吴茱萸碱与脂质体模拟生物膜的相互作用:FTIR和DSC研究

药物与生物膜相互作用的研究对于了解药物药效和改善其生物性能具有重要的意义。但生物膜的组成复杂，直接研究药物活性成分与生物膜的相互作用比较困难。以脂质体作为生物膜模型，研究了吴茱萸碱与脂质体的相互作用，分析了吴茱萸碱分子在脂质体中的包封位置，探讨了吴茱萸碱抗炎作用可能的作用机制。以二棕榈酰磷脂酰胆碱（DPPC）为膜材，应用薄膜分散法制备含有不同摩尔百分比（x）的吴茱萸碱脂质体，应用傅立叶变换红外光谱（FTIR）和差示扫描量热（DSC）技术分析随着脂质体中药物摩尔百分比的增大，DPPC分子各红外特征吸收峰频率、峰形及量热参数的变化情况，从而探讨药物在脂质体中的包封位置及吴茱萸碱分子对脂质体膜流动性的影响。实验数据表明，在0＜x＜10 mol%的浓度范围内，DPPC头部区域磷酸基团的不对称伸缩振动频率没有明显变化，脂质体相变温度和相变焓均随药物摩尔百分比的增大而减小。在0＜x＜5 mol%浓度范围内，DPPC界面区域的水化的羰基峰的吸收波数由1 726.0 cm-1增加到1 731.8 cm-1，当x=10 mol%时，该波数又减小到1 728.0 cm-1。在10 mol%≤x＜20 mol%浓度范围内，磷酸基团的不对称伸缩振动的波数由1 242.0 cm-1减小为1 236.3 cm-1，水化的羰基峰的吸收频率没有明显变化，脂质体相变温度和相变焓均随药物摩尔百分比的增大而增大。纯DPPC脂质体中亚甲基的对称伸缩振动波数为2 848.4 cm-1，载药后该波数都增大到2 850.3 cm-1。这些结果表明吴茱萸碱在脂质体中的包封位置具有浓度依赖性：在0＜x＜10 mol%浓度范围内，吴茱萸碱主要作用于DPPC分子的疏水尾链区域，少部分药物分子作用于DPPC分子的界面区域。在10 mol%≤x＜20 mol%浓度范围内，吴茱萸碱分子则主要作用于DPPC分子的头部区域，少部分药物分子作用于DPPC分子的疏水尾链区。所有载药脂质体的相变温度均低于纯DPPC脂质体的相变温度，即不同浓度的吴茱萸碱均可以使脂质体的膜流动性增加，并且，当药物摩尔百分比为10 mol%时，吴茱萸碱对生物膜流动性的增加效应最为明显。研究工作对于进一步揭示吴茱萸碱与生物膜的相互作用机制具有重要意义。

The Interaction of Evodiamine with Liposome Mimetic Biomembrane: FTIR and DSC Study

The study of the interaction between drugs and biomembrane is of great significance to the understanding of the drug efficacy and the improvment of their biological properties. However, the composition of biomembrane is complex, which makes it difficult to study the interaction between active components of drugs and biomembrane directly. We used liposome as mimetic biomembrane, investigated the interaction of evodiamine with liposome, analyzed the entrapment position of evodiamine among liposome, and the possible mechanism of the anti-inflammatory effect of evodiamine was also discussed. 1,2-Dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) has been used as membrane material in this study and liposomes containing different molar percentage of evodiamine (x) were prepared by thin-film dispersion method. Fourier transform infrared spectroscopy (FTIR) and Differential scanning calorimetry (DSC) were used to analyze the frequency and shape of infrared absorption peaks and the changes of the calorimetric parameters of DPPC molecules with the increasing of the molar percentage of drugs. The entrapment position of the evodiamine in liposome and the effect of this drug on the fluidity of liposome membrane were discussed. Data showed that the frequency of the asymmetric stretching vibration of the phosphate group in the DPPC head region hardly changed in the concentration range of 0＜x＜10 mol%, but the phase transition temperature and enthalpy of the liposome decreased with increasing x in this concentration range. In the concentration range of 0＜x＜5 mol%, the absorption wave number of hydrated carbonyl in the DPPC interface region increased from 1 726.0 to 1 731.8 cm-1, however, this wave number decreased to 1 728.0 cm-1 at x=10 mol%. In the concentration range of 10 mol%≤x＜20 mol%, the wave number of asymmetric stretching vibration of phosphate group decreased from 1 242.0 to 1 236.3 cm-1, but the absorption frequency of hydrated carbonyl hardly changed, and the phase transition temperature and enthalpy of liposome increased with increasing x. The wave number of the symmetrical stretching vibration of methylene in pure DPPC liposomes was 2 848.4 cm-1, which increased to 2 850.3 cm-1 after drug loading. These results indicated that the entrapment location of evodiamine in liposomes is concentration-dependent: in the concentration range of 0＜x＜10 mol%, evodiamine molecules mainly incorporate into the hydrophobic region of DPPC molecules and a few locate at the interfacial region of DPPC molecules. In the range of 10 mol%≤x＜20 mol%, evodiamine molecules mainly incorporate into the hydrophilic head region of the DPPC molecules and a few locate at the hydrophobic tail chain of DPPC molecules. The phase transition temperatures of all drug containing liposomes are lower than those of pure DPPC liposomes. That is to say, the membrane fluidity of the liposomes could be increased by different concentrations of evodiamine. Moreover, at x=10 mol%, the membrane fluidity of liposomes is the largest. This study will play an important role in the further investigation of the interaction mechanism of evodiamine with biomembrane.