Development of collagen based hydrogel from tannery raw trimming waste for biomedical 3D printing applications

• Collagen offers outstanding in vitro / in vivo biocompatibility and tissue-matching physico-chemical characteristics which makes it universal material for biomedical applications. Collagen based hydrogels have been reported for several tissue engineering applications including hydrogel. Hydrogel with low collagen concentration have poor mechanical stability. Hydrogel with lower collagen concentration is limited to produce 3D print constructs. Collagen concentration of 4 mg/mL has been generally used as per the reported literatures. Thus, the necessity of other bio-additives or crosslinking agents is important for constructing a stable structure for 3D bioprinting applications. The stiffness of collagen hydrogels is directly related to the collagen concentration. • Process: Acid solubilized collagen has been extracted from hide/skin with a concentration of 4 mg/mL and cationic polysaccharide concentration of 1.5% was dissolved in 3 M weak organic acid and dialyzed against 0.01 M weak organic acid. The dialyzed cationic polysaccharide was mixed with acid solubilized collagen and pH has been adjusted to 6.5 using alkali and crosslinker was added to prepare the hydrogel for Hydrogel. • Product: Formulated collagen-based hydrogels have structural fidelity and shape retention with cell adhesion properties. Bioprinting is a cutting-edge technique for fabricating biomaterial with significant potential in biomedical applications. This technology offers a robust platform for creating repeatable, tailored end-functional 3D structures. Soft biomaterial-based hydrogels play a crucial role in 3D bioprinting. These hydrogels, often a combination of biopolymers, can be formulated using natural and synthetic biopolymers and other bio-additives to achieve the desired mechanical, rheological, chemical and biological characteristics. Key parameters such as printability and structural stability, coupled with cell proliferation, are critical for hydrogel design. Collagen, a high-value by-product extracted from raw trimming waste generated by the leather industry, is the major structural protein of the extracellular matrix and possesses biocompatible properties favourable for cell growth. The objective of this research work is to develop collagen-based hydrogels from tannery raw trimming waste. A collagen-based hydrogel was formulated by combining collagen with a gelling agent and a crosslinker to formulate a hybrid collagen complex, characterized for its physico-chemical and biological characteristics. Chitosan and glutaraldehyde were used as gelling and crosslinking agent respectively. Optimized hydrogel formulation containing equal parts of collagen and chitosan showed enhanced printability and stability. Optimal structural performance of the hydrogel was observed with the addition of 50-100 µL of 0.25% glutaraldehyde. Cell studies using THP cell lines confirmed that the hydrogels’ ability to support and enhance cell growth. This novel, sustainable approach in utilizing collagen from leather industry waste paves the way for developing materials for bio-printing applications.