Water dynamics in mammalian bone

Bone’s unique properties stem from the hierarchical organization of a mineral (hydroxyapatite) and an organic (collagen) phase across multiple length scales. A key player in the integration of the organic and inorganic components of bone is water, which constitutes about 10% of mammalian bone tissues and has recently been shown to surpass mineral density as a clinical marker of fracture risk. While a physical picture of the role of water in binding the collagen to the mineral phase of bone is emerging, a molecular understanding of the interactions between hydroxyapatite, collagen and water is a frontier area of research.

Water pathways within the various levels of organization of bone tissues, from liquid in cortical pores to loosely or tightly bound in the mineral lattice. Understanding the material properties of bone starts with a detailed investigation of the structure and dynamics of water molecules at the nanoscale.

We contribute to the molecular understanding of the organization of organic and inorganic materials in bone by investigating the effects of confinement, collagen conformation and ionic concentration on water dynamics at the interface. We use ab-initio molecular dynamics (BOMD) to model this system at the level of density functional theory.

Snapshot of an ab-initio molecular dynamics trajectory. A fragment of collagen (triple helix in yellow) sits atop the hydroxyapatite surface in a confined environment.