Amphiphilic Imbalance and Stabilization of Block Copolymer Micelles on‐Demand through Combinational Photo‐Cleavage and Photo‐Crosslinking

An amphiphilic block copolymer of poly(ethylene oxide)‐b‐poly((N‐methacryloxy phthalimide)‐co‐(7‐(4‐vinyl‐benzyloxyl)‐4‐methylcoumarin)) (PEO₄₅‐b‐P(MAPI₃₆‐co‐VBC₄)) is designed to improve the micellar stability during the photo‐triggered release of hydrophobic cargoes. Analysis of absorption and emission spectra, solution transmittance, dynamic light scattering, and transmission electron microscopy supports that polymer micelles of PEO₄₅‐b‐P(MAPI₃₆‐co‐VBC₄) upon the combinational irradiation of 365 and 254 nm light can be solubilized through the photolysis of phthalimide esters and simultaneously crosslinked via the partially reversible photo‐dimerization of coumarins. The photo‐triggered release experiment shows that the leakage of doxorubicin molecules from crosslinked micelles can be predictably regulated by controlling the irradiation time of 365 and 254 nm light.

     

基于可控相转变温度热敏高分子的人IgG酶联荧光免疫分析

以温度敏感高分子聚N－异丙基丙烯酰胺－丙烯酰胺[P(NIP-AA)]作为载体,建立了酶联荧光免疫分析人IgG的新方法。AA摩尔含量为8％的高分子P(NIP-AA)其临界溶解温度为37 °C。竞争型免疫测定中,被固定的IgG和标准溶液（或样品）在33 °C均相条件下竞争性地与辣根过氧化物酶标记抗体反应,升高温度分离出高分子免疫复合物,沉淀重新溶解后通过偶联过氧化氢与对羟基苯乙酸的荧光反应进行定量,线性范围为100-1000 ng/mL,检测限为2.0 ng/mL。方法灵敏、快速操作简便,且提高了免疫反应效率。此外,灵敏度与用传统微孔板做载体相似,但测定时间更快（从100-120分钟减少到30分钟）。该法用于测定人血清中IgG的含量,结果满意。     

Stabilization of Enzyme by Exclusive Volume Effect in Hydrophobically Controlled Polymer Microcapsules

Summary: This communication describes an enzyme stabilization method that allows the use of enzymes irrespective of environmental factors, especially heat, while maintaining their activity for a long time. We have designed enzyme microcapsules that consist of papain enzyme cores, poly(propylene glycol) interlayers, and poly(ε‐caprolactone) walls. By confocal laser scanning microscopy measurements and the thermal stability of papain‐loaded microcapsules, it is demonstrated that the papain is surrounded by a hydrophobic polyol layer and stabilized by the exclusive volume effect. In our study, improved thermal stability can be obtained by using more hydrophobic long‐chained polyols, which is understood to be attributed to the effective formation of a hydrophobic polyol layer between the papain and the polymer wall by means of conformational anchoring in the interface.

(A) A CLSM image of a PCL microcapsule containing FITC‐labeled papain and RBITC‐labeled PPG at the same time. (B) A scheme of the role of hydrophobic polyols in the interface of enzyme and polymer.     

热敏显色微胶囊的制备与表征

热敏显色微胶囊是用于传真、条形码系统、医用图像、各种打印等领域的重要材料,它是一种内部含有染料隐色体的球形胶囊。染料隐色体是一种内酯结构的无色染料,在一定条件下,与显色剂发生显色反应。由于染料隐色体的化学惰性不够理想,易受外界因素的干扰,因而在应用中受到一定限制,所以为了克服其存在的不足,常将其微胶囊化。微胶囊的芯壁结构可以将芯材与外界隔离,提高芯材的稳定性,同时保留芯材原有的化学性质。当环境温度在微胶囊的玻璃化温度以上时,由于形成微胶囊壁的物质透过性显著增加,因此显色成分接触而发生显色反应。本文利用界面聚合法,以聚乙烯醇为保护胶体,曲拉通X-100为表面活性剂,聚氨酯为壁材,染料隐色体为芯材,合成了聚氨酯热敏显色微胶囊。研究了三个主要因素对微胶囊的粒径及其分布、表面形貌和热敏显色性能的影响。结果表明,增大保护胶体浓度,提高乳化速度,增加乳化剂用量,微胶囊的平均粒径变小,粒径分布变窄,表面变得光滑而且致密,具有较高的热敏显色密度。利用红外光谱仪确认了微胶囊的结构,在最优条件下,所制备的微胶囊玻璃化温度为131 ℃,并具有良好的热稳定性。     

Photo‐aligning of polyimide layers for liquid crystals

A series of soluble and highly transparent semi‐alicyclic polyimides (PIs) with designed flexible linkages have been synthesized derived from an alicyclic aromatic dianhydride (1,2,3,4‐cyclobutanetetracarboxylic dianhydride, CBDA) and various aromatic ether‐bridged diamines. The semi‐alicyclic PIs were evaluated as the photo‐alignment layers of liquid crystal (LC) molecules in liquid crystal display (LCD). Experimental results indicate that the photo‐alignment characteristics of LC molecules induced by the photo‐aligned PI layers and the electro‐optical (EO) properties of the LC cell devices are closely related with PI backbone structures. The retardation of the photo‐aligned PI layers is correlated with the ultraviolet (UV) absorption intensity of PI at 220 to approximately 330 nm. The higher UV absorption intensity PI has, the higher retardation and lower pre‐tilt angle the photo‐aligned PI layer exhibits. The defect‐free and photo‐aligned PI layer could result into the uniform LC texture, which is highly desired for in‐plane switching (IPS) mode LCD devices. In comparison, PI layer containing trifluoromethyl moiety shows poor photo‐aligning performance because of the strong electronic withdrawing effect of the fluorinated linkage.     

Gold Nanoparticles Functionalized by a Dextran‐Based pH‐ and Temperature‐Sensitive Polymer

A dextran‐based dual‐sensitive polymer is employed to endow gold nanoparticles with stability and pH‐ and temperature‐sensitivity. The dual‐sensitive polymer is prepared by RAFT polymerization of N‐isopropylacrylamide from trithiocarbonate groups linked to dextran and succinoylation of dextran after polymerization. The functionalized nanoparticles show excellent stability under various conditions and can be stored in powder‐form. UV and DLS measurements confirm that the temperature‐induced optical changes and aggregation behaviors of the particles are strongly dependent on pH.

     

Dynamic Temperature Distribution in Photo‐induced Alignment of Azobenzene Liquid Crystalline Polymer

A theoretical model has been established to describe the dynamic temperature distribution during the alignment of an azobenzene liquid crystalline polymer irradiated by a linearly polarized laser beam. The dynamic heat diffusion equations are used, and the relationship between heat source item and time is introduced, based on experimental results. With the model, the contours of the temperature distribution at different time have been worked out. It can be found from the theoretical model that there is a maximum temperature rise during the photo‐induced alignment, which is coincident with the analysis of experimental observations. The existence of a minimum laser power and an offset photo‐alignment temperature T_off required to carry on photo‐induce alignment are explained based on the theoretical model.

Temperature distribution after two minutes.     

Photo‐ and pH‐Tunable Multicolor Fluorescent Nanoparticle‐Based Spiropyran‐ and BODIPY‐Conjugated Polymer with Graphene Oxide

We report a stimuli‐responsive fluorescent nanomaterial, based on graphene oxide coupled with a polymer conjugated with photochromic spiropyran (SP) dye and hydrophobic boron dipyrromethane (BODIPY) dye, for application in triggered target multicolor bioimaging. Graphene oxide (GO) was reduced by catechol‐conjugated polymers under mildly alkaline conditions, which enabled to formation of functionalized multicolor graphene nanoparticles that can be induced by irradiation with UV light and by changing the pH from acidic to neutral. Investigation of these nanoparticles by using AFM, fluorescence emission, and in vitro cell and in vivo imaging revealed that they show different tunable colors in bioimaging applications and, more specifically, in cancer‐cell detection. The stability, biocompatibility, and quenching efficacy of this nanocomposite open a different perspective for cell imaging in different independent colors, sequentially and simultaneously.     

Stabilization of pH‐Sensitive mPEG–PH–PLA Nanoparticles by Stereocomplexation Between Enantiomeric Polylactides

Methoxy poly(ethylene glycol)–poly(L ‐histidine)–poly(lactide) (mPEG₄₅–PH₃₀–PLA₈₂) triblock copolymers self‐assemble into nanoparticles by sterocomplexation. The properties of the stereocomplex nanoparticles including morphology, stability, and biocompatibility are investigated. The results reveal that the stereocomplexation between PLLA and PDLA segments could prevent the aggregation of the nanoparticles when the pH value is around 6.8. The mean diameter of the stereocomplex nanoparticles is stabilized at about 100 nm when the pH values are changed from 7.9 to 5.0. The cytotoxicity of the stereocomplex nanoparticles is evaluated, and the results demonstrate that the stereocomplexation could decrease the cytotoxicity of the PDLA segments.     

Nano‐Encapsulation of Lipase by Self‐Assembled Nanogels: Induction of High Enzyme Activity and Thermal Stabilization

The effects of self‐assembled polysaccharide nanogels on colloidal and thermal stability of lipase from Pseudomonas cepacia were investigated. The enzyme activity, especially k_cat, drastically increased in the presence of nanogels of cholesterol‐bearing pullulan (CHP). The thermostability of lipase complex increased because the denaturation temperature of lipase increased by more than 20 °C by complexation with CHP nanogels. Lipase denaturation and aggregation upon heating was effectively prevented by complexation with CHP nanogels. Moreover, complexation with CHP nanogels protected lipase from lyophilization‐induced aggregation. Nano‐encapsulation with CHP nanogel is a useful method for colloidal and thermal stabilization of unstable enzyme.

     

Tough Photonic Crystals Fabricated by Photo‐Crosslinkage of Latex Spheres

A general method to enhance the mechanical properties and solvent resistance of photonic crystals (PCs) has been demonstrated. This is carried out by the crosslinkage of latex spheres via photopolymerization of acrylamide (AAm) infiltrated among them. The crosslinked PAAm enhances the interaction among latex spheres of the PCs film, and contributes to the improvement of mechanical strength and solvent resistance. The result provides a simple approach to make tough PCs films by photo‐crosslinkage, and can be extended to a wide variety of materials, will be of great importance for the practical application of PCs.

     

Micelles‐Encapsulated Microcapsules for Sequential Loading of Hydrophobic and Water‐Soluble Drugs

Layer‐by‐layer (LbL) assembly was conducted on CaCO₃ microparticles pre‐doped with polystyrene‐block‐poly(acrylic acid) (PS‐b‐PAA) micelles, and resulted in micelles encapsulation in the microcapsules after core removal. Distribution of the micelles in the templates and capsules was characterized by transmission electron microscopy and confocal laser scanning microscopy. The micelles inside the capsules connected with each other to form a chain and network‐like structure with a higher density near the capsule walls. The hydrophobic PS cores were then able to load small uncharged hydrophobic drugs while the negatively charged PAA corona could induce spontaneous deposition of water‐soluble positively charged drugs such as doxorubicin.

     

Phase Transition Behaviors of Self‐Oscillating Polymer and Nano‐Gel Particles

Summary: Self‐oscillating polymers and nano‐gel particles consisting of N‐isopropylacrylamide and the ruthenium catalyst of the Belousov‐Zhabotinsky reaction have been prepared. In order to clarify the crosslinking effect on the self‐oscillating behavior, the phase transition behaviors were investigated by measuring the transmittance and the fluorescence intensity of the polymer solution and the gel bead suspension. Cooperative effects due to crosslinking will play an important role for the design of nanoactuators.

Chemical structure of poly(NIPAAm‐co‐Ru(bpy)₃).     

Band‐Structure Engineering of ZnO by Anion–Cation Co‐Doping for Enhanced Photo‐Electrochemical Activity

To look for efficient visible light‐driven catalysts for photo‐electrochemical (PEC) water‐splitting, the band structure and optical absorption of monodoped, compensated, and noncompensated n–p pairs of co‐doped bulk ZnO are systemically studied by using both general gradient approximation and hybrid density functional theory approaches (PBE and HSE). Calculations show that n–p co‐doping cannot only enhance the stability that stems from the strong electrostatic attraction between the n‐ and p‐type dopants, but also effectively reduce the band‐gap of ZnO. More importantly, compensated (Ti+C) and noncompensated (Sc+C) and (Cr+C) co‐doped ZnO may be compelling candidates for PEC water‐splitting because of their narrowed band‐gaps, potentially reduced electron–hole recombination centers, appropriate band‐edge positions, enhanced optical absorption, and good stability.     

Photo‐controlled Hierarchical Assembly and Fusion of Coumarin‐containing Polydiacetylene Vesicles

Herein, we synthesize a coumarin‐substituted diacetylene monomer (CODA) and report the novel photo‐controlled reversible assembly and disassembly behavior of the polymerized CODA (PCODA) vesicles. The photo‐triggered dimerization and cleavage reactions of the coumarin groups within the surface of the adjacent PCODA vesicles can be utilized as the driving force to induce assembly and disassembly of PCODA vesicles. Moreover, the boundary of PCODA vesicles in the aggregates becomes more obscure when the irradiation time exceeds 30 min. Fusion occurs upon close docking of target membranes, driven by sufficient dimerization of the coumarin groups within the surface of PCODA vesicles.     

Effect of the Molecular Weights of Poly‐L‐Arginine on Membrane Strength and Permeability of Poly‐L‐Arginine Group Microcapsules

A novel poly‐L ‐arginine group microcapsule was produced to investigate its nutritional function and pharmacological efficacy. The molecular weight of poly‐L ‐arginine is an important parameter for its membrane strength, but does not obviously affect its release property. Thus, poly‐L ‐arginine can be used as a kind of new membrane material in microcapsules, and it is expected to be used as an therapeutic and biodegradable drug carrier.

Influence of the molecular weight of poly‐L ‐arginine on membrane thickness.     

掺杂二氧化锡的二氧化钛的光学性质及其光催化特性

二氧化钛多相催化是一种极具前途的环境污染深度净化技术。 本文以钛酸四丁酯和四氯化锡为原料,无水乙醇为溶剂,采用溶胶-凝胶法制备了掺杂二氧化锡的二氧化钛薄膜和复合氧化物粉体。通过测量薄膜的吸收光谱推算光学能隙,结果发现掺杂样品的光学能隙比纯二氧化钛样品有所变小。随着热处理温度的提高,掺杂和纯二氧化钛样品的光学能隙都略微降低。X-射线衍射分析表明,复合氧化物粉体的热处理温度对样品的晶体结构和光催化性能有重要影响。以掺杂二氧化锡5 % 摩尔比的样品与纯二氧化钛对照,500 ℃以下热处理样品以锐钛矿结构为主,600 ℃热处理样品为锐钛矿与金红石相共存,并显示了较好的光催化性能。透射电子显微镜观察显示,同样600 ℃热处理,掺杂样品要比纯二氧化钛具有更小的颗粒尺寸。在700 ℃热处理的样品中,掺杂样品只存在金红石相而纯二氧化钛样品中仍存有锐钛矿相。用阿伦尼乌斯经验关系式推测的晶粒生长的活化能,纯二氧化钛47.486 kJ.mol, 掺杂5 % 摩尔比的复合氧化物样品33.103 kJ.mol。以亚甲基蓝为降解物质,考察了掺杂量和热处理温度对样品的光催化性能。     

Preparation of Size Controllable Polypyrrole Sub‐Microcapsules Using SEBS Copolymer as the Building Block

Summary: SEBS is used as building blocks to fabricate size controllable polypyrrole (PPy) capsules. Polypyrrole shells grow on the surfaces of the size controllable oxidant sub‐microparticles dispersed in the solution cast film of a SEBS copolymer by vapor phase polymerization. After washing in ethanol, PPy sub‐microcapsules dispersed in a SEBS matrix are obtained. This technique shows advantages of lower cost and less pollution, as compared with the gold‐template method reported in the literature.

A TEM image of polypyrrole sub‐microcapsules dispersed in a SEBS matrix.