乙二醇-聚(咪唑丙基-天冬酰胺)-聚丙氨酸三嵌段共聚物的合成及其pH-响应性药物控制释放性能的研究

聚天冬氨酸及其衍生物是一种具有良好生物相容性和可生物降解性的高分子材料, 被广泛应用于生物医药领域. 本研究通过大分子引发剂ω-胺基-α-甲氧基聚乙二醇引发N-羧基-α-氨基环内酸酐开环聚合和N-(3-氨丙基)咪唑侧基改性, 制备了一种侧链含有咪唑丙基的聚乙二醇-聚(咪唑丙基-天冬酰胺)-聚丙氨酸三嵌段共聚物. 在水溶液中, 此聚合物可自组装形成一种核-壳-冠型的三层共聚物胶束, 其中疏水性的聚丙氨酸链段自聚集形成胶束的核, 聚(咪唑丙基-天冬酰胺)链段形成具有pH-响应性的壳层, 用于包埋和释放药物, 外围的聚乙二醇链段可以提供一个稳定的水合冠层, 延长药物的体内循环时间. 利用咪唑环与游离阿霉素之间的π-π相互作用和疏水相互作用可以在自组装的过程中将阿霉素包埋到胶束内. 研究发现, 载药胶束随环境pH 值的降低药物的释放速率显著增加. 这主要是由于咪唑环在酸性条件下的质子化导致链段亲疏水性质发生明显变化.     

新型核壳型亲水聚合物-硅胶杂化填料的合成及其在蛋白质N-糖链富集中的应用

蛋白质的N-糖基化修饰与多种重要的生理、病理进程密切相关,是多种重大疾病诊断标志物研究的热点。由于糖蛋白本身多是低丰度表达的蛋白质,且糖链结构具有高度微不均一性,这使得蛋白质糖基化修饰的分析具有一定的挑战。本研究利用表面引发-原子转移自由基聚合(SI-ATRP)法,以带有双键的氨基葡萄糖为单体(GMAG),成功制备了新型核壳型亲水聚合物-硅胶杂化填料(pGMAG-SiO₂)。由于在硅胶表面引入致密的亲水聚合物层,该填料不仅保持了硅胶良好的机械强度,而且显著提高了其亲水性,因此非常适合作为亲水填料用于蛋白质的N-糖链富集。以麦芽七糖和鸡卵清蛋白的N-糖链为研究对象,考察了该填料对N-糖链的富集效果,并将该杂化填料成功用于人血浆中糖蛋白N-糖链的富集检测,共鉴定了47种糖型。以上结果表明,pGMAG-SiO₂填料对N-糖链具有较高的亲和性,可以用于N-糖链的高覆盖率鉴定。     

pH响应性含氟三嵌段共聚物的制备及性质研究

以苄醇(BzOH)与氢化钾(KH)反应形成的氧阴离子作为引发剂, 依次引发甲基丙烯酸-2-(N,N-二甲氨基)乙酯(DMAEMA, 简称DMA)、甲基丙烯酸-2-(N,N-二乙氨基)乙酯(DEAEMA, 简称DEA)和甲基丙烯酸-(2,2,3,3,4,4,5,5-八氟)戊酯(OFPMA)进行氧阴离子聚合, 获得含氟三嵌段共聚物PDMA-b-PDEA-b-POFPMA和PDEA-b-PDMA-b-POFPMA. 共聚物的化学结构可以通过不同单体的加料顺序和各种单体的投料量加以控制. 通过¹H NMR, ¹⁹F NMR和GPC测试, 研究聚合物的结构、分子量及分子量分布. 利用表面张力、荧光探针法、Zeta电位和透射电镜等测试方法, 研究共聚物在不同pH值的水溶液中的聚集行为.     

含萘酰亚胺基团的亲水性荧光聚合物作为微生物反应器的荧光探针的研究

研究并制备了一种含有萘酰亚胺荧光基团的新型亲水性共聚物P（NI—HEMA）．在pH值5．8到8．0范围内,该聚合物的薄膜在水溶液中显示出明显的荧光变化和极好的线性相关性．尤其是利用等吸收点406nm作为激发波长,可以避免紫外线的辐射和光密度变化引起的误差．同时,该聚合物的膜显示了很好的稳定性和亲水性．由于合成简单、价格低廉,并且对于pH值有高度线性相关性,该亲水性生物传感器聚合物薄膜可作为廉价高效pH探针,在生物微反应器中的高通量的生物工艺有很大的应用潜力．     

固相萃取-超高效液相色谱-电喷雾串联质谱法同时检测尿样中的麻黄碱和N-甲基麻黄碱

建立了固相萃取-超高效液相色谱-电喷雾串联质谱(SPE-UPLC-ESI MS/MS)联用方法,定量测定尿样中的麻黄碱和N-甲基麻黄碱。样品经Oasis MCX柱提取、纯化和富集后,采用电喷雾(ESI)离子源电离,正离子多反应监测(MRM)模式质谱进行定性和定量分析。麻黄碱和N-甲基麻黄碱在0.0250~2.50 μg/L质量浓度范围内线性关系良好,线性相关系数分别为0.9998和0.9992,提取回收率高于80%,提取效率的RSD小于5.0%,检出限均达到0.01 μg/L,可大大延长尿样检材中麻黄碱和N-甲基麻黄碱的检测周期。结果表明,该方法快速、准确,为尿液中痕量麻黄碱和N-甲基麻黄碱的分析提供了灵敏的分析方法。     

双重响应性生物基自修复凝胶的制备及其性能

为拓宽多重响应性凝胶在生物医学领域中的应用,本文基于生物大分子构筑具有pH响应、糖响应性的可自修复性水凝胶。 本文选用3-氨基苯硼酸(APBA)和2,3-环氧丙基三甲基氯化铵(CHGTA)分别对聚谷氨酸(γ-PGA)和瓜尔胶(GG)进行改性制备了聚谷氨酸-g-氨基苯硼酸(γ-PGA-g-APBA)和阳离子瓜尔胶,在此基础上,对γ-PGA-g-APBA和阳离子瓜尔胶进行物理共混制备生物基凝胶。 通过傅里叶变换红外光谱仪(FTIR)、核磁共振波谱仪(¹H NMR)和流变仪对聚合物化学结构、接枝率、流变性能和力学性能进行表征,并考察了凝胶在不同pH值及糖浓度下刺激响应性。 结果表明,凝胶具有自修复性,修复效率可达100%;具有pH响应性,在环境pH值较高时更易形成凝胶,且凝胶强度随pH值升高而增大;同时所制凝胶具有糖响应性,在4 g/L的葡萄糖溶液中浸泡后即可导致凝胶解体。 这些结果说明功能基团APBA的引入可赋予凝胶多重响应性。 所制的双重响应性生物基凝胶具有良好的生物相容性,有望应用于生物医学、功能器件、传感等领域。     

一种两亲性pH响应嵌段共聚物PEG-b-AAm的合成

以偶氮二异丁腈(AIBN)作为引发剂,通过可逆加成-断裂链转移聚合反应(RAFT)将一种新型的具有pH响应能力的共聚物链段(E)-3-((2-氨基乙基)氨甲酰)-6-甲基丙烯酰胺基-2-甲基-6-氧代苯-2-烯酸,及疏水的甲基丙烯酸丙酯、亲水性的聚乙二醇(PEG)进行共聚,合成了一种具有良好酸性响应能力的两亲性嵌段共聚物(PEG-b-AAm)。性能研究结果表明：嵌段共聚物PEG-b-AAm分子结构特征明确,能在水溶液中有效自组装成粒径100～200 nm的球状胶束;加入pH 5.5的醋酸钠缓冲液后,胶束逐渐发生崩解。     

配体结构对含2-甲基咪唑及N-乙基咪唑的NAMI 衍生物水解及溶液稳定性的影响

制备并用UV、循环伏安(CV)和NMR 法研究了NAMI(新抗肿瘤转移抑制剂, trans-[RuCl₄(DMSO)(imidazole)]Na·2DMSO)衍生物trans-[RuCl₄(DMSO)(2-MeIm)]Na·2DMSO (2-MeIm＝2-甲基咪唑, 化合物1)和trans-[RuCl₄(DMSO)-(N-EtIm)]Na·2DMSO (N-EtIm＝N-乙基咪唑, 化合物2)的水解机理-动力学、溶液稳定性和电化学性质. 化合物1 和化合物2 与NAMI 相似, 在pH 7.40 的缓冲溶液中发生两步脱氯水解反应(I 氯水解及II 氯水解) (分步反应); 在酸性溶液(pH 5.00)中脱DMSO 水解. 通过线性拟合得到各水解反应速率常数k_obs 及半衰期t_1/2. 结果表明化合物在酸性溶液中的稳定性相对较高. 在NAMI 衍生物咪唑环的N 位引入乙基比在2 位引入甲基生成的化合物稳定. 含氮配体相同时,NAMI-A(新抗肿瘤转移抑制剂, A: 该系列中的第一个化合物, trans-[RuCl₄(DMSO)(imidazole)][Himidazole])衍生物略比相应的NAMI 衍生物稳定.     

在硅胶表面制备牛血红蛋白分子印迹聚合物

采用表面印迹法, 以乙烯基三甲氧基硅烷修饰的硅胶为载体, 丙烯酰胺为功能单体, N,N-亚甲基双丙烯酰胺为交联剂, 并将改性聚乙烯醇(PVA)作为辅助识别聚合物链(ARPCs)引入聚合体系中, 制备了牛血红蛋白分子印迹聚合物(MIP). 实验使用红外光谱分析了改性PVA的结构特征, 用扫描电镜(SEM)观察MIP的表面形貌, 考察了ARPCs的含量对MIP吸附性能的影响. 吸附动力学实验研究表明, 聚合体系中ARPCs的引入使MIP对模板牛血红蛋白(BHb)的吸附量明显提高|十二烷基磺酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)结果显示, MIP对BHb的特异性吸附能力明显提高.     

MePEG-b-PCL-b-PDMAEMA的可控合成及性能研究

采用可控开环聚合(ROP)和原子转移自由基聚合(ATRP)相结合的方法制备出一系列单甲氧基聚乙二醇-b-聚(ε-己内酯)-b-聚甲基丙烯酸-N,N-二甲氨基乙酯(MePEG-b-PCL-b-PDMAEMA). 采用核磁(¹H NMR)和凝胶渗透色谱(GPC)研究了聚合物的结构并对聚合物的分子量大小和分布进行了表征. 聚合物的热稳定性能、结晶性能和亲水性能分别由热重分析仪(TGA)、X-衍射仪(XRD)和静态水滴接触角测定. 分别采用荧光光谱法和¹H NMR(以D₂O为溶剂)方法研究了聚合物纳米粒子的形成. 激光光散射(DLS)和透射电镜(TEM)研究结果表明聚合物纳米粒子具有球形结构, 粒子大小在40～70 nm之间并且对外界环境具有pH敏感性能. MePEG-b-PCL-b-PDMAEMA纳米粒子在同时包裹带有正电荷药物以及疏水性药物方面具有潜在的应用前景.     

Electrocatalytic oxidation of some biologically important compounds at conducting polymer electrodes modified by metal complexes

Conducting poly(3-methylthiophene) electrodes were electrochemically prepared. The resulting polymer films were modified with an inorganic complex, ferrocene. The incorporation of the ferrocene/ferrocenium moiety into the polymer film resulted in enhanced charge transfer towards the oxidation of some organic molecules of biological interest. The electrochemical response of the complex-containing polymer electrode was compared to that of the unmodified polymer electrode and that of the substrate. Apparent diffusion coefficients of the redox species were estimated from the cyclic voltammetric data for different biological molecules at the ferrocene-containing polymer electrode. Infra-red spectroscopic measurements for the “as-grown” films revealed the presence of the inorganic complex within the polymer. The modified polymer electrode showed noticeable enhancement for the charge transfer across the film interface and can be used as an electrochemical sensor for biological compounds. Received: 3 June 1997 / Accepted: 7 July 1997     

AgBF4-impregnated poly(vinyl phenyl ketone): an ethylene sensing film

Incorporation of silver tetrafluoroborate (AgBF4) into poly(vinyl phenyl ketone) (PVPK) renders the photoluminescent polymer responsive to ethylene. Polymer films prepared with a 2:1 ratio of Ag+ ions to polymer acetophenone groups responded with a quench of photoluminescence. Conditioned films showed a luminescence quench that was proportional to ethylene concentration before saturation occurred. Stern-Volmer analysis of the photoluminescence response suggested the presence of sites that were accessible and sites that were inaccessible to ethylene. Perturbations in polymer-metal interactions were monitored with infrared spectroscopy, revealing changes upon Ag+ incorporation, polymer film conditioning, and exposure to ethylene.     

Investigation of relative humidity effects on the response behavior of a pH indicator-based OWG vapor sensor

The response of a pH indicator-based optical waveguide sensor was characterized with respect to the effects of relative humidity (RH) on the magnitude of the sensor response, and on the rate of response to both hydrochloric acid and ammonia/ammonium hydroxide vapors. Water vapor constitutes both a chemical and a systematic (optical) interference for the OWG sensor response to hydrochloric acid. Swelling of the polymer films upon exposure to water vapor results in a decrease in the loss of light at the polymer/air interface, resulting in an increase in the sensor signal. In addition, high RH conditions decrease the bromothymol blue indicator response to hydrochloric acid vapor. In contrast, the bromothymol blue indicator response to ammonia increases as the RH increases. High RH levels also increases the rate of diffusion (transport) of hydrochloric acid into (and out of) Nafion films, but does not affect the diffusion rate for poly(vinyl alcohol) polymer films. The RH does not appear to have any significant effect on the rate of transport of ammonia in any of the polymer films studied.     

Electrochemical studies of nafion–trimethylsilyl and nafion–trimethylsilyl/Ru complex-modified electrodes

In this work, we report the electrochemical properties of the nafion–trimethylsilyl (Naf–TMS) polymer. First, we introduce a procedure to dissolve Naf–TMS polymer and the incorporation of ruthenium catalyst complexes into it. The inclusion of the catalysts involved two strategies. The first one concerned the direct formation of a Naf–TMS/Ru complex solution. The second one consists of depositing Naf–TMS solution on a glassy carbon electrode, followed by the incorporation of Ru complexes under potentiodynamic conditions. Electrochemical studies showed the good ion permeation capability of Naf–TMS membranes and its use as a good alternative approach to Nafion ion-conducting membranes. The analytical capabilities of Naf–TMS- and Naf–TMS/Ru-modified glassy carbon electrodes have been tested for the detection of dopamine in standard solutions. Detection limits in the order of nanomolar have been achieved with working ranges extending over three decades in concentration at pH 7.2. Further enhancement in the dopamine oxidation current was achieved by the incorporation of Ru complexes into the Naf–TMS polymer. This study offers a new insight into the investigation of Naf–TMS resin as an ion-conducting polymer.     

[SiNi(H2O)W11O39]6-多层组装膜修饰电极及其电化学行为

采用电化学生长法制备包含杂多酸[SiNi(H2O)W11O39]6-(SiNiW11)和聚合物阳离子PDDA的多层膜修饰电极, 利用循环伏安法研究其电化学行为、 pH的影响及其对BrO3-和NO2-体系还原的电催化性能;并对多层膜电化学过程机理进行了初步探讨. 结果表明: 多层膜的增长均匀, 峰电流随层数的增加而增加;多层膜的峰电流随扫速的增加而增加;还原峰的峰电位随pH的增加而负移.     

Counter-Ion Influence on Polypyrrole Potentiometric pH Sensitivity

The pH sensitivity of conducting polymer films is an important issue from the sensor design point of view. The doping and supporting electrolyte anions effect on the potentiometric sensitivity and response time of polypyrrole (PPy) electrodes towards changes of solution pH were studied. It was found that (i) the response of PPy doped by easily exchangeable common anions (Cl^–, NO₃ ^–, ClO₄ ^–) in their solutions (KCl, KNO₃, NaClO₄) is slow. In contrast, (ii) polypyrrole films deposited in the presence of weak acid anions (phthalates, oxalates, salicylates) were characterised by instantaneous responses in the above mentioned solutions. On the basis of electrochemical experiments (open circuit potential vs. time dependencies, cyclic voltammetry, EQCM), the observed differences were attributed to different mechanisms of pH sensitivity of tested films. The long response times are related to the incorporation of the solution ions into the film in order to compensate charges created due to protonation. On the other hand, if the ion-exchange is hindered as in the case of (ii), instantaneous open circuit responses are observed due to polarisation of the oxidised polymer layer, analogously to the metal electrode. Moreover, for these films the internal pH buffering within the polymer membrane will weaken the pH change effect.The mechanisms were confirmed in the course of studying the pH effect in solutions containing anions easily (KCl, NaClO₄, KNO₃) or hardly exchangeable with polypyrrole (K₂SO₄, sodium poly(4-styrenesulphonate) solutions) acidified with H₂SO₄.     

Kinetics of pH response for copolymer films with dilute carboxylate functionality

We have investigated the effects of film composition and thickness on the rate of pH-induced response of a copolymer film containing predominately polymethylene with randomly distributed carboxylic acid side groups (denoted as PM-CO2H). These responsive films are prepared directly onto a gold electrode surface by surface-catalyzed polymerization and subsequent hydrolysis. We measured electrochemical impedance at fixed frequency (100 Hz) to monitor the barrier properties of the polymer film during a step change in pH. At a 1-3% molar acid content, the copolymer films exhibit a 2 order of magnitude change in impedance at 100 Hz when the contacting solution pH changes from 11 to 4 (or 4 to 11). For all films, the rate of protonation is slower than that of ionization, consistent with a more gradual transfer of protons through an increasingly hydrophobic film at the outermost nanometers during the protonation step. Increased acid content within the film accelerates both the rate of protonation and ionization. Thinner films (50 nm) with the same acid content show faster response rate in both directions, since water and ions have a shorter transfer path. A large and reversible pH response was obtained for all films studied, but selection of appropriate film composition and thickness can greatly influence the rate of response.     

Preparation of Silica-Gel Film with pH Indicators by the Sol–Gel Method

Gel films with various pH indicators were prepared by the sol–gel method without catalysts. The obtained gel films showed good response for various pH solutions as optical pH sensors and no leaching of the indicators was observed. The feature of absorption spectra of the indicators in the gel films was almost the same as that in the aqueous solutions. pKa of the indicators in the gel films was shifted with the increase of the TMOS content in the starting solutions. These results suggest that the pH indicators in the gel films were trapped in similar environment as in the solutions.     

On-line fluorescent monitoring of the degradation of polymeric scaffolds for tissue engineering

Tissue engineering involves culturing, growing and assembling cells and newly generated matrix in polymeric scaffolds. To achieve a functional tissue in vitro, the cell-scaffold constructs are subjected to various stimulations during an incubation phase, which mimics the in vivo environment. In order to monitor the progression of tissue formation, there is a need for on-line and non-destructive methods of monitoring at the cellular and biomolecular level, for example, the assessment of scaffold degradation alongside the measure of matrix production. This study presents a proof of concept for monitoring scaffold degradation on-line within a culture environment. Using a mesoporous silica based approach, a pH sensitive fluorescent probe, fluorescein isothiocyanate (FITC), was incorporated into degradable polymeric scaffolds made from poly(L-lactic acid) which has a slow degradation rate, and poly(lactide-co-glycolide) which has a rapid degradation rate. The fluorescent probe was incorporated into thin films and three dimensional porous scaffolds demonstrating the capabilities of monitoring on-line. Following incubation, the intensity of fluorescence in the rapidly degrading scaffolds reduced with culture time in comparison to slow degrading polymeric scaffolds when observed qualitatively using fluorescent microscopy. The relationship between pH and fluorescent intensity was assessed, and the use of this technique for monitoring by-products via the solid scaffold by microscopy or through culture medium by a luminescence spectrometer is discussed. This study demonstrates that endowing scaffolds with a sensing element could provide an on-line and non-destructive monitoring method for tissue engineering.     

室温自交联丙烯酸酯乳液的制备与表征

使用3种含不饱和双键硅氧烷,乙烯基三(β-甲氧基乙氧基)硅烷(A172)、乙烯基三乙氧基硅烷(VTES)和γ-甲基丙烯酰氧丙基三甲氧基硅烷(A174)为功能单体,采用半连续乳液聚合法制备了室温自交联丙烯酸酯乳液,探讨了硅氧烷功能单体在不同pH条件下水解情况以及其种类和用量对乳液及乳胶膜性能的影响.结果表明,pH在7～9之间时硅氧烷功能单体水解最慢;A172在pH为8.4时5h内就水解完全;增加VTES和A174的用量均能提高乳胶膜的交联度、力学性能和耐水性.控制聚合过程的pH值以抑制硅氧烷功能单体的水解并调节乳液成膜时的pH值以加速硅氧烷功能单体的水解从而增强胶膜的交联程度,发现酸性或碱性条件下得到乳胶膜比中性条件下胶膜的力学和耐水性能均有不同程度的提高,并且在酸性条件下胶膜的性能提高最多.对比使用A174和VTES制备的胶膜,发现这种方法对含有A174胶膜的效果不明显,而含VTES胶膜的性能提高最为显著.