Coronavirus: surfaces that kill germs themselves

We can stop the infection before it gets into our body – if we accurately reproduce the texture of the wings of insects on the surface and begin to cover the elevator buttons and door handles with materials that kill microbes or inhibit their development.

Ten million deaths per year. The figure is incomprehensible, but it is often brought by Gerald Laroy-Momu, a researcher of infectious diseases at Imperial College London (UK).

This will be a sad outcome for our world if all pathogenic microbes develop resistance to antibiotics – the main barrier that we rely on in the fight against disease.

Currently, 700 thousand people a year die from diseases that cannot be treated with drugs. And in the last 10 years, the list of drugs that we can use against harmful bacteria has been declining before our eyes.

Meanwhile, other pathogens – fungi, viruses and parasites – also developed drug resistance, almost at the same rate as we developed new ones. This means that the diseases they cause become harder to treat.

As Larua-Momyu warns, “if nothing is done, then 10 million people will die every year.”

He is one of those scientists who are looking for new ways to break the resistance of germs. Larua-Momu plans to turn into those antimicrobial weapons the very surfaces through which microorganisms are transmitted from person to person.

“The surfaces we touch every day are potential tools for transmitting infections,” says Laroy-Momu.

For example, the Sars-CoV-2 virus, which causes Covid-19 disease, can live on cardboard surfaces for up to 24 hours, and on plastic and metal (stainless steel) up to three days (although scientists argue to what extent he retains his qualities and infectiousness. – Red.).

And some bacteria, including E. coli and Staphylococcus aureus, sometimes remain viable on the surfaces of inanimate objects for several months.

And this only emphasizes the importance of constant disinfection and cleaning of surfaces that we often touch.

Some scientists hope that we can destroy infectious microorganisms even before they enter our bodies – simply by changing the texture of the surfaces or by coating these surfaces with a special layer that kills viruses and bacteria more quickly.

Larua-Momyu relies on copper alloys. Copper ions are both antibacterial and antiviral; they can destroy more than 99.9% of bacteria in just two hours.

Copper is even more effective than silver, which needs moisture to activate antimicrobial properties.

“Copper has been used by mankind for three millennia,” Larua-Momu emphasizes. “Even the ancient Greeks made copper and medical instruments and kitchen utensils.”

Nevertheless, copper is rarely used today in medical facilities. This is an expensive metal, it is more difficult to clean without causing corrosion. Well, and then – not everyone will like a metal toilet seat …

Over time, copper was first replaced by stainless steel, then light and cheap plastic, which, according to Larois-Momu, can simply be thrown out after a single use, without worrying about sterilization.

And although it is not possible to cover all the surfaces around with copper, Larois-Momue believes that in order to restrain the spread of germs and reduce infection, it will be sufficient to use this metal in alloys in those “hot spots” that people constantly touch — elevator buttons, door handles and etc.

In addition, copper surfaces can be laser-treated, creating a rough texture that increases the surface area and, thus, the number of bacteria that it can destroy.

Researchers at Purdue University, Indiana, who developed this technology, found that such a surface can kill even highly concentrated strains of antibiotic-resistant bacteria in just a couple of hours.

And this treatment will be useful not only for door handles, but also, for example, for medical implants when replacing the hip joint, reducing the risk of infection.

There are other suggestions for changing surface texture.

“The wings of cicadas have self-cleaning properties,” says Elena Ivanova, a molecular biochemist at the Royal University of Technology, Melbourne (Australia).

Their wings have hydrophobic properties, droplets of water just slide off them, just like from lotus leaves, along with pollutants.

Even more importantly, she emphasizes, the wings of cicadas are dotted with tiny spikes that prevent the formation of bacterial colonies on the surface.

“This is a unique mechanism created by nature for the destruction of bacterial cells,” explains Ivanova, who has been developing methods for simulating a cicada wing device for almost ten.

Saturation, geometric characteristics, as well as the method and materials for producing such a surface will depend on which microbes it is planned to fight with.

According to Ivanova, a complex zigzag texture is especially effective in water and air filters.

Graphene sheets are very thin, with sharp protrusions that cut through the membrane of bacteria and kill them (although these microscopic razors can damage human skin).

Ivanova is particularly enthusiastic about the possibility of using titanium and titanium alloys. They can be hydrothermally, under the influence of high temperature and pressure, processed so that a thin sheet of metal after that will have sharp protrusions and edges that destroy various types of bacteria.

In addition, titanium dioxide, when it is exposed to ultraviolet radiation, forms reactive oxygen species, such as peroxides, which inactivate (block) microbes. This is already used, for example, in bracket coatings in dentistry.

“Such surfaces do not require any special treatment,” Ivanova emphasizes.

However, the production of these surfaces will require a high degree of accuracy, since their elements are smaller than bacteria.

But, according to Vladimir Baulin, a biophysicist from the University of Rovira i Verhili (Spain), similar technologies can be used against viruses, including coronavirus.

One possible strategy is to trap viral particles between nanocomponents artificially created on the surface. This will help scientists collect viral particles for research and development of vaccines.

Another strategy is to apply such a texture to the surface, sharp protrusions on which could physically pierce the outer membrane of the virus cell. Such a surface could be used, for example, in mask filters.

Nature itself offers us all kinds of options to combat the spread of infectious diseases. “There is a lot of evidence of the effectiveness of essential oils as antibacterial and antiviral ingredients,” said Alejandra Ponce, a chemical engineer at the University of Nacional de Mar del Plata (Argentina).

Take, for example, tea tree oil, a sharp-smelling component of many cosmetic products. According to Ponce, in experimental studies it was found that tea tree oil aerosol has a strong antiviral effect and is able to block virus samples with an efficiency exceeding 95% in just 5-15 minutes of exposure.

Cork has established itself as a highly effective antibacterial material against Staphylococcus aureus.

And hop extracts were used to produce a plastic-like coating that prevented the growth of certain types of bacteria on surfaces.

Similar studies are only at the experimental stage. In theory, such natural materials could be turned into antimicrobial coatings, but much remains to be learned about the exact amount of the main ingredients and the type of microorganisms that these coatings will target.

But in general, the scope of the potential use of antimicrobial surfaces is quite wide. “It seems to me that it is important to emphasize that this is a universal mechanism, and therefore the spectrum of its application is so wide,” says Baulin.

However, do not rely too much on this approach, warns Mengin Ren, an employee of the Swedish network ReAct – Action on Antibiotic Resistance (“Actions in relation to resistance to antibiotics”).

As she notes, no matter how good the technology is, you still need to adhere to the basic requirements for medical institutions – qualified personnel, orderlies, hygiene, conditions for the prevention and control of infectious diseases, as well as the possibility of vaccination. There are no easy solutions.

In poor countries where there is not always reliable access to running water, it is especially difficult to keep those surfaces that need to be often cleaned.

However, according to Ivanova, titanium and titanium alloys are self-cleaning from pathogenic cells. But copper surfaces must be cleaned to limit oxidation, which will make this metal less chemically active.

Wren and her colleagues are worried if there is a risk of pathogens becoming resistant to copper and silver or to new antibacterial surfaces. But Laroy-Momu sure: if the bacteria have not developed resistance to copper in the last 3000 years, then they are unlikely to succeed in the future.

One way or another, it takes time for these technologies to find commercial developers and move on to the wide offer stage. However, a number of examples already exist.

Sharklet (not to be confused with sharklets in aviation – wingtips that improve aerodynamic performance – Ed.) – a plastic film material that imitates shark scales, the surface of which consists of rhombs with sharp cloves-scales, repelling everything alien, including bacteria. This material is already being used in medicine – in products such as catheters, where it is especially important to reduce the risk of infection entering the body.

There is also a MicroShield 360 coating, which is applied to the seats in airliners in order to avoid the accumulation of bacteria on them.

Although 3D printers rarely work at the nanoscale, some of their models can do this. Someday it will be possible to print a micro-repellent surface right at home.

In future confrontations with infectious diseases and pandemics, such surfaces may become an important tool. Already today for the world fighting the Covid-19 virus, the problem of antimicrobial resistance is unprecedentedly relevant.

There is also a significant risk of secondary infections that a patient can catch already in the hospital: as one study showed, 50% of patients who died in a Chinese hospital from Covid-19 were also infected with another pathogen (potentially lethal).

An infected coronavirus is usually given antibiotics (although they do not work against the virus itself). This reinforces concerns about further increasing the resistance of bacteria to drugs.

“We are surrounded by infections, so there is nothing unusual in our current war with coronavirus,” Larua-Momu emphasizes. “And now it’s very important to prepare for the next. It is not known when it will begin.”

–

Read the original of this article in English on the BBC Future website.

–