FRESH 3D Bioprinting of Collagen Types I, II, and III

Collagens play a vital role in the mechanical integrity of tissues as well as in physical and chemical signaling throughout the body. As such, collagens are widely used biomaterials in tissue engineering; however, most 3D fabrication methods use only collagen type I and are restricted to simple cast or molded geometries that are not representative of native tissue. Freeform reversible embedding of suspended hydrogel (FRESH) 3D bioprinting has emerged as a method to fabricate complex 3D scaffolds from collagen I but has yet to be leveraged for other collagen isoforms. Here, we developed collagen type II, collagen type III, and combination bioinks for FRESH 3D bioprinting of millimeter-sized scaffolds with micrometer scale features with fidelity comparable to scaffolds fabricated with the established collagen I bioink. At the microscale, single filament extrusions were similar across all collagen bioinks with a nominal diameter of ∼100 μm using a 34-gauge needle. Scaffolds as large as 10 × 10 × 2 mm were also fabricated and showed similar overall resolution and fidelity across collagen bioinks. Finally, cell adhesion and growth on the different collagen bioinks as either cast or FRESH 3D bioprinted scaffolds were compared and found to support similar growth behaviors. In total, our results expand the range of collagen isoform bioinks that can be 3D bioprinted and demonstrate that collagen types I, II, III, and combinations thereof can all be FRESH printed with high fidelity and comparable biological response. This serves to expand the toolkit for the fabrication of tailored collagen scaffolds that can better recapitulate the extracellular matrix properties of specific tissue types.