Poly (ε-Caprolactone)-Silk Fibroin Based Functional Repair for Annulus Fibrosus Tears
Date
2019-01-24
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Abstract
Intervertebral disc degeneration with an associated bulged/herniated disc is a significant cause of low back pain. Annulus fibrosus (AF) tears and defects are a major clinical problem with no current treatments available for its closure and repair, resulting in risk of re-herniation. This thesis focuses on the chemical and mechanical characterization of a newly-designed biodegradable poly(ɛ-caprolactone)-silk fibroin (PCL-SF) as a potential candidate for the closure of irregular AF defects through minimally-invasive implantation. Thermoset PCL-SF scaffolds were produced with two concentrations of the PCL-diacrylate macromer solution (40% and 60% w/v) and five PCL:SF ratios (100:0, 90:10, 80:20, 70:30, and 60:40). Chemical characterization of the scaffolds confirmed the effective blending of PCL and SF macromolecules with uniform distribution of SF throughout the scaffolds and formation of β-sheet conformation in SF. Mechanical characterization of the scaffolds showed: (i) highly interconnected pores with pore sizes of 260–265 μm, (ii) tensile moduli and yield strains of 0.22-0.31 MPa and 41-61%, respectively, and (iii) compressive moduli of 0.11- 0.27 MPa. The above-mentioned porosities were within the range that reportedly supports AF cell penetration, adhesion, and accumulation of a collagen I rich extracellular matrix. The tensile moduli of tested scaffolds were in the range of human AF tissue in radial and axial directions. The compressive moduli were slightly less than native AF tissue but approximately an order of magnitude higher than those of other AF repair biomaterials. Additionally, the in vitro biodegradation rate of scaffolds was found to be slow enough to provide mechanical support in the time frame needed for AF regeneration. However, scaffolds were unable to exhibit shape-memory capabilities suitable for self-fitting in AF defects. Further optimization of the scaffold design with respect to shape memory capability for minimally-invasive delivery and self-fitting in AF defect will be required for clinical application.
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Keywords
Biomaterials, Porous scaffold, Cross-linking, Chemical and mechanical analyses, In vitro degradation, Annulus fibrosus, Intervertebral disc
Citation
Novin, M. (2019). Poly (ε-Caprolactone)-Silk Fibroin Based Functional Repair for Annulus Fibrosus Tears (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.