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Growth factor-free and antimicrobial elastic nanocomposites for bone regeneration
Elastic platforms have been shown recently to be advantageous for bone tissue engineering. Specifically, PEGylated polyglycerol sebecate has recently been reported in literature as a modification for Poly glycerol sebacate (PGS). It is highly elastic with tunable mechanical properties, rendering it...
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| Format: | Thesis |
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AUC Knowledge Fountain
2019
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| Summary: | Elastic platforms have been shown recently to be advantageous for bone tissue engineering. Specifically, PEGylated polyglycerol sebecate has recently been reported in literature as a modification for Poly glycerol sebacate (PGS). It is highly elastic with tunable mechanical properties, rendering it an interesting candidate for bone regeneration. However, it lacks the bioactive and antimicrobial properties that are essential for bone tissue engineering scaffolds. To address these issues, herein, PEGylated PGS with different PEG ratios was mixed with PCL to obtain uniform electrospun mats. Further functions were added to the structure to render it osteoinductive and antimicrobial through the addition of Laponite and naturally-based antimicrobial system. Nuclear magnetic resonance (NMR) and Fourier-transform infrared spectroscopy (FTIR) confirmed the successful synthesis of the polymer and the integration of the Laponite within the electrospun membranes. Field Emission scanning electron microscopy (FESEM) showed the electrospun membranes to have fibers with diameters in the microscale, which decrease upon increasing the concentration of Laponite. In vitro degradation showed the nanocomposites to be stable for 28 days. Uniaxial mechanical testing indicated the PEGylated PGS scaffolds to be highly elastomeric when the PEG ratio was increased. Nevertheless, the addition of Laponite leads to a drop in the elongation accompanied with a decrease in elastic modulus and an increase in ultimate tensile strength. Despite this drop in the mechanics, the nanocomposites were still within the range suitable for bone tissue engineering. Furthermore, the addition of the AMPs did not have any influence on the mechanical properties. Colony forming unit assay (CFU) showed a significate antimicrobial activity of the nanocomposites containing AMPs after 12 hours against both gram-positive S. aureus and gram-negative E. coli. These results were confirmed by optical density readings over 12 hours and FESEM imaging. In vitro biocompatibility test using preosteoblasts murine stromal cell line W-20-17 iii iv indicated that the addition of the Laponite and the AMPs did not influence the cells viability, with increasing the cells metabolic activity rover time. Moreover, the cells were able to attach and spread on the scaffolds. Further experiments such as Ca2+ deposition assay, alkaline phosphatase activity (ALP) and alizarin red staining (ARS) proved an enhancement in the osteogenic differentiation of the cells cultured on the nanocomposites. This was supported by gene expression quantification using real time PCR (RT-PCR), which showed up-regulation of genes involved in osteogenic differentiation such as ALP, RUNX2 and Axin2 in addition to genes involved in secretion of the extra cellular matrix such as COL1A1. Collectively, the nanocomposites containing AMPs were proven to have an osteoinductive and antimicrobial activity, which deem them desirable for bone tissue engineering. |
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