双网络增强自支撑多层膜的制备

通过石英晶体微天平(QCM)研究不同最外层对单体、交联剂、引发剂扩散入多层膜的结果显示,聚乙烯亚胺( PEI)为最外层的多层膜更有利于负电荷分子扩散.将(聚乙烯亚胺/聚丙烯酸)12-聚乙烯亚胺[( PEI/PAA)12-PEI]多层膜浸入带有单体、引发剂、交联剂的溶液后,经过光聚合交联与热交联后可形成自支撑膜.XPS数...     

壳聚糖修饰纳米纤维膜表面对氧化还原酶行为的影响

采用静电纺丝法制备了丙烯腈/丙烯酸共聚物(PANCAA)纳米纤维膜, 研究了纺丝液浓度对纤维形态的影响, 以扫描电子显微镜观察纤维形貌, 遴选得到最佳纺丝条件. 以1-乙基-3-(N,N-二甲基氨基丙基)碳二亚胺/N-羟基丁二酰亚胺(EDC/NHS)为偶联剂, 在纤维膜表面引入壳聚糖修饰层, 采用衰减全反射傅里叶变换红外光谱(ATR/FTTIR)、水接触角和称重法考察了修饰前后膜的变化. 通过戊二醛将过氧化氢酶固定到壳聚糖修饰的PANCAA纳米纤维膜上, 研究了壳聚糖及戊二醛浓度对固定化过氧化氢酶的影响, 结果表明, 在壳聚糖浓度为25 mg/mL及戊二醛质量分数为5%条件下, 壳聚糖修饰膜的固定化酶活性比空白膜提高了41.7%, 稳定性也得到了不同程度的提高.     

(肝素/壳寡糖/Pluronic(R))静电组装多层膜的构建

以壳寡糖/Pluronic(R)聚合物纳米聚集体(COPNs)、肝素为组装基元构建仿(肝素/壳聚糖)多层膜,验证多层膜负载疏水药物的可行性.Pluronic(R)P123与1,3-丙烷磺内酯反应合成末端磺酸化的Pluronic(R)聚合物,其与Pluronic(R)F127在水溶液中自组装形成表面带负电荷的混合胶束.利用壳寡糖与混合胶束的静电作用,获得COPNs,粒径与表面电位分析、透射电镜表征COPNs为直径(27.61±2.46) nm、表面zeta电位(6.12±1.82)mV、稳定的球形结构.石英晶体微天平(QCM)跟踪检测证明COPNs与肝素可在基材表面实现交替沉积;原子力显微镜(AFM)表征多层膜表面拓扑形貌,证明COPNs在表面沉积过程中稳定.将疏水的荧光探针芘载入COPNs参与多层膜的构建,荧光光谱实验结果表明多层膜可成功包载芘,且多层膜内芘的载入量与组装层数相关.以葛根素为模型药物,载药量测定与体外释药实验结果表明多层膜具有包载和缓释疏水药物的能力.     

硫酸交联壳聚糖膜质子传导行为的研究

制备了硫酸交联壳聚糖膜, 通过研究其质子传导性能、力学性能、化学成分及结构变化, 分析了硫酸与壳聚糖分子间的交联方式, 并对质子传导机理进行了解析. 结果表明, 硫酸交联可显著改善壳聚糖膜的质子传导能力与力学性能, 这种改善作用在交联6 h后趋于稳定, 交联6 h后的壳聚糖湿膜在室温下时质子传导率为0.0472 S• cm^－1, 比未交联的壳聚糖膜提高5倍左右. 硫酸交联壳聚糖膜中的质子传导率与温度的关系符合Arrhenius定律, 质子传导激活能为18 kJ/mol, 其传导机制应属于Grotthus机制. 硫酸对提高壳聚糖膜的质子传导能力主要有两方面的作用: (1) H₂SO₄可使壳聚糖分子中NH₂质子化形成NH₃^＋. (2) 处于两个氨基之间的SO₄^2－在质子传递过程中起离子桥梁作用, 参与以水分子为载体的质子传导过程, 从而减小质子传导的阻力, 提高了质子传导率.     

三偏磷酸钠交联壳聚糖/聚乙烯醇共混膜的制备及其性能研究

将充分溶胀的壳聚糖/聚乙烯醇共混膜置于一定浓度的三偏磷酸钠溶液中进行交联反应制备出交联壳聚糖膜。用红外光谱(FTIR-ATR)、X-射线衍射(XRD)和扫描电镜(SEM)表征了膜的结构,并测试了其吸水率、力学性能、酶降解性能。结果表明,交联作用明显提高了膜的抗张强度和抗水性,并有效地降低了溶菌酶对其降解速率。     

二醛纤维素交联壳聚糖膜的制备及其染料吸附性能

首先通过浓硫酸水解微晶纤维素(MCC)制备纳米纤维素(NCC)悬浮液,然后通过高碘酸钠选择性氧化NCC悬浮液制备二醛纤维素(DAC)水溶液,最后将DAC水溶液与壳聚糖(CTS)醋酸溶液混合,通过溶液浇注、溶剂蒸发法制得DAC交联CTS膜(DAC-CTS交联膜)。采用红外光谱(FT-IR)、交联度测试、耐酸稳定性测试表征了DAC-CTS交联膜的结构及性能,并研究了其作为吸附剂对阴离子染料活性艳蓝KN-R的吸附能力。结果表明:与纯CTS膜相比,DAC-CTS交联膜的耐酸稳定性与拉伸强度均明显提高;当m(DAC)∶m(CTS)=3%时,该交联膜达到最大饱和吸附量1 118.8mg/g;此外,DAC-CTS交联膜对活性艳蓝KN-R的吸附符合Langmuir吸附等温模型和准2级动力学模型。     

可控硬度多层膜对肿瘤细胞行为的影响

以层状组装多层膜为基础,利用电化学方法精确可控的特点,构建了具有不同硬度的多层膜,并研究了该材料体系对细胞行为的影响规律.采用恒电流法,将聚吡咯(PPy)均匀复合进入聚赖氨酸/透明质酸(PLL/HA)多层膜内部,通过控制通电时间得到不同交联度的(PLL/HA)n@PPy多层膜.利用纳米压痕技术测试了多层膜在交联前后的硬度变化,并进一步研究了该多层膜体系对肿瘤细胞的黏附、增殖和迁移行为的影响.     

三偏磷酸钠交联壳聚糖膜的制备及其性能研究

将充分溶胀的壳聚糖膜置于一定浓度的三偏磷酸钠溶液中进行交联反应制备出交联壳聚糖膜。用傅立叶变换红外光谱(FT-IR)、X-射线衍射(XRD)和扫描电镜(SEM)表征了其结构,并测试了其吸水率、力学性能和酶降解性能。研究结果表明,交联作用明显提高了膜的抗张强度和抗水性,并有效地降低了溶菌酶对其降解速率。该交联膜有望用作可控降解生物医用材料。     

PVA/PVP共混交联膜的渗透蒸发分离性质(Ⅰ)

研究了4,4'-双叠氮芪-2,2'-二磺酸钠和戊二醛对聚乙烯吡咯烷酮(PVP)、聚乙烯醇(PVA)共混膜的交联及交联对共混膜分离恒沸点附近的乙醇/水混合物的影响.结果表明,膜的分离性质随着膜中PVP含量的增加而改变;采用混合型交联剂对PVA/PVP共混膜交联能明显改善膜的选择性.     

基于多壁碳纳米管/壳聚糖多层膜修饰玻碳电极邻苯二酚的测定

改进了碳纳米管在壳聚糖溶液中的分散方法,制备了多壁碳纳米管/壳聚糖多层膜修饰玻碳电极,对比了不同修饰层数膜电极的循环伏安和电化学阻抗行为,5层多壁碳纳米管/壳聚糖膜修饰玻碳电极的电化学性能优良.在最优实验条件下,该修饰玻碳电极对邻苯二酚(CAT)有灵敏的响应,CAT浓度在3.99×10-6～9.09×10-4mol/L范围内与氧化峰电流呈良好的线性关系,检出限为2.39×10-6mol/L(S/N=3).该修饰玻碳电极性能稳定,测定4×10-5mol/LCAT溶液,RSD(n=10)为2.1%;15周后,该电极的响应值仅降低1.9%.     

Bioinert solution-cross-linked hydrogen-bonded multilayers on colloidal particles

Bioinert polyelectrolyte multilayers comprised of poly(acrylic acid) and polyacrylamide were deposited on colloidal particles (1.7 microm in diameter) at low pH conditions by layer-by-layer assembly using hydrogen-bonding interactions. The multilayer films were coated uniformly on the colloidal particles without causing any flocculation of the colloids, and the deposited films were subsequently cross-linked by a single treatment of a carbodiimide aqueous solution. The lightly cross-linked multilayer films show excellent stability at physiological conditions (pH 7.4, phosphate-buffered saline), whereas untreated multilayer films dissolved. The multilayer-coated surfaces, both on flat substrates and on colloidal particles, exhibit excellent resistance toward mammalian cell adhesion. With this new solution-based cross-linking method, bioinert H-bonded multilayer coatings offer potential for biomedical applications.     

Robust ion-permselective multilayer films prepared by photolysis of polyelectrolyte multilayers containing photo-cross-linkable and photolabile groups

The azobenzene-containing polyanion PAC-azoBNS was alternately assembled with the polycation diazoresin (DAR) to construct photo-cross-linkable multilayer films of PAC-azoBNS/DAR that contain photolabile groups of azobenzene. Upon mild UV irradiation, the interaction between PAC-azoBNS/DAR multilayers was converted from electrostatic interaction to covalent bonds. Because of the free carboxylic acid groups presented in the film, the photo-cross-linked multilayer film favors the selective permeation of positively charged species. After photolysis of the photo-cross-linked PAC-azoBNS/DAR films with intense UV irradiation, azobenzene groups decompose to produce imine groups, and a photo-cross-linked robust film containing free carboxylic acid and imine groups was fabricated. The resultant film allows the permeation of negatively charged species and meanwhile shows a pH-switchable permselectivity for positively charged species. Because of the covalently cross-linking structure, the photolyzed cross-linked PAC-azoBNS/DAR film shows high reversible switching behavior and has high stability in solution with high ionic strength.     

Mussel-inspired chemistry for robust and surface-modifiable multilayer films

In this article, we report a bioinspired approach to preparing stable, functional multilayer films by the integration of mussel-inspired catechol oxidative chemistry into a layer-by-layer (LbL) assembly. A polyanion of poly(acrylic acid-g-dopamine) (PAA-dopamine) bearing catechol groups, a mussel adhesive protein-mimetic polymer, was synthesized as the building block for LbL assembly with poly(allylamine hydrochloride) (PAH). The oxidization of the incorporated catechol group under mild oxidative condition yields o-quinone, which exhibits high reactivity with amine and catechol, thus endowing the chemical covalence and retaining the assembled morphology of multilayer films. The cross-linked films showed excellent stability even in extremely acidic, basic, and highly concentrated aqueous salt solutions. The efficient chemical cross-linking allows for the production of intact free-standing films without using a sacrificial layer. Moreover, thiol-modified multilayer films with good stability were exploited by a combination of thiols-catechol addition and then oxidative cross-linking. The outstanding stability under harsh conditions and the facile functionalization of the PAA-dopamine/PAH multilayer films make them attractive for barriers, separation, and biomedical devices.     

可交联且可生物降解的高分子膜

高分子膜在生物医用、电子器件、食品包装,以及气体分离等领域有着广泛的应用。实际应用中往往通过交联提高其稳定性、强度等性能。然而,传统的交联高分子膜材料在温和环境下难以降解。针对这一挑战,本文分别基于聚(α-(肉桂酰氧基甲基)-1, 2, 3-三唑)己内酯(PCTCL₁₃₃)及其与己内酯(CL)的无规共聚物P(CL₁₅₆-stat-CTCL₂₈),通过溶液浇铸法制备了两种可交联且可生物降解的高分子膜。由于肉桂酸酯侧链阻止了PCL主链的结晶,因此PCTCL₁₃₃均聚物可形成透明膜,而P(CL₁₅₆-stat-CL₂₈)无规共聚物则形成半透明膜。该高分子膜可进一步在紫外光照射下交联,而所形成的交联膜结构可以在酸催化下充分降解。理论上,这两种膜材料均可完全降解为分子量小于300 g∙mol⁻¹的产物。而通过调节聚合物中己内酯的重量百分数以及膜的交联度,可以有效调节其降解速率、透明度等性能。在此基础上,我们进一步通过分子动力学模拟探究了溶液浇铸过程中高分子的不同初始浓度对膜材料杨氏模量的影响。结果表明,随着初始浓度上升,由于分子链间的缠结程度升高,最终制备的膜材料具有更高的模量。因此,该可交联、可降解,且降解性能可调的高分子膜在生物医用领域具有一定的应用前景,并可拓展到其他领域以实现更为广泛的应用。     

Effect of Different Crosslinking Strategies on Physical Properties and Biocompatibility of Freestanding Multilayer Films Made of Alginate and Chitosan

Freestanding multilayer films prepared by layer‐by‐layer technique have attracted interest as promising materials for wound dressings. The goal is to fabricate freestanding films using chitosan (CHI) and alginate (ALG) including subsequent crosslinking to improve the mechanical properties of films while maintaining their biocompatibility. Three crosslinking strategies are investigated, namely use of calcium ions for crosslinking ALG, 1‐ethyl‐3‐(‐3‐dimethylaminopropyl) carbodiimide combined with N‐hydroxysuccinimide for crosslinking ALG with CHI, and Genipin for crosslinking chitosan inside the films. Different characteristics, such as surface morphology, wettability, swelling, roughness, and mechanical properties are investigated showing that films became thinner, exhibited rougher surfaces, had lower water uptake, and increased mechanical strength after crosslinking. Changes of wettability are moderate and dependent on the crosslinking method. In vitro cytotoxicity and cell attachment studies with human dermal fibroblasts show that freestanding CHI‐ALG films represent a poorly adhesive substratum for fibroblasts, while studies using incubation of plastic‐adherent fibroblast beneath floating films show no signs of cytotoxicity in a time frame of 7 days. Results from cell experiments combined with film characteristics after crosslinking, indicate that crosslinked freestanding films made of ALG and CHI may be interesting candidates for wound dressings.     

Layer-by-layer assembled microgel films with high loading capacity: reversible loading and release of dyes and nanoparticles

Multilayer films containing microgels of chemically cross-linked poly(allylamine hydrochloride) (PAH) and dextran (named PAH-D) were fabricated by layer-by-layer deposition of PAH-D and poly(styrene sulfonate) (PSS). The successful fabrication of PAH-D/PSS multilayer films was verified by quartz crystal microbalance measurements and cross-sectional scanning electron microscopy. The as-prepared PAH-D/PSS multilayer films can reversibly load and release negatively charged dyes such as methyl orange (MO) and fluorescein sodium and mercaptoacetic acid-stabilized CdTe nanoparticles. The loading capacity of the film for MO can be as large as approximately 3.0 microg/cm2 per bilayer, which corresponds to a MO density of 0.75 g/cm3 in the film. The high loading capacity of the PAH-D/PSS films originates from the cross-linked film structure with sufficient binding groups of protonated amine groups, as well as their high swelling capability by solvent. The loaded material can be released slowly when immersing the films in 0.9% normal saline. Meanwhile, the PAH-D/PSS multilayer films could deposit directly on either hydrophilic or hydrophobic substrates such as quartz, polytetrafluoroethylene, polystyrene, poly(ethylene terephthalate), and polypropylene. The microgel films of PAH-D/PSS are expected to be widely useful as matrixes for loading functional guest materials and even for controlled release.     

一种卤键高分子多层膜的层层组装及其稳定性的提高

设计合成了聚甲基丙烯酸2-(4-碘-2,3,5,6-四氟苯氧基)乙酯( PIPEMA)和聚甲基丙烯酸3-(3-吡啶基)丙酯( PPyPMA),经过层层组装和随后的紫外可见光谱的检验,发现可以在丙酮和丁酮中组装PIPEMA/PPyPMA卤键多层膜,但是当以四氢呋喃(THF)或氯仿为组装溶剂时未能获得多层膜.另外,在丁酮中...     

Immobilization of cytochrome c on cysteamine-modified gold electrodes with EDC as coupling agent

Cyclic voltammetry has been applied for the characterization of cross-linked horse heart cytochrome c (HHC) on cysteamine-modified gold electrodes. The cross-linking, i.e. amide bond formation, between the proteins was achieved by using 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) as coupling reagent. The optimal conditions for the formation of the HHC film were determined by varying the HHC concentration. In addition the reproducibility, stability and the influence of the scan rate upon these films were investigated with cyclic voltammetry. The protein film stability in a 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer solution was tested by UV/vis absorption spectroscopy.     

pH-sensitive bipolar ion-permselective ultrathin films

pH-Sensitive bipolar ion-permselective films of polyelectrolyte multilayers were prepared by layer-by-layer (LbL) assembly and photo-cross-linking of benzophenone-modified poly(acrylic acid) (PAA-BP) and poly(allylamine hydrochloride) (PAH-BP). The multilayer structure and ionizable group composition was finely tuned by changing the pH of the dipping solution. This structure and composition was in turn "preserved" by photo-cross-linking, forming highly stable membrane films. Since PAA-BP and PAH-BP are weak polyelectrolytes, it is possible to control the number of unbound, un-ionized -COOH or -NH2 groups in the multilayer by changing the pH. Moreover, the pH of the deposited film also plays an important role in determining selective latter permselectivity. For example, PAA-BP/PAH-BP multilayers deposited from two pH conditions, pH = 3 (PAA-BP) and pH = 6 (PAH-BP), showed pH-switchable permselectivity for both cationic (pH = 10) and anionic (pH = 3) probe molecules in a single film. The system offers advantages in film stability and introducing reversible selective ion permeability over previous multilayer film and cross-linking methods.     

An Anticoagulant Activity System Using Nanoengineered Autofluorescent Heparin Nanotubes

Heparin (HEP) and periodate‐oxidized heparin (O‐HEP) nanotubes were prepared by combining the template method with a layer‐by‐layer (LbL) technique. The tubular structure was obtained and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and confocal laser scanning microscopy (CLSM). O‐HEP is one of the HEP derivatives that contains anticoagulant activity and preserves its ability for other effects. Chitosan (CHI) and O‐HEP have been used to fabricate nanotubes by covalent cross‐linking Schiff base reactions. It is demonstrated that the obtained nanotubes have the significant feature of autofluorescence without the addition of any fluorescent dyes and they retain their anticoagulation activity. Compared with O‐HEP/CHI nanotubes, HEP/CHI nanotubes show high anticoagulation activity and do not have autofluorescence. Furthermore, this method could be extended to other copolysaccharide derivatives for the preparation of autofluorescent nanomaterials.