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Nanoparticle Technology Holds Promise for Protecting Against Many Coronavirus Strains at Once

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Mosaic vaccine
A new coronavirus vaccine approach works by attaching many spike protein receptor-binding domains (RBDs) to an engineered protein-based nanoparticle. In mice, the vaccine induced a cross-reactive antibody response capable of neutralizing many different coronavirus strains. Credit: Adapted from image by A. Cohen via BioRender

It’s truly encouraging to witness people all across our nation rolling up their sleeves to get their COVID-19 vaccines. That is our best chance to end this pandemic. But this is the third coronavirus to emerge and cause serious human illness in the last 20 years, and it’s probably not the last. So, this is also an opportunity to step up our efforts to develop vaccines to combat future strains of disease-causing coronavirus. With this in mind, I’m heartened by a new NIH-funded study showing the potential of a remarkably adaptable, nanoparticle-based approach to coronavirus vaccine development [1].

Both COVID-19 vaccines currently authorized for human use by the Food and Drug Administration (FDA) work by using mRNA to instruct our cells to make an essential portion of the spike protein of SARS-CoV-2, which is the novel coronavirus that causes COVID-19. As our immune system learns to recognize this protein fragment as foreign, it produces antibodies to attack SARS-CoV-2 and prevent COVID-19. What makes the new vaccine technology so powerful is that it raises the possibility of training the immune system to recognize not just one strain of coronavirus—but up to eight—with a single shot.

This approach has not yet been tested in people, but when a research team, led by Pamela Bjorkman, California Institute of Technology, Pasadena, injected this new type of vaccine into mice, it spurred the production of antibodies that react to a variety of different coronaviruses. In fact, some of the mouse antibodies proved to be reactive to related strains of coronavirus that weren’t even represented in the vaccine. These findings suggest that if presented with multiple different fragments of the spike protein’s receptor binding domain (RBD), which is what SARS-like coronaviruses use to infect human cells, the immune system may learn to recognize common features that might protect against as-yet unknown, newly emerging coronaviruses.

This new work, published in the journal Science, utilizes a technology called a mosaic nanoparticle vaccine platform [1]. Originally developed by collaborators at the University of Oxford, United Kingdom, the nanoparticle component of the platform is a “cage” made up of 60 identical proteins. Each of those proteins has a small protein tag that functions much like a piece of Velcro®. In their SARS-CoV-2 work, Bjorkman and her colleagues, including graduate student Alex A. Cohen, engineered multiple different fragments of the spike protein so each had its own Velcro-like tag. When mixed with the nanoparticle, the spike protein fragments stuck to the cage, resulting in a vaccine nanoparticle with spikes representing four to eight distinct coronavirus strains on its surface. In this instance, the researchers chose spike protein fragments from several different strains of SARS-CoV-2, as well as from other related bat coronaviruses thought to pose a threat to humans.

The researchers then injected the vaccine nanoparticles into mice and the results were encouraging. After inoculation, the mice began producing antibodies that could neutralize many different strains of coronavirus. In fact, while more study is needed to understand the mechanisms, the antibodies responded to coronavirus strains that weren’t even represented on the mosaic nanoparticle. Importantly, this broad antibody response came without apparent loss in the antibodies’ ability to respond to any one particular coronavirus strain.

The findings raise the exciting possibility that this new vaccine technology could provide protection against many coronavirus strains with a single shot. Of course, far more study is needed to explore how well such vaccines work to protect animals against infection, and whether they will prove to be safe and effective in people. There will also be significant challenges in scaling up manufacturing. Our goal is not to replace the mRNA COVID-19 vaccines that scientists developed at such a remarkable pace over the last year, but to provide much-needed vaccine strategies and tools to respond swiftly to the emerging coronavirus strains of the future.

As we double down on efforts to combat COVID-19, we must also come to grips with the fact that SARS-CoV-2 isn’t the first—and surely won’t be the last—novel coronavirus to cause disease in humans. With continued research and development of new technologies such as this one, the hope is that we will come out of this terrible pandemic better prepared for future infectious disease threats.

References:

[1] Mosaic RBD nanoparticles elicit neutralizing antibodies against SARS-CoV-2 and zoonotic coronaviruses. Cohen AA, Gnanapragasam PNP, Lee YE, Hoffman PR, Ou S, Kakutani LM, Keeffe JR, Barnes CO, Nussenzweig MC, Bjorkman PJ. Science. 2021 Jan 12.

Links:

COVID-19 Research (NIH)

Bjorkman Lab (California Institute of Technology, Pasadena)

NIH Support: National Institute of Allergy and Infectious Diseases


Teaming Magnetic Bacteria with Nanoparticles for Better Drug Delivery

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Nanoparticles hold great promise for delivering next-generation therapeutics, including those based on CRISPR gene editing tools. The challenge is how to guide these tiny particles through the bloodstream and into the right target tissues. Now, scientists are enlisting some surprising partners in this quest: magnetic bacteria!

First a bit of background. Discovered in the 1960s during studies of bog sediments, “magnetotactic” bacteria contain magnetic, iron-rich particles that enable them to orient themselves to the Earth’s magnetic fields. To explore the potential of these microbes for targeted delivery of nanoparticles, the NIH-funded researchers devised the ingenious system you see in this fluorescence microscopy video. This system features a model blood vessel filled with a liquid that contains both fluorescently-tagged nanoparticles (red) and large swarms of a type of magnetic bacteria called Magnetospirillum magneticum (not visible).

At the touch of a button that rotates external magnetic fields, researchers can wirelessly control the direction in which the bacteria move through the liquid—up, down, left, right, and even “freestyle.” And—get this—the flow created by the synchronized swimming of all these bacteria pushes along any nearby nanoparticles in the same direction, even without any physical contact between the two. In fact, the researchers have found that this bacteria-guided system delivers nanoparticles into target model tissues three times faster than a similar system lacking such bacteria.

How did anyone ever dream this up? Most previous attempts to get nanoparticle-based therapies into diseased tissues have relied on simple diffusion or molecular targeting methods. Because those approaches are not always ideal, NIH-funded researchers Sangeeta Bhatia, Massachusetts Institute of Technology, Cambridge, MA, and Simone Schürle, formerly of MIT and now ETH Zurich, asked themselves: Could magnetic forces be used to propel nanoparticles through the bloodstream?

As a graduate student at ETH Zurich, Schürle had worked to develop and study tiny magnetic robots, each about the size of a cell. Those microbots, called artificial bacterial flagella (ABF), were designed to replicate the movements of bacteria, relying on miniature flagellum-like propellers to move them along in corkscrew-like fashion.

In a study published recently in Science Advances, the researchers found that the miniature robots worked as hoped in tests within a model blood vessel [1]. Using magnets to propel a single microbot, the researchers found that 200-nanometer-sized polystyrene balls penetrated twice as far into a model tissue as they did without the aid of the magnet-driven forces.

At the same time, others in the Bhatia lab were developing bacteria that could be used to deliver cancer-fighting drugs. Schürle and Bhatia wished they could direct those microbial swarms using magnets as they could with the microbots. That’s when they learned about the potential of M. magneticum and developed the experimental system demonstrated in the video above.

The researchers’ next step will be to test their magnetic approach to drug delivery in a mouse model. Ultimately, they think their innovative strategy holds promise for delivering nanoparticles carrying a wide range of therapeutic payloads right to a tumor, infection, or other diseased tissue. It’s yet another example of how basic research combined with outside-the-box thinking can lead to surprisingly creative solutions with real potential to improve human health.

References:

[1] Synthetic and living micropropellers for convection-enhanced nanoparticle transport. Schürle S, Soleimany AP, Yeh T, Anand GM, Häberli M, Fleming HE, Mirkhani N, Qiu F, Hauert S, Wang X, Nelson BJ, Bhatia SN. Sci Adv. 2019 Apr 26;5(4):eaav4803.

Links:

VIDEO: Synthetic and Living Micropropellers Stir Up Nanoparticles for Enhanced Drug Transport Powered by Magnetism

Nanotechnology (NIH)

What are genome editing and CRISPR-Cas9? (National Library of Medicine/NIH)

Sangeeta Bhatia (Massachusetts Institute of Technology, Cambridge, MA)

Simone Schürle-Finke (ETH Zurich, Switzerland)

NIH Support: National Cancer Institute; National Institute of General Medical Sciences


‘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


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


Watching Cancer Cells Play Ball

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Credit: Ning Wang, University of Illinois at Urbana-Champaign

As tumor cells divide and grow, they push, pull, and squeeze one another. While scientists have suspected those mechanical stresses may play important roles in cancer, it’s been tough to figure out how. That’s in large part because there hadn’t been a good way to measure those forces within a tissue. Now, there is.

As described in Nature Communications, an NIH-funded research team has developed a technique for measuring those subtle mechanical forces in cancer and also during development [1]. Their ingenious approach is called the elastic round microgel (ERMG) method. It relies on round elastic microspheres—similar to miniature basketballs, only filled with fluorescent nanoparticles in place of air. In the time-lapse video above, you see growing and dividing melanoma cancer cells as they squeeze and spin one of those cell-sized “balls” over the course of 24 hours.


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