| Summary: | 碩士 === 臺灣大學 === 藥學研究所 === 95 === 英文摘要
Triblock copolymers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) are nonionic surfactant with wide range of hydrophilic-lipophilic balance (HLB). They have been used and investigated extensively in pharmaceutical researches. Recently, pluronics were found to be able to seal broken cell membranes and then leave as the cell membranes restored. This special function of Pluronics might provide a new therapeutic route. The aim of the present study is to investigate the relationship between Pluronics, chemical structures and their interfacial properties at the air/water interface by surface techniques, and the interactions between pluronics and membrane lipid monolayers by penetration experiments.
Combining the results of Π-A isotherms and surface elasticity of Pluronics monolayers at 25 oC, most Pluronics appeared two phase transitions. According to the analysis, it was found that the phase transition I was mainly affected by the number of EO monomers of the Pluronics, and the phase transition II was mainly affected by the number of PO monomers.
In the study of interactions between Pluronics and DPPC monolayers, under condition of Pluronics 2 x 10-4 mg/mL in subphase, the penetration ability of Pluronics to DPPC monolayers was determined by PEO、PPO chains length and molecule weight of the Pluronics,. It was found that more Pluronics molecules may penetrate into DPPC interface than expectedwhen compared the penetration results with a theoretical line of no interaction. It suggested that some kinds of attractive interactions may exist between Pluronics and DPPC monolayers. The Π-A isotherms of cholesterol/DPPC 20/80 and 40/60 mol% mixed monolayers indicated that the cholesterol would stabilize the mixed monolayers especially at higher surface pressures. In the study of interactions between Pluronics and Chol/DPPC 40/60 mol% mixed monolayers, it is most likely that hydrogen bond attractions may exist between the 3β-hydroxyl of the cholesterol and ether oxygen of PEO chains. Such interactions may lead Pluronic F68, a Pluronic with the longest PEO chain in this study, to exhibit obviously higher penetration ability than the others. As for Pluronics with the same EO number but different PO numbers, they exhibited almost equal attractive interaction with DPPC monolayers and Chol/DPPC mixed monolayers due to a weaker hydrogen bond attractions between the 3β-hydroxyl of cholesterol and ether oxygen of PPO chains. In the series of Pluronic L35、P65 and P105, L35 has more hydroxyl end groups per unit weight than the others, the attractions between L35 and mixed monolayers were higher than L35 and DPPC monolayers.
The results of this study provide us information to know how the structure of Pluronics affected the interactions between Puronics and membrane lipids such as the DPPC and the cholesterol. It would help us to understand the behavior of Pluronics observed in other studies such as the research of drug delivery systems.
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