本研究藉由Langmuir trough及Brewster angle顯微鏡分析技術，探討氣/液界面上L-α-distearoyl phosphatidylcholine(DSPC)/dihexadecyl- dimethylammonium bromide (DHDAB)混合單分子層的行為。此外，針對DSPC/DHDAB所形成的液胞，利用粒徑、zeta potential，以及螢光偏極化特性的分析，探討其物理穩定性及雙層膜的流動性。
根據單分子層的等溫線，可知DSPC和DHDAB在空氣/水界面上是可以混合的。熱力學分析進一步顯示當DSPC的莫耳分率(XDSPC)為0.7時，混合單分子層具最佳的穩定性。此外，在固定表面壓30mN/m的情況下，面積鬆弛曲線顯示含DSPC較多的混合單分子層是較穩定的。BAM的影像則顯示在不同的混合單分子層中，由於分子間作用的不同，造成單分子層形態的差異。若以純水為連續相製備DSPC/DHDAB液胞，當 XDSPC=0.5時，所形成之液胞的粒徑穩定性最好，但液胞的界面電位似乎不隨DHDAB比率的提高而有明顯改變。此外，螢光偏極化特性的分析顯示XDSPC=0.5之組成所形成的液胞，液胞雙層膜結構中分子間的作用最顯著。
當DSPC/DHDAB混合單分子層分布在磷酸鹽緩衝溶液之氣/液界面上時，熱力學分析顯示DSPC和DHDAB在界面上是可以混合的，且與在純水之氣/液界面上的狀態相比，混合前後之自由能變化的絕對值是較小的。然而，固定表面壓30mN/m時的面積鬆弛曲線顯示含DHDAB較多的混合單分子層，在緩衝溶液之氣/液界面上比在純水之氣/液界面上具較佳的穩定性。此外，利用緩衝溶液做為製備DSPC/DHDAB液胞的連續相時，液胞的粒徑穩定性皆不理想。

This study investigated the mixed monolayer behavior of L-α-distearoyl phosphatidylcholine/dihexadecyl- dimethylammonium (DSPC/DHDAB) at the air/liquid interface by using the Langmuir trough technique and Brewster angle microscopy. Moreover, the physical stability and the bilayer fluidity of DSPC/DHDAB vesicles were investigated by the size and zeta potential measurements with the fluorescence polarization analysis.
The monolayer isotherms indicated that DSPC and DHDAB were miscible at the air/water interface, and the thermodynamic analysis suggested that the mixed monolayer with XDSPC=0.7 had the best stability. In addition, the relaxation curves obtained at a constant surface pressure of 30mN/m implied that the mixed monolayers containing more DSPC were more stable. The BAM images demonstrated that the difference in the molecular interaction in various mixed monolayers resulted in the variations of monolayer morphology. For the DSPC/DHDAB vesicles prepared in water, the best physical stability was found for the vesicles with XDSPC=0.5. However, the zeta potential of the vesicles did not change significantly with the increase in XDHDAB. Furthermore, the fluorescence polarization analysis indicated that the most pronounced molecular interaction in the bilayer structures was found for the vesicles with XDSPC = 0.5.
For the mixed DSPC/DHDAB monolayers spread at the interface of air/phosphate buffer solution (PBS), the thermodynamic analysis suggested that DSPC and DHDAB were miscible at the interface, and the absolute value of the free energy change of mixing was less than that found at the air/water interface. However, the relaxation curves obtained at a constant surface pressure of 30mN/m indicated that the DHDAB-rich monolayers at the air/PBS interface had better stability than that at the air/water interface. Moreover, the poor physical stability was always found for the DSPC/DHDAB vesicles prepared in the PBS.

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