磁性微胶囊的制备及其药物缓控释性能

用乳液-凝胶法制备了磁性壳聚糖/海藻酸钠微胶囊. 在壳聚糖/海藻酸钠微胶囊中掺入Fe3O4磁性中空球, 使微胶囊具有磁靶向性能. 以头孢拉定作为模型药物研究了载药磁性微胶囊的载药量、包封率及药物缓控释性能等. 结果表明, 提高头孢拉定的初始浓度可以提高载药量, 却不利于提高药物的包封率. 所制备的微胶囊在各种缓冲溶液中长时间内具有显著的缓释效果, 并具有pH 刺激响应释放的性能, 即在模拟胃液中的药物释放率大大降低, 而在模拟体液和肠液中的释放时间大大延长, 可达50 h以上. 另外, 在外加磁场作用下, 微胶囊表现出良好的磁定向运动性能, 为磁靶向药物输送提供基础.     

Facile fabrication of drug-loaded PEGDA microcapsules for drug evaluation using droplet-based microchip

Droplet-based microfluidic technology can be utilized as a microreactor to prepare novel functional monodisperse microcapsules. In this study, a droplet-based microfluidic chip with surface modification,which allowed the one-step preparation of double emulsion microcapsules. An O/W/O double emulsion using polyethylene(glycol) diacrylate(PEGDA) solution as the intermediate water phase was prepared by regulating the hydrophilicity and hydrophobicity of the chip surface, with PEGDA microcapsules pr...     

A general strategy for one-step fabrication of biocompatible microcapsules with controlled active release

Fabrication of biocompatible core-shell microcapsules in a controllable and scalable manner remains an important but challenging task.Here,we develop a one-step microfluidic approach for the highthroughput production of biocompatible microcapsules,which utilizes single emulsions as templates and controls the precipitation of biocompatible polymer at the water/oil interface.The facile method enables the loading of various oils in the core and the enhancement of polymer shell strength by polyelectrolyte coating.The resulting microcapsules have the advantages of controllability,scalability,biocompatibility,high encapsulation efficiency and high loading capacity.The core-shell microcapsules are ideal delivery vehicles for programmable active release and various controlled release mechanisms are demonstrated,including burst release by vigorous shaking,pH-triggered release for targeted intestinal release and sustained release of perfume over a long period of time.The utility of our technique paves the way for practical applications of core-shell microcapsules.     

Effect of poly(ethylene oxide) on the release behaviors of poly(epsilon-caprolactone) microcapsules containing erythromycin

The biodegradable poly(epsilon-caprolactone) (PCL)/poly(ethylene oxide) (PEO) microcapsules and the analyzing of form and features for the manufacturing conditions were investigated in a prospective drug delivery systems (DDS) through drug release. The effects of emulsifier, emulsifier concentration, and stirring rate on the diameter and form of the microcapsules were examined using image analyzer (IA) and scanning electron microscope (SEM). The role of interfacial adhesion between PCL/PEO and drug was determined by contact angle measurements, and the drug release rate of the microcapsules was characterized by UV-vis spectroscopy. As a result, the microcapsules were made in spherical forms with a mean particle size of 170 nm approximately 68 microm. And the work of adhesion between water and PCL/PEO was increased with increasing the PEO content, which is due to higher hydrophilicity of PEO. The drug release rate of the microcapsules was significantly increased as the PEO content increased, which could be attributed to the increasing of the hydrophilic groups or the degree of adhesion at the interfaces.     

Fast and effective paper based sensor for self-diagnosis of bacterial vaginosis

In this contribution we present a sensitive colorimetric bioactive paper fabricated to determine sialidase-related diseases like bacterial vaginosis (BV) in a one-step and dry format spot assay with fast response and good storage stability. The paper was prepared by three simple steps. The first step involves preparation of poly(ethyleneimine) (PEI) microcapsules, the second step is to incubate positively charged microcapsules in negatively charged 5-bromo-4-chloro-3-indolyl-a-d-N-acetylneuraminic acid (BCIN) solution, a color enhancer nitro blue tetrazolium (NBT), and in the third step, paper was fabricated by incorporating incubated microcapsules into paper pulp. This paper changes color from white to dark purple in the presence of sialidase in as little as 6 min, and color could be enhanced with increased length of reaction time. In this reaction system, BCIN was the substrate for sialidase, NBT was the color enhancer, and PEI microcapsules acted as catalyst. The loading efficiency of BCIN was about 22.2%, and filtered BCIN solution could be reused for the next fabrication.     

Effect of oxygen plasma treatment on the release behaviors of poly(epsilon-caprolactone) microcapsules containing tocopherol

The biodegradable poly(epsilon-caprolactone) microcapsules (PCL) containing tocopherol (TC) were prepared by emulsion solvent evaporation method, and microcapsules were treated by oxygen plasma to enhance the hydrophilic microcapsules. The morphologies and thermal properties of the microcapsules were determined by SEM and DSC measurements. The microcapsules studied were characterized by surface free energy or work of adhesion through contact angle measurement. As a result, the features of the microcapsules could be adjusted by manufacturing condition, such as surfactant and core ratio. The surface free energy or work of adhesion of the microcapsules was increased with increasing the time of plasma treatment, which could be attributed to the increased hydrophilic groups during oxygen plasma treatment. The release profile of the microcapsules was determined by UV-vis spectroscopy and the microcapsules containing tocopherol showed the rapid release rate, as compared with untreated ones.     

Full‐Spectrum Photonic Pigments with Non‐iridescent Structural Colors through Colloidal Assembly

Structurally colored materials could potentially replace dyes and pigments in many applications, but it is challenging to fabricate structural colors that mimic the appearance of absorbing pigments. We demonstrate the microfluidic fabrication of “photonic pigments” consisting of microcapsules containing dense amorphous packings of core–shell colloidal particles. These microcapsules show non‐iridescent structural colors that are independent of viewing angle, a critical requirement for applications such as displays or coatings. We show that the design of the microcapsules facilitates the suppression of incoherent and multiple scattering, enabling the fabrication of photonic pigments with colors spanning the visible spectrum. Our findings should provide new insights into the design and synthesis of materials with structural colors.     

Layer-by-layer assembly of polyoxometalates into microcapsules

The polyoxometalate (POM) chemistry world has been experiencing an unparalleled development of rapid synthesis of new compounds and slow development of POM-based functional materials and devices. Meanwhile, researchers in the microcapsule world, encouraged by the introduction of the layer-by-layer method, are pursuing good components for constructing functional capsule devices. Here, in view of the versatile properties that POM-based microcapsules may possess, various types of POM-polyelectrolyte composite microcapsules were constructed using the layer-by-layer method. Microscopy reveals that polyoxometalates form nanoparticles on the shell in the presence of cationic polyelectrolytes. These nanoparticles connected with polyelectrolytes constitute the shell and support the microcapsule from collapse after drying, and this is an interesting characteristic different from those of common composite and polyelectrolyte capsules. Fourier transform infrared (FTIR), UV-vis absorption, and X-ray photoelectron spectroscopy (XPS) were used to examine the properties of the POMs in the microcapsules. The obtained microcapsules exhibit higher thermal stability than polyelectrolyte microcapsules. Furthermore, the functions of POMs were maintained when they were assembled into microcapsules. It is proved that microcapsules bearing POMs with redox activity can provide a reduction environment, which can lead to the realization of in situ synthesis of materials, and that microcapsules with photoluminescent POMs as a component can also have a photoluminescent property, providing a way to develop functional capsule devices. This work may provide an opportunity to enrich both the polyoxometalate chemistry and the capsule field.     

高效氯氰菊酯微胶囊的制备、表征及释放性能

以高效氯氰菊酯为芯材, 乙基纤维素为壁材, 采用溶剂蒸发法制备了微胶囊, 并对其理化性能进行表征, 通过单因素实验研究了工艺参数对微胶囊外观形貌、 粒径大小及分布、 包封率、 载药量和缓释性能的影响. 结果表明, 乳化剂种类和剪切时间可以显著影响微胶囊的外观形貌; 随着乳化剂用量增大, 微胶囊粒径减小, 分布变窄, 当Tween-80用量从4%增加至8%时, 微胶囊平均粒径从59.9 μm减少到29.8 μm, 跨距也从1.21减少到0.72. 随着芯壁比(质量比)减小, 微胶囊粒径和包封率均逐渐增大, 载药量逐渐减小, 当芯壁比为1:1.75时, 包封率可以达到70%以上. 微胶囊释放动力学模型符合Ritger-Peppas模型(lgQ=lgk+nlgt); 平均粒径相近而载药量不同时, 初期载药量最小的样品释放速率慢, 累积释放率低; 载药量相近而平均粒径不同时, 粒径大的样品释放速率低, 累积释放率也低.     

Electrospun Polymeric Fibers Decorated with Silk Microcapsules via Encapsulation and Surface Immobilization for Drug Delivery

Hollow polymer microcapsules as drug carriers have the advantages of drug protection, storage, and controlled release. Microcapsules combined with tissue engineering scaffolds such as electrospun microfibers can enhance long-term local drug retention. However, the combination methods of microcapsules and fibers still need to be further explored. Here, different technical approaches to functionalize electrospun polycaprolactone (PCL) microfibers with silk fibroin (SF) microcapsules through encapsulation and surface immobilization are developed, including direct blending and emulsion electrospinning for encapsulation, as well as covalent and cleavable disulfide-linkage for surface immobilization. The results of “blending” approach show that silk microcapsules with different sizes could be uniformly encapsulated inside electrospun fibers without aggregation. To further reduce the use of organic solvents, the microcapsules in the aqueous phase can be uniformly distributed in the PCL organic phase and successfully electrospun into fibers using surfactant span-80. For surface immobilization, silk microcapsules are efficiently covalent binding to the surface of electrospun PCL fibers via click chemistry and exhibited noncytotoxic. Based on this method, with the incorporation of a disulfide bond, the linkages between microcapsule and fiber could be cleaved under reducing conditions. These microcapsule-electrospun fiber combination methods provide sufficient options for different drug delivery requirements.     

One-step controlled precipitation to fabricate glucose-responsive microcapsules

Advanced multi-compartmental concanavalin A (Con A)/glycogen complex microcapsules incorporated with polymeric micelles were successfully fabricated by a facile, one-step controlled precipitation method. Dropwise addition of Con A solution into glycogen solution results in Con A/glycogen complex precipitates, which are captured by polyethyleneimine-modified CaCO₃ microparticles, forming a continuous shell structure. Removal of the carbonate cores yields hollow capsules of Con A/glycogen complex, which have variable sizes and wall thicknesses under different precipitation conditions. The capsules show molecular-recognizable response to glucose and dextran (M _w, 20 and 40 kDa), leading to breakdown of the capsule structure and release of the incorporated substances such as poly(styrene-b-acrylic acid) micelles.     

Multilayer Microcapsules for FRET Analysis and Two‐Photon‐Activated Photodynamic Therapy

Microcapsules obtained by layer‐by‐layer assembly provide a good platform for biological analysis owing to their component diversity, multiple binding sites, and controllable wall thickness. Herein, different assembly species were obtained from two‐photon dyes and traditional photosensitizers, and further assembled into microcapsules. Fluorescence resonance energy transfer (FRET) was shown to occur between the two‐photon dyes and photosensitizers. Confocal laser scanning microscopy (CLSM) with one‐ and two‐photon lasers, fluorescence lifetime imaging microscopy (FLIM), and time‐resolved fluorescence spectroscopy were used to analyze the FRET effects in the microcapsules. The FRET efficiency could easily be controlled through changing the assembly sequence. Furthermore, the capsules are phototoxic upon one‐ or two‐photon excitation. These materials are thus expected to be applicable in two‐photon‐activated photodynamic therapy for deep‐tissue treatment.     

Controlled release by polyelectrolyte microcapsule membranes

Polyelectrolyte submicron microcapsules were prepared by interfacial crosslinking of an aqueous salt solution of poly(ethyleneimine) and a toluene solution of brominated poly-(2,6-dimethylphenylene oxide). The two solutions were brought together and mixed by sonication. As a result, a stable emulsion was obtained, which was subsequently cast into a membrane in which the microcapsules were embedded. The salt solution contained in the microcapsules could be released under controlled conditions. The rates of release were measured. They could be controlled by applying osmotic pressures, by additional quaternization of the membrane, or by modification of the structure of the capsule wall by introduction of a surfactant.     

Preparation of protein microcapsules with narrow size distribution by sonochemical method

Protein microcapsules with narrow size distribution have been prepared by sonochemical method which is a simple, fast, environmental friendly and cost-effective method. The prepared microcapsules are composed of a water-insoluble core and an outer protein shell. The hydrophobic drugs could be encapsulated into protein microcapsules directly via sonochemical method by dissolving drugs in the nontoxic and edible vegetable oil before ultrasonication, which is a potential solution for drug resistance by hiding cytotoxic drugs in the carrier and allows for the delivery of high doses in relatively small volume. The size and size distribution of protein microcapsules are very important for their practical application. In this paper, the factors affecting the size and size distribution of protein microcapsules are investigated in detail. Moreover, confocal laser scanning microscopy and transmission electron microscopy confirmed that the protein microcapsules with narrow size distribution were obtained.     

Fundamental investigation on effect of microencapsulated water on expansion behavior of microcapsules

The microcapsules containing water were prepared with the suspension polymerization method, and the fundamental investigation was performed to make the effect of microencapsulated water on expansion behavior of microcapsules clear. In the experiment, only the volume of water added into styrene monomer was changed to make the effect of microencapsulated water volume clear, and three kinds of water contents were measured: namely, the initial water content for the microcapsules just after preparation, the middle water content for the microcapsules dried at 44°C for 24 hours, and the final water content for the microcapsules dried at 110°C for 1 hours. With increasing the added water volume, the initial water content increased; the middle water content decreased after increasing halfway through, and the final water content gradually decreased. Also, with increasing the added water volume, the drying rate of the microcapsules increased and the expansion ratio decreased. The water volume required to expand the microcapsules, in other words, the critical shell thickness required to prevent evaporation of water and to contribute to expansion of microcapsules is discussed.     

Multicore-shell PNIPAm-co-PEGMa microcapsules for cell encapsulation

The overall goal of this study was to fabricate multifunctional core-shell microcapsules with biological cells encapsulated within the polymer shell. Biocompatible temperature responsive microcapsules comprised of silicone oil droplets (multicores) and yeast cells embedded in a polymer matrix (shell) were prepared using a novel microarray approach. The cross-linked polymer shell and silicone multicores were formed in situ via photopolymerization of either poly(N-isopropylacryamide)(PNIPAm) or PNIPAm, copolymerized with poly(ethylene glycol monomethyl ether monomethacrylate) (PEGMa) within the droplets of an oil-in-water-in-oil double emulsion. An optimized recipe yielded a multicore-shell morphology, which was characterized by optical and laser scanning confocal microscopy (LSCM) and theoretically confirmed by spreading coefficient calculations. Spreading coefficients were calculated from interfacial tension and contact angle measurements as well as from the determination of the Hamaker constants and the pair potential energies. The effects of the presence of PEGMa, its molecular weight (M(n) 300 and 1100 g/mol), and concentration (10, 20, and 30 wt %) were also investigated, and they were found not to significantly alter the morphology of the microcapsules. They were found, however, to significantly improve the viability of the yeast cells, which were encapsulated within PNIPAm-based microcapsules by direct incorporation into the monomer solutions, prior to polymerization. Under LSCM, the fluorescence staining for live and dead cells showed a 30% viability of yeast cells entrapped within the PNIPAm matrix after 45 min of photopolymerization, but an improvement to 60% viability in the presence of PEGMa. The thermoresponsive behavior of the microcapsules allows the silicone oil cores to be irreversibly ejected, and so the role of the silicone oil is 2-fold. It facilitates multifunctionality in the microcapsule by first being used as a template to obtain the desired core-shell morphology, and second it can act as an encapsulant for oil-soluble drugs. It was shown that the encapsulated oil droplets were expelled above the volume phase transition temperature of the polymer, while the collapsed microcapsule remained intact. When these microcapsules were reswollen with an aqueous solution, it was observed that the hollow compartments refilled. In principle, these hollow-core microcapsules could then be filled with water-soluble drugs that could be delivered in vivo in response to temperature.     

Study on In-Situ Compatibilization of the PP/PA6 Blends in Twin Screw Extruders

The in-situ compatibilization of PP/PA6 blend was studied in a twin screw extruder. The maleic anhydride (MA) content, peroxide concentration, shear rate and feeding order were among the variables investigated. Degree of grafting of samples collected prior to feeding of PA6 into the extruder was measured using titration combined with FTIR technique. From the SEM results it was found that the increasing of initial MA concentration led to larger PA particle size which could be related to secondary reactions between excess MA and PA. The melt linear viscoelastic measurements performed on the blend samples and the obtained relaxation time spectra showed shorter form relaxation time and interfacial relaxation time for one-step compatibilized sample compared to the sample prepared by the two-step method with the same degree of grafting. This was attributed to the stronger interfacial interaction of the one-step compatibilized blend samples which could be resulted from greater efficiency of grafting and/or compatibilization. These results were supported by SEM results which showed smaller particle size for the one-step compatibilized samples. It was demonstrated that melt linear viscoelastic measurement could provide a great insight into understanding the compatibilization process in twin screw extruder.     

Polymeric microcapsules with internal cavities for ultrasonic imaging: efficient fabrication and physical characterization

Polymeric microcapsules are of great potential in ultrasonic imaging due to their characteristic hollow structure. Water-in-oil-in-water (W₁/O/W₂) double emulsion-solvent evaporation technique is a versatile strategy applicable to most hydrophobic polymers for fabricating microcapsules; however, the adjustment of the size and inner structure of resultant microcapsules have not been systematically studied until now. Here, we evaluate in detail the parameters in double emulsification and find that the W₁/O volume ratio is a pivotal parameter which controls the hollow structure of microcapsules. In addition, an appropriate concentration of emulsifier in W₂ is essential to guarantee the hollow structure as well. For quantitatively characterizing the hollow structure of microcapsules, we propose the concept of Hollow Ratio (HR) and Hollow Degree (HD) to evaluate the percent of hollow microcapsules in products and the hollow characteristic of the microcapsules. Our study demonstrates that the HR of microcapsules can vary between 25% and 98% by only adjusting the W₁/O volume ratio. The size of microcapsule has a close relationship to its HD. Moreover, the microcapsules with both single cavity and multicavities have been fabricated by altering the energy of the second emulsification. Further, acoustic studies reveal that the microcapsules with different HD display obviously different sound attenuation spectrum and resonance frequency, which demonstrates that the adjustment of hollow structure should be an effective approach to control the acoustical properties of microcapsules for ultrasonic imaging.     

Synthesis of functional microcapsules containing suspensions responsive to electric fields

A sort of functional microcapsules, which contain a suspension responsive to electric fields, is prepared by in situ polymerization of urea and formaldehyde. The suspension is made up of pigment phthalocyanine green (PPG) and tetrachloroethylene. In order to solve the particles' separation from the suspension during the microencapsulation and to obtain microcapsules applying to electronic ink display, the dispersibility of the particles, the contact angles between the particles and the tetrachloroethylene, and the influences of different emulsifiers on the microencapsulation are investigated. It is found that the dispersion extent and lipophilicity of the PPG particles are improved due to their surface modification with octadecylamine. The contact angles between the modified PPG particles and the tetrachloroethylene increase, and the PPG particles modified with 2 wt% octadecylamine have the best affinity for tetrachloroethylene. The interfacial tension between C(2)Cl(4) and H(2)O with urea-formaldehyde prepolymer descends from 43 to 35 mN/m, which indicates that the polymer has certain surface activity. However, water-soluble emulsifiers have an important influence during the microencapsulation because they can absorb on the surfaces of internal phase and prevent the resin of urea-formaldehyde from depositing there. From the SEM images of shell surface and cross section, the microcapsules have relatively smooth surfaces and the average thickness is about 4.5 mum. When the microcapsules are prepared with agitation rates of 1000 and 600 rpm, the mean diameters of the obtained microcapsules are 11 and 155 mum, respectively. The particles in the capsules move toward positive electrode with a responsive time of several hundred milliseconds while providing an electric field.     

Supramolecular hydrogel microcapsules via cucurbit[8]uril host–guest interactions with triggered and UV-controlled molecular permeability

Host–guest assembly in droplet-based microfluidics opens a new avenue for fabricating supramolecular hydrogel microcapsules with high monodispersity and controlled functionality. In this paper, we demonstrate a single emulsion microdroplet platform to prepare microcapsules with supramolecular hydrogel skins from host molecule cucurbit[8]uril and guest polymer anthracene-functionalized hydroxyethyl cellulose. In contrast to construction of microcapsules from a droplet-in-droplet double emulsion, here the electrostatic attraction between charged polymer and surfactant facilitates formation of defined supramolecular hydrogel skins in a single emulsion. Furthermore, by taking advantage of dynamic interactions and the tunable cross-linked supramolecular hydrogel network, it is possible to prepare microcapsules with triggered and UV-controlled molecular permeability. These could be potentially used in a delivery system for e.g. agrochemicals, nutraceuticals or cosmetics.