Fabrication of a mechanically anisotropic poly(glycerol sebacate) membrane for tissue engineering

Poly(glycerol sebacate) (PGS) has been used successfully as a scaffolding material for soft tissue engineering. PGS scaffolds, however, are usually mechanically isotropic, which may restrict their use in tissue repairs as many soft tissues in the body have anisotropic mechanical behaviors. Although various methods have been used to fabricate anisotropic scaffolds, it remains challenging to make anisotropic scaffolds from thermoset PGS. Here a new, simple method to fabricate an anisotropic PGS membrane which can then be used to construct thicker three-dimensional anisotropic scaffolds was developed. First, an aligned sacrificial poly(vinyl alcohol) fibrous membrane was prepared by electrospinning. The fibrous membrane was then partially immersed in PGS prepolymer solution, resulting in a composite membrane upon drying. After curing, the sacrificial fibers within the membrane were removed by water, supposedly leaving aligned cylindrical pores in the membrane. Both SEM and AFM illustrated aligned grooves on the surface of the resultant PGS membrane, indicating the successful removal of sacrificial fibers. The PGS membrane was validated to be mechanically anisotropic using uniaxial tensile testing along and perpendicular to the predominant pore direction. The in vitro cytocompatibility of the PGS membrane was confirmed. As a demonstration of its potential application in vascular tissue engineering, a tubular scaffold was constructed by wrapping a stack of two axisymmetric pieces of the anisotropic PGS membranes on a mandrel. The compliance of the scaffold was found to depend on the pitch angle of its double helical structure, imitating the anisotropic mechanical behavior of the arterial media.