Tunable 3D Nanofiber Architecture of Polycaprolactone by Divergence Electrospinning for Potential Tissue Engineering Applications

George Z Tan,Yingge Zhou

doi:10.1007/s40820-018-0226-0

Abstract

The creation of biomimetic cell environments with micro and nanoscale topographical features resembling native tissues is critical for tissue engineering. To address this challenge, this study focuses on an innovative electrospinning strategy that adopts a symmetrically divergent electric field to induce rapid self-assembly of aligned polycaprolactone (PCL) nanofibers into a centimeter-scale architecture between separately grounded bevels. The 3D microstructures of the nanofiber scaffolds were characterized through a series of sectioning in both vertical and horizontal directions. PCL/collagen (type I) nanofiber scaffolds with different density gradients were incorporated in sodium alginate hydrogels and subjected to elemental analysis. Human fibroblasts were seeded onto the scaffolds and cultured for 7 days. Our studies showed that the inclination angle of the collector had significant effects on nanofiber attributes, including the mean diameter, density gradient, and alignment gradient. The fiber density and alignment at the peripheral area of the 45°-collector decreased by 21% and 55%, respectively, along the z-axis, while those of the 60°-collector decreased by 71% and 60%, respectively. By altering the geometry of the conductive areas on the collecting bevels, polyhedral and cylindrical scaffolds composed of aligned fibers were directly fabricated. By using a four-bevel collector, the nanofibers formed a matrix of microgrids with a density of 11%. The gradient of nitrogen-to-carbon ratio in the scaffold-incorporated hydrogel was consistent with the nanofiber density gradient. The scaffolds provided biophysical stimuli to facilitate cell adhesion, proliferation, and morphogenesis in 3D.

Highlights

A novel 3D divergence electrospinning technique of tunable fibrous microarchitecture for tissue engineering. Versatile capability of controlling both the microstructure and macroscopic shape of the scaffold. Nanofiber scaffold with microstructure gradient coupled with element gradient
The 3D microstructures of the nanofiber scaffolds were characterized through a series of sectioning in both vertical and horizontal directions
PCL/collagen nanofiber scaffolds with different density gradients were incorporated in sodium alginate hydrogels and subjected to elemental analysis

Summary

Introduction

The fabrication of biomimetic cell microenvironments closely resembling native tissues is critical for regenerative medicine. Recent bioinspired approaches have focused on creating biomimetic cell microenvironments that closely resemble the natural gradients of cell distribution, extracellular matrix (ECM), and tissue topology. One of the important biofabrication strategies is to integrate tunable microarchitecture in heterogeneous scaffolds to closely resemble the patterned structures of native tissues [4, 5]. Electrospinning has been extensively studied as a nanofiber fabrication technique for tissue engineering. We present a novel 3D divergence electrospinning technique of preparing tunable fibrous microarchitecture for potential musculoskeletal tissue engineering. The scaffolds provided microtopographical cues to promote cell adhesion, proliferation, and morphogenesis.

Configuration of the Divergence Electrospinning

Characterization of Scaffold Microstructure

Cell Culture

Hydrogel with Element Gradient

Results and Discussion

Conclusion