生物还原敏感可降解聚合物纳米载体的构建与应用

生物可降解聚合物纳米载体具有较长的体内循环时间、能靶向并富集到肿瘤组织、降低毒副作用、增加药物利用率以及在体内可降解等优越性能,已成为实现肿瘤靶向治疗最有前景的载体系统之一。但是,临床试验结果表明,聚合物纳米药物的治疗效果与人们的预期相差甚远,其中一个重要原因是纳米药物在靶点处药物释放少且缓慢。因此,开发智能型纳米载体使其在到达靶点后即迅速释放包裹的药物成为近年的研究热点。肿瘤组织,尤其是肿瘤细胞内的谷胱甘肽(glutathione,GSH)浓度较高(2~10mM),大约是体液和细胞外基质的100~1000倍(2~10μM)。基于肿瘤独特的还原势能,人们构建了各种不同类型的还原敏感聚合物纳米载体,实现抗癌药物在肿瘤组织和肿瘤细胞内的快速高效释放。生物还原敏感聚合物纳米载体具有以下特点:(1)在生理条件下稳定;(2)对肿瘤细胞内还原环境响应快,触发药物快速释放;(3)无需任何外在刺激装置,简单方便。本文将结合我们课题组的工作介绍各种还原敏感可降解聚合物纳米载体的构建和应用,主要包括还原敏感生物可降解聚合物胶束、囊泡、纳米凝胶等。     

温敏性聚膦腈及其在药物释放体系中的应用

温敏性聚合物能通过感知温度而实现环境响应,作为药剂可依靠对此类信号的自反馈响应而释放药物或中止释放,极大地增强了释药的持续性和专一性,从而提高了药物的药效和安全性.温敏性聚膦腈是一类新型的温敏材料,它具有良好的生物可降解性质,优良的生物相容性.因此,温敏性聚膦腈作为药物载体用于药物释放体系具有很好的应用前景,近年来备受关注.本文对聚膦腈的温敏性质、生物降解性质进行了评述,并探讨了LCST的影响因素,以及在药物释放体系的应用进展.     

利用超分子接枝聚合物体系制备具有pH响应能力的高分子囊泡及其在药物控制释放方面的应用

利用自由基聚合的链转移反应,制备了以羧基为端基的聚(N-异丙基丙烯酰胺)(PNIPAM-COOH),然后以该聚合物作为亲水的侧链,利用其羧端基和聚(4-乙烯基吡啶)(PVPy)疏水主链上的吡啶基团间的相互作用,在共溶剂DMF中形成超分子两亲接枝聚合物体系,在上述体系中逐滴加入水可以使其通过自组装形成高分子囊泡.通过控制PVPy与PNIPAM-COOH的质量比在1～3之间,可以控制囊泡尺寸在130～330nm之间.由于囊泡中含有吡啶基团,因而该囊泡具有pH敏感性.以日落黄为药物模型,以这些pH敏感性囊泡作为药物载体,通过调节环境的pH值可以实现对药物的控制释放.     

同轴电喷-去模板法制备具有金属基质蛋白酶响应性的纳米载体

通过化学键偶联的形式在聚乳酸(PLA)分子链中引入了可被金属基质蛋白酶(MMP-2)特异性降解的多肽peptide(GPLGIAGQ)单元,得到具有金属基质蛋白酶响应性的聚合物PLA-b-peptide-b-PLA.通过同轴电喷方法制备得到以PLA-b-peptide-b-PLA和抗肿瘤药物DOX的混合物作为内核,亲水性聚乙二醇(PEG)作为外壳的,具有核-壳结构的载药微球.其中水溶性的PEG壳层可在水环境中迅速脱除,将载药微球的尺寸从微米级减小到纳米尺度,可以达到药物载体系统在输运的循环过程中的尺寸递减.制备的纳米载体可在金属基质蛋白酶存在的环境中,响应性释放所包载的抗肿瘤药物,实现药物的控制释放.     

超支化/星型双亲性聚合物作为药物载体研究新进展

双亲性聚合物是一类既具有良好的亲水性质,又具有疏水性质的聚合物,作为药物载体有很好的应用潜力。由于超支化聚合物及星型聚合物具有独特的拓扑结构,分子内存在空腔,可以包埋更多的药物,并且聚合物含有丰富的端基官能团,可以将较多的亲水基团引入端基,使其与体液有更好的相容性,所以超支化/星型聚合物作为药物载体已经成为研究的热点。本文综述了近些年来超支化/星型双亲性聚合物应用在药物传导领域的研究状况,重点介绍了超支化聚合物和星型聚合物载药体系,包括超支化聚甘油药物载体和含聚己内酯的星型聚合物药物载体。对聚合物作为药物载体所涉及的负载与释放方式进行了总结。     

pH响应型苯硼酸酯缀合物的制备、表征和智能释放研究

以葡聚糖(Dextran)作为主链,将罗丹明B(Rh B,荧光智能释放药物模型/示踪显像)、3-羟基苯硼酸(PBA)酯化后,缀合到葡聚糖上,形成一种新型p H响应的高分子缀合物.由于该高分子缀合物中存在硼酸酯键,使得其负载模型药物到达肿瘤细胞的溶酶体之后释放出罗丹明B,不仅降低了药物毒性,还能够示踪药物的递送过程.体外模拟释放结果表明,缀合物在癌细胞的溶酶体/内涵体(p H 5)内能很好地释放出罗丹明B,而在药物输送过程(p H 7.4)中有很少的罗丹明B释放出来.另外,高分子载体葡聚糖的存在,使聚合物体现出良好的生物相溶性,从而减少了对正常组织的伤害,在抗癌药物的智能释放方面具有很好的应用前景.     

一种新型的可生物降解的热敏凝胶微粒的制备

聚合物水凝胶是由高分子组成的三维空间交联网络与水的混合体系,有望在药物控制释放等领域获得广泛应用,某些水凝胶还具有显著的环境响应性,构成了一类主流的智能材料,在生物医用材料领域,对于材料的可降解性有严格要求,而单一的可降解药物缓释载体材料和单一的智能型水凝胶材料已有较多报道,但能够将这两种特性结合在同一种材料中的报道则很少,其中智能响应范围合适、降解速率易于大范围调节的合成水凝胶则更少。     

含醛基可降解嵌段共聚物的合成及其生物缀合

以PEO-DDMAT为大分子RAFT试剂、BPO为引发剂,调控含醛基单体4-乙烯基苯甲醛(VBA)与不饱和环缩醛单体5,6-苯基-2-亚甲基-1,3-二氧七环(BMDO)的RAFT共聚合,获得一种新型含醛基、可降解的两亲性嵌段共聚物PEO-b-poly (VBA-co-BMDO),并对不同单体投料比下的共聚行为进行了研究.由于聚合物主链含有酯基,可以在水中碱性条件下进行降解.细胞毒性分析表明其具有良好生物相容性.该嵌段聚合物还可以通过醛基-氨氧基“点击”反应和模型生物分子氨氧基胆固醇(H2NO-Chol)形成稳定的聚合物-生物分子缀合物,该缀合物能在水溶液中自组装成纳米胶束.结果表明PEO-b-poly (VBA-co-BMDO)可以作为聚合物载体缀合含氨氧基的药物分子,在生物医药方面有良好的应用前景.     

壳聚糖基质与蛋白质药物的释放

为了达到治疗的目的,很多蛋白质药物正在被广泛地研究,但是目前蛋白质药物仍然存在着很多问题,如容易变性,被蛋白酶降解而失去疗效等等。如果使用合适的药物载体,就可以保护蛋白质药物不被酶降解并能控制药物的释放,达到缓释或者控释的目的,这将有助于延长药物在体内的生物活性。壳聚糖作为天然的生物大分子,被广泛地应用在生物材料、制药工业和医疗卫生领域中。本文主要介绍了壳聚糖基质具有适合作为药物缓释载体的特性,并分析了影响药物包封率和微球释放药物速率的因素。     

聚合物/SiO2杂化材料在药物控制释放中的应用*

聚合物用作药物控制释放载体时,具有释药浓度可控、药物的生物利用率高、可实现靶向治疗等优点。但有些聚合物也存在机械强度低、化学稳定性差、生物相容性不理想等缺点。二氧化硅(SiO₂)具有多孔、无毒、生物相容性好、化学和机械稳定性高、表面易功能化等优点。但SiO₂用作药物控制释放载体时,有时也存在载药量低、不能装载大分子药物、不能实现靶向释放等缺点。聚合物/SiO₂杂化材料作为药物控制释放载体,可有效结合二者的优点,并克服二者的缺陷。根据聚合物的种类和杂化体系性质的不同,我们分别对温敏性聚合物/SiO₂杂化材料、聚电解质/SiO₂杂化材料、生物高分子/SiO₂杂化材料以及其它一些聚合物/SiO₂杂化材料体系在药物控制释放中的应用进行了介绍,并展望了该领域今后的研究发展方向。     

Use of quasi-SMILES to model biological activity of “micelle–polymer” samples

The basic task of the drug discovery is the establishing of molecular structure of new pharmaceutical agents. To define the molecular structure is only half of the way to new drug. The transport of active molecules to appropriate targets in an organism should be elucidated in details. The selection of polymeric structures playing the role of basis for transport of therapeutic agents into the body is one of the ways to solve the task. Drug loading capacity (DLC) and critical micelle concentration (CMC) are measures of ability of “polymer–micelle” systems to be suitable for the process of the transport of therapeutic agents into an organism. Polymeric micelles are a type of complex multi-phase and multicomponent chemical process and can be used to transport drug into an organism. Prediction of ability of “micelle–polymer” systems to be a tool for transport of therapeutic agents to targets in organism is an important task. Models, which are a mathematical function of available eclectic information about architecture of micelles and polymers, are suggested. The eclectic data are represented via the so-called quasi-simplified molecular input-line entry system (SMILES), which are analogy of traditional SMILES. The quasi-SMILES contain some additional information besides the molecular architecture (physicochemical and biochemical conditions). Predictive potential of these models is good.

     

Effect of Oxygen on Surface Properties and Drug Release Behavior of Plasma Polymer of n-Butyl Methacrylate

The effects of oxygen on the chemical structure, morphology, hydrophilicity and drug release behavior of radio-frequency plasma poly n- butyl methacrylate （PPBMA） thin film were carded out for the first time. ATR-FTIR and XPS showed that oxygen had little influence on the chemical structure and composition of PPBMAs, which did not agree with the thought that the presence of oxygen gas would increase the oxidized carbon functionalities in the plasma polymer. SEM and static contact angle measurement indicated that in case of deposition with oxygen, the smoothness and hydrophilicity of PPBMA were dramatically improved. The drug release behavior showed that drug release from the PPBMA coating without oxygen was biphasic patterns, while from PPBMA coating with oxygen was Higuchi release. These results were helpful for the design and tailoring of the PPBMA polymer film and other of plasma polymers film, but could provide a new idea for the drug release controlled form.     

Swelling and drug release behavior of poly(2-hydroxyethyl methacrylate/itaconic acid) copolymeric hydrogels obtained by gamma irradiation

The new copolymeric hydrogels based on 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) were prepared by gamma irradiation, in order to examine the potential use of these hydrogels in controlled drug release systems. The influence of IA content in the gel on the swelling characteristics and the releasing behavior of hydrogels, and the effect of different drugs, theophylline (TPH) and fenethylline hydrochloride (FE), on the releasing behavior of P(HEMA/IA) matrix were investigated in vitro. The diffusion exponents for swelling and drug release indicate that the mechanisms of buffer uptake and drug release are governed by Fickian diffusion. The swelling kinetics and, therefore, the release rate depends on the matrix swelling degree. The drug release was faster for copolymeric hydrogels with a higher content of itaconic acid. Furthermore, the drug release for TPH as model drug was faster due to a smaller molecular size and a weaker interaction of the TPH molecules with(in) the P(HEMA/IA) copolymeric networks.     

Mathematical Modeling of Drug Release from Microemulsions: Theory in Comparison with Experiments

The topic of this paper is the study of the drug release from a drug-loaded microemulsion by reverting to a new mathematical model overcoming some drawbacks of previously proposed models. In particular, attention is focused on the mathematical expression of the drug fluxes existing between the oil and water phases during drug release. Indeed, not only the drug release kinetics, but also the drug oil-water partition coefficient strongly depend on these fluxes. Two microemulsion are considered: the first is composed by water, Tween80 as surfactant, and Triacetin as oil phase, while the second is composed by water, Tween80 as surfactant, and a Triacetin-benzylic alcohol mixture (1 : 1) as oil phase. Both of them are loaded by Nimesulide, an oil-soluble drug of considerable industrial relevance. The drug release is performed by resorting to a permeation experiment (Franz cells apparatus) as it demonstrated to be the most reliable methodology. The good agreement between the experimental permeation data and the model best-fitting ensures that the most important phenomena ruling this kind of drug release were properly accounted for by the new proposed model. Copyright 2000 Academic Press.     

质子交换膜燃料电池及电池组模型分析

本文对现有质子交换膜燃料电池以及电池组模型进行比较分析,认为数学模型的建立,可以增加对燃料电池及电池组内部的传递现象和反应机理的认识,同时可以预测电池以及电池组的性能,并且对优化电池结构参数具有指导意义.模型分析包括了现阶段质子交换膜燃料电池单电池模型和电池组模型的基本类别,它们是单电池CFD数值模拟模型、单电池以及电池组性能模拟模型、燃料电池组气体分配模型、系统模型和非稳态模型.比较了几种模型的建模方式及不同模型的应用范围和各自的优缺点.     

Cellular automata models of chemical systems

This paper describes the use of kinematic, asynchronous, stochastic cellular automata to model liquid properties, solution phenomena and kinetic phenomena encountered in complex biological systems. Cellular automata models of dynamic phenomena represent in silico experiments designed to assess the effects of competing factors on the physical and chemical properties of solutions and other complex systems. Specific applications include solution behavior, separation of immiscible liquids, micelle formation, diffusion, membrane passage, first- and second-order chemical kinetics, enzyme activity and acid dissociation. Cellular automata is thus considered as providing an exploratory method for the analysis of dynamic phenomena and the discovery and understanding of new, unexpected phenomena.     

A Method to Determine the Dimension of Long-Time Dynamics in Multi-Scale Systems

Modeling reaction kinetics in a homogeneous medium usually leads to stiff systems of ordinary differential equations the dimension of which can be large. The problem of determination of the minimal number of phase variables needed to describe the characteristic behavior of large scale systems is extensively addressed in current chemical kinetics literature from different point of views. Only for a few of these approaches there exists a mathematical justification. In this paper we describe and justify a procedure allowing to determine directly how many and which state variables are essential in a neighborhood of a given point of the extended phase space. This method exploits the wide range of characteristic time-scales in a chemical system and its mathematical justification is based on the theory of invariant manifolds. The procedure helps to get chemical insight into the intrinsic dynamics of a complex chemical process.     

欠电位沉积研究现状——I.欠电位沉积理论

欠电位沉积(upd)具有重要的理论和应用价值, 一直是电化学领域的研究热点. upd 过程理论研究的实质主要为围绕沉积基体、沉积物种和阴离子(或其他有机添加剂)三者在upd过程中的相互作用关系和规律的研究. 本文从upd 过程热力学和动力学两个方面出发, 系统地概述了近年来国内外在upd 理论研究方面的进展.在upd过程热力学方面, 从欠电位位移(ΔE_upd)、upd电吸附价(γ)、温度对upd的影响和电化学吸附等温线四个方面进行了阐述, 概括和分析了upd 过程热力学研究中涉及的相关数学表达式及其应用; 在其动力学方面, 主要概述了upd成核和生长过程动力学, 总结介绍了借助相关数学模型在分析upd过程动力学特征方面的研究. 此外, 简单介绍了计算化学在upd 研究中的应用成果; 最后, 总结了upd 的理论研究现状并展望了upd 的未来研究方向.     

A comprehensive study of concepts and phenomena of the nonspecific adsorption of beta-lactoglobulin.

We investigate nonspecific protein adsorption processes by comparing experimentally measured adsorption kinetics of beta-lactoglobulin with mathematical models. The adsorption and desorption behavior of this protein on a hydrophilic glass surface in citrate buffer (pH 3.0), monitored for a large set of different bulk concentrations (0.5x10(-8) M-1.5x10(-6) M) using a supercritical angle fluorescence (SAF) biosensor, is reported. Increasing adsorption rates and overshootings in the beginning of the adsorption are observed as well as a transition to an almost irreversibly bound state of the protein in the long term. Furthermore, rinsing experiments prove that adsorbed proteins abruptly change their desorption behavior from irreversible to reversible when a critical surface coverage theta(crit) is reached. Based on all experimental observations, a mathematical model composed of three adsorbed states differing in their surface affinity is proposed. Terms to account for lateral interactions between surface-bound proteins are included, which yield an excellent fit of the measured kinetics. For the first time, several phenomena that have been discussed in theoretical studies are confirmed by comparing experimental data with a single model.     

Contribution of concentration-dependent surface diffusion in ternary adsorption kinetics of ethane, propane and n-butane in activated carbon

The role of concentration-dependent surface diffusion in the adsorption kinetics of a multicomponent system is investigated in this paper. Ethane, propane and n-butane are selected as the model adsorbates and Ajax activated carbon as the model adsorbent. Adsorption equilibrium isotherm and dynamic parameters extracted from single-component systems are used to predict the ternary adsorption equilibria and kinetics. The effect of concentration-dependent surface diffusion on the adsorption kinetics predictions is studied by comparing the results of two mathematical models with the experimental data. Three diffusion mechanisms, macropore, surface and micropore diffusions are incorporated in both models. The distinction between these two models is the use of the chemical potential gradient as the driving force for the diffusion of the adsorbed species in one model and the concentration gradient in the other. It was found that the model using the chemical potential gradient provides a better prediction of the ternary adsorption kinetics data, suggesting the importance of the concentration dependency of the surface diffusion, which is implicitly reflected in the chemical potential gradient. The kinetic model predictions are also affected by the way how single-component adsorption equilibrium isotherm data are fitted.