Effects of Cyclic Loading and Binding to Extracellular Matrix on Macromolecular Transport in Soft Biological Tissue - Progress in Organic and Physical Chemistry: Structures and Mechanisms - page 103

model was used to compare the process of the solute uptake from the bath solution due
to free diffusion and due to advection-diffusion mechanism, induced by cyclic load-
ing. The goal was to find the governing parameters for solute transport acceleration
by the fluid flow.
The main results are the following:
(1) Dynamic deformation enhances both bound and unbound concentrations with-
in the tissue in comparison to free diffusion. The beneficial effect for unbound
solute is greater.
(2) The maximum gain for unbound solute uptake could be several times higher
(2.5 times for parameters of fibrin gel and plasmin) for solutes that have an
ability to bind the matrix, compared with the gain for non binding solutes.
(3) The effect of loading is considerable in the surface layer of the gel that is
involved in the deformation, and approaches zero deeper in the gel. The thick-
ness of this surface layer depends on loading frequency and material param-
eters of the gel.
(4) For the loadings with the same displacement amplitude the solute transport
acceleration in the surface layer increases with frequency because strain am-
plitude will be higher for higher frequency.
(5) For the loadings with the same strain amplitude (or, equally, loading pressure
amplitude) there exists an optimal frequency at which the solute transport ac-
celeration reaches its maximum. This frequency depends on characteristics of
the gel and on the parameters of the solute binding to extracellular matrix.
Finally, we conclude that solute binding to the matrix is an ef¿ cient mechanism
that is synergistically acting along with cyclic convection on solute transport in dy-
namically loaded gels. The enhancement in transport of nutrients, morphogens or drug
molecules can potentially trigger response of the cells, thus providing a mechanism of
sensitivity of mechanical stimulus by the cells in healthy or regenerating tissue.
The applications of the model comprise predictions of optimal mechanical stimu-
lation of the implant for better integration into bone. Also it can be used for deriving
mechanical properties for implant coatings, designing of controlled drug delivery de-
vices involving cyclic deformation of the carrier, and calculating drug distribution in
the loaded tissues.

KEYWORDS

• Biphasic theory

• Cyclic deformation

• Molecular transport

• Solute binding

• Tissue mechanics