Stress-sensitive tissue regeneration in viscoelastic biomaterials subjected to modulated tensile strain

This research contribution addresses the mechanochemistry of intra-tissue mass transfer for nutrients, oxygen, growth factors, and other essential ingredients that anchorage-dependent cells require for successful proliferation on biocompatible surfaces. The unsteady state reaction-diffusion equation (i.e., modified diffusion equation) is solved according to the von Kármán-Pohlhausen integral method of boundary layer analysis when nutrient consumption and tissue regeneration are stimulated by harmonically imposed stress. The mass balance with diffusion and stress-sensitive kinetics represents a rare example where the Damköhler and Deborah numbers appear together in an effort to simulate the development of mass transfer boundary layers in porous viscoelastic biomaterials. The Boltzmann superposition integral is employed to calculate time-dependent strain in terms of the real and imaginary components of dynamic compliance for viscoelastic solids that transmit harmonic excitation to anchorage-dependent cells. Rates of nutrient consumption under stress-free conditions are described by third-order kinetics which include local mass densities of nutrients, oxygen, and attached cells that maintain dynamic equilibrium with active protein sites in the porous matrix. Thinner nutrient mass transfer boundary layers are stabilized at shorter dimensionless diffusion times when the stress-free intra-tissue Damköhler number increases above its initial-condition-sensitive critical value. The critical stress-sensitive intra-tissue Damköhler number, above which it is necessary to consider the effect of harmonic strain on nutrient consumption and tissue regeneration, is proportional to the Deborah number and corresponds to a larger fraction of the stress-free intra-tissue Damköhler number in rigid biomaterials.

von Kármán-Pohlhausen boundary layer predictions for nutrient diffusion and stress-sensitive consumption in porous biomaterials that experience viscoelastic relaxation (i.e., De = 1)Research Highlights► Reaction-diffusion equation: is analyzed in porous biomaterials that contain anchorage-dependent cells subjected to harmonic tensile stress. ► Critical intra-tissue Damköhler number: ratio of nutrient consumption rate relative to the rate of intra-tissue diffusion is quantified in the presence of mechanical stress. ► Boltzmann superposition integral: is employed to calculate time-dependent strain in rigid and mobile viscoelastic biomaterials. ► Effect of viscoelastic relaxation on chemical kinetics: time-dependent strain is used to modify reaction rates in stress-sensitive systems. ► von Kármán nutrient boundary layer thickness is calculated to estimate the time required for regenerative tissue growth.