The fabrication of biomimetic biphasic CAN-PAC hydrogel with a seamless interfacial layer applied in osteochondral defect repair

Abstract

Cartilage tissue engineering based on biomimetic scaffolds has become a rapidly developing strategy for repairing cartilage defects. In this study, a biphasic CAN-PAC hydrogel for osteochondral defect (OCD) regeneration was fabricated based on the density difference between the two layers via a thermally reactive, rapid cross-linking method. The upper hydrogel was cross-linked by CSMA and NIPAm, and the lower hydrogel was composed of PECDA, AAm and PEGDA. The interface between the two layers was first grafted by the physical cross-linking of calcium gluconate and alginate, followed by the chemical cross-linking of the carbon-carbon double bonds in the other components. The pore sizes of the upper and lower hydrogels were ~187.4 and ~112.6 μm, respectively. The moduli of the upper and lower hydrogels were ~0.065 and ~0.261 MPa. This prepared bilayer hydrogel exhibited the characteristics of mimetic composition, mimetic structure and mimetic stiffness, which provided a microenvironment for sustaining cell attachment and viability. Meanwhile, the biodegradability and biocompatibility of the CAN-PAC hydrogel were examined in vivo. Furthermore, an osteochondral defect model was developed in rabbits, and the bilayer hydrogels were implanted into the defect. The regenerated tissues in the bilayer hydrogel group exhibited new translucent cartilage and repaired subchondral bone, indicating that the hydrogel can enhance the repair of osteochondral defects.

Biomaterials: Dual-layered hydrogel aids bone and cartilage repair

A dual-layered polymer hydrogel could help to treat injuries to cartilage and bone. Yunfeng Lin and colleagues from Sichuan University in Chengdu, China, developed a relatively simple recipe for synthesizing a biphasic hydrogel with an upper layer that mirrors the properties of articular cartilage and a lower one that resembles subchondral bone. In cell culture, the upper and lower layers maintained the viability of cartilage cells and bone-forming osteoblast cells, respectively. The hydrogel broke down with minimal inflammation when implanted inside rats, demonstrating its biodegradability and biocompatibility. Experiments in rabbits with leg injuries showed that the hydrogel served as a temporary scaffold to enhance regeneration before being replaced by native tissue. The researchers suggest that this or similar dual-layered hydrogels could be used in the future application of bone and cartilage tissue engineering to people.

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