Experimental Investigation and CFD Modeling of Supercritical Adsorption Process

The kinetics of the supercritical adsorption process was experimentally studied by the example of ”ibuprofen-silica aerogel” composition obtainment at various parameters: Pressure 120–200 bar and temperature 40–60 °C. Computational Fluid Dynamics (CFD) model of the supercritical adsorption process in a high-pressure apparatus based on the provisions of continuum mechanics is proposed. Using supercritical adsorption process kinetics experimental data, the dependences of the effective diffusion coefficient of active substance in the aerogel, and the maximum amount of the adsorbed active substance into the aerogel on temperature and pressure are revealed. Adequacy of the proposed model is confirmed. The proposed mathematical model allows predicting the behavior of system (fields of velocity, temperature, pressure, composition, density, etc.) at each point of the studied medium. It makes possible to predict mass transport rate of the active substance inside the porous body depending on the geometry of the apparatus, structure of flow, temperature, and pressure.

Alginate-Based Aerogel Particles as Drug Delivery Systems: Investigation of the Supercritical Adsorption and In Vitro Evaluations

The present work focuses on the preparation of alginate-based aerogels in the form of particles for their further study as potential drug delivery systems (solid dosage forms). The dripping method was used to prepare certain gel particles, and supercritical drying was used to obtain final alginate-based aerogel particles. Three model active substances (ketoprofen, nimesulide, loratadine) were impregnated into the obtained aerogels using the supercritical adsorption process. Using the method of X-ray analysis, it was shown that the in the obtained drug-loaded aerogels the corresponding active substances are in an amorphous state, and the stability of this state after six months of storage is confirmed. In vitro dissolution tests for obtained drug-loaded aerogels was performed. For each sample, an appropriate dissolution medium (with certain pH) was determined. In vitro investigations showed the increasing of the release rate for all model active substances. Time was required to release and dissolve 50% of the active drug from drug-loaded aerogels (T1/2), reduced in comparison with pure active drugs in crystalline form. Obtained results provide insight into the application of alginate-based aerogel particles as a drug delivery system to improve pharmacokinetic properties of certain active drugs.

Eumelanin Coating of Silica Aerogel by Supercritical Carbon Dioxide Deposition of a 5,6-Dihydroxyindole Thin Film

Eumelanin integration in silica aerogel (SA) was achieved via supercritical adsorption of 5,6-dyhydroxyindole (DHI) from CO2. Notably, after the supercritical treatment, DHI evolved towards spontaneous polymerization, which resulted in uniform pigment development over the SA. The new material was characterized for its morphological and physicochemical properties, disclosing the formation of a eumelanin-like coating, as confirmed by UV–vis and electron paramagnetic resonance (EPR) spectroscopy.