Study on Adsorption of Essential Oils on Polylactic Acid Microparticles

Polylactic acid (PLA) is a biodegradable polymer that is widely used in medical devices, drug delivery systems, fibers for packaging containers and textiles. However, given that interactions between the polymer and the materials in contact with it affect its applications, it is important to study its adsorption and diffusion properties. The adsorption capacity of different polylactic acid particles regarding different additives, e.g. essential oils (Thymus vulgaris, Melissa officinalis and Foeniculum vulgare), was investigated. PLA microparticles of various sizes were prepared by a solvent emulsification evaporation method. In this study, the specific adsorption of essential oils on PLA microparticles was also investigated, which is related to the solubility parameters of essential oils. The experiments were performed using three different solutions of essential oils and ethanol as a solvent. Two sets of PLA microparticles were prepared with different solvents using three different particle sizes. PLA microparticles exhibited different adsorption properties depending on the solvent that was used for their production. Samples of particles prepared using the solvent dichloromethane had a higher essential oil uptake than those prepared with chloroform. The uptake of essential oil solution did not change significantly (∼60%) by varying either the type of solvent used for PLA preparation or PLA particle size. The solubility of the essential oils affects the specific adsorption of essential oils on the microparticles. Among the components of the Hansen solubility parameters (HSPs), the polarity of essential oils is strongly related to adsorption.