Aerogel sponges of silk fibroin, hyaluronic acid and heparin for soft tissue engineering: Composition-properties relationship

This work aims to design biocompatible aerogel sponges that can host and control the release of stromal cellderived factor-1 alpha (SDF-1 alpha or CXCL12), a key protein for applications ranging from regenerative medicine to cancer therapy (notably for neural tissues). Miscibility of silk fibroin (SF) and hyaluronic acid (HA) was investigated by means of fluorescence and scanning electron microscopy to identify processing conditions. Series of freeze-dried sponges were prepared by associating and cross-linking within the same 3D structure, HA, SF, poly-c-lysine (PLL) and heparin (hep). Aerogel sponges presented high swelling degree and porosity (similar to 90 %), adequate mean pore diameter (ca. 60 mu m) and connectivity for welcoming cells, and a soft texture close to that of the brain (6-13 kPa Young's Modulus). Addition of SF yielded sponges with slower biodegradation. SF-HA and SF-HA-hep sponges retained 75 % and 93 % of the SDF-1 alpha respectively after 7 days and were found to be cytocompatible in vitro.