Synthesis of Fibrin-Type I Collagen Biomaterials via an Acidic Gel

Abstract

Fibrin-Type I collagen composite gels have been widely studied as biomaterials, in which both networks are usually formed simultaneously at a neutral pH. Here, we describe a new protocol in which mixed concentrated solutions of collagen and fibrinogen were first incubated at acidic pH to induce fibrinogen gel formation, followed by a pH change to neutral inducing collagen fiber formation. Thrombin was then added to form fibrin-collagen networks. Using this protocol, mixed gels containing 20 mg.mL−1 fibrin and up to 10 mg.mL−1 collagen could be prepared. Macroscopic observations evidenced that increasing the content of collagen increases the turbidity of the gels and decreases their shrinkage during the fibrinogen-to-fibrin conversion. The presence of collagen had a minor influence on the rheological properties of the gels. Electron microscopy allowed for observation of collagen fibers within the fibrin network. 2D cultures of C2C12 myoblasts on mixed gels revealed that the presence of collagen favors proliferation and local alignment of the cells. However, it interferes with cell differentiation and myotube formation, suggesting that further control of in-gel collagen self-assembly is required to elaborate fully functional biomaterials.

Recent Advances in Engineering Bioinks for 3D Bioprinting

“…[52] At low temperatures (2-8 °C), type I collagen exists in a liquid state; however, it forms a fibrous hydrogel when the temperature rises (37 °C) or at a neutral pH. [53,54] This characteristic allows the printing of collagen at low temperature and retention of the printed structure at high temperature. However, it takes approximately 30 min for type I collagen to form a gel at 37 °C, which may easily facilitate the collapse of a printed product; thus, collagen cannot be used alone without supporting materials.…”

Harnessing oriented arrangement of collagen fibers by 3D printing for enhancing mechanical and osteogenic properties of mineralized collagen scaffolds

“…But as the pH continues to rise from 9, the spacing of ColF increases, and the fibers are gradually separated. [23,24] Therefore, the parallel and connected structure of the fibers can be stabilized by adjusting pH = 6-8.…”