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‘Nanoantennae’ Make Infrared Vision Possible

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Nanoparticles for infrared vision
Caption: Nanoparticles (green) bind to light-sensing rod (violet) and cone (red) cells in the mouse retina. Dashed lines (white) highlight cells’ inner/outer segments.
Credit: Ma et al. Cell, 2019

Infrared vision often brings to mind night-vision goggles that allow soldiers to see in the dark, like you might have seen in the movie Zero Dark Thirty. But those bulky goggles may not be needed one day to scope out enemy territory or just the usual things that go bump in the night. In a dramatic advance that brings together material science and the mammalian vision system, researchers have just shown that specialized lab-made nanoparticles applied to the retina, the thin tissue lining the back of the eye, can extend natural vision to see in infrared light.

The researchers showed in mouse studies that their specially crafted nanoparticles bind to the retina’s light-sensing cells, where they act like “nanoantennae” for the animals to see and recognize shapes in infrared—day or night—for at least 10 weeks. Even better, the mice maintained their normal vision the whole time and showed no adverse health effects. In fact, some of the mice are still alive and well in the lab, although their ability to see in infrared may have worn off.

When light enters the eyes of mice, humans, or any mammal, light-sensing cells in the retina absorb wavelengths within the range of visible light. (That’s roughly from 400 to 700 nanometers.) While visible light includes all the colors of the rainbow, it actually accounts for only a fraction of the full electromagnetic spectrum. Left out are the longer wavelengths of infrared light. That makes infrared light invisible to the naked eye.

In the study reported in the journal Cell, an international research team including Gang Han, University of Massachusetts Medical School, Worcester, wanted to find a way for mammalian light-sensing cells to absorb and respond to the longer wavelengths of infrared [1]. It turns out Han’s team had just the thing to do it.

His NIH-funded team was already working on the nanoparticles now under study for application in a field called optogenetics—the use of light to control living brain cells [2]. Optogenetics normally involves the stimulation of genetically modified brain cells with blue light. The trouble is that blue light doesn’t penetrate brain tissue well.

That’s where Han’s so-called upconversion nanoparticles (UCNPs) came in. They attempt to get around the normal limitations of optogenetic tools by incorporating certain rare earth metals. Those metals have a natural ability to absorb lower energy infrared light and convert it into higher energy visible light (hence the term upconversion).

But could those UCNPs also serve as miniature antennae in the eye, receiving infrared light and emitting readily detected visible light? To find out in mouse studies, the researchers injected a dilute solution containing UCNPs into the back of eye. Such sub-retinal injections are used routinely by ophthalmologists to treat people with various eye problems.

These UCNPs were modified with a protein that allowed them to stick to light-sensing cells. Because of the way that UCNPs absorb and emit wavelengths of light energy, they should to stick to the light-sensing cells and make otherwise invisible infrared light visible as green light.

Their hunch proved correct, as mice treated with the UCNP solution began seeing in infrared! How could the researchers tell? First, they shined infrared light into the eyes of the mice. Their pupils constricted in response just as they would with visible light. Then the treated mice aced a series of maneuvers in the dark that their untreated counterparts couldn’t manage. The treated animals also could rely on infrared signals to make out shapes.

The research is not only fascinating, but its findings may also have a wide range of intriguing applications. One could imagine taking advantage of the technology for use in hiding encrypted messages in infrared or enabling people to acquire a temporary, built-in ability to see in complete darkness.

With some tweaks and continued research to confirm the safety of these nanoparticles, the system might also find use in medicine. For instance, the nanoparticles could potentially improve vision in those who can’t see certain colors. While such infrared vision technologies will take time to become more widely available, it’s a great example of how one area of science can cross-fertilize another.

References:

[1] Mammalian Near-Infrared Image Vision through Injectable and Self-Powered Retinal Nanoantennae. Ma Y, Bao J, Zhang Y, Li Z, Zhou X, Wan C, Huang L, Zhao Y, Han G, Xue T. Cell. 2019 Feb 27. [Epub ahead of print]

[2] Near-Infrared-Light Activatable Nanoparticles for Deep-Tissue-Penetrating Wireless Optogenetics. Yu N, Huang L, Zhou Y, Xue T, Chen Z, Han G. Adv Healthc Mater. 2019 Jan 11:e1801132.

Links:

Diagram of the Eye (National Eye Institute/NIH)

Infrared Waves (NASA)

Visible Light (NASA)

Han Lab (University of Massachusetts, Worcester)

NIH Support: National Institute of Mental Health; National Institute of General Medical Sciences


Skin Cells Can Be Reprogrammed In Vivo

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Daniel Gallego-Perez
Credit: The Ohio State University College of Medicine, Columbus

Thousands of Americans are rushed to the hospital each day with traumatic injuries. Daniel Gallego-Perez hopes that small chips similar to the one that he’s touching with a metal stylus in this photo will one day be a part of their recovery process.

The chip, about one square centimeter in size, includes an array of tiny channels with the potential to regenerate damaged tissue in people. Gallego-Perez, a researcher at The Ohio State University Colleges of Medicine and Engineering, Columbus, has received a 2018 NIH Director’s New Innovator Award to develop the chip to reprogram skin and other cells to become other types of tissue needed for healing. The reprogrammed cells then could regenerate and restore injured neural or vascular tissue right where it’s needed.

Gallego-Perez and his Ohio State colleagues wondered if it was possible to engineer a device placed on the skin that’s capable of delivering reprogramming factors directly into cells, eliminating the need for the viral delivery vectors now used in such work. While such a goal might sound futuristic, Gallego-Perez and colleagues offered proof-of-principle last year in Nature Nanotechnology that such a chip can reprogram skin cells in mice. [1]

Here’s how it works: First, the chip’s channels are loaded with specific reprogramming factors, including DNA or proteins, and then the chip is placed on the skin. A small electrical current zaps the chip’s channels, driving reprogramming factors through cell membranes and into cells. The process, called tissue nanotransfection (TNT), is finished in milliseconds.

To see if the chips could help heal injuries, researchers used them to reprogram skin cells into vascular cells in mice. Not only did the technology regenerate blood vessels and restore blood flow to injured legs, the animals regained use of those limbs within two weeks of treatment.

The researchers then went on to show that they could use the chips to reprogram mouse skin cells into neural tissue. When proteins secreted by those reprogrammed skin cells were injected into mice with brain injuries, it helped them recover.

In the newly funded work, Gallego-Perez wants to take the approach one step further. His team will use the chip to reprogram harder-to-reach tissues within the body, including peripheral nerves and the brain. The hope is that the device will reprogram cells surrounding an injury, even including scar tissue, and “repurpose” them to encourage nerve repair and regeneration. Such an approach may help people who’ve suffered a stroke or traumatic nerve injury.

If all goes well, this TNT method could one day fill an important niche in emergency medicine. Gallego-Perez’s work is also a fine example of just one of the many amazing ideas now being pursued in the emerging field of regenerative medicine.

Reference:

[1] Topical tissue nano-transfection mediates non-viral stroma reprogramming and rescue. Gallego-Perez D, Pal D, Ghatak S, Malkoc V, Higuita-Castro N, Gnyawali S, Chang L, Liao WC, Shi J, Sinha M, Singh K, Steen E, Sunyecz A, Stewart R, Moore J, Ziebro T, Northcutt RG, Homsy M, Bertani P, Lu W, Roy S, Khanna S, Rink C, Sundaresan VB, Otero JJ, Lee LJ, Sen CK. Nat Nanotechnol. 2017 Oct;12(10):974-979.

Links:

Stroke Information (National Institute of Neurological Disorders and Stroke/NIH)

Burns and Traumatic Injury (NIH)

Peripheral Neuropathy (National Institute of Neurological Disorders and Stroke/NIH)

Video: Breakthrough Device Heals Organs with a Single Touch (YouTube)

Gallego-Perez Lab (The Ohio State University College of Medicine, Columbus)

Gallego-Perez Project Information (NIH RePORTER)

NIH Support: Common Fund; National Institute of Neurological Disorders and Stroke


Building Nanoparticles for Kidney Disease

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Eun Ji Chung
Photo courtesy of Eun Ji Chung

Great things sometimes come in small packages. That’s certainly true in the lab of Eun Ji Chung at the University of Southern California, Los Angeles. Chung and her team each day wrap their brains around bioengineering 3-D nanoparticles, molecular constructs that measure just a few billionths of a meter.

Chung recently received an NIH Director’s 2018 New Innovator Award to bring the precision of nanomedicine to autosomal dominant polycystic kidney disease (ADPKD), a relatively common inherited disorder that affects about 600,000 Americans and 12 million people worldwide.

By age 60, about half of those battling ADPKD will have kidney failure, requiring dialysis or a kidney transplant to stay alive. For people with ADPKD, a dominantly inherited gene mutation causes clusters of fluid-filled cysts to form in the kidneys that grow larger over time. The cysts can grow very large and displace normal kidney tissue, progressively impairing function.

For Chung, the goal is to design nanoparticles of the right size and configuration to deliver therapeutics to the kidneys in safe, effective amounts. Our kidneys constantly filter blood, clearing out wastes that are removed via urine. So, Chung and her team will exploit the fact that most molecules in the bloodstream measuring less than 10 nanometers in diameter enter the kidneys, where they are gradually processed and eliminated from the body. This process will give nanoparticles time to bind there and release any therapeutic molecules they may be carrying directly to the cysts that cluster on the kidneys of people with ADPKD.

Chung’s research couldn’t be more timely. Though ADPKD isn’t curable right now, the Food and Drug Administration (FDA) last year approved Jynarque™ (tolvaptan), the first treatment in the United States to slow the decline in kidney function in ADPKD patients, based on tests of the rate of kidney filtration. Other approved drugs, such as metformin and rapamycin, have shown potential for repurposing to treat people with ADPKD. So, getting these and other potentially life-saving drugs directly to the kidneys, while minimizing the risk of serious side effects in the liver and elsewhere in the body, will be key.

Most FDA-approved nanoparticle therapies are administered intravenously, often for treatment of cancer. Because ADPKD is chronic and treatment can last for decades, Chung wants to develop an easy-to-take pill to get these nanoparticles into the kidneys.

But oral administration raises its own set of difficulties. The nanoparticles must get from the stomach and the rest of the gastrointestinal tract to the bloodstream. And then if nanoparticles exceed 10 nanometers in diameter, the body typically routes them to the liver for clearance, rather than the kidneys.

While Chung brainstorms strategies for oral administration, she’s also considering developing a smart bandage to allow the nanoparticles to pass readily through the skin and, eventually, into the bloodstream. It would be something similar to the wearable skin patch already featured on the blog.

In the meantime, Chung continues to optimize the size, shape, and surface charge of her nanoparticles. Right now, they have components to target the kidneys, provide a visual signal for tracking, enhance the nanoparticle’s lifespan, and carry a therapeutic molecule. Because positively charged molecules are preferentially attracted to the kidney, Chung has also spent untold hours adjusting the charge on her nanoparticles.

But through all the hard work, Chung and her team continue to prove that great things may one day come in very small packages. And that could ultimately prove to be a long-awaited gift for the millions of people living with ADPKD.

Links:

Polycystic Kidney Disease (National Institute of Diabetes and Digestive and Kidney Diseases/NIH)

Video: Faculty Profile – Eun Ji Chung (University of Southern California, Los Angeles)

Chung Laboratory (USC)

Chung Project Information (NIH RePORTER)

NIH Director’s New Innovator Award (Common Fund)

NIH Support: Common Fund; National Institute of Diabetes and Digestive and Kidney Diseases


Nanodiamonds Shine in Root Canal Study

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Nanodiamonds

Caption: An artistic rendering of nanodiamonds
Credit: Ho Lab

When the time comes to get relief from a dental problem, we are all glad that dentistry has come so far—much of the progress based on research supported by NIH’s National Institute of Dental and Craniofacial Research. Still, almost no one looks forward to getting a root canal. Not only can the dental procedure be uncomfortable and costly, there’s also a risk of failure due to infection or other complications. But some NIH-supported researchers have now come up with what may prove to be a dazzling strategy for reducing that risk: nanodiamonds!

That’s right, these researchers decided to add tiny diamonds—so small that millions could fit on the head of the pin—to the standard filler that dentists use to seal off a tooth’s root. Not only are these nanodiamonds extremely strong, they have unique properties that make them very attractive vehicles for delivering drugs, including antimicrobials that help fight infections of the sealed root canal.


Snapshots of Life: Virus Hunting with Carbon Nanotubes

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H5N2 trapped in carbon nanotubes

Credit: Penn State University

The purple pods that you see in this scanning electron micrograph are the H5N2 avian flu virus, a costly threat to the poultry and egg industry and, in very rare instances, a health risk for humans. However, these particular pods are unlikely to infect anything because they are trapped in a gray mesh of carbon nanotubes. Made by linking carbon atoms into a cylindrical pattern, such nanotubes are about 10,000 times smaller than width of a human hair.

The nanotubes above have been carefully aligned on a special type of silicon chip called a carbon-nanotube size-tunable-enrichment-microdevice (CNT-STEM). As described recently in Science Advances, this ultrasensitive device is designed to capture viruses rapidly based on their size, not their molecular characteristics [1]. This unique feature enables researchers to detect completely unknown viruses, even when they are present in extremely low numbers. In proof-of-principle studies, CNT-STEM made it possible to collect and detect viruses in a sample at concentrations 100 times lower than with other methods, suggesting the device and its new approach will be helpful in the ongoing hunt for new and emerging viruses, including those that infect people.


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