Experimental and theoretical characterization of the release kinetic of carvacrol as inclusion complexes with β-cyclodextrin in poly(lactic acid) and Mater-Bi® processed by supercritical impregnation

The incorporation of active compounds into polymeric matrices using traditional methods has several drawbacks mainly due to the high volatility and thermal sensitivity of these substances. A solution to this problem could be the incorporation of bioactive compounds forming inclusion complexes as a strategy to improve the chemical stability, bioactivity and achieve controlled release. In this work, beta-cyclodextrin/carvacrol inclusion complex was prepared by spray drying to be incorporated into poly(lactic acid) (PLA) and Mater-Bi (R) films by supercritical CO2 impregnation. The impregnation process was carried out at pressures of 10, 15 and 20 MPa and at 40 degrees C. Both polymers showed the highest amount of incorporated inclusion complex at 15 MPa, where the percentage of impregnation varied from 0.6 % to 7.1 % in Mater-Bi (R) and PLA, respectively. Release tests for PLA films impregnated with inclusion complex showed a slow release of the active compound, which did not reach equilibrium after 350 h under the experimental conditions. This prolonged release was not observed in Mater-Bi (R) due to the lower incorporation of the inclusion complex. The release rate was described herein by a comprehensive phenomenological model considering the decomplexation kinetics combined with the equilibrium and mass transfer expressions.