Preparation of macroporous alginate-based aerogels for biomedical applications

Aerogels are a special class of ultra-light porous materials with growing interest in biomedical
applications due to their open pore structure and high surface area. However, they usually
lack macroporosity, while mesoporosity is typically high. In this work, carbon dioxide
induced gelation followed by expansion of the dissolved CO2 was performed to produce
hybrid calcium-crosslinked alginate-starch hydrogels with dual meso- and macroporosity. The
hydrogels were subjected to solvent exchange and supercritical drying to obtain aerogels.
Significant increase in macroporosity from 2 to 25 % was achieved by increasing expansion
rate from 0.1 to 30 bar/min with retaining mesoporosity (BET surface and BJH pore volume
in the range 183 – 544 m2/g and 2.0 – 6.8 cm3/g, respectively). In vitro bioactivity studies
showed that the alginate-starch aerogels are bioactive, i.e. they form hydroxyapatite crystals
when immersed in a simulated body fluid solution. Bioactivity is attributed to the presence of
calcium in the matrix. The assessment of the biological performance showed that the aerogels
do not present a cytotoxic effect and the cells are able to colonize and grow on their surface.
Results presented in this work provide a good indication of the potential of the alginate-starch
aerogels in biomedical applications, particularly for bone regeneration. aerogels, alginate, starch, tissue engineering, supercritical fluids, CO2 induced gelation.