Preparation of glucose-sensitive microcapsules with a porous membrane and functional gates

A glucose-sensitive microcapsule with a porous membrane and with linear-grafted polyacrylic acid (PAAC) chains and covalently bound glucose oxidase (GOD) enzymes in the membrane pores acting as functional gates was successfully prepared. Polyamide microcapsules with a porous membrane were prepared by interfacial polymerization, PAAC chains were grafted into the pores of the microcapsule membrane by plasma-graft pore-filling polymerization, and GOD enzymes were immobilized onto the PAAC-grafted microcapsules by a carbodiimide method. The release rates of model drug solutes from the fabricated microcapsules were significantly sensitive to the existence of glucose in the environmental solution. In solution, the release rate of either sodium chloride or VB(12) molecules from the microcapsules was low but increased dramatically in the presence of 0.2mol/L glucose. The prepared PAAC-grafted and GOD-immobilized microcapsules showed a reversible glucose-sensitive release characteristic. The proposed microcapsules provide a new mode for injection-type self-regulated drug delivery systems having the capability of adapting the release rate of drugs such as insulin in response to changes in glucose concentration, which is highly attractive for diabetes therapy.     

聚酰胺微胶囊的制备及其在处理低浓度含铬废水中的应用研究

如何处理低浓度的含铬废水一直是工业生产中亟待解决的问题之一 ,作者就这一问题进行了大量的基础研究 .首先采用界面缩聚法制备了聚酰胺微胶囊 ,将制得的微胶囊经表面处理后使其具有主动输送功能 ,具有这一特性的微胶囊可以高效、快速提取低浓度废水中的铬 .作者还讨论了微胶囊处理含铬废水的机理、提取速率 .实验证明 ,用微胶囊处理低浓度的含铬废水是行之有效的新技术     

Acid-degradable solid-walled microcapsules for pH-responsive burst-release drug delivery

Acid-degradable microcapsules were prepared via an interfacial polymerization. Degradation of the thin wall of the capsules leads to all-or-nothing cargo release. The only byproducts of degradation are acetone, and a non-toxic triamide. Proof-of-concept experiments showed that cargo can be delivered to and released in cells.     

THE DESIGN AND IN VITRO RELEASE CHARACTERIZATION OF HUMAN CROSS-LINKED HAEMOSLDBIN MICROCAPSULES CONTAINING DOXORUBICIN FOR POTENTIAL CHEMOEMBOLIZATION USE

Cross-linked human haemoglobin microcapsules were prepared by reacting native haemoglobin with terephthaloyl chloride using an interfacial polymerization process. Low cross-linking agent concentration, and short time reaction produced weakly cross-linked microcapsules which incorporated 707. of the doxorubicin by adsorption from aqueous solution. Only small amounts of doxorubicin were released from the microcapsules in distilled water over 24 hours. However, the presence of electalytes in the aqueous sink solution altered profoundly the release profile of doxorubicin and significantly increased the release rate of the drug. These results suggest that there was a competitive fixation of the cation an the binding sites, identified as carboxyl groups available to the drug molecules. Release profile of doxorubicin from the microcapsules was analyzed according to kinetic models using the non-linear regression search procedure. Doxorubicin release from the microcapsules was found to be controlled by an ion-exchange particle diffusion process. This was confirmed by the “interruption test” which is considered the best technique for distinguishing between particle and film diffusion controlled kinetic process     

Preparation and barrier properties of the microcapsules added nanoclays in the wall

Preparation of microcapsules applied to the fabrication of self‐healing composites has attracted a lot of attention. However, the leakage of core material from the microcapsule is a major problem in self‐healing microcapsules. Proper dispersion of layered silicates within the wall of microcapsule is a strategy for improving the barrier properties of the microcapsule. In the present study, poly(urea‐formaldehyde) (PUF) microcapsules containing dicyclopentadiene (DCPD) were prepared by in situ polymerization. For the preparation of UF/clay nanocomposite microcapsules, acid‐modified montmorillonite (H‐MMT) was used as an effective catalyst for the condensation of urea and formaldehyde, and the condensation polymerization in the galleries resulted in the delamination of the clay, as confirmed by TEM and XRD analysis. Scanning electron microscopy (SEM) was applied to observe the morphology of the microcapsules and the barrier property of microcapsules was investigated by thermal gravimetry (TG) analysis and mass release method. On comparison with conventional microcapsules (CMs), nanocomposite microcapsules (NCMs) have better barrier property. This can be attributed to the nanocomposite structure of the microcapsules, where nanosized montmorillonite dispersed in UF to decrease the core material cross‐over. Copyright © 2008 John Wiley & Sons, Ltd.     

Assembly of MOF Microcapsules with Size‐Selective Permeability on Cell Walls

The assembly of metal–organic frameworks (MOFs) into microcapsules has attracted great interest because of their unique properties. However, it remains a challenge to obtain MOF microcapsules with size selectivity at the molecular scale. In this report, we used cell walls from natural biomaterials as non‐toxic, stable, and inexpensive support materials to assemble MOF/cell wall (CW) microcapsules with size‐selective permeability. By making use of the hollow structure, small pores, and high density of heterogeneous nucleation sites of the cell walls, uniform and continuous MOF layers could be easily obtained by inside/outside interfacial crystallization. The prepared MOF/CW microcapsules have excellent stability and enable the steady, slow, and size‐selective release of small molecules. Moreover, the size selectivity of the microcapsules can be adjusted by changing the type of deposited MOF.     

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。     

Preparation and characterization of poly(melamine-formaldehyde) microcapsules filled with propisochlor

A novel propisochlor microcapsules suspension (CS) was prepared via in-situ polymerization. The preparation of melamine-formaldehyde resin microcapsules containing propisochlor with different ratios of core-shell material was investigated. The synthesized microcapsules were characterized by Fourier Transform Infrared spectrometer, Scanning Electron Microscope, Ultraviolet spectrometry, Thermogravimetric analyses and particle size analyzer. As the ratio of core/shell was 1, the diameter of the prepared microcapsules was the smallest (3.55?µm), while narrowest size distribution (span: 1.19) and the melamine formaldehyde microcapsules possessed the highest encapsulation efficiency (93.26%). The surface of the microcapsules was smooth and the microcapsules had poor adhesion. These microcapsules had compact microstructures and global shapes, which had a good thermal stability and propisochlor could be preserved better in the poly(melamine-formaldehyde) (PMF) microcapsules. These results indicated that the prepared microcapsule had better performance. Additionally, the propisochlor was easily degraded through microorganisms and had a short half-life. The microcapsule suspension of propisochlor hasn’t been researched yet. Therefore, it is significant to prepare microcapsule suspension. The technology of controlled release has effectively prolonged the persistence of active ingredients. More importantly, there is no use of organic solvents in the preparation of microcapsules suspension, which avoided the pollution of solvents to the ecological environment.     

Permeability of dye through poly(urea-urethane) microcapsule membrane prepared from mixtures of di- and tri-isocyanate

Poly(urea-urethane) microcapsules were prepared by the interfacial polymerization with using mixtures of tri- and di-isocyanate monomers as wall forming materials, and dioctyl phthalate containing an oil-soluble dye as a core material. The time course of the dye release in dispersing tetrahydrofuran was measured as a function of the weight fraction of tri-isocyanate monomer in the total monomer w and the core/wall material-weight ratio g. The dye release curves were well represented by an exponential function C=Ceq(1-e-t/tau), where C is the concentration of the dye in the dispersing medium, Ceq that at equilibrium state, t the elution time and tau is a time constant. tau increased linearly against w at high g, suggesting controllability of the release rate of microcapsules by varying tri-isocyanate/di-isocyanate ratio.     

Study of the interfacial polycondensation of isocyanate in the preparation of benzalkonium chloride loaded microcapsules

The preparation of benzalkonium chloride loaded microcapsules was performed by interfacial polycondensation of isocyanates. The present study was made in order to clarify parameters affecting microcapsule wall formation during the course of polymerization. The results presented here show that many interrelated parameters are involved during the microcapsule formation. Each individual component introduced in the preparation was shown to have an effect either on the morphology of the microcapsules or on the mechanical resistance. Benzalkonium chloride seemed to interact mainly in the interfacial polymer precipitation step through a salt effect, or influence the polycondensation reaction rate acting as a catalyst. A contribution of the hydroxylic functions of the surfactant in the polycondensation reaction of the isocyanate was also highlighted. Finally, the organic phase composition was found to be able to modulate the reactivity of hydroxylic functions of the surfactant, leading to very slow reactions in pure xylene. These effects were related to the characteristics of the microcapsules obtained according to different compositions of the formulation system.     

Effects of protective colloids on the preparation of poly(l-lactide)/poly(butylene succinate) microcapsules

Poly(l-lactide)/poly(butylene succinate) microcapsules containing an aqueous solution of sodium(+)-tartrate dihydrate were prepared by the interfacial precipitation method through solvent evaporation from (w/o)/w emulsion. The effects of poly(vinyl alcohol) used as a protective colloid in the microencapsulation were investigated regarding thermal properties, particle size distributions, surface morphologies, and release behaviors of the biodegradable microcapsules. It was concluded that encapsulation efficiency, surface morphologies, thermal properties, and releasing speed were closely related to the particle size distributions of microcapsules under different conditions of the protective colloid.     

Synthesis and Characterization of Microcapsules with Chlorpyrifos Cores and Polyurea Walls

Microcapsules with chlorpyrifos cores and polyurea walls were synthesized with 2,4-tolylene diisocyanate as an oil-soluble monomer and ethylenediamine as a water-soluble monomer via an interracial polycondensation reaction. The products were characterized by means of Fourier transform infrared spectrometry, ^13C NMR spectrometry and ^31p NMR spectrometry. The morphology, the particle size and the particle size distribution, and the thermal properties were also evaluated. The prepared microcapsules exhibit clear and smooth surfaces and have a mean diameter of 28. 13 μm. These microcapsules also have a good thermal stability for long-term use, and have potential applications in minimizing the toxicity of chlorpyrifos through controlled release.     

电泳显示微胶囊的制备和性能

以有机颜料联苯胺黄为显色粒子, 四氯乙烯和甲苯混合溶液为分散介质, 油溶性蓝N为吸光染料, 用超分散剂CH-2C分散颜料粒子, 脲醛树脂为壁材, 通过一步原位聚合法制备了电泳显示微胶囊. 通过显微镜检查微胶囊的表面形貌及粒径, 并对微胶囊内颜料粒子的电场响应特性和显示性能进行考察. 结果表明, 所得微胶囊表面光滑, 囊壁透明, 囊内颜料粒子对电场变化能够快速可逆地响应, 并具有双稳显示特性.     

Preparation of chitosan/alginate microcapsules by high-voltage electrostatic method

Chitosan and sodium alginate have the opposite charges; they can become a gelatin by the electrostatic attraction, High-voltage electrostatic droplet generator method was used to prepare chitosan-sodium alginate microcapsule. Multi-layer chitosan-sodium alginate microcapsule was prepared through layer-by-layer self-assembly, and the morphology was investigated. In addition, the release property of ofloxacin in microcapsules was studied by UV-Vis microscopy under different conditions such as pH value, layer number, etc. The results showed that the prepared microcapsules have a smooth surface with average particle size about 100 μm. The result of controlled release indicated that the prepared microcapsules are pH-independent, and the rate of release decreased when the layer number increases.     

Highly selective uptake and release of charged molecules by pH-responsive polydopamine microcapsules

A systematic study of the permeation of small molecules through Pdop microcapsules is reported. The zwitterionic Pdop microcapsules are prepared by oxidative polymerization of dopamine on polystyrene microspheres followed by core removal with THF. Rhodamine 6G, methyl orange and alizarin red are chosen as differently charged probing dyes. The loading amount is affected by pH and dye concentration. Highly selective and unidirectional uptake and release of charged molecules through Pdop microcapsules can be achieved by controlling pH value: at low pH, the Pdop particles incorporate cationic dye (rhodamine 6G); at high pH, they incorporate anionic dyes (methyl orange and alizarin red). In each case, the uptake is highly selective.     

Size effect of complexing microcapsules on copper ion extraction

In a previous work [J. Microencapsulation, in press], polyamide microcapsules containing a poly(acrylic acid) gel as a macromolecular ligand (PAA-CAPS) with a mean diameter of 210 μm were prepared using an original two-step polymerization process combining interfacial polycondensation and radical polymerization in a water in oil inverse emulsion system. Extractions of many divalent cations were examined. In this work, we proposed to synthesise by the same process, smaller microcapsules with a mean diameter of 10 μm (PAA-μCAPS). Reference polyamide microcapsules, i.e. without ligand were also synthesized (μCAPS) and (CAPS) [J. Microencapsulation, in press]. Microcapsule wall thickness was evaluated by SEM and TEM observations of microcapsule cross-section cuts, microcapsule water content was determined by thermogravimetric experiments. Specific surface area and total volume of the pore of microcapsules were determined by BET method based on N₂ adsorption/desorption. The comparison of the extractabilities and the stripping of Cu(II) into the various kind of microcapsules were examined.     

有机颜料酞菁蓝微胶囊的原位微悬浮法制备及其表征

通过简单的超声分散及强力剪切将滤饼中的有机颜料颗粒以初级粒子形式均匀稳定地分散到单体分散液和微悬浮液中的单体小液滴内,经有机颜料单体分散液的预聚处理和原位微悬浮聚合制备得到一系列具有高颜料包裹率和窄粒径分布特点的微米级聚合物胶粒.实验观察和粒径分析DLS证明,预聚处理可明显提高微悬浮体系中单体液滴相的黏度,因而可有效改...     

Microfluidics assisted synthesis of well-defined spherical polymeric microcapsules and their utilization as potential encapsulants

In this article, the development of a novel technique to fabricate spherical polymeric microcapsules by utilizing microfluidic technology is presented. Atom transfer radical polymerization (ATRP) was employed to synthesize well-defined amphiphilic block copolymers. An organic polymer solution was constrained to adopt the spherical droplets in a continuous water phase at a T-junction microchannel, and the generation of the droplets was studied quantitatively. The flow conditions of two immiscible solutions were adjusted for the successful generation of the polymer droplets. The morphology of the microcapsules was examined. The efficiency of these polymer microcapsules as containers for the storage and controlled release of loaded molecules was evaluated by encapsulating the microcapsules with Congo-red dye and investigating the release performance using temperature controlled UV-VIS spectroscopy.     

脲甲醛缩聚物制备电子墨水微胶囊研究

在原位聚合法制备脲甲醛树脂微胶囊的过程中 ,使用水溶性低分子量脲甲醛缩聚物代替传统的脲甲醛预聚体 (一羟甲基脲、二羟甲基脲 )作为反应单体 ,由于脲甲醛缩聚物比后者更容易吸附在分散相液滴表面 ,解决了用原位聚合法制备脲甲醛微胶囊所常有的结块、粘连、表面粗糙、产率低的问题 .研究了低分子量脲甲醛缩聚物水溶液的粘度特征和表面活性及其与胶囊包封率的关系 .使用这种方法制备出了电子墨水微胶囊     

Microcapsule synthesis via RAFT photopolymerization in vegetable Oil as a green solvent

Polymeric capsules with an aqueous core have great potential for a wide range of applications, for example food/biomedical applications. However, synthesis of such capsules often involves the use of toxic organic solvents. Herein, an organic solvent‐free approach is developed for the synthesis of polymeric microcapsules with an aqueous core. The method is based on RAFT polymerization of divinyl monomer around the periphery of inverse emulsion water droplets acting as templates, with an amphiphilic macroRAFT species fulfilling the dual roles of RAFT agent and colloidal stabilizer. Vegetable oils, which are non‐toxic and renewable, are used as the continuous phase of these inverse emulsions, which are prepared using membrane emulsification to control the emulsion droplet size and size distribution. Relatively monodisperse emulsions with tunable droplet size in the range of approximately 10–30 µm are prepared, followed by the RAFT polymerization step to generate polymeric microcapsules having similar size as the initial droplets. This approach will be beneficial for various applications where toxic solvents need be minimized or removed completely to avoid adverse effects. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 831–839