Post-decellularized printing of cartilage extracellular matrix: distinction between biomaterial ink and bioink

In tissue engineering and regenerative medicine, nature's template is the extracellular matrix (ECM) which provides mechanical support and biochemical signals to encourage cell attachment and modulate cell behavior. Biological and biomimetic materials derived from the decellularized ECM (dECM) are successfully used in a variety of biomedical therapies both in preclinical studies and clinical applications. One of the main goals of decellularization is the elimination of cellular components from tissue samples or whole organs while maintaining their resident regulatory molecules and mechanical integrity. The coupling of decellularized bioproducts with computer-aided fabrication technologies such as three-dimensional (3D) printing, is revolutionizing tissue engineering and regenerative medicine. Following the growth of different computer-aided scaffolding methods, 3D bioprinting offers the possibility of incorporating different cells into the biomaterial formulation to produce a cell-laden structure. Suitable materials for 3D bioprinting are often referred to as bioinks and have become an important field research area. The concept of bioink, originally considered a printable hydrogel that incorporated living cells, has recently changed. That is to say, biomaterials that can be printed and subsequently seeded with cells after printing, do not qualify as a bioink. However, the 3D printing of biomaterial inks and bioinks of dECM for cartilage regeneration is still burgeoning. Cartilage possesses uniquely complex mechanical properties that are integral to tissue function and can be attributed to the ECM network. Hence, using a printed dECM scaffold could be an encouraging approach to engineering cartilage while preserving its depth-dependent ECM structure. This paper provides an overview of the composition and structure of cartilage ECM and 3D printing and bioprinting of dECM-related scaffolds, emphasizing cartilage function.