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Title: Development of Poly (3-Hydroxybutyrate-Co-3-Hydroxyhexanoate)/Polycaprolactone Blend
Authors: LIM JING
Keywords: Poly (3-Hydroxybutyrate-Co-3-Hydroxyhexanoate), Polycaprolactone, Polymer blend, Human fetal Mesenchymal Stem cells, Degradation
Issue Date: 16-Jan-2012
Source: LIM JING (2012-01-16). Development of Poly (3-Hydroxybutyrate-Co-3-Hydroxyhexanoate)/Polycaprolactone Blend. ScholarBank@NUS Repository.
Abstract: Poly(3-hydroxybutyrate-co-3-hydroxyhexanote) (PHBHHx) belongs to the family of polyhydroxyalkanoates and has shown improved ductility and biocompatibility over its other members, leading to its increased usage in tissue engineering research. However, its ductility can be further enhanced in order to widen its range of applications. Therefore, the aim of this thesis was to blend PHBHHx with highly ductile medical grade polycaprolactone (mPCL), and it was hypothesized that PHBHHx/mPCL blend will show improved ductility. Degradation and cytocompatibility studies were also conducted. PHBHHx/mPCL were blended in seven different proportions (100% PHBHHx/0% mPCL, 90% PHBHHx/10% mPCL, 70% PHBHHx/30% mPCL, 50% PHBHHx/50% mPCL, 30% PHBHHx/70% mPCL, 10% PHBHHx/90% mPCL, 0% PHBHHx/100% mPCL), and their mechanical properties were characterized using tensile testing. Results indicated that ductility was enhanced with the addition of mPCL. More specifically, yield strain was improved (0.0819 ? 0.004, p<0.05) and at 30 PHBHHx/ 70 mPCL, high yield strength was also achieved. PHBHHx/mPCL blends were immiscible after analyzing their thermal properties, with two distinct melting temperatures present across all blends. In addition, crystallinity increased with increased mPCL. At 30% PHBHHx/70% mPCL, crystallinity (31.7 %) was comparable to 0% PHBHHx/100% mPCL (46.6 %). Investigation of its surface morphology using scanning electron microscopy (SEM) led to the conclusion that PHBHHx/mPCL were incompatible as each component displayed distinct morphologies. Under cross-polarized light, PHBHHx showed a single reddish tint while mPCL displayed a multi-colored, characteristic Maltese cross pattern which was an indication of the presence of lamellar crystals. Molecular weight (Mw) of PHBHHx/mPCL decreased with the addition of mPCL due to its lower Mw (117606 ? 694 g/mol). Surface hydrophilicity, which is indicative of the effectiveness of cell-biomaterial interaction, improved as the amount of mPCL increased. In summary, PHBHHx/mPCL showed improved ductility, and 30% PHBHHx/70% mPCL displayed the highest yield strain and good yield strength. The second part of this thesis investigated the cytocompatibility of non-surface treated 100% PHBHHx/0% mPCL, 30% PHBHHx/70% mPCL, and 0% PHBHHx/100% mPCL using human fetal mesenchymal stem cells (hfMSCs). Qualitative analysis of cell proliferation and morphology under confocal laser scanning microscopy (CLSM) over 5 days of culture revealed that hfMSCs might have a preference for PHBHHx. Proliferation of hfMSCs on day 3 and day 5 were higher on 100% PHBHHx/0% mPCL and 30 PHBHHx/ 70 mPCL. This suggested that cytocompatibility was not compromised in 30 PHBHHx/ 70 mPCL, and the proliferation capacity of 30% PHBHHx/70% mPCL could possibly be due to the presence of 30% PHBHHx. The final part of this thesis characterized the degradation properties of 100% PHBHHx/0% mPCL, 30% PHBHHx/70% mPCL. Hydrolytic degradation was conducted over 14 days in accelerated conditions of 0.5M sodium hydroxide at 37oC. 30% PHBHHx/70% mPCL showed a slow rate of degradation over the first 5 days with a mass loss/surface area of 0.5 ? 0.2 mg/cm2. From SEM, pits were observable from day 3, and they increased in quantity, size and depth as degradation time increased. Crystallinity and Mw decreased with increase in degradation time. Consolidating the results in the three parts, 30% PHBHHx/70% mPCL displayed higher yield strain and good yield strength, slow initial degradation rate, and good cytocompatibility with hfMSCs. As such, 30% PHBHHx/70% mPCL could potentially be a biomaterial in bone tissue engineering.
Appears in Collections:Master's Theses (Open)

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