(95i) Novel Method for the Release of Hydrocortisone from Molecularly Imprinted Polymers Thin Films by Supercritical Fluid Extraction

The release of template molecules from molecularly imprinted polymers (MIPs) depends upon the rate of diffusion of a competing solvent and the relaxation of the polymer chain. The diffusion of large template molecules out of MIPs is hindered in most cases by the complex entanglement of the polymer chains. One challenge in the removal of template molecules from thin films in conventional extraction methods, which rely almost exclusively on the solvating properties of a competing solvent, is the release of template molecules while maintaining the membrane intact. The release of hydrocortisone from MIPs by supercritical fluid extraction with supercritical carbon dioxide (CO2) is being studied as an alternative release mechanism. Contrary to regular solvents, supercritical fluids share the diffusivity properties of gases with the dissolving ability of liquids. Additionally, supercritical CO2 promotes swelling of polymer membranes, reducing the diffusion resistance caused by chain entanglement. Since supercritical CO2 is a relatively non-polar solvent, the use of a cosolvent ? a solution of methanol with 10% acetic acid ? was required to improve the solubility of hydrocortisone. A solubility analysis, with and without cosolvent, was performed within the range of temperatures of 40 to 60°C and pressures of 120 to 150 bar. This analysis was used to determine the optimum conditions of solubility of hydrocortisone in supercritical CO2 as well as the effect of the cosolvent in the solubility. The results from this analysis demonstrated that hydrocortisone was virtually insoluble in supercritical CO2, but demonstrated high solubility in the presence of the cosolvent. Further studies will compare the solvation removal method with the proposed supercritical extraction method.