Abstract
Treatments to alleviate chronic lower back pain, caused by intervertebral disc herniation as a consequence of degenerate annulus fibrosus (AF) tissue, fail to provide long-term relief and do not restore tissue structure or function. This study aims to mimic the architecture and mechanical environment of AF tissue using electrospun fiber scaffolds made from synthetic biopolymers-poly(ε-caprolactone) (PCL) and poly(L-lactic) acid (PLLA). Pure polymer and their blends (PCL%:PLLA%; 80:20, 50:50, and 20:80) are studied and material properties-fiber diameter, alignment, % crystallinity, tensile strength, and water contact angle-characterized. Tensile properties of fibers angled at 0°, 30°, and 60° (single layer scaffolds), and ±0°, ±30°, and ±60° (bilayer scaffolds) yield significant differences, with PCL being significantly stiffer with the addition of PLLA, and bilayer scaffolds considerably stronger. Findings suggest PCL:PLLA 50:50 fibers are similar to human AF properties. Furthermore, in vitro culture of AF cells on 50:50 fibers demonstrates attachment and proliferation over seven days. The optimal polymer composition for production of scaffolds that closely mimic AF tissue both structurally, mechanically, and which also support and guide favorable cell phenotype is identified. This study takes a step closer towards successful AF tissue engineering and a long-term treatment for sufferers of chronic back pain.
Highlights
Injury to, or degeneration of the annulus fibrosus (AF) can result in herniation of the intervertebral disc (IVD) and compression of the nerve root, resulting in chronic lower back pain [1]
We propose a new composition of electrospun fibers based on a blend of PCL with poly-L-lactic acid (PLLA), a well-known biocompatible and rigid polymer, to ensure fibers continue to mimic the native AF, whilst conferring desirable mechanical properties
This study aims to determine the ideal blend of PCL with PLLA to closely replicate the morphological, structural, and mechanical properties of AF lamella sheets in order to take a step closer towards the repair of degenerate IVD [8]
Summary
Degeneration of the annulus fibrosus (AF) can result in herniation of the intervertebral disc (IVD) and compression of the nerve root, resulting in chronic lower back pain [1]. Treatments such as medications or surgical procedures are able to relieve symptoms but fail to restore the native structure and function [1]. Each lamella is oriented at 30◦ to adjacent layers and collagen fibers within each lamella are aligned parallel to each other [3,4] This cross-aligned fibrous structure is critical for complex mechanical behavior, such as tension, which has nonlinear anisotropic behavior. In order to mimic the properties of native AF using biomaterials, it is essential the scaffold closely replicate the structural architecture and physical properties
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