Antibacterial fabric sheets for various uses are undergoing feasibility tests these days and were found to be active even after 65 washes at a temperature of 92 degrees.
Have you ever thought about germicidal bedding? These probably have a promising future in the hospitals, where the bacteria celebrate and multiply without interruption. Well, there are those who have thought about it and germicidal cloth sheets for various uses are undergoing feasibility tests these days and were found to be active even after 65 washes at a temperature of 92 degrees. This will be testified by Prof. Aharon Gadenkan from the Chemistry Department in Bar-Ilan who developed a method that makes it possible to coat fabrics, bed linen for example, or metal particles, catheters for example, thereby preventing the activity of bacteria in hospitals and on devices inserted into the body. But this is only the tip of the iceberg. These days Gdankan published an article in which there is another application of his method: coating paper with antibacterial nanoparticles that will be used, among other things, to preserve and extend the shelf life of food products.
Those who do the work are nano particles that are produced using high frequency sound waves. "When you bombard a liquid solution with high-frequency sound waves, which in scientific jargon is called ultra-sonication, something happens," explains Gadanken. "The liquid solution swirls rapidly and masses of microscopic bubbles are formed in it that collapse into themselves. When the collapse process occurs near a solid surface such as a smooth surface of glass or metal, or even a millimeter grain of a material, liquid streams move at a very high speed to the surface of the solid and throw the particles from the solution onto it at enormous speeds. The particles are embedded in the solid and cannot be removed by washing. In this way it is possible to give the solid different properties that it did not have in the first place. For example, antibacterial, magnetic, electrical properties and more. This is how, for example, antibacterial substances can be embedded in fabrics or any other material."
The growing resistance of bacteria to most types of antibiotics has led to the focus of attention on silver solutions, which have been used for many years for disinfection, and have proven effective in killing hundreds of types of bacteria. Gadenkan therefore decided to apply the ultrasonic method he had developed to the silver solution and see if he could obtain from the solution silver nanoparticles with antibacterial activity, coat them on paper and obtain paper that kills bacteria. The mission was successful. "Our method is very simple and includes only one step - sonication of the metal ions together with the material we wish to observe", says Gadanken. "We started with fabrics. Today we produce anti-bacterial fabrics in which the silver particles are anchored between the fabric fibers. The silver gives the fabrics antibacterial activity that is maintained over time in extreme temperature conditions. Now we've moved to paper."
Ronen Gottsman, a graduate student in Gedanken's research lab who was in charge of the task, was able to coat paper with silver nanoparticles. "In the process, we inserted pieces of baking paper that we bought at the supermarket into the sonication vessel. In the vessel we prepared metallic silver particles in a solution, which were thrown in the sonication process onto the surface of the paper and embedded in it. Later we tested the antibacterial activity of the paper, while introducing it to cultures of bacteria, including intestinal bacteria such as coli and staphylococci. The bacteria were eliminated in less than an hour. The antibacterial activity of the paper remained unchanged even a year after the coating was performed," Gutesman says.
"The development of paper coated with silver particles with anti-bacterial properties can be used as an alternative to food preservation methods used today such as irradiating the food, preserving it at low temperatures, or using anti-bacterial additives," the researchers write in the article. "Furthermore, with the emphasis on 'green chemistry', today's interest is focused on the adoption of materials and methods that will make it possible to reduce the use of toxic chemicals", which is exactly what the method enables. In addition, it turned out that the uniform coating of the metallic silver can transmit an electric current, and it can be used to develop paper-based detectors for fast and portable detection of chemical substances.
Finally, the researchers write: "We believe that such coated paper has a useful potential in the food industry as a packaging material with a long shelf life. At the same time, the sonication process we used can be used to produce other nanomaterials with different functions for different uses."
