Evaluation of Fracture Toughness for Articular Cartilage and Hydrogels in Cartilage Tissue Engineering

Abstract

Recently, biomaterials-based tissue engineering strategies such as hydrogels have offered great promising in repairing articular cartilage. Mechanical failure testing in outcome analyses is given the crucial clinical importance to the success of engineered constructs. Besides, interpenetrating networks (IPNs) are gaining more attention due to their superior mechanical integrity. Extensive fracture toughness (here refers to the apparent fracture toughness) work has been performed on articular cartilage but seldom performed on regenerative biomaterials such as hydrogels. The objective of this study was to provide a combination testing method of apparent fracture toughness applied to both articular cartilage and hydrogels in cartilage tissue engineering. In this study, apparent fracture toughness of three groups was evaluated: acellular hydrogels, cellular hydrogels, and articular cartilage based on the modified single-edged notch test and American Society for Testing and Materials (ASTM) standards on the single-edged notch test and compact tension test. The results obtained in this thesis demonstrated that the toughness of articular cartilage (348±43 MPa*mm½) was far more than that of hydrogels. 6K molecular weight (MW) 20% acellular IPNs look promising with a toughness value of 10.8±1.4 MPa*mm½, which was the highest among the hydrogel groups. This method preserved the integrity of the articular cartilage and the consistency of each specimen to obtain the data as accurate as possible. Although geometry limitations existed, a new method was developed to evaluate hydrogels and cartilage in a manner to enable a more relevant direct comparison for fracture testing of hydrogels for cartilage tissue engineering.