Microstructure, Spectroscopic Studies and Nanomechanical Properties of Human Cortical Bone with Osteogenesis Imperfecta
- PDF / 206,662 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 42 Downloads / 189 Views
Microstructure, Spectroscopic Studies and Nanomechanical Properties of Human Cortical Bone with Osteogenesis Imperfecta 1
Chunju Gu1, Dinesh R. Katti1, Kalpana S. Katti1 Civil and Environmental Engineering, North Dakota State University, Fargo, ND 58102, U.S.A.
ABSTRACT Bone is a natural protein (collagen)-mineral (hydroxyapatite) nanocomposite with hierarchically organized structure. Our previous work has demonstrated orientational differences in stoichiometry of hydroxyapatite resulting from orientationally dependent collagen-mineral interactions in bone. The nature of these interactions has been investigated both through molecular dynamics simulations as well as nanomechanical and infrared spectroscopic experiments. In this study, we report experimental studies on human cortical bone with osteogenesis imperfecta (OI), a disease characterized by fragility of bones and other tissues rich in type I collagen. About 90% of OI cases result from causative variant in one of the two structural genes (COL1A1 or COL1A2) for type I procollagens. OI provides an interesting platform for investigating how alterations of collagen at the molecular level cause changes in structure and mechanics of bone. Fourier transform spectroscopy, electron microscopy (SEM), and nanomechanical experiments describe the structural and molecular differences in bone ultrastructure due to presence of diseases. Photoacoustic-Fourier transform infrared spectroscopy (PA-FTIR) experiments have been conducted to investigate the orientational differences in molecular structure of OI bone, which is also compared with that of healthy human cortical bone. Further, in situ SEM static nanomechanical testing is conducted in the transverse and longitudinal directions in the OI bone. Microstructural defects and abnormities of OI bone were ascertained using scanning electron microscopies. These results provide an insight into molecular basis of deformation and mechanical behavior of healthy human bone and OI bone. INTRODUCTION Osteogenesis imperfecta (OI) is a heritable disease that is characterized by fragility of bones and other tissues rich in type I collagen. The two structural genes, COL1A1 and COL1A2, which encode the proĮ1(I) and proĮ2(I) chains of type I procollagen, are known to exhibit over 2000 distinct mutations in the event of osteogenesis imperfecta1. These mutations range in complexity from simple deletions, insertions, and single base substitutions that convert a codon for glycine to a codon for a bulkier amino acid. These mutations not only affect collagen molecules and other bone cell matrix components, but also affect the mineral phase with higher average mineralization density2, smaller, less well aligned mineral crystal size, and highly packed and disoriented mineral crystals3-5 . Our previous work has demonstrated orientational differences in stoichiometry of hydroxyapatite in healthy bone which is influenced by collagen-mineral interaction6. In addition extensive multiscale modeling experiments in our group7 have also demonstrated the dire
Data Loading...
