Thixotrophy property of hydrogels to evaluate the cell growing on the inside of the material bulk (Amber effect).

The realization of injectable hydrogels is one of the most challenging aims of biomedical research. Most injectable hydrogels are obtained by photopolymerization in situ. A hydrogel which is able to pass through a needle without losing its structure once crosslinked would be of great interest for several biomedical applications. In this work, hyaluronane and alginate-based 50% hydrogels were synthesized, their thixotrophic behavior was verified and their mechanical properties (G' and G'') were determined before and after the passage through the needle. A morphological analysis by scanning electron microscopy (SEM) was also performed in order to evaluate the effect of the passage of the hydrogel through the needle on the morphological structure of the material. The thixotrophic property of these hydrogels is used to realize a cell-containing material that supports cell proliferation and growth permitting in vivo engineering of new tissues. In fact, thixotrophic hydrogel can be sucked together with cell suspension and in this way cells remain entrapped inside the hydrogel structure (Amber effect). A comparison of the cell growth using this technique with the classical seeding technique (cell seeding onto the hydrogel) was performed. A different behavior was found between hyaluronane and alginate-based hydrogels.