Tailoring mechanical properties of decellularized extracellular matrix bioink by vitamin B2-induced photo-crosslinking.

We have developed two-step process that uses sequential vitamin B2-induced UVA crosslinking and thermal gelation to solidify decellularized extracellular matrix (dECM) bioink; this process enables tailoring of mechanical properties of 3D-printed bioconstructs. This is the first evaluation of vitamin B2 for use in 3D bioprinting. The developed printing process offers easy control of the width of printed lines, and can therefore ensure that functional living tissue in printed with high fidelity. Using a dECM bioink combination that mimics a native microenvironment, a bioconstruct was designed to match the biomechanical properties of native cardiac tissue. The printed bioconstruct supported high cell viability and active proliferation of cardiac progenitor cells, and ultimately increased cardiomyogenic differentiation. This printing strategy is an additional tool for regulating biomechanical cues, and therefore provides new approaches to dECM-based cell printing. STATEMENT OF SIGNIFICANCE: 3D cell printing is an emerging strategy to create an engineered tissue construct by depositing biological components. The printable material used while printing cells is called "bioink"; to prevent cell damage during printing process. Recent development of printable tissue-specific dECM bioink has enabled 3D fabrication of tissues that are much more functionally matched than their predecessors. Demand for a method to tailor the mechanical properties of dECM bioink to improve both printability and tissue function has increased; thus, we here describe mechanical tailoring of dECM bioink by using vitamin B2 and UVA irradiation. By using this approach, we could fabricate a bioconstruct that has stiffness similar to that of the target tissue.