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

Abstract

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.

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

“…Nerurkar et al [35][36][37] have assessed the mechanics of aligned poly-(e-caprolactone) scaffolds and their ability to induce alignment in AF cells and tissue. The high surface to volume ratio of these scaffolds is also expected to favor cell attachment and retention of cell phenotype [33,38]. The purpose of this study was to characterize a biodegradable electrospun PU nanofiber biomaterial and determine its suitability for use in repairing the AF.…”

“…Recent work has shown that a degradable polycarbonate urethane (PU) previously reported in Ref. [32] could be processed, with the addition of anionic dihydroxyl oligomers (ADO), which enhance cell attachment [33], using electrospinning applications to fabricate aligned fibers. These structures mimic the aligned nature of the AF, and thus provide an appropriate scaffold to support the growth of such a tissue.…”

The challenge and advancement of annulus fibrosus tissue engineering

“…PU nanofibrous scaffolds in the absence or presence of different amounts of ADO were similar in appearance. Increasing the material surface's polar character of the scaffolds resulted in a positive enhancement of AF cell attachment [95]. Both the tensile strength and initial modulus of aligned scaffolds were higher than the random fiber scaffold.…”

“…The mechanical tests revealed that POM has an excellent deformability: the compressive stress, young's modulus, and tensile strength markedly increased as the polymerization time increased. There was no permanent deformation after 500 press-loading and release cycles with Poly-D-L-lactide/Bioglass [90,91] Silk [92,93] Genipin crosslinked fibrin [94] Single unit with fiber orientation Aligned alginate/chitosan [88] Polycarbonate polyurethane linked with dihydroxyl oligomer [95,96] Polycaprolactone [97,98] Poly-L-Lactide [99] Silk fibers/chondroitin sulphate [100] Collagen fibrils [101] Biphasic scaffold Poly (polycaprolactone triol malate)/DBM [102] Composite scaffold Poly-L-Lactide as AF and hyaluronic acid hydrogel as NP [24] Polyglycolic Acid/poly-l-lactic as AF and alginate hydrogel as NP [103] Silk scaffold as AF and silicon as NP or hyaluronic acid as NP [104,105] 30 % maximum strain. When implanted into mice back subcutaneous pocket, there were no inflammation responses were found [89].…”

Hydrogel-Based Platforms for the Regeneration of Osteochondral Tissue and Intervertebral Disc

“…Some research groups have considered electrospinning as a powerful technique to manufacture scaffolds for annulus tissue engineering [124,[133][134][135]. The basic idea was that the electrospun fibers can closely reproduce the scale of collagen fibers present in most soft tissues, whilst the collection onto a rotating mandrel may provide an aligned mesh consisting of nanofibers.…”