Morphological features control drug release from nanostructured borosilicate – alginate aerogels and xerogels

Different drug delivery systems are formulated from chemically identical borosilicate-alginate xerogels and aerogels. The backbones of these gels are prepared in a common sol-gel procedure, but the loading of the nicotinic acid drug, as well as the final drying of the impregnated wet gels were realized using different strategies. It is shown that adding the nicotinic acid during gelation and drying the wet gel under ambient conditions leads to dense xerogels with high drug loading, which is released in a moderately retarded manner in simulated gastric and intestinal fluids. Highly porous aerogels are also formulated from the identical wet gels that are impregnated with nicotinic acid post-gelation and dried using supercritical CO 2 . Nicotinic acid is deposited in an amorphous form in these aerogels, and the drug dissolves practically instantaneously in the mentioned simulated body fluids. Supercritical CO 2 drying is essential to achieve the advantageous drug solubilization feature, because drying identical gels under ambient pressure yielded xerogels that do not display burst drug release. The thorough characterization (SEM, EDS, N 2 -sorption, XRD, FT-IR, Raman spectroscopy, ζ-potential) of the different gel formulations reveals the most important chemical and morphological features that control the distinct mechanisms of the release of nicotinic acid from the different gels. • Borosilicate-alginate composite aerogels and xerogels for oral drug delivery. • Drug impregnation during solvent-exchange, and supercritical CO 2 assisted drying. • Different solid gel fabrication strategies yield distinct drug release properties. • Morphological and interfacial properties are related to drug release mechanisms.