Cross-linking methods of type I collagen-based scaffolds for cartilage tissue engineering

Cartilage defects are one of the hardest injures to cure, given the limited regenerative ability of cartilage tissues. Moreover, cartilage defects affect an increasing number of people worldwide. Therefore, scientists have attempted to develop effective strategies to repair cartilage defects in recent years. Recent advances in tissue engineering have led to the strategies for inducing cartilage regeneration. Among the emerging strategies, scaffolds are commonly used in cartilage tissue engineering (CTE) as they provide favorable environment for the growth and proliferation of chondrocytes. An ideal scaffolding material should be highly biocompatible. Type I collagen is one such material, which is widely used in CTE. However, type I collagen has poor mechanical properties and stability, which limit its use. Cross-linking is a simple method known to improve degradability, biological and mechanical properties of biomaterials by enhancing chemical and physical interactions between polymers. Cross-linking can be induced through chemical, physical or biological processes. In this review, we present cross-linking methods that can enhance the mechanical strength of type I collagen for CTE and highlight future directions in this field.