电制备巨囊泡的方法和机理探索

利用倒置显微镜研究电制备巨囊泡, 并分析其形成和成长的动力学机理. 由于磷脂头部的电特性, 电场对水化的磷脂双层的静电力促使磷脂膜内双层之间分离. 在动力学的作用下, 双层两叶的不对称受力引发其弯曲、出芽、膨胀、封闭以及相互融合. 结果表明, 电场参数、干磷脂膜的均匀性、缓冲液以及温度等因素影响巨囊泡的粒径、形状和稳定性.     

多聚赖氨酸诱导的负电性磷脂巨囊泡形变

利用荧光显微技术表征了多聚赖氨酸诱导的负电性磷脂巨囊泡的动力学响应行为.研究发现,多聚赖氨酸可吸附至二油酰磷脂酰胆碱和二油酰磷脂酸混合磷脂巨囊泡的表面,诱导其发生粘连、出"绳"及破裂现象.分析认为,在低盐环境中,膜形变由多聚赖氨酸吸附于二油酰磷脂酸富集区引起的膜两叶应力不对称,以及静电相互作用等因素产生.研究结果对基于聚合物-巨囊泡体系的药物输运控释、细胞形变、微控反应和基因治疗等方面的研究提供有价值的支持.     

多组分磷脂巨囊泡的相结构和胆固醇对微畴成长的影响

巨囊泡作为细胞的简化模型,其相分离与出芽动力学规律已引起许多领域科学家的关注.本实验采用DPPC/DOPC/Chol的三组分形成的巨囊泡作为模型,借助荧光显微镜观察该三组分体系侧向分离的相结构图,并对微畴的成长过程作了系统的观察研究和理论分析.实验发现:从高温的均相区域淬灭到低温的分相区域,膜表面发生侧向分离形成微畴.体系内胆固醇的掺入量的多少会影响磷脂膜的相结构和膜内微畴的成长,固定DOPC/DPPC为1:1的前提下,微畴尺寸随着胆固醇掺入量的增加而变大.     

多组分磷脂巨囊泡的相结构和胆固醇对微畴成长的影响

摘要：巨囊泡作为细胞的简化模型,其分相与出芽机理及动力学规律已引起许多领域科学家的关注。在富含胆固醇的典型生物膜体系如二棕榈酰磷脂酰胆碱DPPC(2-dihexadecanoyl-rac-glycero-3phosphocholine)/二油酰磷脂酰胆碱DOPC(dioleoyl-phosphatidylcholine)/胆固醇(Chol)的三组分形成的巨囊泡作为模型,从高温退火至低温会发生相分离,形成微畴。实验中借助荧光显微镜观察生物膜体系侧向分离的相结构图。实验发现,体系各组分的不同会影响磷脂膜的相结构和膜内微畴的成长,固定 DOPC/DPPC为1:1的前提下,微畴尺寸随着胆固醇参入量的增加而变大。最后运用理论进一步分析了微畴的成长机理。     

磷脂微滴囊泡化的介观模拟

发展了一种非显示溶剂的粗粒化三粒子磷脂模型,该模型明确反映磷脂分子的双尾结构．模型分别采用变形的MIE作用势和Harmonic作用势描述分子间非成键和分子内成键相互作用,粗粒化力场参数通过拟合DPPC双分子层的结构和力学性质获得．该粗粒化模型成功重现了磷脂分子从随机初始态到双分子层和从盘状结构到囊泡的形成过程．应用该模型系统研究了球形和柱形磷脂微滴囊泡化的过程,结果表明此模型能有效地模拟介观尺度下复杂磷脂囊泡的形成及演化．     

蜂毒肽浓度和磷脂组分对巨囊泡泄露的影响

蜂毒肽作为一种广谱抗菌肽已经得到广泛认知,用蜂毒肽构建载药体系攻击癌细胞研究正在兴起.基于仿生物膜模型探索其破坏机理,可以避免潜在活性细胞过程的影响.在此,我们选用细胞尺寸的单层巨囊泡膜模型,可在光学显微镜下直接观察和操作,获得仿正常细胞膜和仿癌细胞膜在不同蜂毒肽浓度刺激下的响应.研究得出,低浓度蜂毒肽诱导囊泡泄露实验表明中性磷脂囊泡以孔模式为主泄露,负电性磷脂囊泡以爆裂模式为主泄露;高浓度蜂毒肽诱导囊泡泄露实验表明负电性磷脂相较于中性磷脂可延迟蜂毒肽作用效果;蜂毒肽色氨酸残基荧光光谱表明囊泡膜表面蜂毒肽吸附量以及泄露模式依赖于磷脂组分.此外,推断了蜂毒肽对不同组分磷脂膜的破坏作用模型.研究为蜂毒肽在肿瘤细胞的作用机制及其衍生物的优化设计提供参考.     

蜂毒肽浓度和磷脂组分对巨囊泡泄露的影响

蜂毒肽作为一种广谱抗菌肽已经得到广泛认知,用蜂毒肽构建载药体系攻击癌细胞研究正在兴起.基于仿生物膜模型探索其破坏机理,可以避免潜在活性细胞过程的影响.在此,我们选用细胞尺寸的单层巨囊泡膜模型,可在光学显微镜下直接观察和操作,获得仿正常细胞膜和仿癌细胞膜在不同蜂毒肽浓度刺激下的响应.研究得出,低浓度蜂毒肽诱导囊泡泄露实验表明中性磷脂囊泡以孔模式为主泄露,负电性磷脂囊泡以爆裂模式为主泄露;高浓度蜂毒肽诱导囊泡泄露实验表明负电性磷脂相较于中性磷脂可延迟蜂毒肽作用效果;蜂毒肽色氨酸残基荧光光谱表明囊泡膜表面蜂毒肽吸附量以及泄露模式依赖于磷脂组分.此外,推断了蜂毒肽对不同组分磷脂膜的破坏作用模型.研究为蜂毒肽在肿瘤细胞的作用机制及其衍生物的优化设计提供参考.     

流场环境下复杂囊泡的动力学行为

采用非平衡态分子动力学方法研究了二维复杂囊泡在剪切流中的动力学行为. 模拟发现了复杂囊泡经典的翻滚(tumbling)、摇摆(trembling)和坦克履(tank-treading)行为, 还观察到由坦克履行为向平动行为(translating)的转变. 囊泡的平动行为与剪切率大小、复杂囊泡的形状密切相关. 当大囊泡均匀嫁接较多数目的小囊泡后, 其平动方式消失. 该研究有益于加深对囊泡在剪切流场中复杂性行为的理解.     

反透析法测定阿奇霉素囊泡的包封率

建立阿奇霉素囊泡的包封率测定方法.以紫外分光光度法为分析手段,采用反透析法测定阿奇霉素囊泡的包封率.反透析法透析平衡时间为8h,游离药物的绝对回收率符合要求.该方法测得自制阿奇霉素囊泡的平均包封率为92.51％±0.56％,10h内没有渗漏,方法重现性好.该法操作准确、简便,可用于测定阿奇霉素囊泡的包封率.     

模拟囊泡形变动力学的新方法离散空间变分法

提出了全新的离散空间变分法研究二维囊泡形变动力学过程，克服了原先解析或数值解囊泡形状方程遇到的困难，结果表明动力学终态与已有理论方法的计算结果完全一致；说明这一方法正确而且解法稳定有效，这一方法可进一步推广至研究三维无对称性的囊泡形状以及膜与膜之间有长程相互作用的情形，这为囊泡形状的研究提供了新的理论手段. 关键词： 离散空间变分法 囊泡 动力学 Helfrich方程     

Influence of lipid composition and membrane curvature on fluorescence and solvent relaxation kinetics in unilamellar vesicles

Time-resolved fluorescence on unilamellar vesicles shows that increasing amounts of anionic, natural lipid lead to a larger increase in polarity close to the headgroups than in the hydrophobic core of the bilayer. The region close to the headgroups is less polar in vesicles containing phosphatic acid rather than phosphatidylserine. A greater membrane curvature increases the mobility of the hydrated headgroups.     

Transmembrane transport of multicomponent liposome-nanoparticles into giant vesicles

With the emergence and rapid development of nanotechnology, the nanoparticles hybridized with multicomponent lipids are more and more used in gene delivery. These vectors interact with the cell membrane before entering into the cell. Therefore, the nature of this interaction is important in investigating multicomponent liposome-nanoparticle (MLP) transport across the cell membrane. In this paper the transport of MLPs across the membranes of giant vesicles (GVs) in solvents is studied by using the self-consistent field theory (SCFT). Based on the analysis of the MLP permeating the GV membranes, a simple transport model is proposed. The effects of the difference in membrane morphology and the size of the nanoparticle on the endocytosis are discussed systematically. The role of energy barriers in quasi-equilibrium is also examined. The results indicate that the interaction between MLP and GV is a spontaneous process and the energy barrier needs overcoming to form metastable intermediates. The results provide theoretical reference for better understanding the transmembrane transport process of nanoparticles, and guidance for relevant experimental studies as well.     

Influence of cholesterol on the bilayer properties of monounsaturated phosphatidylcholine unilamellar vesicles

The influence of cholesterol on the structure of unilamellar-vesicle (ULV) phospholipid bilayers is studied using small-angle neutron scattering. ULVs made up of short-, mid- and long-chain monounsaturated phospholipids (diCn :1PC, n = 14 , 18, 22, respectively) are examined over a range (0-45mol %) of cholesterol concentrations. Cholesterol's effect on bilayer structure is characterized through changes to the lipid's transmembrane thickness, lateral area and headgroup hydration. For all three lipids, analysis of the experimental data shows that the addition of cholesterol results in a monotonic increase of these parameters. In the case of the short- and mid-chain lipids, this is an expected result, however, such a finding was unexpected for the long-chain lipid. This implies that cholesterol has a pronounced effect on the lipid's hydrocarbon chain organization.     

Transfer of pyrene-dietherphosphatidylcholine to serum lipoproteins

The nonhydrolyzable fluorescent diether analog of phosphatidylcholine, 1-O-hexadecyl-2-0-pyrenedecyl-sn-glycero-3-phosphocholine, has been synthesized as a stable probe for the determination of phospholipid transfer to different lipoprotein classes with potential phospholipase activities. After incubation of total human serum with the new probe at 37°C for 3 hours a characteristic partition equilibrium between the main lipoprotein fractions was observed. The fluorescent lipid was not degraded under these conditions and, therefore, served as a marker for choline glycerophospholipid distribution between and transport to serum lipoproteins.     

Size and viscoelasticity of spatially confined multilamellar vesicles

We studied viscoelastic properties and scaling behavior of multilamellar vesicles (MLVs) confined between two parallel plates as a function of the shear rate and sample thickness (gap size between parallel plates). The rheological properties are classified into two regimes; the shear-thinning regime at high shear rates and the shear-thickening regime at low shear rates. In the former, the MLV radius results from the mechanical balance between the effective surface tension σ_eff and viscous stress force. The MLV radius is independent of the gap size. σ_eff estimated by van der Linden model is 2.1 ±0.15 ×10^-4 Nm^-1 corresponding to the same value obtained by SANS measurement. Power law exponents for the steady state viscosity and yield stress against pre-shear rate ( , ) well agree with prediction based on the layering of membranes. Therefore, viscoelastic properties in this regime could be modeled by assuming that the dynamics of MLVs are driven by layering of MLV polydomains, which could be accompanied by the viscous dissipation, i.e., the stress relaxation on the MLV, induced by continuous sequence of yields of MLVs. The flow curve is empirically explained by the assumption of a relaxation time for the MLV shape. In the latter, however, scaling laws observed in the shear-thinning regime break down. The MLV radius increases when the gap size is reduced below the threshold value and MLV is no longer formed at very small gap sizes. Different dynamics from the shear-thinning regime seem to dominate the viscoelasticity.     

TbDyFe薄膜对三明治膜巨磁阻抗效应的影响

将600℃退火后的超磁致伸缩材料(Tb0.27Dy_0.73)_0.3Fe_0.7薄膜作为Ni_80.2Fe_14.1Si_0.2Mn_0.4Mo_5.1三明治膜的基底，制备出四层膜.结果表明：附加的磁致伸缩并没有减小材料的巨磁阻抗(GMI)效应，而由于磁场下磁致伸缩材料的应力效应影响了三明治膜中的各向异性场，使三明治膜的GMI效应增大了4倍.再将制备态的四层膜在280℃下真空退火，退火态四层膜也增大了三明治膜的GMI效应，但可能由于磁致伸缩向磁性层中的扩散，其GMI效应相对于制备态四层膜则有所降低. 关键词： 巨磁阻抗(GMI)效应 三明治膜 TbDyFe薄膜 各向异性场     

Ablation depth control with 40 nm resolution on ITO thin films using a square,flat top beam shaped femtosecond NIR laser

We reported on the ablation depth control with a resolution of 40 nm on indium tin oxide (ITO) thin film using a square beam shaped femtosecond (190 fs) laser (λ_p=1030 nm). A slit is used to make the square, flat top beam shaped from the Gaussian spatial profile of the femtosecond laser. An ablation depth of 40 nm was obtained using the single pulse irradiation at a peak intensity of 2.8 TW/cm². The morphologies of the ablated area were characterized using an optical microscope, atomic force microscope (AFM), and energy dispersive X-ray spectroscopy (EDS). Ablations with square and rectangular types with various sizes were demonstrated on ITO thin film using slits with varying x–y axes. The stereo structure of the ablation with the depth resolution of approximately 40 nm was also fabricated successfully using the irradiation of single pulses with different shaped sizes of femtosecond laser.