The strain-generated electrical potential in cartilaginous tissues: a role for piezoelectricity

摘要

The IVD under a compressive load (F), highlighting the major ECM macromolecules of collagen fibres and proteoglycans, with detail views on the different mechanisms of the SGP. a Donnan potential. Non-uniform strain (ε) of the matrix yields a higher concentration of FCD on the right-hand side. This generates a Donnan potential (φD) from areas of less-concentrated FCD to areas of higher-concentrated FCD, separated here by the dashed line. b Diffusion potential. Loading generates net fluid flow (f) that pulls the distributed charged ions (denoted by “+” and “−” symbols) with it. This generates a diffusion current (Id) in the opposite direction to fluid flow by disrupting the balance of positive and negative ions in the ECM. c Streaming potential. The double-layer of charged ions by each macromolecule is disrupted by the convection of ions. As shown by the fluid velocity profile (vf), the outer charged layer is disrupted, generating a streaming current (Is) in the direction of fluid flow and an opposing conduction current (Ic). The differential disruption of the double-layer generates a zeta potential (ζ) acting from the molecule surface to the fluid bulk. d Piezoelectricity. The noncentrosymmetric structure of collagen, owing to its non-uniform distribution of charged groups along the triple helix, generates dipole moments when subject to strain (as shown by tensile forces (Ft) here in the AF). This generates a net zeta potential (ζ) acting out from the surface