Temperature- and pH-responsive chitosan-based injectable hydrogels for bone tissue engineering

Spontaneous bone regeneration is heavily restricted because of bone defects, and external mediation is required to enhance repair and regeneration. Bone tissue engineering (BTE) is a multidisciplinary field that offers promising substitutes to traditional methods—namely, autografts, allografts, and xenografts. Amidst the various scaffolds for BTE applications, it has been demonstrated that hydrogels are promising templates for bone regeneration owing to their similarities to the natural extracellular matrix. Regardless of the development of a variety of biomaterials, chitosan (CS) as a natural biopolymer has drawn tremendous attention in recent years for its use as a valuable graft material to form thermo/pH-responsive injectable hydrogels. Formulations of CS-based injectable hydrogels are advantageous in terms of their high-water imbibing capability, minimal invasiveness, porous networks, and ability to mold perfectly into an irregular defect. In this review, the physicochemical properties and applications of thermo/pH-responsive CS-based hydrogels and their future perspectives in BTE are briefly outlined.