title: The Behavior of Water in Collagen and Hydroxyapatite Sites of Cortical Bone: Fracture, Mechanical Wear, and Load Bearing Studies.
abstract: The mechanical properties of cortical bone, which is largely comprised of collagen, hydroxyapatite, and water, are known to hinge on hydration. Recently, the characteristics of water in bone have drawn attention as potential markers of bone quality. We report on the dynamics, diffusion, population, and exchange of water in cortical bone by NMR relaxation and diffusion methodologies. Relaxation measurements over timescales ranging from 0.001 to 4.2 s reveal two distinguishable water environments. Systematic exposure to ethylenediaminetetraacetic acid or collagenase reveals one peak in our 2D relaxation map belonging to water present in the hydroxyapatite rich environment, and a second peak with shorter relaxation times arising from a collagen rich site. Diffusion-T2measurements allowed for direct measurement of the diffusion coefficient of water in all observable reservoirs. Further, deuterium relaxation methods were applied to study cortical bone under an applied force, following mechanical wear or fracture. The tumbling correlation times of water reduce in all three cases, indicating that water dynamics may be used as a probe of bone quality. Lastly, changes in the relative populations and correlation times of water in bone under an applied force suggest that load bearing occurs largely in the collagen rich environment and is reversible.
authors.affiliation: Department of Physics, Brooklyn College of The City University of New York, Brooklyn, New York 11210, United States.
authors.forename: Farhana
authors.initials: F
authors.lastname: Gul-E-Noor
authors.affiliation: Center of Biomedical Research, SGPGIMS Campus, Raibarelly Road, Lucknow 226014, India ; School of Biotechnology, Banaras Hindu University, Varanasi 221005 India.
authors.forename: Chandan
authors.initials: C
authors.lastname: Singh
authors.affiliation: The Graduate Center of The City University of New York, Department of Physics, New York, United States.
authors.forename: Antonios
authors.initials: A
authors.lastname: Papaioannou
authors.affiliation: Center of Biomedical Research, SGPGIMS Campus, Raibarelly Road, Lucknow 226014, India.
authors.forename: Neeraj
authors.initials: N
authors.lastname: Sinha
authors.affiliation: Department of Physics, Brooklyn College of The City University of New York, Brooklyn, New York 11210, United States ; The Graduate Center of The City University of New York, Department of Physics, New York, United States.
authors.forename: Gregory S
authors.initials: GS
authors.lastname: Boutis
keywords: 2H Relaxation; Cortical bone; Diffusion; NMR