Characterization of a biodegradable electrospun polyurethane nanofiber scaffold: Mechanical properties and cytotoxicity.

The current study analyzes the biodegradation of a polycarbonate polyurethane scaffold intended for the growth of a tissue-engineered annulus fibrosus (AF) disc component. Electrospun scaffolds with random and aligned nanofiber configurations were fabricated using a biodegradable polycarbonate urethane with and without an anionic surface modifier (anionic dihydroxyl oligomer), and the mechanical behavior of the scaffolds was examined during a 4 week biodegradation study. Both the tensile strength and initial modulus of aligned scaffolds (sigma=14+/-1 MPa, E=46+/-3 MPa) were found to be higher than those of random fiber scaffolds (sigma=1.9+/-0.4 MPa, E=2.1+/-0.2 MPa) prior to degradation. Following initial wetting of the scaffold, the initial modulus of the aligned samples showed a significant decrease (dry: 46+/-3 MPa; pre-wetted: 9+/-1 MPa, p<0.001). The modulus remained relatively constant during the remainder of the 4 week incubation period (aligned at 4 weeks: 8.0+/-0.3 MPa). The tensile strength for aligned fiber scaffolds was affected in the same manner. Similar changes were not observed for the initial modulus of the random scaffold configuration. Biodegradation of the scaffold in the presence of cholesterol esterase (a monocyte derived enzyme) yielded a 0.5 mg week(-1) weight loss. The soluble and non-soluble degradation products were found to be non-toxic to bovine AF cells grown in vitro. The consistent rate of material degradation along with stable mechanical properties comparable to those of native AF tissue and the absence of cytotoxic effects make this polymer a suitable biomaterial candidate for further investigation into its use for tissue-engineering annulus fibrosus.