Fabrication of macromolecular gradients in aligned fiber scaffolds using a combination of in-line blending and air-gap electrospinning

Publication date: Available online 22 December 2016
Source:Acta Biomaterialia
Author(s): Alysha P. Kishan, Andrew B. Robbins, Sahar F. Mohiuddin, Mingliang Jiang, Michael R. Moreno, Elizabeth M. Cosgriff-Hernandez
Although a variety of fabrication methods have been developed to generate electrospun meshes with gradient properties, no platform has yet to achieve fiber alignment in the direction of the gradient that mimics the native tendon-bone interface. In this study, we present a method combining in-line blending and air-gap electrospinning to address this limitation in the field. A custom collector with synced rotation permitted fiber collection with uniform mesh thickness and periodic copper wires were used to induce fiber alignment. Two poly(ester urethane ureas) with different hard segment contents (BPUR 50, BPUR 10) were used to generate compositional gradient meshes with and without fiber alignment. The compositional gradient across the length of the mesh was characterized using a fluorescent dye and the results indicated a continuous transition from the BPUR 50 to the BPUR 10. As expected, the fiber alignment of the gradient meshes induced a corresponding alignment of adherent cells in static culture. Tensile testing of the sectioned meshes confirmed a graded transition in mechanical properties and an increase in anisotropy with fiber alignment. Finite element modeling was utilized to illustrate the gradient mechanical properties across the full length of the mesh and lay the foundation for future computational development work. Overall, these results indicate that this electrospinning method permits the fabrication of macromolecular gradients in the direction of fiber alignment and demonstrate its potential for use in interfacial tissue engineering.Statement of significanceThe native tendon-bone interface contains a gradient of properties that ensures stability of the joint. Notably, tendon cells are oriented in the direction of the interfacial gradient. Without this transition, failure can occur due to stress concentration at the bone insertion site. Electrospinning is a method commonly used to produce gradient fibrous meshes, however no current method allows for gradients in the direction of fiber alignment. As alignment can influence cellular behavior, and gradient properties can reduce stress concentration, a gradient parallel to fiber alignment could permit improved regeneration of the tendon-bone interface. This work details a novel electrospinning method to produce gradients (macromolecular, biochemical, cellular cues) in the direction of fiber alignment in order to better mimic transitional zones.

Graphical abstract

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