Fabrication and evaluation of homogeneous alginate/polyacrylamide–chitosan–gelatin composite hydrogel scaffolds based on the interpenetrating networks for tissue engineering

Interpenetrating polymer network (IPN) is generally considered to be one of the most effective methods for imparting high-strength mechanical properties to hydrogel materials. To broaden the application of alginate hydrogel in skeletal muscle or muscle tissue engineering, the interpenetrating network technology and layer-by-layer (LBL) electrostatic assembly were proposed to fabricate the homogeneous alginate/polyacrylamide–chitosan–gelatin (Alg/PAAM–CS–GT) composite hydrogel scaffolds, using the hydroxyapatite/ d -glucono-δ-lactone (HAP/GDL) complex as the gelling system. The effects of different components of alginate/polyacrylamide (Alg/PAAM) on the morphology, mechanical properties, swelling, degradability, and cytocompatibility of the hydrogel scaffolds were comparatively characterized. Experimental results showed that the as-prepared Alg/PAAM–CS–GT composite hydrogel scaffolds exhibited sharp edges and regular 3D structures. Their pore structure could be regulated by changing the content of PAAM in Alg/PAAM–CS–GT composite hydrogel scaffolds. And the filling of PAAM reduced the pores and thickened the pore walls, which obviously enhanced the mechanical properties of Alg/PAAM–CS–GT composite hydrogel scaffolds. FT-IR and thermogravimetric analysis showed that O‧‧‧N hydrogen bonding between  COOH of SA and  NH 2 of PAAM could be helpful to improve the thermal stability of the composite hydrogel scaffolds. The swelling and biodegradation measurements indicated that the swelling and degradation of Alg/PAAM–CS–GT composite hydrogel scaffolds could be effectively regulated by changing the component content of the composite hydrogel. In addition, the in vitro cytocompatibility analysis showed that the Alg/PAAM–CS–GT composite hydrogel scaffolds could support the growth of MC3T3-E1 cells and promote cell proliferation and differentiation. According to the in vitro cytocompatibility test results, the optimum PAAM content for the Alg/PAAM–CS–GT composite hydrogel scaffolds was 60%. Because of good morphology, well-developed pores, excellent mechanical properties, and high biological activity of Alg/PAAM–CS–GT composite hydrogel scaffolds, they could be suitable for application in the tissue engineering field.