复合荧光CdSe量子点-脂质体的制备与表征

通过脂质体方法成功地将三辛基氧化膦(TOPO)包覆的CdSe发光量子点从非极性有机溶剂转移到生物相容性的水溶液中.分别通过透射电镜(TEM)、荧光Mapping图像,以及光致发光(PL)光谱进行表征.TEM照片显示制备的CdSe核量子点为球形,具有良好的单分散特性,平均粒径约为3nm.CdSe-脂质体复合体的平均尺寸大约20nm,TEM清楚地显示了CdSe量子点被诱捕在脂质体中.荧光Mapping显示了CdSe-脂质体复合体的发光强度分布.脂质体方法转移TOPO包覆的CdSe量子点,借助了磷脂的双分子链与CdSe表面的TOPO配体之间的疏水相互作用,在CdSe的第一配体层外部形成第二配体层,保留了CdSe的存在环境,光致发光光谱表明,量子点-脂质复合体基本保持了CdSe核量子点的发射效率.     

基于荧光光谱的脂质体制备与稳定性的研究

利用L-α-磷脂酰胆碱和胆固醇分子制备脂质体体系,通过监测脂质体内部包裹的对pH变化敏感的荧光指示剂8-羟基芘-1,3,6-三磺酸三钠盐的荧光强度变化实现对脂质体稳定性的表征。研究发现,在脂质体磷脂膜中引入一定比例的胆固醇分子有助于提高脂质体的稳定性(L-α-磷脂酰胆碱∶胆固醇=4∶1)。利用温水浴-液氮多次冻融循环,在强烈外界温差作用条件下,L-α-磷脂酰胆碱和胆固醇形成的贴壁薄膜重组成内外两侧均为亲水头部而疏水尾部均指向脂双层膜内部的稳定脂质体,在10min内稳定性高达99%,9 200s内稳定性依然可以达到92%。基于以上研究成果,我们在脂质体的外部环境中引入K+载体缬氨霉素,结果表明缬氨霉素可以成功的插入至磷脂双分子层膜中并高效运输K+。     

硫杂杯[4]芳烃基胶束自组装荧光探针的结构性质及检测性能的研究

水体中重金属污染因威胁生态环境和人类健康而被受广泛关注。荧光探针由于具有快速高效检测重金属的特性,一直是该领域的研究热点。通常,荧光探针在结构上包括对待测物质起识别作用的受体和能产生信号响应的荧光体,并逐步形成了内在型、共轭型、系综型和模板辅助自组装型等四种结构类型。近年来,基于受体和荧光体在表面活性剂胶束内自组装而形成的胶束自组装型荧光探针因结构简单、易于制备、能直接应用于水环境等特点逐渐受到重视。以对铜离子具有优异结合性能的对叔丁基硫杂杯[4]芳烃（TCA）为受体,以芘、荧蒽、蒽、菲、苝等分子为荧光体,通过表面活性剂胶束自组装制备针对Cu2+检测的胶束自组装型荧光探针,采用参比法测定了胶束自组装荧光探针的荧光量子产率,采用稳态荧光法测定了胶束聚集数,同时通过计算荧光猝灭率分别考察了荧光体种类、复配表面活性剂等因素对该探针的Cu2+检测性能的影响情况。实验结果显示,采用十二烷基硫酸钠（SDS）、曲拉通100（TX-100）、聚氧乙烯月桂醚（Brij35）等三种不同的表面活性剂对探针荧光体的荧光量子产率产生了明显影响,测得的荧光探针荧光量子产率介于0.25~0.47,且三者逐渐增大,说明表面活性剂改变了胶束内荧光分子芘所处微环境的极性,且不同类型表面活性剂对微环境极性的影响程度有所差异,微环境极性的增强对极性更大的激发态芘具有更强的稳定作用。而受体TCA的加入对荧光体所处微环境极性影响较小,未对荧光量子产率产生较大影响。但TCA的加入使探针的胶束聚集数明显减少,这归因于具有两亲性的受体TCA分子通过胶束自组装进入并分散在表面活性剂分子层中,形成共胶束结构,从而改变了表面活性剂分子的聚集状态。荧光体变更对荧光探针的Cu2+检测性能有显著影响,在同样条件下,以荧蒽、蒽、菲作为荧光体的探针检测Cu2+所得到的荧光猝灭率远高于芘、苝,这主要是因为不同荧光体在从激发态返回基态时辐射跃迁所释放能量不同,其能量与受体TCA识别Cu2+所需能量之间的匹配度越高,荧光猝灭率越大。不同类型的表面活性剂之间的复配能明显提升荧光探针检测性能,当非离子/阴离子、非离子/阳离子型复配表面活性剂之间的复配比例分别为7∶3和1∶1时荧光猝灭率达到最大值,且均高于单一表面活性剂时的荧光猝灭率。这说明不同类型表面活性剂复配的最佳比例存在较大差异,但均有效地增强了受体与荧光体的分散性及自组装性能,提高了对Cu2+的检测性能。研究结果将为新型胶束自组装荧光探针的设计和应用提供数据参考。     

芘与1,4—二氰基苯形成的三分子激基复合物

本文用稳态和瞬态荧光光谱技术研究了芘与１，４－二氰基苯体系形成三分子激基复合物的条件。测定了该体系中激基缔合物，激基复合物，三分子激基复合物的稳态荧光光谱及荧光强度随时间变化的行为和特性，测定了芘在苯溶液中的荧光衰减寿命，讨论了三分子激基复合物形成的光物理机理。     

钙钛矿晶体的电荷复合动力学研究（英文）

本文利用紫外吸收光谱和稳态荧光光谱技术结合理论模型,研究了钙钛矿材料CH_3NH_3PbI_3晶体在光激发过程中的电荷复合动力学行为,进而获得晶体的扩散长度.电荷载体的扩散长度是判断光电材料的重要参数.研究通过合成两种不同缺陷态浓度的CH_3NH_3PbI_3晶体,测量这两种晶体在0.019～4.268μJ/cm~2的激光激发下的时间分辨荧光光谱,利用动力学模型对光谱进行拟合,可以获得每个晶体的掺杂浓度,空穴浓度以及电荷复合参数.将这些参数结合已有公式,最终可获得每个晶体的电荷载体的扩散长度.     

CdTe纳米晶及层状纳米晶薄膜的生长及其光荧光性质

用湿化学法在水溶液中合成了单分散的、大小尺寸可控的、巯基包裹的胶体CdTe纳米晶体,并利用CdTe纳米晶体和双功能分子poly（diallyldimethylammonium chloride）（PDDA）在Si衬底表面自组织生长了有序的层状纳米晶薄膜,荧光光谱研究了层状纳米晶体之间的共振能量迁移过程.结果表明：层状自组织生长的样品中纳米晶粒的间隔几乎一样,表明它们是有序排列的;而用直接干燥形成的样品中,小尺寸和大尺寸的纳米晶体之间间隔较短,发生荧光共振能量迁移,较小尺寸的纳米晶粒荧光峰（即波长较短处的晶 关键词： CdTe纳米晶体 量子限制效应 共振能量迁移     

钙钛矿晶体的电荷复合动力学研究

本文利用紫外吸收光谱和稳态荧光光谱技术结合理论模型，研究了钙钛矿材料CH₃NH₃PbI₃晶体在光激发过程中的电荷复合动力学行为，进而获得晶体的扩散长度. 电荷载体的扩散长度是判断光电材料的重要参数. 研究通过合成两种不同缺陷态浓度的CH₃NH₃PbI₃晶体，测量这两种晶体在0.019∽4.268 μJ/cm²的激光激发下的时间分辨荧光光谱，利用动力学模型对光谱进行拟合，可以获得每个晶体的掺杂浓度，空穴浓度以及电荷复合参数. 将这些参数结合已有公式，最终可获得每个晶体的电荷载体的扩散长度.     

脂溶性CdSe/ZnS量子点脂质体复合物的制备及表征

在油相中成功合成了脂溶性CdSe/ZnS核壳量子点纳米粒,粒径平均为4.5 nm,量子产率达29%,发射波长为540 nm。通过薄膜分散法,以蛋黄卵磷脂、胆固醇为膜材,将脂溶性的CdSe/ZnS核壳量子点包覆于脂质体磷脂双分子层中,由于磷脂分子的两亲性,使得脂溶性的CdSe/ZnS核壳量子点同时又具有亲水性。通过透射电镜对脂质体形态进行了表征,倒置荧光显微镜证实了发光CdSe/ZnS核壳量子点成功包埋于脂质体双分子层中,包裹的发光CdSe/ZnS核壳量子点具有更稳定的发光及抗光漂白性质。     

两亲性壳聚糖基聚合物碳点的合成及其在载药方面的应用

通过水热法合成了系列具有高荧光量子产率（42.9%）辛基化壳聚糖基两亲性聚合物碳点荧光材料。利用红外光谱、紫外吸收光谱、光电子能谱、透射电镜、X射线衍射及荧光光谱对聚合物碳点进行了表征。以阿霉素为模型药物,研究了聚合物碳点对阿霉素的载药性能。当辛基取代度为76.42%时,其最大载药量和包封率分别为49.6%与47.4%。在磷酸盐缓冲液中,载药纳米胶束呈前期快速释放,后期缓慢释放的双相特征。将载药纳米胶束与鼻咽癌细胞作用,发现其存活率随着载药纳米胶束加入量的增加而降低,说明该纳米胶束对鼻咽癌细胞有一定的抑制作用。总之,该聚合物碳点材料在药物载体与荧光示踪方面有潜在的应用价值。     

基于密度泛函理论下多肽光谱性质研究

多肽类物质在生物医药等领域是一种重要的生物大分子,而紫外-可见吸收光谱和荧光光谱是研究生物分子精细结构的重要手段。采用密度泛函理论（DFT/RI）计算了生长激素释放肽（GHRP-6）和催产素（Oxytocin）两种多肽的结构模型和分子前线轨道;在含时密度泛函理论（TDDFT）的基础上,引入了TDA等近似,建立了多肽类物质的紫外-可见吸收光谱和荧光光谱的理论模型。结果表明,实验测得到GHRP-6的紫外-可见吸收光谱最大吸收波长为279 nm,计算得到的最大吸收波长为282 nm,误差为3 nm,误差百分比约为1%;Oxytocin紫外-可见吸收光谱的实验值为275 nm,计算值为269 nm,误差百分比约为2%。GHRP-6荧光光谱计算值为368 nm,实验值为360 nm,误差百分比约为2%;Oxytocin荧光光谱计算值为305 nm,实验值为312 nm,误差百分比约为2%。GHRP-6产生荧光的发射波长与色氨酸产生的荧光波长范围相近,说明GHRP-6产生荧光的主要贡献为色氨酸残基上的π→π*轨道跃迁,Oxytocin荧光峰位置与酪氨酸产生的荧光波长范围相近,Oxytocin产生荧光的主要贡献为酪氨酸残基上的π→π*轨道跃迁。根据该模型计算得到的光谱与实验结果吻合度较高,表明该模型能够准确计算多肽类物质紫外-可见吸收光谱和荧光光谱,为实验提供可靠的理论依据。     

Pair interaction of bilayer-coated nanoscopic particles

The pair interaction between bilayer membrane-coated nanosized particles has been explored by using the self-consistent field (SCF) theory. The bilayer membranes are composed of amphiphilic polymers. For different system parameters, the pair-interaction free energies are obtained. Particular emphasis is placed on the analysis of a sequence of structural transformations of bilayers on spherical particles, which occur during their approaching processes. For different head fractions of amphiphiles, the asymmetrical morphologies between bilayers on two particles and the inverted micellar intermediates have been found in the membrane fusion pathway. These results can benefit the fabrication of vesicles as encapsulation vectors for drug and gene delivery.     

The engineering of doxorubicin-loaded liposome-quantum dot hybrids for cancer theranostics

In the fabrication of phase change random access memory(PRAM) devices, high temperature thermal processes are inevitable. We investigate the thermal stability of Ge2Sb2Te5(GST) which is a prototypical phase change material. After high temperature process, voids of phase change material exist at the interface between Ge2Sb2Te5 and substrate in the initial open memory cell. This lower region of Ge2Sb2Te5 is found to be a Te-rich phase change layer. Phase change memory devices are fabricated in different process conditions and examined by scanning electron microscopy and energy dispersive X-ray. It is found that hot-chuck process, nitrogen-doping process, and lower temperature inter-metal dielectric(IMD) deposition process can ease the thermal impact of line-GST PRAM cell.     

Vectorial photoinduced electron transfer in phospholipid vesicles and LB bilayers

Summary Photoinduced electron transfer (PET) was studied in phospholipid vesicles and in Langmuir-Blodgett bilayers in the attempt to produce a model for electron transfer processes in biological media. Spatial organization of the reaction centers in lipid membranes needs to be controlled in order to provide high efficiency of light-to-chemical energy conversion. We designed a phospholipid system where the donor is localized in the inner bilayer whereas the acceptor is at the polar groups-water interface. We used dipalmitoylphosphatidic acid vesicles containing low molar fractions of dipalmitoylphosphatidylcholine with pyrene (donor) bound to one of the alkyl chains. Methylviologen (acceptor) was added to the external aqueous phase; upon photoexcitation of the donor we observed the electron transfer to take place in a unidirectional manner from the inside of the bilayer to the interface. Information about the location of the donor was obtained studying the photophysical properties of the pyrene chromophore in vesicles and in LB layers. The photoinduced electron transfer reaction was evidenced by quenching of pyrene fluorescence in the presence of increasing concentrations of acceptor, the process was studied both with steady-state and time-resolved fluorescence emission. Fluorescence intensity was found to decrease with increasing concentration of methylviologen, similar results were obtained for vesicles and LB layers of analog composition immersed in a methylviologen solution. Lifetimes of the excited species were found to be of the same order of magnitude in vesicle and LB-layer systems. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.     

Bilayers of neutral lipids bear a small but significant charge

Many experiments done on neutral lipid bilayers in pure water show weak repulsions. These weak forces prevent vesicles from adhering and are generally overcome by adding some salt in the aqueous medium. They also appear as stray repulsions in surface forces measurements made on lipid bilayers. Using a surface forces apparatus in pure water and in salt solution, we have measured the forces between two stearoyl-oleoyl-phosphatidyl-choline (SOPC) bilayers and between two dimiristoyl-phosphatidyl-ethanolamine (DMPE) bilayers. The results show that the repulsions are due to a small amount of negative charges coming from impurities in SOPC. This was quantitatively confirmed by electrophoretic measurements. There are 3 times less charges in the case of DMPE layers. The effect of these charges which is negligible at high salt concentration may significantly affect the adhesion energy and behaviour of neutral lipid bilayers between 0 and salt. Received 18 December 1998     

Europium Coordination Complexes as Potential Anticancer Drugs: Their Partitioning and Permeation Into Lipid Bilayers as Revealed by Pyrene Fluorescence Quenching

The present study was undertaken to evaluate the membrane-associating properties of a series of novel antitumor agents, Eu(III) coordination complexes (EC), using the pyrene fluorescence quenching as an analytical instrument. Analysis of EC-induced decrease in pyrene fluorescence intensity in terms of partition and solubility-diffusion models allowed us to evaluate the partition and permeation coefficients of the examined compounds into the lipid vesicles prepared from zwitterionic lipid phosphatidylcholine (PC) and its mixtures with cholesterol (Chol) and anionic lipid cardiolipin (CL). The drug-lipid interactions were found to have the complex nature determined by both EC structure and lipid bilayer composition. High values of the obtained partition and permeation coefficients create the background for the development of EC liposomal formulations.     

Novel type of isoprenoid membrane anchors: an investigation of binding properties with dipalmitoylphosphatidylcholine vesicles

In this work, we present a new type of amphiphilic membrane‐anchoring agents that can be easily obtained by the Diels‐Alder reaction between terpene myrcene and N‐substituted maleimides. The interaction between the compounds and small unilamellar dipalmitoylphosphatidylcholine vesicles was investigated using infrared spectroscopy, microgravimetry, and turbidimetry. The ability of the compounds to embed in the phospholipid membrane was shown to be strongly dependent on the charge of their polar group. The insertion of the compounds studied into the lipid bilayer did not lead to disruption of the dipalmitoylphosphatidylcholine vesicles up to the highest tested drug to lipid molar ratio of 0.5 to 0.6. Low lipid solubilization ability of the compounds as well as their rigid nonplanar structure makes them an interesting alternative to the common membrane‐anchoring structural motifs.     

Magnetic lipid nanoparticles loading doxorubicin for intracellular delivery: Preparation and characteristics

Tumor intracellular delivery is an effective route for targeting chemotherapy to enhance the curative effect and minimize the side effect of a drug. In this study, the magnetic lipid nanoparticles with an uptake ability by tumor cells were prepared dispersing ferroso-ferric oxide nanoparticles in aqueous phase using oleic acid (OA) as a dispersant, and following the solvent dispersion of lipid organic solution. The obtained nanoparticles with 200 nm volume average diameter and −30 mV surface zeta potential could be completely removed by external magnetic field from aqueous solution. Using doxorubicin (DOX) as a model drug, the drug-loaded magnetic lipid nanoparticles were investigated in detail, such as the effects of OA, drug and lipid content on volume average diameter, zeta potential, drug encapsulation efficiency, drug loading, and in vitro drug release. The drug loading capacity and encapsulation efficiency were enhanced with increasing drug or lipid content, reduced with increasing OA content. The in vitro drug release could be controlled by changing drug or lipid content. Cellular uptake by MCF-7 cells experiment presented the excellent internalization ability of the prepared magnetic lipid nanoparticles. These results evidenced that the present magnetic lipid nanoparticles have potential for targeting therapy of antitumor drugs.     

RSM and ANN modeling-based optimization approach for the development of ultrasound-assisted liposome encapsulation of piceid

Piceid, a naturally occurring derivative of resveratrol found in many plants, has recently been considered as a potential nutraceutical. However, its poorly water-soluble property could cause a coupled problem of biological activities concerning drug dispersion and absorption in human body, which is still unsolved now. Liposome, a well-known aqueous carrier for water-insoluble ingredients, is commonly applied in drug delivery systems. In this study, a feasible approach for solving the problem is that the targeted piceid was encapsulated into a liposomal formula as aqueous substrate to overcome its poor water-solubility. The encapsulation process was assisted by ultrasound, with investigation of lipid content, ultrasound power and ultrasound time, for controlling encapsulation efficiency (E.E%), absolute loading (A.L%) and particle size (PS). Moreover, both RSM and ANN methodologies were further applied to optimize the ultrasound-assisted encapsulation process. The data indicated that the most important effects on the encapsulation performance were found to be of lipid content followed by ultrasound time and ultrasound power. The maximum E.E% (75.82%) and A.L% (2.37%) were exhibited by ultrasound assistance with the parameters of 160 mg lipid content, ultrasound time for 24 min and ultrasound power of 90 W. By methodological aspects of processing, the predicted E.E% and A.L% were respectively in good agreement with the experimental results for both RSM and ANN. Moreover, RMSE, R² and AAD statistics were further used to compare the prediction abilities of RSM and ANN based on the validation data set. The results indicated that the prediction accuracy of ANN was better than that of RSM. In conclusion, ultrasound-assisted liposome encapsulation can be an efficient strategy for producing well-soluble/dispersed piceid, which could be further applied to promote human health by increased efficiency of biological absorption, and the process of ultrasound-mediated liposome encapsulation can be well established by a methodological approach using either RSM or ANN, but it is worth mentioning that the ANN model used here showed the superiority over RSM for predicting and optimizing encapsulation.     

Fluorescence Study of Intermolecular Interactions in Diluted Aqueous Solutions of Some Cationic Amphiphilic Polysaccharides

The intermolecular hydrophobic association in diluted aqueous solutions of some cationic amphiphilic polysaccharides was investigated using fluorescence techniques. Dextran and dextran carrying N-alkyl-N,N-dimethyl-N(2-hydroxypropylene) ammonium chloride groups as side chains were single labeled with pyrene or naphthalene. The intensity of the pyrene excimer peak and the ratio I₃/I₁ determined from the fluorescence emission spectra of pyrene-labeled amphiphilic polymer increased with increasing polymer concentration and were higher than in the solution containing pyrene-labeled dextran. Emission spectra of diluted solution (0.008–0.2 g/dl) containing mixtures of pyrene and naphthalene single-labeled amphiphilic polymers proved the occurrence of a nonradiative energy transfer between labels at very a low polymer concentration (<10^?2 g/dl). The energy transfer was not observed in mixtures of single-labeled unmodified dextran. All these results suggest that the intermolecular hydrophobic association of alkyl substituents takes place at a very low concentration of amphiphilic polymers.     

Conformational effects on the fluorescence of pyrene-labeled alkyldiacyl glycerols in different model membranes

We synthesized two isomeric alkyldiacyl glycerols containing pyrene as a fluorescent reporter group bound to the omega end of both acyl chains. If located in the phospholipid monolayer of a vesicle both isomers showed intramolecular pyrene excimer fluorescence, indicating parallel orientation of both pyreneacyl chains in the lipid molecule. In micelles only pyrene monomer fluorescence was observed. Thus, in this system the labeled lipids adopt a conformation with both pyreneacyl chains extending into different directions. Using vesicles, lipase activities could be continuously determined from the increase of pyrene monomer fluorescence.