(586d) Characterization of Collagen Type I and II Blended Hydrogels for Articular Cartilage Tissue Engineering

Title: Characterization of Collagen Type I and II Blended Hydrogels for Articular Cartilage Tissue Engineering

Authors: Claire E. Kilmer [1], Nelda Vazquez-Portalatin [2], Alyssa Panitch [2], Julie C. Liu, Ph.D. [1,2]

Department/Affiliations: [1] School of Chemical Engineering and [2] Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN

Osteoarthritis (OA) is a debilitating condition that affects over 27 million people in the United States alone and is defined by degradation in articular cartilage extracellular matrix (ECM). Although there is no cure for OA, there are many treatment options including osteochondral grafting, autologous chondrocyte implantation, and marrow stimulation. However, these options usually promote the growth of fibrocartilage, which is inferior to the mechanical properties of native, hyaline cartilage. The overall goal of this project is to create a scaffold that will replace damaged cartilage and ease the pain of the condition while simultaneously preventing further cartilage deterioration. This study characterized and compared the properties of gels made of collagen type I and II blends, which have the potential to be implemented as a tissue-engineered scaffold.

Collagen type II makes up 90-95% of the collagen produced by chondrocytes in the ECM and is a promising scaffold material for use in articular cartilage. It has been shown that collagen type II hydrogels promote the differentiation of embedded mysenchymal stem cells to chondrocytes more efficiently than collagen type I gels. However, when compared to collagen type I, collagen type II forms fibrils of smaller diameter and exhibits poor mechanical properties when forming a hydrogel without crosslinking. It was hypothesized that hydrogels made with a blend of collagen type I and II will have superior mechanical properties compared to gels made with collagen type II alone. In addition, GAGs attach to proteoglycans within the extracellular matrix and allow articular cartilage to withstand compressive forces. Thus, we are interested in the interactions between a blend of collagen type I, collagen type II, and GAGs such as chondroitin sulfate (CS).

The hydrogels were prepared at different ratios of collagen type I to collagen type II (1:0, 3:1, 1:1, 1:3, and 0:1), and the amounts of collagen types I and II in the gel were measured. The collagen network structure was analyzed with cryo-scanning electron microscopy, and oscillatory tests on a rheometer were performed to analyze the mechanical properties of the scaffolds. From the experiments conducted, the 3:1 gels were able to incorporate both collagen type I and collagen type II within the gels. The 3:1 gels also retained a significantly higher amount of chondroitin sulfate than the other blends. Initial results show that the addition of collagen type II alters gel formation, network structure, and mechanical properties. Moreover, the 3:1 gels exhibited a void space percentage of 36.4% which was lower than the 1:1 gels (46.5%). The storage, loss, and complex moduli were larger for the 3:1 gels (Gâ?? = 4.9 ± 1.0 Pa, Gâ??â?? = 1.2 ± 0.1 Pa, and G* = 5.0 ± 0.9 Pa) compared to the 1:1 gels (Gâ?? = 1.2 ± 0.2 Pa, Gâ??â?? = 0.3 ± 0.1 Pa, and G* = 1.2 ± 0.2 Pa). From the different blends that were investigated, the 3:1 blend was able to form more consistent gels with superior mechanical properties as compared to the other blends. Thus, the 3:1 blend has the potential to be implemented as a scaffold for articular cartilage tissue engineering.