When the EU project SONO began in 2009, Gedanken already knew that it was possible to coat textiles – and solids – with anti-bacterial nanoparticles. The team simply needed to build large machines able to do so in roll-to-roll mode – and then show the world the results.
The project was so successful that Bar-Ilan University, where Gedanken is based in Israel, has patented the technology to turn textiles into bacteria killers, and sold the rights to use it. Two machines were built during SONO and are currently in operation.
The secrets to the project’s success are nanoparticles and sonochemistry – "definitely the best coating technique" in Gedanken’s view. The process begins when a solution containing zinc acetate is submitted to ultrasonic waves. Bubbles form, grow and collapse, creating very high temperatures. When the bubbles collapse, zinc oxide nanoparticles are formed. If a bubble collapses near a solid surface, micro jets of liquid shoot the newly formed nanoparticles towards the surface at high speed. The particles then become embedded into the material because of the sheer force with which they hit it.
Zinc oxide has long been known for its antibacterial properties, and is used in creams to repair damaged tissue and heal wounds.
From theory to practice
The SONO team built two machines able to carry out the coating – in France and in Russia – which were sent to companies in Italy and Romania. An Israeli company then followed up on technical development, making operation fully automatic.
It was not long before the devices were up and running, coating various textiles with zinc oxide nanoparticles. When testing effectiveness, the team concentrated on eight bacteria identified by doctors as posing the biggest risk to patients.
The fabrics were found to kill all eight bacteria efficiently – and importantly, could continue doing so after the fabric was washed 65 times in hospital washing machines at 75°C or 92°C (which reflect international standards applied across hospitals). Microscopic photographs also showed the continued presence of the antibacterial nanoparticles after washing.
"This result makes our technique different from all others – exceptional even. Nobody else can demonstrate this," says Gedanken.
Pyjamas to food packaging
The ultimate test took place in Bulgaria, where 22 patients were kitted out with coated bed sheets, pillow cases and pyjamas, while 19 used standard hospital linen. The result was confirmation of all other tests: swabs from the first group exhibited far fewer dangerous bacteria.
What makes the antibacterial coating even more exciting is that it also kills certain bacteria that have become resistant to antibiotics.
But is it affordable? Operating the coating machine over five years will push up costs by 25%, explains Gedanken. After five years, costs will be just 4-5% higher. But the savings from reduced infection rates, which are currently a huge economic burden for healthcare providers, will more than compensate.
It is no surprise, then, that healthcare providers have shown a keen interest in the technology and have begun placing orders. But the process could also be applied in other areas. Gedanken points to food packaging – antibacterial coating could keep food safe for longer than is possible with traditional packaging.
First inspired by a challenge to create antibacterial socks, it’s likely we will be hearing much more about antibacterial nanoparticles in the future.