Electrospinning of Biosyn(®)-based tubular conduits: structural, morphological, and mechanical characterizations

Abstract

Electrospinning has garnered special attention recently due to its flexibility in producing extracellular matrix-like non-woven fibers on the nano-/microscale and its ability to easily fabricate seamless three-dimensional tubular conduits. Biosyn(®), a bioabsorbable co-polymer of glycolide, dioxanone, and trimethylene carbonate, was successfully electrospun into tubular conduits for the first time for soft tissue applications. At an electric field strength of 1 kV cm(-1) over a distance of 22 cm (between the Taylor cone and the collector) and at a flow rate of 1.5 ml h(-1) different concentrations of Biosyn/HFP solutions (5-20%) were spun into nanofibers and collected on a rotating mandrel (diameter 4 mm) at 300 and 3125 r.p.m. Scaffolds were characterized for structural and morphological properties by differential scanning calorimetry and scanning electron microscopy and for mechanical properties by uniaxial tensile testing (in both the circumferential and longitudinal directions). Biosyn(®) tubular scaffolds (internal diameter 4 mm) have been shown to exhibit a highly porous structure (60-70%) with a randomly oriented nanofibrous morphology. The polymer solution concentration directly affects spinnability and fiber diameter. At very low concentrations (≤5%) droplets were formed due to electrospraying. However, as the concentration increased the solution viscosity increased and a "bead-on-string" morphology was observed at 10%. A further increase in concentration to 13% resulted in "bead-free" nanofibers with diameters in the range 500-700 nm. Higher concentrations (≥20%) resulted in the formation of microfibers (1-1.4 μm diameter) due to increased solution viscosity. It has also been noted that increasing the mandrel speed from 300 to 3125 r.p.m. produced a reduction in the fiber size. Uniaxial tensile testing of the scaffolds revealed the mechanical properties to be attractive for soft tissue applications. As the fiber diameters of the scaffold decrease the tensile strength and modulus increase. There is no drastic change in tensile properties of the scaffolds tested under hydrated and dry conditions. However, a detailed study on the biodegradation and biomechanics of electrospun Biosyn conduits under physiological pressure conditions is required to ensure potential application as a vascular graft.