Inverted colloidal crystal scaffolds for uniform cartilage regeneration.

A uniform distribution of chondrocytes in 3D scaffolds is a critical challenge to cartilage regeneration. This study aims to resolve the problem by showing uniformly distributed chondrogenesis in chitin/chitosan matrix with pores of inverted colloidal crystal (ICC) structure. The results revealed that the effect of solvent on the regularity of colloidal crystal arrays was in the order of ethanol > ethylene glycol > acetone. When the concentration of chitin/chitosan gel was <2.5%, the porosity of ICC scaffolds with pure ethanol was approximately 84%. The highly porous freeform scaffolds produced random and unconnected pores, in general. The viability of bovine knee chondrocytes (BKCs) in ICC constructs was >92%. Over 4 weeks of cultivation, the percentage of biodegradation of ICC scaffolds with pure ethanol was approximately 34%. The order in the produced BKCs, glycosaminoglycans (GAGs), and collagen was freeform constructs > ICC constructs with pure ethanol > ICC constructs with 95% acetone. However, the spatial distribution of BKCs in ICC constructs was more uniform than that in freeform constructs. In addition, BKCs could secrete GAGs and type II collagen in the core of ICC constructs, indicating the maintenance of phenotypic chondrocytes and their metabolism. The ICC constructs with well-controlled pore regularity and unique topography can generate uniform tissue-engineered cartilage.