Microencapsulation of red and white thyme oil in poly(lactic‐co‐glycolic) acid: Assessment of encapsulation efficiency and antimicrobial capacity of the produced microcapsules

Abstract

AbstractIn this work, microcapsules were formed by coating thyme oil with a biodegradable polymer, poly(lactic‐co‐glycolic) acid (PLGA), through a coacervation process recently developed at our laboratory and previously studied for poly lactic acid (PLA). The coacervation method involves dissolution of the polymer (PLGA 50:50) in dimethylformamide. After adding this solution to the oil/water (o/w) emulsion, and due the insolubility of the polymer in water, polymer deposition occurs around the oil droplets and microcapsule formation starts. PLGA was chosen due to its easy biodegradation and biocompatibility. The active principle, thyme oil, is characterized by excellent antimicrobial activity ascribed to the presence of thymol and carvacrol, its major components. Two types of thyme oil (red and white) were microencapsulated and the produced microcapsules were characterized using optical microscopy, particle size analysis, and gas chromatography (used to evaluate encapsulation efficiency). Antimicrobial activity was preliminarily evaluated following ASTM E2149‐01. Microscopy and particle size analysis confirmed the existence of microcapsules with round shapes, smooth surfaces, particle diameters between ∼45–49 μm, and wall thicknesses ∼3.5 μm. Global encapsulation efficiencies of thyme oil (both red and white) were 70 % and 57 %, respectively. The produced microcapsules exhibited a sustained oil release that ensures a level of antimicrobial activity maintenance desirable for cosmetic applications.