The objective of this work is to develop a novel coacervation process to produce
microcapsules of PLA to encapsulate thyme oil that will be used in cosmetics. PLA is
soluble in organic solvents but insoluble in water. Generally, PLA is used to encapsulate
water soluble active principles such as drugs, pesticides and dye-stuffs by coacervation,
mainly by means of microspheres production or by using double emulsion techniques
(o/w/o). However, the objective of this work is to encapsulate thyme oil, a water
insoluble active principle that needs, in a first step, the preparation of an oil-in-water
emulsion. The novelty of our process consists on dissolving PLA in dimethylformamide
(DMF) which is a good solvent for PLA but in addition has high solubility in water.
Upon contact with water, the homogeneous solution of PLA in DMF, promotes the
precipitation of PLA around the thyme oil core. With this work we demonstrate a new,
easy and executable method of coacervation by introducing modifications on
microencapsulation process that allow the encapsulation of an oily active principle by
simply preparing an o/w emulsion. Control of size and wall thickness of microcapsules,
encapsulation efficiency, the influence of surfactants and release of thyme oil were
studied. The produced microcapsules have bimodal particle size distributions in volume
with a mean particle size of 40 μm. Microcapsules analysis by microscopy have
confirmed the spherical shape, the rough surface, and allowed the estimation of the wall
thickness around 5 μm. Quantification of the encapsulated thyme oil was performed by
gas chromatography and allowed to evaluate the quality of the encapsulated oil and
pointed out for a preferential encapsulation of thyme oil apolar compounds.FCT: Grant SFRH/BD/43215/2008
