Nanostiffness of collagen fibrils extracted from osteoarthritic cartilage characterized with AFM nanoindentation

Osteoarthritis (OA) is a prevalent and deliberating joint disorder, which acts as the leading cause for the disability and poor quality of life of the middle-age and elderly people. It is generally believed that OA is degeneration of articular cartilage. However, the debate remains on the role of subchondral bone in pathogenesis of OA. In this study, the nanostiffness of collagen fibrils from articular cartilage in patients with entirely different bone metabolism, that is, OA, osteoporosis (OP), and health, was quantitatively measured with AFM nanoindentation technique. It was found that the stiffness of individual collagen fibril from healthy cartilage was 2.67 ± 0.12GPa under ambient condition and 11.24 ± 0.74MPa in hydrated state respectively. The collagen fibrils were softer in osteoporosis (OP) group (ambient: 1.64 ± 0.12GPa; hydrated: 8.59 ± 0.59MPa). By contrast, the extracted fibrils from OA cartilages were stiffer (ambient: 4.65 ± 0.25GPa; hydrated: 17.26 ± 1.77MPa). The results obtained demonstrated that the collagen fibrils extracted from OA patients are stiffer than those from healthy patients, and therefore the nanomechanical characterization of extracted collagen fibrils may be a promising way for early diagnosis of OA.