Germ-killing nanosurface opens up new front in hygiene (Update)

Nov 26, 2013
A cicada is pictured on a tree on July 28, 2013 in Marseille, France

Imagine a hospital room, door handle or kitchen countertop that is free from bacteria—and not one drop of disinfectant or boiling water or dose of microwaves has been needed to zap the germs.

That is the idea behind a startling discovery made by scientists in Australia.

In a study published on Tuesday in the journal Nature Communications, they described how a dragonfly led them to a nano-tech surface that physically slays .

The germ-killer is black silicon, a substance discovered accidentally in the 1990s and now viewed as a promising semiconductor material for solar panels.

Under an electron microscope, its surface is a forest of spikes just 500 nanometres (500 billionths of a metre) high that rip open the cell walls of any bacterium which comes into contact, the scientists found.

It is the first time that any water-repellent surface has been found to have this physical quality as bactericide.

Last year, the team, led by Elena Ivanova at Swinburne University of Technology in Melbourne, were stunned to find cicada wings were potent killers of Pseudomonas aeruginsoa—an opportunist germ that also infects humans and is becoming resistant to antibiotics.

Looking closely, they found that the answer lay not in any biochemical on the wing, but in regularly-spaced "nanopillars" on which bacteria were sliced to shreds as they settled on the surface.

They took the discovery further by examining nanostructures studding the translucent forewings of a red-bodied Australian dragonfly called the wandering percher (Latin name Diplacodes bipunctata).

It has spikes that are somewhat smaller than those on the black silicon—they are 240 nanometres high.

This video is not supported by your browser at this time.
Watch a video comparison of 3D models of black silicon and Diplacodes bipunctata wings.

The dragonfly's wings and black silicon were put through their paces in a lab, and both were ruthlessly bactericidal.

Smooth to the human touch, the surfaces destroyed two categories of bacteria, called Gram-negative and Gram-positive, as well as spores, the protective shell that coats certain times of dormant germs.

The three targeted bugs comprised P. aeruginosa, the notorious Staphylococcus aureus and the ultra-tough spore of Bacillus subtilis, a wide-ranging soil germ that is a cousin of anthrax.

The killing rate was 450,000 bacterial cells per square centimetre per minute over the first three hours of exposure.

This is 810 times the minimum dose needed to infect a person with S. aureus, and a whopping 77,400 times that of P. aeruginosa.

If the cost of making is an obstacle, many other options are around for making nano-scale germ-killing surfaces, said the scientists.

"Synthetic antibacterial nano-materials that exhibit a similar effectiveness... can be readily fabricated over large areas," they wrote.

Explore further: Researchers create compounds that boost antibiotics' effectiveness

More information: www.nature.com/ncomms/2013/131126/ncomms3838/full/ncomms3838.html

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User comments : 8

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pepe2907
1 / 5 (10) Nov 26, 2013
How about the other living cells - like human? Does anybody researched how human body reacts on contact with these surfaces? Aren't they damaging to skin cells?
qquax
1 / 5 (3) Nov 26, 2013
36 minutes ago
Picture:
http://www.nature..._F1.html

Picture:
http://www.nature..._F2.html

Link:
http://www.nature...838.html

Nik, your links are good which is why I repeat them here. Your comments are highly inappropriate. We don't see this nonsense with male authors, do we?

qquax
3 / 5 (6) Nov 26, 2013
How about the other living cells - like human? Does anybody researched how human body reacts on contact with these surfaces? Aren't they damaging to skin cells?


Human skin is far thicker than the cell membranes and the top layer is made of dead, flat skin cells that shed about every 2 weeks. You can't hurt what's already dead.

http://dermatolog...tomy.htm
robweeve
1 / 5 (6) Nov 26, 2013
toilet handles
ViperSRT3g
1 / 5 (1) Nov 27, 2013
Two things that this article left me wondering.

1. What IS the cost of producing black silicon?
2. How exactly are the bacteria ripped to shreds on the material?
bertibus
1 / 5 (4) Nov 27, 2013
The measurements are with the surface in a pristine state.
What would be the effects of various spills and such on the surface, and would any cleaning fluids create any short or long term degradation in the surface's structure?
Shootist
1 / 5 (5) Nov 28, 2013


Nik, your links are good which is why I repeat them here. Your comments are highly inappropriate.


Who is Nik? And your links are not good.
paulfeakins
1 / 5 (1) Dec 10, 2013
"It is the first time that any water-repellent surface has been found to have this physical quality as bactericide."

Perhaps but silver is known to have antibacterial properties: http://en.wikiped...f_silver

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