Applications of Amyloid Fibril-Based Hybrid Biomaterials: Preparation of Antibacterial Composite Hydrogels Consisting of Amyloid Fibrils and Polyphenolic Molecules

• Main Authors: Shang-Yu Shen, 沈尚諭
• Other Authors: 王勝仕
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/ry29vv

碩士 === 國立臺灣大學 === 化學工程學研究所 === 107 === In this study, we attempted to produce antimicrobial composite hydrogels consisting of amyloid fibrils and polyphenolic molecules. The amyloid fibrils were made from hen egg-white lysozyme (HEWL), and myricetin and resveratrol were chosen as the polyphenolic molecules. The antibacterial capability, morphology and fluid property of the hydrogels prepared under different conditions were analyzed. The effects of these two polyphenols on amyloid fibrils were also evaluated. Our results showed that, as opposed to the conditions at pH 2 and pH 9, HEWL amyloid fibrils were able to form hydrogels at pH 6 and pH 7.4 after the addition of polyphenols. The antibacterial activity assay was carried out with a high concentration of Gram-negative bacteria E. coli which was mixed with the hydrogel. The mixture was sampled at different times using the spread-plate method to observe for the colony formation. We found that the hydrogels incorporated with myricetin possessed a better antibacterial activity and eliminated bacteria within 8 hr. On the contrary, the amyloid fibril-based hydrogels with resveratrol and amyloid fibrils alone displayed negligible antibacterial activity. The results from the rheological analysis indicated that the viscosity of hydrogels is correlated with the pH value, concentration of polyphenol, and types of polyphenol. Moreover, it was found that the viscosity of the amyloid fibrils increased upon the addition of polyphenols. However, the more the amount of myricetin was added, the less the increase in viscosity. which might be attributed to the fact that the amyloid fibrils may be degraded by myricetin, resulting in structural instability. It should be noted that the similar trend was not seen in the groups with resveratrol. It could be found from the ThT binding analysis that the effects of myricetin and resveratrol on amyloid fibrils were significantly different. The myricetin molecule exhibited a strong competition with ThT for binding positions or ability to degrade amyloid fibrils. Therefore, in the groups of high concentrations of myricetin, the fluorescence intensity was observed to be much lower than that of amyloid fibrils alone. An analogous situation was also encountered in ANS binding analysis- showing that the occupation of exposed hydrophobic area of amyloid fibrillar structure by myricetin likely contributed to the reduction of ANS fluorescence intensity. However, this drastic reduction in ANS fluorescence emission was not perceived in the hydrogels combined with resveratrol. Moreover, hydrogels with the molar ratio of lysozyme fibril to myricetin at 0.1:1 showed better antibacterial ability and mechanical property. Therefore, this hydrogel is a promising antibacterial composite material. The outcome from this study is in support of the potential application of amyloid fibrils as functional biomaterials.