From your favorite t-shirt to your car upholstery, fabric is an integral part of our lives. Fabrics and textiles also attract homes for microbial life such as fungi or bacteria. Fabrics tend to hold moisture well, and the natural fibers they are made of provide nutrients and energy for microbes in the form of carbohydrates or proteins. These common properties of substances make it easy for microorganisms to grow and survive. We can wash our clothes to keep these microorganisms in check, but what if we made the fabrics resistant in the first place?
Fabrics are sometimes coated with chemicals known as fabric antimicrobial finishes that prevent bacteria and fungi from growing. Antimicrobial finishes also prevent odors and can even be used to treat skin infections. However, many modern surface treatments are harmful to the environment and can be potentially dangerous to humans. For this reason, there is a need for antimicrobial finishes that are biodegradable and non-toxic.
A team of researchers in the UK, funded by the European Commission, studied the antimicrobial properties of an essential oil finish on fabrics. Essential oils are chemical compounds extracted from plants that are responsible for their unique scent – or essence. The researchers showed that these essential oils can exhibit powerful antimicrobial properties when used as finishing touches to fabrics.
Essential oils can be volatile, which means that they evaporate quickly when exposed to air. They are also sensitive to degradation by light and oxygen. To protect the oils during application, the researchers used a process called microemulsification to create a water-oil mixture that was applied to the fabric.
The researchers first examined 10 different essential oils and combinations thereof to determine the antimicrobial potential against five different microorganisms. All essential oils were tested by placing a 25 μL sample of the essential oil on a disc with cultured microorganisms on the surface and measuring how much the essential oils increased the growth of the microorganism compared to the control disc which had no essential oils added were inhibited.
After testing bergamot, citronella, lemon, litsea, bitter orange, sweet orange, peppermint, rosemary, rosewood, and wild thyme, and every double and triple combination of these, they found that a combination of lemon and litsea had the greatest success in inhibiting growth from the microorganisms. The five species these were tested against are the causes of common infections such as staph infections and athlete’s foot. These were E. coli, P. aeruginosa, S. aureus, S. epidermidis, and T. rubrum, and only P. aeruginosa resisted inhibition by any of the essential oils.
Now it was time to test this antimicrobial property on fabrics. The team made a microemulsion of the lemon-Litsea mixture and soaked sterilized cotton in it. After drying, the team infected swatches of fabric with samples of the same microorganisms previously used with the exception of P. aeruginosa, as they already showed that the essential oils did not inhibit its growth. These tissue samples showed a complete reduction in the bacteria tested within 24 hours and a complete reduction in the fungus tested (T. rubrum) within 48 hours. These antimicrobial properties were lost after washing the fabrics at 40 ° C.
The research team recognizes that further research is needed to further improve the stability of the essential oils. They also encourage further research to investigate whether the attachment of the essential oils to the fabrics allows for further applicability beyond the single-use treatment. Regardless, this shows a clear potential for a more environmentally conscious and less potentially dangerous antimicrobial coating of fabrics through the use of the essential oil microemulsions.
