Yuanwen Jiang did the material development and characterization on the project. The biological part of the collaboration was done in the lab of Francisco Bezanilla, the Lillian Eichelberger Cannon Professor of Biochemistry and Molecular Biology, by postdoc João L. Carvalho-de-Souza. They were, said Tian, the “heroes” of the work.

I was a little puzzled about the use of the word ‘micro’ in a context suggesting it was smaller than something measured at the nanoscale. Dr. Tian very kindly cleared up my confusion with this response in a July 4, 2016 email,

In fact, the definition of ‘micro’ and ’nano’ have been quite ambiguous in literature. For example, microporous materials (e.g., zeolite) usually refer to materials with pore sizes of less than 2 nm — this is defined based on IUPAC [International Union of Pure and Applied Chemistry] definition (http://goldbook.iupac.org/M03853.html). We used ‘micro-bridges’ because they come from the ‘micropores’ in the original template.

Thank you Dr. Tian for that very clear reply and Steve Koppes for forwarding my request to Dr. Tian!

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

Heterogeneous silicon mesostructures for lipid-supported bioelectric interfaces by Yuanwen Jiang, João L. Carvalho-de-Souza, Raymond C. S. Wong, Zhiqiang Luo, Dieter Isheim, Xiaobing Zuo, Alan W. Nicholls, Il Woong Jung, Jiping Yue, Di-Jia Liu, Yucai Wang, Vincent De Andrade, Xianghui Xiao, Luizetta Navrazhnykh, Dara E. Weiss, Xiaoyang Wu, David N. Seidman, Francisco Bezanilla, & Bozhi Tian. Nature Materials (2016)  doi:10.1038/nmat4673 Published online 27 June 2016

This paper is behind a paywall.

I gather animal testing will be the next step as they continue to develop this exciting technology. Good luck!

Casimir and its reins: engineering nanostructures to control quantum effects

Thank you to whomever wrote this headline for the Oct. 22, 2013 US National Institute of Standards and Technology (NIST) news release, also on EurekAlert, titled: The Reins of Casimir: Engineered Nanostructures Could Offer Way to Control Quantum Effect … Once a Mystery Is Solved, for getting the word ‘reins’ correct.

I can no longer hold back my concern over the fact that there are three words that sound the same but have different meanings and one of those words is often mistakenly used in place of the other.

reins

reigns

rains

The first one, reins, refers to narrow leather straps used to control animals (usually horses), as per this picture, It’s also used as a verb to indicate situation where control must be exerted, e.g., the spending must be reined in.

Reining Sliding Stop Mannheim Maimarkt 2007 Date 01.05.2007 Source  Own work Author AllX [downloaded from http://en.wikipedia.org/wiki/File:Reining_slidingstop.jpg]

Reining Sliding Stop Mannheim Maimarkt 2007 Date 01.05.2007 Credit: AllX [downloaded from http://en.wikipedia.org/wiki/File:Reining_slidingstop.jpg]

 This ‘reign’ usually references people like these,

“Queen Elizabeth II greets employees on her walk from NASA’s Goddard Space Flight Center mission control to a reception in the center’s main auditorium in Greenbelt, Maryland where she was presented with a framed Hubble image by Congressman Steny Hoyer and Senator Barbara Mikulski. Queen Elizabeth II and her husband, Prince Philip, Duke of Edinburgh, visited the NASA Goddard Space Flight Center as one of the last stops on their six-day United States visit.” Credit: NASA/Bill Ingalls [downloaded from http://en.wikipedia.org/wiki/File:Elizabeth_II_greets_NASA_GSFC_employees,_May_8,_2007_edit.jpg]

“Queen Elizabeth II greets employees on her walk from NASA’s Goddard Space Flight Center mission control to a reception in the center’s main auditorium in Greenbelt, Maryland where she was presented with a framed Hubble image by Congressman Steny Hoyer and Senator Barbara Mikulski. Queen Elizabeth II and her husband, Prince Philip, Duke of Edinburgh, visited the NASA Goddard Space Flight Center as one of the last stops on their six-day United States visit.” Credit: NASA/Bill Ingalls [downloaded from http://en.wikipedia.org/wiki/File:Elizabeth_II_greets_NASA_GSFC_employees,_May_8,_2007_edit.jpg]

 And,

Thailand's King Bhumibol Adulyadej waves to well-wishers during a concert at Siriraj hospital in Bangkok on September 29, 2010. Credit: Government of Thailand [downloaded from http://en.wikipedia.org/wiki/File:King_Bhumibol_Adulyadej_2010-9-29.jpg]

Thailand’s King Bhumibol Adulyadej waves to well-wishers during a concert at Siriraj hospital in Bangkok on September 29, 2010. Credit: Government of Thailand [downloaded from http://en.wikipedia.org/wiki/File:King_Bhumibol_Adulyadej_2010-9-29.jpg]

Kings, Queens, etc. reign over or rule their subjects or they have reigns, i.e., the period during which they hold the position of queen/king, etc. There are also uses such as this one found in the song title ‘Love Reign O’er Me’ (Pete Townshend)

I’ve lost count of the times I’ve seen ‘reigns’ used in place of ‘reins’, the worst part being? I’ve caught myself making the mistake. So, a heartfelt thank you to the NIST news release writer for getting it right. As for the other ‘rains’, neither I not anyone else seems to make that mistake (so far as I’ve seen).

Now on to the news,

You might think that a pair of parallel plates hanging motionless in a vacuum just a fraction of a micrometer away from each other would be like strangers passing in the night—so close but destined never to meet. Thanks to quantum mechanics, you would be wrong.

Scientists working to engineer nanoscale machines know this only too well as they have to grapple with quantum forces and all the weirdness that comes with them. These quantum forces, most notably the Casimir effect, can play havoc if you need to keep closely spaced surfaces from coming together.

Controlling these effects may also be necessary for making small mechanical parts that never stick to each other, for building certain types of quantum computers, and for studying gravity at the microscale.

In trying to solve the problem of keeping closely spaced surfaces from coming together, the scientists uncovered another problem,

One of the insights of quantum mechanics is that no space, not even outer space, is ever truly empty. It’s full of energy in the form of quantum fluctuations, including fluctuating electromagnetic fields that seemingly come from nowhere and disappear just as fast.

Some of this energy, however, just isn’t able to “fit” in the submicrometer space between a pair of electromechanical contacts. More energy on the outside than on the inside results in a kind of “pressure” called the Casimir force, which can be powerful enough to push the contacts together and stick.

Prevailing theory does a good job describing the Casimir force between featureless, flat surfaces and even between most smoothly curved surfaces. However, according to NIST researcher and co-author of the paper, Vladimir Aksyuk, existing theory fails to predict the interactions they observed in their experiment.

“In our experiment, we measured the Casimir attraction between a gold-coated sphere and flat gold surfaces patterned with rows of periodic, flat-topped ridges, each less than 100 nanometers across, separated by somewhat wider gaps with deep sheer-walled sides,” says Aksyuk. “We wanted to see how a nanostructured metallic surface would affect the Casimir interaction, which had never been attempted with a metal surface before. Naturally, we expected that there would be reduced attraction between our grooved surface and the sphere, regardless of the distance between them, because the top of the grooved surface presents less total surface area and less material. However, we knew the Casimir force’s dependence on the surface shape is not that simple.”

Indeed, what they found was more complicated.

According to Aksyuk, when they increased the separation between the surface of the sphere and the grooved surface, the researchers found that the Casimir attraction decreased much more quickly than expected. When they moved the sphere farther away, the force fell by a factor of two below the theoretically predicted value. When they moved the sphere surface close to the ridge tops, the attraction per unit of ridge top surface area increased.

“Theory can account for the stronger attraction, but not for the too-rapid weakening of the force with increased separation,” says Aksyuk. “So this is new territory, and the physics community is going to need to come up with a new model to describe it.”

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

Strong Casimir force reduction through metallic surface nanostructuring by Francesco Intravaia, Stephan Koev, Il Woong Jung, A. Alec Talin, Paul S. Davids, Ricardo S. Decca, Vladimir A. Aksyuk, Diego A. R. Dalvit, & Daniel López. Nature Communications 4, Article number: 2515 doi:10.1038/ncomms3515 Published 27 September 2013.

This article is open access.