Antimicrobial activity of essential oils and their controlled release from the smart PLA fabric

Abstract

In this study, “smart”, stimuli responsive PLA fabrics with controlled antimicrobial activity were tailored, by the application of microgel based on temperature responsive poly(N-isopropylacrylamide) (poly-NiPAAm) and pH responsive chitosan, with incorporated β-cyclodextrine (PNCS/CD microgel), and subsequent embedment of essential oils (EO). Antimicrobial activity of lavender, thymol, savory and cinnamon bark EO was tested in 1 – 5 % concentrations. Based on the results, the 4% concentration of savory and cinnamon EO were chosen and prepared as emulsion, allowing further embedment into the PNCS/CD microgel using in-situ procedure on the PLA fabric. Morphological and chemical changes of the studied samples were assessed using scanning electron microscopy (SEM) and Fourier-transform infrared (FT-IR) spectroscopy. Temperature responsiveness was analyzed by determining moisture content (MC) at 20- and 40 °C, antimicrobial activity was determined by evaluating the reduction of gram-positive Staphylococcus aureus and gram-negative Escherichia coli, thus controlled release of the EO was tested by determining the zone of inhibition at 20- and 37°C. The results show that the embedment of the EO emulsion did not affect the temperature responsiveness of the PNCS/CD microgel. The PNCS/CD microgel proved to be a suitable carrier of antimicrobial agents, assuring the effective controlled release of EO emulsion and excellent antimicrobial activity. Temperature related controlled release of the EO emulsion was proven by the formation of zone of inhibition, which occurred only at conditions dictating shrinkage of the microgel particles.