Stress relaxation and stress-strain characteristics of porcine amniotic membrane

Abstract

Background:

Recently, amniotic membrane (AM) as scaffold is accumulating much more attention in tissue engineering. It is well-known that the mechanical properties of the scaffold inevitably affect the biological process of the incorporated cells.

Objective:

This study investigates the stress relaxation and stress-strain characteristics of AM, which have not been sufficiently elucidated before.

Methods:

Porcine AM samples were prepared at four different AM regions and at three different directions. Ramp-and-hold and stretch-to-rupture tests were conducted on a uniaxial tensile apparatus. A nonlinear viscoelastic model with two relaxation coefficients is proposed to fit the ramp-and-hold data. Rupture strain, rupture stress, and elastic modulus of the linear portion of the stress-strain curve are used to characterize the strength properties of the AM.

Results:

Sample direction has no significant effect on the mechanical properties of the AM. Samples at the ventral region has the maximum rupture strength and elastic modulus, respectively, $2.29\pm 0.99\text{MPa}$ and $6.26\pm 2.69\text{MPa}$ . The average of the relaxation coefficient for the fast and slow relaxation phases are $12.8\pm 4.4\text{s}$ and $37.0\pm 7.7\text{s}$ , respectively.

Conclusions:

AM is a mechanically isotropic and heterogeneous material. The nonlinear viscoelastic model is suitable to model the AM viscoelasticity and potential for other biological tissues.