It has been known for centuries that silver and copper have antiseptic properties. There are several mechanisms proposed on how copper (more precisely Cu2+ and Cu+ ions) kills bacteria. It can be due to disrupting bacterial metabolism or plasma membrane by generation of reactive oxygen species and degrading bacterial DNA.
Copper and a large number of its alloys were certified as antimicrobial by the US Environmental Protection Agency (EPA). However solid silver or copper alloys are prohibitively expensive for uses for hospital furniture; also, there are challenges in manufacturing complex shapes from sheet metal. A cost effective solution can be to coat a very thin metal layer on frequently touched surfaces. Twin wire arc spray is well known as one of the less expensive thermal spraying processes capable of producing dense coatings at high deposition rates.
At CACT, we have developed technique for deposition of copper alloy coatings with antibacterial properties on various substrates such as wood, plastic, or metal, using the twin wire arc process. These durable metal surfaces with long lasting antibacterial properties could provide a non-toxic, cost-effective, and eco-friendly way of countering bacterial contaminations in hospitals, nursing homes, and other public places.
Numerous biocidal studies by CACT, Department of Cells & Systems Biology, and University Health Network (UofT) were conducted for evaluation of such coatings, and the results were presented on conferences and published in journals. These results show that the coatings can kill bacteria within a few minutes of exposure.
Recently, a large project supported by the Grand Challenges Canada grant was concluded with participation of two hospitals with significantly different environments, cleaning protocols, and bacterial loads. The participating hospitals were Mount Sinai Hospital in Toronto and Instituto de Medicina Tropical Alexander von Humboldt in Lima, Perú.
Escherichia coli on stainless steel surface
The same bacteria, Escherichia coli, on a copper alloy coating after 5 min of exposure.