Hydrogel-based 3D hybrid bioprinting towards cartilage application

Three-dimensional (3D) bioprinting has been applied to fabricate constructs that facilitate cartilage regeneration, as it provides the ability to assemble biomaterials with cells in a spatially controlled manner. For conventional bioprinting, the bioink is applied alone to fabricate constructs. However, this strategy is hitting a bottleneck due to the challenging requirements of bioink formulation. The bioinks applied in conventional bioprinting have to fulfill both the physicochemical requirements for fabrication, as well as the biological requirements associated with the processing of the embedded cells. To address this issue, hybrid bioprinting techniques that simultaneously apply two (or multiple) inks have been explored since 2011. Hybrid bioprinting strategies using thermoplastics and hydrogels have demonstrated benefits for fabricating cartilage constructs with controlled stiffness and complex structure. Nevertheless, the adhesion between the thermoplastics as reinforced structure and cell-laden hydrogels is poor, resulting in compromised integrity of fabricated constructs. The present work developed a hybrid bioprinting strategy using two hydrogel-based inks and explored the potential of this approach in cartilage tissue engineering.