The Virus Trap

To date, there are no effective antidotes against most virus infections. An interdisciplinary research team at the Technical University of Munich (TUM) has now developed a new approach: they engulf and neutralize viruses with nano-capsules tailored from genetic material using the DNA origami method. The strategy has already been tested against hepatitis and adeno-associated viruses in cell cultures. It may also prove successful against corona viruses.

There are antibiotics against dangerous bacteria, but few antidotes to treat acute viral infections. Some infections can be prevented by vaccination but developing new vaccines is a long and laborious process.

Now an interdisciplinary research team from the Technical University of Munich, the Helmholtz Zentrum München and the Brandeis University (USA) is proposing a novel strategy for the treatment of acute viral infections: The team has developed nanostructures made of DNA, the substance that makes up our genetic material, that can trap viruses and render them harmless.

Lined on the inside with virus-binding molecules, nano shells made of DNA material bind viruses tightly and thus render them harmless.

Even before the new variant of the corona virus put the world on hold, Hendrik Dietz, Professor of Biomolecular Nanotechnology at the Physics Department of the Technical University of Munich, and his team were working on the construction of virus-sized objects that assemble themselves.

In 1962, the biologist Donald Caspar and the biophysicist Aaron Klug discovered the geometrical principles according to which the protein envelopes of viruses are built. Based on these geometric specifications, the team around Hendrik Dietz at the Technical University of Munich, supported by Seth Fraden and Michael Hagan from Brandeis University in the USA, developed a concept that made it possible to produce artificial hollow bodies the size of a virus.

In the summer of 2019, the team asked whether such hollow bodies could also be used as a kind of “virus trap”. If they were to be lined with virus-binding molecules on the inside, they should be able to bind viruses tightly and thus be able to take them out of circulation. For this, however, the hollow bodies would also have to have sufficiently large openings through which viruses can get into the shells.

None of the objects that we had built using DNA origami technology at that time would have been able to engulf a whole virus – they were simply too small,” says Hendrik Dietz in retrospect. “Building stable hollow bodies of this size was a huge challenge.”

Starting from the basic geometric shape of the icosahedron, an object made up of 20 triangular surfaces, the team decided to build the hollow bodies for the virus trap from three-dimensional, triangular plates. For the DNA plates to assemble into larger geometrical structures, the edges must be slightly beveled. The correct choice and positioning of binding points on the edges ensure that the panels self-assemble to the desired objects.

In this way, we can now program the shape and size of the desired objects using the exact shape of the triangular plates,” says Hendrik Dietz. “We can now produce objects with up to 180 subunits and achieve yields of up to 95 percent. The route there was, however, quite rocky, with many iterations.”

By varying the binding points on the edges of the triangles, the team’s scientists can not only create closed hollow spheres, but also spheres with openings or half-shells. These can then be used as virus traps.


Mimicking Insect Wings To Fight Superbugs

The wings of cicadas and dragonflies are natural bacteria killers, a phenomenon that has spurred researchers searching for ways to defeat drug-resistant superbugs. New anti-bacterial surfaces are being developed, featuring different nanopatterns that mimic the deadly action of insect wings, but scientists are only beginning to unravel the mysteries of how they work.

In a post published in Nature Reviews Microbiology, researchers have detailed exactly how these patterns destroy bacteria stretching, slicing or tearing them apart. Lead author, RMIT University’s Distinguished Professor Elena Ivanova, said finding non-chemical ways of killing bacteria was critical, with more than 700,000 people dying each year due to drug-resistant bacterial infection.

The nanopillars on the surface of a dragonfly wing (magnified 20,000 times)

Bacterial resistance to antibiotics is one of the greatest threats to global health and routine treatment of infection is becoming increasingly difficult,” Ivanova said. “When we look to nature for ideas, we find insects have evolved highly effective anti-bacterial systems. “If we can understand exactly how insect-inspired nanopatterns kill bacteria, we can be more precise in engineering these shapes to improve their effectiveness against infections. “Our ultimate goal is to develop low-cost and scaleable anti-bacterial surfaces for use in implants and in hospitals, to deliver powerful new weapons in the fight against deadly superbugs.”

The wings of cicadas and dragonflies are covered in tiny nanopillars, which were the first nanopatterns developed by scientists aiming to imitate their bactericidal effects. Since then, they’ve also precisely engineered other nanoshapes like sheets and wires, all designed to physically damage bacteria cellsBacteria that land on these nanostructures find themselves pulled, stretched or sliced apart, rupturing the bacterial cell membrane and eventually killing them.

The new review for the first time categorises the different ways these surface nanopatterns deliver the necessary mechanical forces to burst the cell membrane. “Our synthetic biomimetic nanostructures vary substantially in their anti-bacterial performance and it’s not always clear why,” Ivanova explained. “We have also struggled to work out the optimal shape and dimensions of a particular nanopattern, to maximise its lethal power“While the synthetic surfaces we’ve been developing take nature to the next level, even looking at dragonflies, for example, we see that different species have wings that are better at killing some bacteria than others. “When we examine the wings at the nanoscale, we see differences in the density, height and diameter of the nanopillars that cover the surfaces of these wings, so we know that getting the nanostructures right is key.”