Shear viscosity assessment in nanoconfined water inside 3D model human mineralized collagen fibril

This work presents a 3D numerical model of the human mineralized collagen fibril developed to quantitatively analyse the shear viscosity and diffusion of nanoconfined water within bone tissue at the nanoscale based on a 3D random walk approach. The analysis of transport properties has been conducted at different longitudinal reference quotes and along the three main directions of the fibril to quantify the tissue non-homogeneity and anisotropy by considering a physiological volume fraction. The diffusion has been characterised by analysing the Brownian motion of water molecules, and the shear viscosity by using the Stokes-Einstein-Sutherland relation. The results indicate non-homogeneous and anisotropic properties of water within the bone nanostructure, and notably different values than the bulk water at the macroscale with no structural confinements. Transport properties of water play a key role in the bone mechanobiology by influencing the supply of mineral ions and growth factors, the nucleation process and the tissue remodelling activity. This model can support the design and features of biomimetic scaffolds and enhance the understanding of bone mechanobiology at the nanoscale.