Polar surface chemistry of nanofibrous polyurethane scaffold affects annulus fibrosus cell attachment and early matrix accumulation.

Regeneration of the annulus fibrosus (AF), one of the three components of the intervertebral disc (IVD), is challenging because of the tissue complexity and our limited knowledge about AF cell biology. The purpose of this study was to determine if modulating surface chemistry of polycarbonate polyurethane (PU) scaffolds would influence annulus fibrosus cell adhesion and early tissue formation. To vary surface energy, a novel anionic dihydroxyl oligomer (ADO) was synthesized and incorporated into the PU base polymer at three different concentrations [0.05, 0.5, and 5% (wt %)]. The polymeric materials were fabricated into nanoscale fibrous scaffolds using electrospinning. PU nanofibrous scaffolds in the absence or presence of different amounts of ADO were similar in appearance. Surface energy was significantly enhanced with increasing ADO content, as indicated by the decreasing water contact angle measurements. Increasing the material surface's polar character for the scaffolds resulted in a positive enhancement of AF cell attachment. The mechanism of this effect was complex as at higher ADO concentrations, increased cell adhesion was mediated by both serum and newly synthesized proteins, whereas at low ADO concentrations the latter had minimal effect. Collagen but not proteoglycan accumulation was also modulated by increasing ADO content. This study demonstrated that nanoscale fibrous PU scaffolds containing ADO may be appropriate candidates in the formation of tissue engineered annulus fibrosus tissue, and that material surface polar character can be used to influence AF cell attachment and collagen accumulation.