HHS Public Access Author manuscript Author Manuscript
Bone. Author manuscript; available in PMC 2016 December 01. Published in final edited form as: Bone. 2015 December ; 81: 315–326. doi:10.1016/j.bone.2015.07.024.
RAMAN SPECTRAL CLASSIFICATION OF MINERAL- AND COLLAGEN-BOUND WATER’S ASSOCIATIONS TO ELASTIC AND POST-YIELD MECHANICAL PROPERTIES OF CORTICAL BONE Mustafa Unala and Ozan Akkusa,b,c,*
Author Manuscript
aDepartment
of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH 44106, USA bDepartment
of Orthopaedics, Case Western Reserve University, Cleveland, OH 44106, USA
cDepartment
of Biomedical Engineering, Case Western Reserve University, Cleveland, OH
44106, USA
Abstract
Author Manuscript
Water that is bound to bone’s matrix is implied as a predictor of fracture resistance; however, bound water is an elusive variable to be measured nondestructively. To date, the only nondestructive method used for studying bone hydration status is magnetic resonance variants (NMR or MRI). For the first time, bone hydration status was studied by short-wave infrared (SWIR) Raman spectroscopy to investigate associations of mineral-bound and collagen-bound water compartments with mechanical properties. Thirty cortical bone samples were used for quantitative Raman-based water analysis, gravimetric analysis, porosity measurement, and biomechanical testing. A sequential dehydration protocol was developed to replace unbound (heat drying) and bound (ethanol treatment) water in bone. Raman spectra were collected serially to track the OH-stretch band during dehydration. Four previously identified peaks were investigated: I3220/I2949, I3325/I2949 and I3453/I2949 reflect status of organic-matrix related water (mostly collagen-related water) compartments and collagen portion of bone while I3584/I2949 reflects status of mineral-related water compartments and mineral portion of bone. These spectroscopic biomarkers were correlated with elastic and post-yield mechanical properties of bone. Collagenwater related biomarkers (I3220/I2949 and I3325/I2949) correlated significantly and positively with toughness (R2=0.81 and R2=0.79; p
Bone. Author manuscript; available in PMC 2016 December 01. Published in final edited form as: Bone. 2015 December ; 81: 315–326. doi:10.1016/j.bone.2015.07.024.
RAMAN SPECTRAL CLASSIFICATION OF MINERAL- AND COLLAGEN-BOUND WATER’S ASSOCIATIONS TO ELASTIC AND POST-YIELD MECHANICAL PROPERTIES OF CORTICAL BONE Mustafa Unala and Ozan Akkusa,b,c,*
Author Manuscript
aDepartment
of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH 44106, USA bDepartment
of Orthopaedics, Case Western Reserve University, Cleveland, OH 44106, USA
cDepartment
of Biomedical Engineering, Case Western Reserve University, Cleveland, OH
44106, USA
Abstract
Author Manuscript
Water that is bound to bone’s matrix is implied as a predictor of fracture resistance; however, bound water is an elusive variable to be measured nondestructively. To date, the only nondestructive method used for studying bone hydration status is magnetic resonance variants (NMR or MRI). For the first time, bone hydration status was studied by short-wave infrared (SWIR) Raman spectroscopy to investigate associations of mineral-bound and collagen-bound water compartments with mechanical properties. Thirty cortical bone samples were used for quantitative Raman-based water analysis, gravimetric analysis, porosity measurement, and biomechanical testing. A sequential dehydration protocol was developed to replace unbound (heat drying) and bound (ethanol treatment) water in bone. Raman spectra were collected serially to track the OH-stretch band during dehydration. Four previously identified peaks were investigated: I3220/I2949, I3325/I2949 and I3453/I2949 reflect status of organic-matrix related water (mostly collagen-related water) compartments and collagen portion of bone while I3584/I2949 reflects status of mineral-related water compartments and mineral portion of bone. These spectroscopic biomarkers were correlated with elastic and post-yield mechanical properties of bone. Collagenwater related biomarkers (I3220/I2949 and I3325/I2949) correlated significantly and positively with toughness (R2=0.81 and R2=0.79; p
