Hairy nanoparticles put viruses in a deadly embrace | Science News for Students

Hairy nanoparticles put viruses in a deadly embrace

The discovery could lead to teeny-tiny treatments for a wide range of diseases
Feb 23, 2018 — 6:45 am EST
virus nanoparticles
In this artist’s illustration, gold nanoparticles (bright blue) covered in tiny hairs (shown in purple) surround a virus and attach to it. As more hairs attach, they squeeze the soft surface of the virus to find places to stick. That squeezing builds enough pressure to squash the virus.
Francesco Stellacci

This is one in a series presenting news on technology and innovation, made possible with generous support from the Lemelson Foundation.

Our tiniest enemies are some of the hardest to fight. The viruses that infect people with influenza and HIV kill millions of people each year. Doctors still don’t have good weapons to quash the germs responsible. Most common viruses, such as those that cause colds, can’t even be treated with drugs. Drugs that do exist work against just a few types of viruses. And they only weaken these germs; they don’t destroy them. Now scientists have figured out how to slay many types of harmful viruses. Their new weapon of choice: nanoparticles.

Francesco Stellacci is a materials scientist who works in Switzerland at the École Polytechnique Fédérale in Lausanne. Some nanoparticles that he worked with appeared similar to a protein that sticks to viruses. And that was his inspiration. He suspected that if he could create a new nanoparticle that worked this way, it would grab onto a virus and not let go.

The particle he created is just five nanometers wide. For perspective, a human hair is 2,000 times that width. The particle is made from a tiny crystal of gold. A forest of even tinier threads cover its surface. Those threads are made from carbon-based compounds.

Stellacci’s group tested these tiny particles against a broad range of viruses. And they now report success.

The nanoparticles destroyed common germs like the herpes virus and human papilloma virus. The first triggers a range of symptoms, including cold sores in the mouth. The second is responsible for the most common type of sexually transmitted infection — one that can cause genital warts and even cancer. The hairy spheres also quashed respiratory syncytial (Sin-SISH-ul) virus. It infects the lungs, causing cold-like symptoms — except in babies and the elderly. It can leave them with life-threatening pneumonia.

Finally, the new nanoparticles killed dengue (DEN-gay) virus. It infects some 400 million people each year. There has been no treatment for this tropical illness, which is spread by mosquitoes. Symptoms include severe eye, muscle and joint pain; vomiting; bleeding gums; difficulty breathing and black tarry stools.

Clearly, the new nanospheres appear to hold a lot of promise.

Stellacci’s team described them and how they work in the February Nature Materials.

A physical attack

To reproduce, a virus must enter the body’s cells. There it starts to hijack those cells to make many copies of itself. Afterward, the infected cell bursts. This releases a legion of new viruses that can spread to other cells in this person or others.

Today’s antiviral drugs work by stopping a virus from multiplying after it enters a healthy cell. They defeat the virus — but only temporarily. If the patient stops taking the drug, the virus can return. And because these drugs attack viruses using chemicals, they can sometimes produce toxic side effects.

“Viruses are made from similar things [to what] we are made of,” Stellacci explains. “So if you want to chemically damage them, you will damage the host cells, too.”

His group’s nanoparticles stop the germs differently. First, they attack a virus before it enters a healthy cell. Then, instead of fighting it with toxic chemicals, these hairy balls begin a physical attack. Those hairs on the outside of a nanoparticle grab onto the virus with an unbreakable bond. Then they apply pressure. Eventually, Stellacci says, “That pressure blows up the virus.”

How do tiny nanoparticles put the squeeze a virus that is many, many times their size? It comes down to those hairs.

These attach to tiny physical structures on the outside of a virus known as receptors. Receptors are spaced much farther apart than the hairs. So as more and more hairs attach, they gradually pull on the receptors. This brings them closer and closer together, squeezing the germs’ soft surface. The pressure of this big squeeze builds, especially if many nanoparticles grab on. Apply enough pressure — and pop! The virus is a goner.

Hairy helpers

Scientists have been studying nanoparticles for a long time. But they’ve only recently begun learning how to use them in medicine, says Alexander Spokoyny. He’s a chemist at the University of California, Los Angeles. Stellacci combined properties that nanoparticles already had and used them in an innovative, new way, Spokoyny says.

“If you can take some relatively simple chemistry and learn how to control it, you can create very complex assemblies that potentially solve a very important problem,” he says.

Because the nanoparticles were already covered with hairs, Stellacci says, it was easy to adapt them to fight viruses. But now that scientists know how well they work, he said it should be possible to engineer new types of particles to do the same thing.

Stellacci’s team has already started testing the nanoparticles in animals. That’s the next step toward someday turning them into a drug to treat people. He also hopes other scientists will become inspired with their own ideas on how to turn his discovery into medicine that might save lives.

“I’m trying to explain to the community that there is a new way of fighting infection,” he says.

Power Words

(for more about Power Words, click here)

antiviral     A virus-killing substance prescribed as a medicine.

bond     (in chemistry) A semi-permanent attachment between atoms — or groups of atoms — in a molecule. It’s formed by an attractive force between the participating atoms. Once bonded, the atoms will work as a unit. To separate the component atoms, energy must be supplied to the molecule as heat or some other type of radiation.

carbon     The chemical element having the atomic number 6. It is the physical basis of all life on Earth. Carbon exists freely as graphite and diamond. It is an important part of coal, limestone and petroleum, and is capable of self-bonding, chemically, to form an enormous number of chemically, biologically and commercially important molecules.

cell     The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells. Most organisms, such as yeasts, molds, bacteria and some algae, are composed of only one cell.

chemical     A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.

chemistry     The field of science that deals with the composition, structure and properties of substances and how they interact. Scientists use this knowledge to study unfamiliar substances, to reproduce large quantities of useful substances or to design and create new and useful substances. (about compounds) Chemistry also is used as a term to refer to the recipe of a compound, the way it’s produced or some of its properties. People who work in this field are known as chemists.

crystal     (adj. crystalline) A solid consisting of a symmetrical, ordered, three-dimensional arrangement of atoms or molecules. It’s the organized structure taken by most minerals. Apatite, for example, forms six-sided crystals. The mineral crystals that make up rock are usually too small to be seen with the unaided eye.

dengue     A potentially lethal infectious disease transmitted by mosquitoes. No vaccine yet exists to prevent infection with the virus responsible for the disease, which causes high fevers, severe headache, joint pain, pain behind the eyes, rash, bone pain and sometimes mild bleeding. A more severe form of the disease, known as dengue hemorrhagic fever can cause uncontrolled bleeding if not treated right away.

engineer     A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.

HIV     (short for Human Immunodeficiency Virus) A potentially deadly virus that attacks cells in the body’s immune system and causes acquired immune deficiency syndrome, or AIDS.

host      (in biology and medicine) The organism (or environment) in which some other thing resides. Humans may be a temporary host for food-poisoning germs or other infective agents.

infection     A disease that can spread from one organism to another. It’s usually caused by some type of germ.

influenza     (also known as flu) A highly contagious viral infection of the respiratory passages causing fever and severe aching. It often occurs as an epidemic.

materials scientist     See materials science.

molecule     An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).

nanoparticle     A small particle with dimensions measured in billionths of a meter.

physical     (adj.) A term for things that exist in the real world, as opposed to in memories or the imagination. It can also refer to properties of materials that are due to their size and non-chemical interactions (such as when one block slams with force into another).

pressure     Force applied uniformly over a surface, measured as force per unit of area.

protein     A compound made from one or more long chains of amino acids. Proteins are an essential part of all living organisms. They form the basis of living cells, muscle and tissues; they also do the work inside of cells. Among the better-known, stand-alone proteins are the hemoglobin (in blood) and the antibodies (also in blood) that attempt to fight infections. Medicines frequently work by latching onto proteins.

receptor     (in biology) A molecule in cells that serves as a docking station for another molecule. That second molecule can turn on some special activity by the cell.

respiratory     Of or referring to parts of the body involved in breathing (called the respiratory system). It includes the lungs, nose, sinuses, throat and other large airways.

side effects     Unintended problems or harm caused by a procedure or treatment.

toxic     Poisonous or able to harm or kill cells, tissues or whole organisms. The measure of risk posed by such a poison is its toxicity.

virus     Tiny infectious particles consisting of RNA or DNA surrounded by protein. Viruses can reproduce only by injecting their genetic material into the cells of living creatures. Although scientists frequently refer to viruses as live or dead, in fact no virus is truly alive. It doesn’t eat like animals do, or make its own food the way plants do. It must hijack the cellular machinery of a living cell in order to survive.

Citation

Journal:​ ​​V. Cagno et al. Broad-spectrum non-toxic antiviral nanoparticles with a virucidal inhibition mechanism. Nature Materials. Vol. 17, February 2018, p. 195. doi:10.1038/nmat5053