Self-assembled Nanostructures and Luminescent Supramolecular Hydrogel of Amino Acids Modified Tetraphenylethylene

• Main Authors: Chu, Nien-Tzu, 祝念慈
• Other Authors: Lin, Hsin-Chieh
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/q69hjg

碩士 === 國立交通大學 === 材料科學與工程學系所 === 106 === In recent years, a series of short peptides sequences involve fluorophores to form fluorescent nanostructures reveal a great potential in applications of biomaterials. In this study, we explored tetraphenylethylene(-TPE)-based conjugation with ultrashort peptides to form luminescent hydrogels, and investigated its self-assembled nanostructures and photophysical properties. In the first part of this research, we developed TPE/single amino acid conjugateds TPE-X( X=Gly, Ala, Ser, Asp ) that self-assembled into hydrogel with the smallest molecular weight under neutral environment. Side chains ( R group ) with different hydrophobic/hydrophilic degrees were found not only affected the self-assembled nanostructures but also stability of hydrogelation. TPE-Gly could self-assemble into nanobelts, but others formed nanosheets. TPE-Ser could form high stable hydrogel among TPE/single amino acid derivatives. In addition, we demonstrated that these derivatives depended on hydrogen bonding and aromatic π-π stacking interaction as the driving force to form self-assembled hydrogel, as demonstrated by circular dichroism, FTIR and fluorescence spectrum. Interestingly, TPE-Gly was the only achiral molecule, but it could exhibit cotton effect, which its self-assembled in a differently compared to others. Therefore, we designed a series of TPE-X-COOH( X=NH( Gly )、O、CH2 ) hydrogelators to get a deep insight into material properties of TPE-Gly. 2 wt% TPE-CH2-COOH self-assembled nanofibers to form high stable hydrogel under neutral environment, but TPE-O-COOH couldn’t get a gel under similar condition. It was worth to be mentioned that thin fibers were released from nanobelts after hydrogelation of TPE-Gly was diluted, and the fibers were obtained from diluted hydrogelation of TPE-CH2-COOH. Diameters of the both nanofibers were similar. We investigated the self-assembled difference between TPE-Gly and TPE-CH2-COOH through circular dichroism, FTIR , XRD and fluorescence spectrum. We surmised the NH part of TPE-Gly was a key to form nanobelts. In terms of cytotoxicity, TPE-Gly and TPE-Ala showed good cell viability with WS1 and 3A6 cells. In terms of its application in cell imaging, TPE-Ala was showed to stain cells easily with minimal background. In the second part of the research, we successfully developed TPE-based derivatives with different color conjugated with dipeptide FY to form amphiphilic hydrogelators, TPE-Blue-FY, TPE-Green-FY and TPE-Yellow-FY. They could form stable hydrogels under alkaline and neutral environment. We found that self-assembled nanofibers of TPE-Blue-FY turned into nanotubes through adjusting pH value. We also further investigated the self-assembly process of TPE-Blue-FY by controlling concentration and time, demonstrating TPE-Blue-FY was the first one to form TPE-based dipeptide nanotubes. In addition, we analyzed the difference in the self-assembled process between these dipeptide derivatives under base and neutral aqueous solution by circular dichroism, FTIR and fluorescence spectrum. In cytotoxicity, TPE-Yellow-FY possessed good biocompatibility toward 3A6 cells among these peptide derivatives. Furthermore, the three dipeptide derivatives all exhibited AIE property with emission color themselves. Given the promising results in terms of biocompatibility, it could be concluded that TPE-Yellow-FY was a good choice for contrast medium.