Characterization and assessment of new fibrillar collagen inks and bioinks for 3D printing and bioprinting

Collagen is a cornerstone protein for tissue engineering and 3D bioprinting due to its outstanding biocompatibility, low immunogenicity, and natural abundance in human tissues. Nonetheless, it still poses some important challenges, such as complicated and limited extraction processes, usually accompanied by batch- to-batch reproducibility and influence of factors, such as temperature, pH, and ionic strength. In this work, we evaluated the suitability and performance of new, fibrillar type I collagen as standardized and reproducible collagen source for 3D printing and bioprinting. The acidic, native fibrous collagen formulation (5% w/w) performed remarkably during 3D printing, which was possible to print constructs of up to 27 layers without collapsing. On the other hand, the fibrous collagen mass has been modified to provide a fast, reliable, and easily neutralizable process. The neutralization with TRIS-HCl enabled the inclusion of cells without hindering printability. The cell-laden constructs were printed under mild conditions (50-80 kPa, pneumatic 3D printing), providing remarkable cellular viability (>90%) as well as a stable platform for cell growth and proliferation in vitro. Therefore, the native, type I collagen masses characterized in this work offer a reproducible and reliable source of collagen for 3D printing and bioprinting purposes.