Hydrogel-based scaffolds for bone and cartilage tissue engineering and regeneration

Tissue engineering to replace an injured/defective organ is considered a complex process by which the required biological functionalities are restored. As an effective strategy to restore the damaged tissue/organs, tissue regeneration is based on the use of safe scaffolds supplemented with necessary bioactive substances and incorporated with live cells. To have the maximal biological impacts, the cells are incorporated into a safe bioactive scaffold and implanted for regenerating the desired tissue of the defected organ. Such a complex process is largely dependent on (i) the physicochemical properties of the scaffold used, (ii) the integrity of the incorporated cells, and (iii) the biological setting in which the cell-embedded scaffold is implanted. In bone and cartilage tissue engineering, advanced biomimetic hydrogels offer a remarkable 3D matrix with desired properties, upon which they can permissively accommodate the embodied cells. Advanced bioactive hydrogels offer extraordinary features, including safety and biocompatibility, high water absorption capacity, resemblance to the normal extracellular matrix, mechanical strength, capability to accommodate cells, and potential to incorporate the necessary substances such as growth factors necessary for tissue regeneration, and flexibility in production. The current review aims to provide deep insights into the design, fabrication techniques of hydrogels, and application of bioactive substances for the regeneration of bone and cartilage tissues.