FRESH 3D\nBioprinting of Collagen Types I, II, and\nIII

Collagens play a vital role in the mechanical integrity\nof tissues\nas well as in physical and chemical signaling throughout the body.\nAs such, collagens are widely used biomaterials in tissue engineering;\nhowever, most 3D fabrication methods use only collagen type I and\nare restricted to simple cast or molded geometries that are not representative\nof native tissue. Freeform reversible embedding of suspended hydrogel\n(FRESH) 3D bioprinting has emerged as a method to fabricate complex\n3D scaffolds from collagen I but has yet to be leveraged for other\ncollagen isoforms. Here, we developed collagen type II, collagen type\nIII, and combination bioinks for FRESH 3D bioprinting of millimeter-sized\nscaffolds with micrometer scale features with fidelity comparable\nto scaffolds fabricated with the established collagen I bioink. At\nthe microscale, single filament extrusions were similar across all\ncollagen bioinks with a nominal diameter of ∼100 μm using\na 34-gauge needle. Scaffolds as large as 10 × 10 × 2 mm\nwere also fabricated and showed similar overall resolution and fidelity\nacross collagen bioinks. Finally, cell adhesion and growth on the\ndifferent collagen bioinks as either cast or FRESH 3D bioprinted scaffolds\nwere compared and found to support similar growth behaviors. In total,\nour results expand the range of collagen isoform bioinks that can\nbe 3D bioprinted and demonstrate that collagen types I, II, III, and\ncombinations thereof can all be FRESH printed with high fidelity and\ncomparable biological response. This serves to expand the toolkit\nfor the fabrication of tailored collagen scaffolds that can better\nrecapitulate the extracellular matrix properties of specific tissue\ntypes.