Tuning bio-aerogel properties. Part 3: Exploring silica-pectin composite aerogels for drug delivery

The release of the model drug theophylline from silica-pectin aerogels was investigated. The composite aerogels were prepared via impregnation of pectin alcogels with silica sol, followed by in situ silica gelation and drying with supercritical CO₂. The structural and physico-chemical properties of the aerogels were tuned via the preparation conditions (type of silica sol, calcium crosslinking of pectin or not). Theophylline was loaded via impregnation and its release into simulated gastric fluid was studied during 1 h followed by release into simulated intestinal fluid. The swelling, mass loss and theophylline release behavior of the composites were analyzed and correlated with material properties. It followed that only aerogels prepared with calcium-crosslinked pectin and polyethoxydisiloxane were stable in aqueous systems, exhibiting a slow theophylline release governed by near-Fickian diffusion.