Antibacterial biocomposite materials based on essential oils embedded in sol–gel hybrid silica matrices

Abstract

For the design of antibacterial materials comprising hybrid silica-containing plant oils capable of performing a controlled release of essential oil components, tests of lemongrass, citronella, basil, rosemary, eucalyptus, tea tree, lavender, clove and cinnamon against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Micrococcus luteus showed the essential oil of cinnamon to have the greatest antimicrobial activity. Hybrid organic–inorganic silica materials functionalized with methyl groups (methyl/Si, molar proportions 0.04–1.00), prepared with a sol–gel method, served as host matrices for the essential oil of cinnamon. The antibacterial and release properties of this oil in hybrid silicas were tested with disk diffusion experiments on bacterial cultures. The methyl–silica material with methyl/Si molar ratio 0.75 and load 7.5 % by mass of the encapsulated cinnamon essential oil presented adequate mechanical stability and maintained antibacterial properties for a prolonged period. This work has produced the first application of hybrid organic–inorganic silicas containing an essential oil for the design of antibacterial materials.