Fig. 6.

Triphasic/multiphasic scaffolds in cartilage and osteochondral tissue engineering. A. A triphasic scaffold was fabricated through a “iterative layering” freeze-drying technique using similar basic materials of hyaluronic acid, type I collagen and HAp, but type II collagen was added in addition in the intermediate and upper layers to imitate the native cartilaginous components. Reproduced with permission [247]. 2014, Elsevier. B. The single-unit scaffold based on PEGDA consists three layers with depth-varying pore architecture, mineral and cell environment: the hydrogel top layer, the cryogel middle layer with anisotropic pore structure and the biomineralized bottom layer. Reproduced with permission [250]. 2018, Elsevier. C. Based on composite materials of SA, chitosan and HAp with different micro and nano sizes, an intermediate calcified cartilage layer as well as a subjacent electrospun fibre membrane for cell migration prevention was designed in the four-layered scaffold to repair osteochondral defects. Reproduced with permission [162]. 2018, Elsevier. D. Multiphasic scaffold fabrication strategy was applied in mimicking the complex stratified architecture of articular cartilage structurally, chemically and mechanically. Reproduced with permission [253]. 2015, Elsevier. Multiphasic gradient and continuous gradient scaffolds.