Development of sustainable cotton fabrics with natural immortelle essential oil for antimicrobial and mosquito repellent functions

Vector-borne infectious diseases, such as malaria, dengue fever, yellow fever and plague, are prevalent in subtropical regions. The malaria parasite can be spread via the bites of infected mosquitos. All travellers from non-malarial countries are highly vulnerable to the disease due to a lack of inherent immunity. There is an increasing demand for sustainable textile materials with functional properties, such as insect-repellence and antimicrobial protection. The current research work is to explore the possibility of using natural antimicrobials to achieve cotton fabrics with antimicrobial and mosquito-repellent functions through an eco-friendly processing against Escherichia coli & Staphylococcus aureus and Aedes aegypti respectively. A coacervation phase separation technique was used whereby immortelle essential oil (EO) (30%) was emulsified with 1% w/v chitosan and 0.025% w/v sodium alginate to form novel green microcapsules. The microcapsules were padded onto the scoured and bleached woven cotton fabric using Mercedes-Benz Pad-dry laboratory device. The antimicrobial activity was assessed using the adapted qualitative BS EN ISO 20645:2004 and quantitative BS EN ISO 20743:2013 test standards. Mosquito-repellency of the treated cotton fabrics against Aedes aegypti mosquito species were tested by using Y-tube Olfactometer according to WHO guidelines (Guidelines for efficacy testing of spatial repellents). The cotton coated with immortelle EO microcapsules showed no antimicrobial against the gram-negative E.coli, but was effective against the gram-positive skin microorganism S. aureus. Zones of inhibition of 2 cm were observed and the treated cotton reduced S. aureus growth by 86% compared to the control where only 40% reduction in growth was observed. 57% repellent rate against Aedes aegypti mosquitos was observed when the EO was added directly to the cotton textile, once microencapsulated the repellent rate increased to 100%. Further studies are being undertaken to optimise the concentration of immortelle essential oil to be used and to improve the efficiency of microencapsulation of immortelle essential oil for the control release of bioactive oils to achieve the long lasting efficacy of mosquito-repellency.