Molecular Recognition Ability of Molecularly Imprinted Polymer Nano- and Micro-Particles by Reversible Addition-Fragmentation Chain Transfer Polymerization

The role of molecularly imprinted polymers (MIPs) is changing from academic to applied researches. Challenging problems about MIP will be more highlighted in applicable uses and solving these problems is vital. The controlled/“living” radical polymerization (CLRP) techniques are applicable to solve the challenging problems in MIPs. The “living” nature of CLRP helps to improve the heterogeneity of binding sites in MIPs as a main challenge where precise control over sizes, compositions, and surface functionalities is achieved. Among different techniques of CLRP, reversible addition-fragmentation chain transfer (RAFT) technique presents distinguished benefits such as compatibility and tolerance to a wide range of functional monomers and mild reaction conditions rather than other CLRP techniques. In this review, in order to obtain more insights into the potential benefits of RAFT polymerization in fabrication of nano and micro MIP networks, recent research in advanced MIP materials for different templates with improved morphology, efficiency, and binding capacities with respect to traditional free radical polymerization (FRP) will be discussed. MIPs prepared via RAFT method have advantages of MIPs as high performance molecular recognition devices and CLRP as controllable polymerization mechanism, simultaneously.     

An alternative approach to controlled release of oxprenolol from the implantable delivery system based on biodegradable copolymer and genistein

This paper describes the development of covalent star-shaped poly(L-lactide/?-caprolactone) random copolymer-oxprenolol (OXP) conjugates as a potential approach to controlling drug release from implantable delivery systems. We prepared synthesized materials containing 14–17 mol% OXP, which were conjugated via an ester bond. The conjugates, which were composed of biodegradable copolyester chains, natural genistein as a central core and drug, were characterized by hydrogen nuclear magnetic resonance (¹H-NMR), Fourier transform infrared spectroscopy (FTIR) and viscosity methods. We evaluated the cyto- and genotoxicity of the synthesized copolymeric matrices, followed by the conjugates, with bacterial luminescence, protozoan and Salmonella typhimurium TA1535 assays. Furthermore, we performed in vitro mammalian assays of the obtained products with V79 cells. We found that the in vitro release of OXP from the obtained star-shaped conjugates was dependent on the structure of the synthesized biodegradable matrices.     

可降解磷酸酯聚合物的合成与应用研究进展

磷酸酯类聚合物在自然界中可以降解,是环境友好的化学品.其中,分子量高的聚磷酸酯近年来在医药、塑料助剂等方面有广泛应用,分子量相对较低的磷酸酯类聚合物在饲料、表面活性剂等方面很重要.按用途的不同,综述了可降解磷酸酯聚合物的合成与应用近况.     

Drug permeation modeling through the thermo-sensitive membranes of poly(N-isopropylacrylamide) brushes grafted onto micro-porous films

Temperature-sensitive N-isopropylacrylamide (NIPAAm) polymer brushes of known molecular weight (20k–25k) were grafted onto micro-porous polycarbonate (PC) films (pore size 0.4 μm) using argon plasma treatment. The resulting composite membranes were tested for controlled drug release at various grafted chain density, which was controlled using 1–3% polymer concentrations. The composites were also characterized in terms of graft yield, membrane thickness, Fourier transform infrared (FTIR) spectra and scanning electron micrography (SEM). The drug permeabilities of 4-acetamidophenol and ranitidine HCl in the resulting membranes were determined at temperatures between 30 and 40 °C. The drug permeability changed remarkably at 34 °C, near the lower critical solution temperature (LCST). The drug passage was regulated by swelling (which occurs at a temperature lower than the LCST) or shrinkage (occurring at an elevated temperature) of the PNIPAAm polymer brushes. These membranes demonstrated on–off ratios of drug permeabilities up to 11 and 14 for the model drugs, respectively. These values are higher than most literature data with similar-size model molecules. The excellent on–off valve mechanism was discussed in terms of the suitable molecular weight and grafted chain density in relation to the pore size and porosity of the PC support. A mathematical model was proposed to predict the drug permeation flux based on the gel conformation data, graft density, characteristics of the micro-porous support, and drug concentrations and diffusivities in water and in the PNIPAAm gel. The model can successfully estimate the drug permeation flux through the composite with higher (0.42 mg cm⁻²) graft density with a coefficient of determination of 0.95. The discrepancy between the predicted and experimental data at the lower graft density (0.12 mg cm⁻²) was ascribed to pore channel narrowing resulting from the uneven polymer chain distribution.     

pH/温度双重敏感性微凝胶的合成与应用

智能微凝胶是一类具有独特物理、化学性质的聚合物网络和溶剂组成的体系, 在众多的领域具有潜在的应用.本文介绍了近年来pH和温度双重敏感性微凝胶的研究概况、制备方法及其在药物控制释放、分离纯化和光子晶体方面的应用.     

以混合表面活性剂为模板可控合成MCM-48和MCM-41分子筛

利用阳离子和三嵌段共聚物混合表面活性剂为模板,在水热条件、碱性介质中可控合成出MCM-48和MCM-41分子筛。在固定P123(聚氧乙烯-聚氧丙烯-聚氧乙烯三嵌段共聚物):TEOS(正硅酸乙酯)(物质的量的比)为0.01875的体系中,调节CTAB(十六烷基三甲基溴化铵)∶TEOS(正硅酸乙酯)物质的量比值m,当m在0.12~0.13范围合成出MCM-48分子筛;当m在0.04~0.08范围合成出MCM-41分子筛。通过XRD,TEM,N2物理吸附,IR等方法进行了表征。结果表明:聚氧乙烯-聚氧丙烯-聚氧乙烯三嵌段共聚物(P123)的加入可以更大程度地降低合成介孔材料所需阳离子表面活性剂的用量;可控合成的介孔材料具有高比表面积、高度有序的孔道结构、较集中的孔径分布。     

Influences of evolved gases on the thermal decomposition of zinc carbonate hydroxide evaluated by controlled rate evolved gas analysis coupled With TG

The influences of atmospheric CO₂ and H₂O on the kinetics of the thermal decomposition of zinc carbonate hydroxide, Zn₅(CO₃)₂(OH)₆, were investigated by means of controlled rate evolved gas analysis (CREGA) coupled with TG. Although CO₂ and H₂O were evolved simultaneously in a single mass-loss step of the thermal decomposition, different effects of those evolved gases on the kinetic rate behavior were observed. No distinguished effect of atmospheric CO₂ was detected within the possible range of self-generated CO₂ concentration. On the other hand, apparent acceleration effect by the increase in the concentration of atmospheric H₂O was observed as the reduction of reaction temperature during the course of constant rate thermal decomposition. The catalytic effect was characterized by the decrease in the apparent activation energy for the established reaction with increasing the concentration of atmospheric H₂O, accompanied by the partially compensating decrease in the pre-exponential factor.     

Improved Molecular Weight Control in Ring‐Opening Metathesis Polymerization (ROMP) Reactions with Ru‐Based Olefin Metathesis Catalysts Using N Donors and Acid: A Kinetic and Mechanistic Investigation

The effect of the addition of H₃PO₄ on the ROMP activity of cyclooctene (COE) with first‐ [Cl₂(PCy₃)₂Ru?CHPh] and second‐generation [(H₂IMes)Cl₂(PCy₃)Ru?CHPh] Grubbs’ catalysts 1 and 4 (Cy=cyclohexyl, Ph=phenyl, Mes=2,4,6‐trimethylphenyl (mesityl)), their inhibited mixtures with 1‐methylimidazole (MIM), as well as their isolated bis‐N,N′‐dimethylaminopyridine (DMAP) derivatives [Cl₂(PCy₃)(DMAP)₂Ru?CHPh)] ( 5 b ) and [Cl₂(H₂IMes)(DMAP)₂Ru?CHPh] ( 7 b ) (DMAP=dimethylaminopyridine), a novel catalyst, has been investigated. The studies include the determination of their initiation rates, as well as a determination of the molecular weights and molecular weight distributions of the polymers obtained with these catalysts and catalyst mixtures from the exo‐7‐oxanorbornene derivative 11 . The structure of catalyst 7 b was confirmed by means of X‐ray diffraction. All N‐donor‐bearing catalysts or N‐donor‐containing catalyst mixtures not only exhibited elevated activity in the presence of acid, but also increased initiation rates. Using the reversible inhibition/activation protocol with MIM and H₃PO₄ enabled us to conduct controlled ROMP with catalyst 4 producing the isolated exo‐7‐oxanorbornene‐based polymer 12 with predetermined molecular weights and narrow molecular weight distributions. This effect was based on fast and efficient catalyst initiation in contrast to the parent catalyst 4 . Hexacoordinate complex 5 b also experienced a dramatic increase in initiation rates upon acid‐addition and the ROMP reactions became well‐controlled in contrast to the acid‐free reaction. In contrast, complex 7 b performs well‐controlled ROMP in the absence of acid, whereas the polymerization of the same monomer becomes less controlled in the presence of H₃PO₄. The closer evaluation of catalysts 5 b and 7 b demonstrated that their initiation rates exhibit a linear dependency on the substrate concentration in contrast to catalysts 1 and 4 . As a consequence, their initiation rates are determined by an associative step, not a dissociative step as seen for catalysts 1 and 4 . A feasible associative metathesis initiation mechanism is proposed.     

麦饭石含量对载药复合凝胶小球释药性能的影响

以瓜尔胶-g-聚丙烯酸/麦饭石复合水凝胶(GG-g-PAA/MS)和海藻酸钠(SA)为原料,双氯芬酸钠(DS)为模拟药物,采用离子凝胶法制备了载药复合凝胶小球,考察了pH敏感性以及MS含量对复合凝胶小球的包封率、载药率、溶胀性和药物释放行为的影响.结果表明:凝胶小球具有明显的pH敏感性,在不同pH介质中溶胀率和释放速率...     

载银二氧化钛纳米管表面pH敏感膜构建及其抑菌特性

采用表面涂覆硅烷偶联剂KH550、两步光接枝、阳极氧化等方法,在钛表面成功制备出一种pH型敏感膜覆盖的载银二氧化钛（TiO₂）纳米管阵列。利用扫描电镜（SEM）、透射电镜（TEM）、能谱分析（EDS）、原子吸收光谱（AAS）对该pH敏感膜覆盖的载银TiO₂纳米管阵列理化性能进行了表征,采用抑菌环实验定性考察了样品的抗菌特性,并计算其抑菌率。结果表明,含银离子溶液在毛细管力作用下大量进入TiO₂纳米管中,并在pH型敏感膜的调控下,使银离子在不同pH环境下具备不同的释放行为,从而达到良好的控释效果;载银TiO₂纳米管的抑菌率与银离子负载量成正比,且抗菌性能持久。