PLLA/ZrO2 nanocomposite material for coronary stent application
Tong, Shan Wen
Date of Issue2016
School of Materials Science and Engineering
DESs have been recognized as novel treatments for coronary artery stenosis besides providing transient vessel support with drug-delivery capability. However, long-term limitations of metallic stents such as late stent thrombosis and hypersensitivity reactions have hampered the overall effectiveness of this device. Bioresorbable scaffold (BRS) was seen as a solution pertaining to this issue and various studies have been conducted to determine the overall effectiveness of the BRS stent. This study aims to evaluate the effect of radiopaque fillers, zirconia (ZrO2) and barium sulphate (BaSO4) of different particle sizes and loading on the mechanical properties of the biodegrable pure PLLA polymer such as tensile strength, tensile modulus and percentage elongation at break. The incorporation of ZrO2 and BaSO4 nanoparticles have yielded a range of tensile modulus between 5 to 6 GPa with a relative tensile strength of 0.11GPa. These attributes were higher than that of the pure PLLA fibers. In general, the tensile modulus and tensile strength of pure PLLA fibers did increased upon addition of ZrO2 fibers up till a certain particle loading before regression occurs. However, the percentage elongation at break shown to have dropped as compared to pure PLLA in all tested particle loadings. Also, there was no significance to be found in the increment of tensile strength and modulus of ZrO2/PLLA fibers across particle loadings. There were no noticeable trends observed in the comparisons made between different particle sizes and loading owing to poor dispersibility and agglomeration of nanoparticles. BaSO4 nanoparticle of 20nm was considered and examined in this study but no significance can be drawn from the increment of tensile modulus and tensile strength from across all particle loadings. Similarly, the results obtained from the comparison of ZrO2 and BaSO4 nanoparticles in terms of tensile modulus, tensile strength and percentage elongation at break did not yield any particular significance. In conclusion, the incorporation of ZrO2 and BaSO4 nanoparticles could enhanced the overall mechanical properties of the biodegradable PLLA stent. Nonetheless, further tests and studies can be done on improving the dispersibility of the nanoparticle into the polymer matrix through physical or chemical modification of inorganic nanoparticle filler so as to avoid agglomeration. In addition, broader range of nanoparticle sizes from 5nm to 100nm can be considered as there might be changes in the behaviour of the polymer matrix composites.
Final Year Project (FYP)
Nanyang Technological University