Chitosan scaffolds with enhanced mechanical strength and elastic response by combination of freeze gelation, photo-crosslinking and freeze-drying

In this study, a new scaffold fabrication method based on the combination of a series of stabilization processes was set up to obtain chitosan scaffolds with improved mechanical properties for regeneration of load-bearing tissues. Specifically, thermally induced phase separation (TIPS) of chitosan solutions was used to obtain an open structure which was then stabilized by freeze-gelation and photo cross-linking. Freeze-gelation combined with freeze-drying permitted to obtain a porous structure with a 95 μm-mean pore size suitable for osteoblast cells' housing. Photo-crosslinking improved by ca. three times the scaffold compressive modulus, passing from 0,8 MPa of the uncrosslinked scaffolds to 2,2 MPa of the crosslinked one. Hydrated crosslinked scaffolds showed a good elastic response, with an 80% elastic recovery for at least 5 consecutive compressive cycles. The herein reported method has the advantage to not require the use of potentially toxic cross-linking agents and may be extended to other soft materials.