A self-disinfecting polymer, effective against pathogenic bacteria

22-Aug-08

A team led by Wendelin Stark, assistant professor at the Institute for Chemical and Bioengineering of ETH Zurich has developed a self-disinfecting polymer that is effective against pathogenic bacteria and only becomes active in a targeted manner if bacteria are growing in the vicinity, making it cost effective. The film coated with nanoparticles of silver and calcium phosphate could be used in food processing plants and packaging to inhibit pathogen growth. Findings demonstrate that the film is significantly more lethal against the bacterium E coli than conventional silicon-based silver preparations. Within 24 hours of the plastic film being applied to a surface, less than one bacterium out of one million bacteria will survive. Bacteria rely on calcium for their metabolism and the calcium phosphate particles are used by the micro-organisms as nutrition. When the bacteria consume the calcium phosphate, thousands of small silver nanometre particles are released. It is these tiny silver particles that kill the bacteria and prevent germs from growing and spreading. The calcium phosphate substrate had an efficiency factor of up to 1,000 times stronger than silicon dioxide on E. coli, claims the study, with a five to six log reduction after 24 hours. Silver has traditionally been used as an antiseptic and disinfectant and recent studies have found that impregnating other materials with silver nanoparticles is a practical way to exploit its germ-fighting properties, in particular because of its low toxicity to humans. Major consumer goods manufacturers already produce goods that utilise the antibacterial properties of silver nanoparticles. Current applications for silver nanoparticle-impregnated materials include household items, clothing (for example, socks to prevent foot infections for soldiers deployed in jungles), and laundry detergents. The film will be of interest to food manufacturers as microbial growth can affect food quality and safety and can damage a firms reputation and profits following costly recalls. The food handling and processing industries could benefit from self-sterilizing surfaces- like walls, machine covers and conveyor belts thst could be covered with the film to inhibit recontamination from product-touching surfaces. Packaging of perishables like meat, fish, pastry and convenience food are also interesting applications.