Evaluation and applications of poly(N-isopropylacrylamide) for biomedical materials

• Main Authors: Chun-Te Tao, 陶鈞德
• Other Authors: 楊台鴻
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/23657373239323848842

博士 === 國立臺灣大學 === 醫學工程學研究所 === 95 === In this study, we evaluate the applications of the thermosensitive poly(N-isopropylacrylamide) (PNIPAAm) for biomedical materials. The preparation and characterizations of the thermosensitive PNIPAAm membrane substrate, behaviors of neural stem cells (NSCs) on thermosensitive substrate and the influence of the PNIPAAm to the cells were included in this study. First of all, we tried to prepare PNIPAAm membrane by using the traditional polymer-solvent-nonsolvent system at ambient temperature but it was found that there exist no nonsolvents at room temperature for PNIPAAm. Fortunately, it is shown that there are cononsolvents for PNIPAAm composed of water and methanol. Thus, we were encouraged to prepare PNIPAAm membrane by the cononsolvent system. In addition, the complete phase diagram of PNIPAAm-water-methanol was performed by using modified Flory-Huggins theory and the mechanism of cononsolvency was also discussed. The results show that the ternary interaction parameter can not be neglected to calculate the phase behavior of the cononsolvent system. In addition, although the mechanical strength of the PNIPAAm membrane prepared by the cononsolvent system is poor, it is proved that polymeric membranes can be prepared via the cononsolvent system. From the calculation results, it is suggested that the cononsolvency may be originated from the interaction perturbation of two component in the existence of the third component. PNIPAAm membrane prepared by the cononsolvent system exerted a very poor mechanical strength due to the macrovoid in the cross-section of the membrane. In this study, PNIPAAm chains were grafted on poly(ethylene-co-vinyl alcohol) (EVAL) membrane by the redox initiation method. Embryoic rat cortical neural stem cells were subjected to culture on this thermosensitive substrate and the behaviors of the cell were explored at both 25 and 37℃. Two dimensional cell sheet manipulations for tissue engineering were also studied in this work. Results show that NSCs hardly attach on PNIPAAm-g-EVAL and the attached NSCs can be induced to detach from the thermosensitive surface via low temperature treatment. When FBS was added, almost all NSCs can attach on PNIPAAm-g-EVAL surface easily and proliferate to form a cell confluence. Consequently, NSCs confluence can be successfully induced to transfer to poly lysine-coated TCPS under low temperature treatment. Linear PNIPAAm, hydrogels, nano(micron) particles and membranes were extensively studied in the past few years. Although good performance of PNIPAAm was revealed, the influences and disadvantages of the PNIPAAm to tissues or cells were rarely mentioned. In this study, PNIPAAm nanoparticles were prepared and the influence on macrophage and osteoblast at different temperatures, including cytotoxicity, cell function and immune-responses, were explored. Results show that PNIPAAm-based particles exhibit more cytotoxicity at 37 than 25℃, and they stimulate strong immune responses to macrophage. The cytotoxicity and immune-responses can be lowered by introducing chitosan to PNIPAAm particles.