Tuning bio-aerogel properties for controlling drug delivery. Part 2: Cellulose-pectin composite aerogels.

The release of the model drug theophylline from cellulose-pectin composite aerogels was investigated. Cellulose and pectin formed an interpenetrated network, and the goal was to study and understand the influence of each component and its solubility in simulated gastric and intestinal fluids on the kinetics of release. Cellulose was dissolved, coagulated in water, followed by impregnation with pectin solution, crosslinking of pectin with calcium (in some cases this step was omitted), solvent exchange and supercritical CO2 drying. Theophylline was loaded via impregnation and its release into simulated gastric fluid was monitored for 1 h followed by release into simulated intestinal fluid. The properties of the composite aerogels were varied via the cellulose and pectin concentrations as well as the calcium content in the precursor solutions. The release kinetics was correlated with aerogel specific surface area, bulk density as well as network swelling and erosion. The Korsmeyer-Peppas model was employed to identify the dominant release mechanisms during the various stages of the release.

Tuning bio-aerogel properties for controlling theophylline delivery. Part 1: Pectin aerogels.

A comprehensive study of release kinetics of a hydrophilic drug from bio-aerogels based on pectin was performed. Pectin aerogels were made by polymer dissolution, gelation (in some cases this step was omitted), solvent exchange and drying with supercritical CO2. Theophylline was loaded and its release was studied in the simulated gastric fluid during 1 h followed by the release in the simulated intestinal fluid. Pectin concentration, initial solution pH and concentration of calcium were varied to tune the properties of aerogel. The kinetics of theophylline release was monitored and correlated with aerogel density, specific surface area, and aerogel swelling and erosion. Various kinetic models were tested to identify the main physical mechanisms governing the release.

Aeropectin: fully biomass-based mechanically strong and thermal superinsulating aerogel.

Monolithic pectin aerogels, aeropectins, were prepared via dissolution-gelation-coagulation and subsequent drying with supercritical CO2. Aeropectin had pore sizes that varied from mesopores to small macropores and compression moduli in the range from 4 to 18 MPa. Aeropectins show plastic deformation up to 60% strain before the pore walls collapse. Pectin aerogels have a thermal conductivity below that of air in ambient conditions, making them new thermal superinsulating fully biomass-based materials. The contribution of gas and solid conduction plus radiative heat transfer were determined and discussed.