Combating Superbugs Through Sonochemistry

More than 4 million people each year in the EU suffer from hospital acquired infection (HAIs) such as MRSA and E. coli and around 37,000 die as a direct result of the infections. HAIs are also thought to be a contributing factor to a further 100,000 deaths each year. In the UK the cost associated with HAIs is estimated to be around £1 billion per year.

Current infection control programmes have proved effective in reducing the levels of HAIs but still the problem remains. The large number of textile items used in hospitals are a key element in the spread of these infections. Once contaminated, textiles can sometimes harbour micro-organisms for many weeks. Coventry University is part of a €15 million EU-funded project working towards finding a more effective way of combating these.

HAIs are being targeted using new antimicrobial fabrics.  This is a large scale project which brings together the expertise of 16 partners from 10 different European countries. Coventry University’s renowned Sonochemistry Centre is working on two aspects of the work: the design of the equipment used in the fabrication of the materials and in the microbiological testing of these fabrics.

Dr Eadaoin Joyce explained: ‘There are many applications of sonochemistry including environmental protection, electrochemistry, food processing, material science and therapeutic ultrasound. This project involves using sonochemistry to produce and impregnate nanoparticles in textiles forming a protective ‘antibacterial’ layer within the fabric.’

Eadaoin has investigated the use of a range of different elements and combinations of materials in the project. She explains: ‘Many metals are well known to have antibacterial properties including silver, copper, magnesium and zinc. The recorded use of silver to prevent infection dates to ancient Greece and Rome and nanoparticles have been used in suncreams and makeup for years. We’ve been working on different combinations of these elements to create the most effective combination to prevent diseases.’

The microbiology team involved in the work at Coventry which also includes Dr Jamie Beddow and a PhD student, Mr. Gagandeep Singh, are using industrial standard methods (ISO20743) to assess how well the coated fabrics can prevent the growth of different types of bacteria. In the antibacterial tests, samples of the fabrics are inoculated with known amounts of bacteria, incubated at 37ºC overnight and the number of viable bacteria are recorded. Bacteria grow very well on samples with no nanoparticles but for those which have been impregnated, all the bacteria are normally killed. One key goal of the project is to produce coated fabrics which can be repeatedly washed without completely losing their antimicrobial properties. In the last 6 months the research team have shown that sonochemically-coated fabrics can retain their antibacterial properties even after 100 industrial standard wash cycles at 70ºC. This kind of wash durability will be very important for the commercial success of the product.

The next phase of the pilot project will involve impregnating a range of medical textiles including cotton, polyester and a cotton/polyester mix using two different machines each using different methods of applying sonochemistry at textile manufacturers in Italy and Romania. The team will continue to test samples from these machines over the next two years. The fabrics will ultimately be used to manufacture hospital textiles such as bed sheets, pillow cases and curtains as well as pyjamas and medical staff uniforms for a hospital trial at the Emergency Medical Institute in Bulgaria.


What is sonochemistry

Sound is normally associated with communication and music; it is seldom thought of as an energy source. However, sound can be used to sterilise water, improve electroplating, produce better face creams, treat cancer and much more. These remarkable effects come from the energy released by cavitation bubbles generated in a liquid by sound waves. Cavitation bubbles act as microreactors, sometimes referred to as energy “hotspots”, and are very different from the more gentle soap bubbles blown by children or foam on the surface of coffee or even the bubbles fizzing in a glass of champagne.

Researchers at Coventry University began to study the energy from cavitation bubbles in 1975 and looked at effects on chemistry in a subject that became known as sonochemistry. Nowadays the applications of ultrasound have expanded well beyond chemistry and follow five main areas of research: Environmental Protection, Electrochemistry, Food Processing, Material Science and Therapeutic Ultrasound.