A Critical Review on the Evolution of Chitosan‐Based Injectable Hydrogels in Bone Regeneration

ABSTRACT The injectable hydrogels are redefining strategies in the field of bone and tissue engineering, offering a minimally invasive approach to the conventional procedures of grafting. Amongst all natural polymers, chitosan (CS) is found to be a decent candidate because of its intrinsic biodegradability and biocompatibility. This review gives an overview of the advancements in chitosan‐based hydrogel systems for the regeneration of bone. The mechanisms of sol–gel transition include physical and chemical strategies that permit the formation of a scaffold in situ. Particular emphasis is given to addressing the key drawbacks of chitosan, like its low mechanical strength and others. Reinforcing strategies that include bioactive ceramics and multistage growth factor delivery mechanisms that help in increasing angiogenesis and osteoconduction are discussed. The review also emphasises the creation of “smart” hydrogels that respond to biological stimuli such as reactive oxygen species (ROS) and enzymes, for application in osteochondral injuries and infected bone defects. Such multifunctional systems may contribute to improved treatment outcomes, reduced disease‐associated complications, and more accessible and inclusive health interventions. We assess these biomaterials' translational potential and pinpoint major obstacles to clinical adoption by combining data from recent in vitro and in vivo studies, opening the door for next‐generation, customized regenerative treatments.