Mechanical Analysis of Mineral and Collagen Phases in Bone by Raman Spectroscopy

Abstract

Bone is often regarded as a composite of mineral particles of apatite crystals and organic matrix of Type I collagen in microscopic scale. The aim of this study are to observe the mechanical behaviors of mineral and collagen phases in bone tissues by using Raman spectroscopy, and to investigate the effects of mechanical properties related to bone ageing.

Cortical bone specimens of bovine femoral diaphyses (Age: 23 months and 9 years old) were prepared, where the longer edges of specimens were aligned to the parallel or perpendicular to the femoral axis. Raman microscope system was used for the analysis of mechanical response of bone tissue under tensile loading by the micro-tensile device. The relationship between the Raman shift and applied stress were investigated by analyzing the Raman spectrum of bone tissues.

From all experiments, the Raman shifts of mineral and collagen phases to lower wave numbers were observed with increase of applied tensile stress. The changes in Raman shifts under femoral axial stress were relatively larger than that under circumferential stress. Also, the changes in the collagen shifts of 9-year old bone tissue significantly increased compared with 23-month old one. From these results, the Raman shifts of mineral and collagen phases in bone tissues were well related to the applied tensile stress. In addition, those relationships were dependent to the mechanical properties related to structural anisotropy or degree of ageing. It was confirmed that the mechanical analysis by Raman spectroscopy was sufficiently useful for the bone quality assessment for bone degeneration as osteoporosis.