Tissue-Derived Insoluble Type I and Type II Collagen Inks for 3D Printing of Fibrillar Collagen Scaffolds

Collagen is the primary structural component of the extracellular matrix, yet most printable collagen systems rely on soluble collagen, support baths, secondary polymers, or photochemical crosslinking. Here, we developed tissue derived insoluble type I and type II collagen inks for direct extrusion-based 3D printing without a sacrificial support bath. Type I collagen was isolated from bovine Achilles tendon and type II collagen from bovine articular cartilage. Both inks exhibited shear thinning with a predominantly elastic response that facilitated extrusion and supported shape retention after printing. The formulations were printed into grid scaffolds with infill densities of 25, 35, 40, and 50 percent and into multilayer constructs measuring approximately 20*20*20 mm. The printed constructs were treated with ammonium hydroxide to induce fibrillization and subsequently lyophilized, producing dimensionally stable and readily handleable scaffolds. Scanning electron microscopy revealed comparable porous morphologies in both scaffold types. Live and Dead staining showed abundant viable human bone marrow derived mesenchymal stem cells across the scaffold surfaces and internal regions. Cells appeared predominantly spindle shaped on type I collagen and rounded on type II collagen, suggesting distinct cell responses to the two matrices. To our knowledge, this is the first study to report 3D printable tissue derived insoluble type I and type II collagen inks within a common fabrication platform, including direct fabrication of 3D scaffolds from tissue derived type II collagen. These collagen dominant scaffolds offer promising platforms for musculoskeletal tissue engineering, regenerative grafts, and 3D in vitro models.