From your favorite T-shirt to your car upholstery, fabric is an integral part of our lives. Fabrics and textiles are also enticing homes to microbial life, like fungi or bacteria. Fabrics tend to retain moisture well, and the natural fibers they are made of offer nutrients and energy for microbes in the form of carbohydrates or proteins. These common properties found in fabrics make it easy for microorganisms to grow and survive. While we can wash our clothes to keep these microorganisms at bay, what if we made the fabrics resistant to begin with?
Fabrics are sometimes coated with chemicals, called antimicrobial textile finishes, that prevent bacteria and fungi from growing. Antimicrobial finishes also prevent odors and can even be used to treat skin infections. However, many contemporary finishes are environmentally damaging and can be potentially hazardous to humans. Because of this, there is a demand for antimicrobial finishes that are biodegradable and non-toxic.
A team of researchers in the United Kingdom, funded by the European Commission, looked at 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 their essence. The researchers showed that these essential oils may provide powerful antimicrobial properties when applied as a finish for fabrics.
Essential oils can be volatile, meaning they evaporate quickly when exposed to air. They are also sensitive to degradation by both light and oxygen. To protect the oils during application, the researchers used a process called microemulsification to create a water-oil blend to be applied to the fabric.
The researchers first screened 10 different essential oils and combinations of them to determine antimicrobial potential against five different microorganisms. All of the essential oils were tested by introducing a 25 μl sample of the essential oil onto a disk with cultured microorganisms on its surface and measuring how much the essential oils inhibited the microorganism’s growth when compared to the control disk, which had no essential oils introduced.
After testing bergamot, citronella, lemon, litsea, bitter orange, sweet orange, peppermint, rosemary, rosewood, and wild thyme and each double and triple combination of them, they found a lemon and litsea combination to have the most success inhibiting the growth of the microorganisms. The five species that these were tested against are the causes of common infections like staph infections and athlete’s foot. These were E. coli, P. aeruginosa, S. aureus, S. epidermidis and T. rubrum and only P. aeruginosa resisted being inhibited by any of the essential oils.
Now it was time to test this antimicrobial property on fabric. The team created a microemulsion of the lemon and litsea mixture and soaked sterilized cotton in it. After this finish dried, the team inoculated fabric samples with samples of the same microorganisms previously used except P. aeruginosa, since they already showed that the essential oils failed to inhibit its growth. These fabric samples showed a complete reduction of the bacteria tested within 24 hours and a complete reduction of the fungus tested (T. rubrum) within 48 hours. These antimicrobial properties were lost after washing the fabrics at 40° Celsius.
The research team recognizes that further research is needed to continue to improve the essential oils’ stability. They also encourage further research to investigate if the essential oils’ attachment to the fabrics allows for further applicability beyond single-use treatments. Regardless, this shows clear potential for a more environmentally conscious and less potentially hazardous antimicrobial coating for fabrics by using the essential oil microemulsions.