Mousetrap for bacteria: nanosilver in a delicious package
Trojan NanoconThe Second coming of the silver antiseptic
Elizaveta Alekseeva, Independent NewspaperThe healing properties of silver have been known since antiquity.
The Persian king Cyrus kept water in silver vessels. Egyptian warriors applied silver plates to wounds – it was believed that this way they heal faster. To prevent the drinking water from spoiling, the sailors dipped a silver coin into it. Russian proverb: "To be proud of gold, and to be treated with silver." Even in poor families, it was customary to give a silver spoon to a baby "by the tooth". And the wealthier ones always used silver appliances.
In medicine, the disinfecting properties of silver were used. With the discovery of penicillin, the effectiveness of silver as an antiseptic and a weapon against bacteria lost importance and was forgotten for a long time.
In the era of nanotechnology, the ability of this metal to destroy bacteria and fungi was recalled again. Deutsche Welle reports on the creation of bactericidal coatings for hospital rooms and furniture, and those that would allow you to do without traditional disinfectants. Swiss researchers Professor Wendelin Stark and his colleagues from the Zurich Higher Technical School are developing a self-adhesive polymer bactericidal film based on silver nanoparticles. And not just bactericidal, but also actively luring bacteria in order to destroy them. "For this purpose, we enclosed silver particles in calcium phosphate particles," explains Professor Stark. "Calcium phosphate is an important nutrient for bacteria, which they need for normal growth, so microorganisms literally pounce on it and quickly die, poisoned by silver."
The production of such a Trojan nanocon for bacteria requires two consecutive technological operations. First, the active component of the coating is manufactured, which is a whitish-brown nanopowder. The diameter of the nutrient particles is on average from 20 to 50 nanometers. These are already extremely small particles, roughly corresponding in size to the molecules of some enzyme. But the silver particles, in order to fit inside the calcium phosphate particles and get inside the bacteria with them, must be even smaller. Therefore, the diameter of silver particles is only 1-2 nanometers, in fact, these are small groups of atoms – about 50 to 200 pieces.
The second stage of production consists in applying the thinnest even layer of nanopowder to a self-adhesive polymer film. The mass of this active layer is no more than 2% of the total mass of the film, so that all its physical properties remain unchanged. As for the bactericidal effect, such a coating is 1000 times more effective than conventional silver preparations. During the tests, Swiss scientists placed about a million bacteria of the widespread species Escherichia coli on their polymer film – none of these E. coli survived.
Based on the results of these studies, the production of bactericidal films of several varieties will be established in Switzerland. Already this year, a transparent antiseptic film for food packaging should appear. Then it will be the turn of self–adhesive film for widespread use in medical institutions - it can be applied to door handles, hospital beds, and furniture in wards. Since the concentration of silver nanoparticles in such a coating is very small, the film will be quite affordable. In addition, it is much more environmentally friendly than the previous silver preparations. And in the longer term, Swiss researchers plan to create a bactericidal nanopowder in the form of an additive to liquid dyes. With such dyes, it will be possible to update the active layer of the film after all the calcium phosphate with silver inside has been used up over time.
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27.10.2009