Porous Microcapsules Research Articles

Synthesis of calcium phosphate microcapsules using yeast-based biotemplate

Calcium phosphate (CP) microcapsules with a typical diameter of 5–10 μm were fabricated via a biomimetic mineralization process with yeast cells (YCs) as a template core modified with the self-assembling of poly(diallyldimethylammonium chloride) and poly(acrylic acid), followed by removal of the biotemplate with calcinations to obtain porous microcapsules.

Influence of 1-D silica nanotubes as drug adsorbent on release behaviors of tulobuterol-loaded porous microcapsules

Porous poly(ɛ-caprolactone) (PCL)/Eudragit RS 100 (ERS-100) microcapsules containing tulobuterol-adsorbed silica nanotubes (S-NTs) were prepared using a solvent evaporation method. The release behaviors of the PCL/ERS-100 microcapsules were investigated as a function of S-NT content. The PCL/ERS-100 microcapsules showed a stable and porous surface compared to the PCL microcapsules prepared without ERS-100. The drug loading and encapsulation efficiencies of the microcapsules were increased slightly by the addition of S-NTs due to the adsorption of the drugs on the S-NTs. In an acidic release medium, the PCL/ERS-100 microcapsules containing the tulobuterol-loaded S-NTs showed a slow drug release, which was dependent on the S-NT content. These behaviors are most likely due to the reduced diffusion rate of the drug from the hydrated microcapsules, which results from the strong interaction between the porous S-NTs and the drug.

Multiplexed Sensing of Ions with Barcoded Polyelectrolyte Capsules

Multiplexed detection of analytes is a challenge for numerous medical and biochemical applications. Many fluorescent particulate devices are being developed as ratiometric optical sensors to measure the concentration of intracellular analytes. The response of these sensors is based on changes of the emission intensity of analyte-sensitive probes, entrapped into the carrier system, which depends on the concentration of a specific analyte. However, there are a series of technical limits that prevent their use for quantitative detection of several analytes in parallel (e.g., emission crosstalk between different sensor molecules). Here we demonstrate that double-wall barcoded sensor capsules can be used for multiplexed analysis of proton, sodium, and potassium ions. The sensor detection methodology is based on porous microcapsules which carry ion-sensitive probes in their inner cavity for ion detection and a unique QD barcode in their outermost wall as tag for identification of individual sensors. The engineering of QD barcodes to capsules walls represents a promising strategy for optical multianalyte determination.

Fabrication of Hollow Metal Microcapsules with Mesoporous Shell Structure: Application as Efficient Catalysts Recyclable by Simple Magnetic Separation

Monodispersed porous NiO and <TEX>$Co_3O_4$</TEX> microcapsules with a hollow core were synthesized using SBA-16 silica sol and PS as a hard template. The porous hollow microcapsules were characterized by XRD, TEM and <TEX>$N_2$</TEX> adsorption/desorption analysis. After <TEX>$H_2$</TEX> reduction of metal oxide microspheres, they were conducted as an active catalyst in the reduction of chiral butylronitrile and cyanobenzene. The mesoporous metals having a hollow structure showed a higher activity than a nonporous metal powder and an impregnated metal on the carbon support.

Evaluation of a magnetic polysulfone microcapsule containing organic modified montmorillonite as a novel solid-phase extraction sorbent with chlorophenols as model compounds

A porous polysulfone microcapsule containing organic modified montmorillonite and magnetic nanoparticles (OMMT-Fe3O4@PSF) has been successfully prepared by a phase-inversion method and evaluated as a magnetic solid-phase extraction (MSPE) sorbent for clean-up and enrichment of 4-chlorophenol (4-CP) and 2-chlorophenol (2-CP) in aqueous samples. Compared with a microcapsule containing the conventional extraction sorbent C18 (C18-Fe3O4@PSF), OMMT-Fe3O4@PSF had much lower cost, a faster adsorption rate, and superior uptake amounts for the investigated analytes. The proposed microcapsule has been developed for the extraction of 4-CP and 2-CP from environmental water samples and their analysis by high-performance liquid chromatography with UV detection (HPLC-UV). Various parameters, such as pH, extraction time, the mass of sorbent, and the desorption conditions, have been evaluated and the calibration curves of the chlorophenols were linear (R2≥0.9985) in the range from 1.01 to 104.5ngmL−1. The limits of detection at a signal-to-noise (S/N) ratio of 3 were 0.22 and 0.17ngmL−1 and the limits of quantification calculated at S/N=10 were 1.52 and 1.07ngmL−1 for 2-CP and 4-CP, respectively. The recoveries of 2-CP and 4-CP from natural water and the treated wastewater samples were in the range of 84.4–115% with relative standard deviations (RSDs) lower than 7.0%. The results have demonstrated the suitability of the MSPE approach for the analysis of trace chlorophenols in aqueous samples.

Porous microcapsule formation with microsieve emulsification

A simple route is presented to prepare core–shell Eudragit microcapsules through a solvent extraction method with the use of microsieve emulsification. Droplets from a solution of Eudragit FS 30D (a commercial copolymer of poly(methyl acrylate-co-methyl methacrylate-co-methacrylic acid) 7:3:1) and hexadecane in dichloromethane are dispersed into water, using a micro-engineered membrane with well-defined pores, in a cross-flow setting. The dichloromethane is extracted from the droplets, which induces demixing in the droplets, leading to a hexadecane-rich core, and an Eudragit-rich shell. The obtained microcapsules have a narrow size distribution due to the microsieve emulsification process. The capsules have a porous shell as shown by SEM and AFM measurements. Their porosity and pore size is dependent on the ratios of Eudragit and hexadecane in the dispersed phase. At pH 7.1 and above Eudragit (FS 30D) dissolves in water; this pH change is used to release the contents of the microcapsule.

Preparation and Characterization of Highly Porous Direct Compression Carrier Particles with Improved Drug Loading During an Interactive Mixing Process

The aim of this study was to prepare highly porous carrier particles by emulsion solvent evaporation and compare the loading capacity of these beads with two traditional carriers, sugar beads, and microcrystalline cellulose granules during an interactive mixing process. The porous carrier particles were prepared by an emulsion solvent evaporation process using cellulose propionate as a binder, anhydrous dibasic calcium phosphate, and ion exchange resins as a fillers, and polyethylene glycol as a pore inducer. Micronized furosemide or griseofulvin powder was mixed with the same volume of each carrier in an interactive mixing process. The tableting properties, drug loading per unit volume of carrier, content uniformity of the mixtures, and dissolution of the drugs from the mixtures were measured. The results showed that highly porous microcapsules with desirable hardness equivalent to that of sugar beads and MCC granules were successfully prepared. On average the loading capacity of the new carrier was 310% that of sugar beads and 320% that of MCC granules during an interactive mixing process with very good content uniformity. The tableting properties of the microcapsules were equivalent to that of microcrystalline cellulose granules, and the dissolution of the drugs from interactive mixtures prepared with the new carrier was equivalent to that of drug suspensions. This showed that the prepared microcapsule carrier could be used to improve the loading capacity during an interactive mixing and to prepare tablets by direct compression.

Hybrid lipid–silica microcapsules engineered by phase coacervation of Pickering emulsions to enhance lipid hydrolysis

We report on the fabrication of dry hybrid lipid-silica microcapsules for enhanced lipid hydrolysis using Pickering emulsion templates formed by interfacial nanoparticle-emulsifier electrostatic interaction. The microcapsules are produced by controlled precipitation of emulsion droplets by oppositely charged silica nanoparticles at room temperature. Microcapsule formation is driven by the interfacial structure of the initial Pickering emulsion, which is in turn controlled by the nanoparticle to lipid ratio. In the region of charge reversed, precipitated and aggregated droplets, droplet-nanoparticle networks have been identified by freeze-fracture SEM imaging. The microcapsules have diameters in the range 20-50 mum and contain approximately 65% oil distributed within an internal matrix structure composed of a labyrinth of interconnected pores approximately 20-100 nm. Pore distribution and diameters depend on the silica to nanoparticle ratio that in turn determines droplet coating and stability. The microcapsules facilitate enhanced lipid hydrolysis kinetics, i.e. their pseudo first-order rate constant for lipid hydrolysis is approximately 3 times greater than for equivalent submicron lipid droplets. This behaviour is attributed to the increased oil surface area within the microcapsule due to the specific porous structure that causes rapid release of submicron and micron size oil droplets. The simple route for fabrication of porous microcapsule morphologies may present new opportunities for applications in encapsulation, delivery, coatings, and catalysis.

Characterization and release behaviors of porous PCL/Eudragit RS microcapsules containing tulobuterol

In this work, porous poly(ɛ-caprolactone) (PCL)/Eudragit RS 100 (ERS-100) microcapsules containing tulobuterol base as a model drug were prepared by a solvent evaporation method and the effect of the quaternary ammonium groups of ERS-100 on the release behaviors of the microcapsules was investigated. The microcapsules prepared with PCL alone showed a stable and smooth surface, whereas porous microcapsules were formed with the addition of ERS-100. Drug loading and encapsulation efficiency of the microcapsules were slightly decreased with an increase of ERS-100 content, resulting from an increase in the porosity of the microcapsules. In an acidic release medium, PCL microcapsules showed slow drug release, whereas PCL/ERS-100 microcapsules showed a faster release rate with an increasing ERS-100 content. These behaviors are likely due to an increase in the diffusion rate of the drugs stemming from an increased hydration of the microcapsules, which results from the interaction between the carboxyl group of the release medium and the quaternary ammonium group of ERS-100.

A microfluidic approach to fabricate monodisperse hollow or porous poly(HEMA–MMA) microspheres using single emulsions as templates

We have successfully developed a novel and simple method to controllably prepare monodisperse poly(hydroxyethyl methacrylate–methyl methacrylate) (poly(HEMA–MMA)) microspheres with two distinct structures using single emulsions as templates. By employing a microfluidic emulsification approach to fabricate monomer-contained oil-in-water (O/W) emulsions as templates, and introducing proper initiators and different types of porogens, poly(HEMA–MMA) microspheres with hollow or porous structure are prepared in a controllable way. The shell thickness of hollow microspheres or the porosity of porous microspheres is controllably achieved by simply adjusting the porogen concentration. The prepared poly(HEMA–MMA) microspheres with controllable hollow or porous structures are favored for various potential applications. Furthermore, by using the simple preparation methodology proposed in this study, fabrication of monodisperse porous microspheres or hollow microcapsules with other materials can also be easily achieved.

Release Profiles of Encapsulated Actives from Colloidosomes Sintered for Various Durations

This paper presents the formation of low temperature colloidosomes from colloidal poly(styrene-co-butyl acrylate) particles for both water-in-oil and oil-in-water systems. An investigation into the sintering conditions examines the ultimate shell morphology formed, with longer sintering times and higher sintering temperatures producing less porous microcapsules. This has been verified by the release of an encapsulated dye from the aqueous core microcapsules, in which slower release has been detected for longer sintering times. The results are subsequently fitted with a diffusion equation to give a diffusion coefficient of fluorescein through the polymeric shell of 10(-17) m(2)/s.

Poly (DADMAC) encapsulation in PES microcapsules utilizing gamma radiation

In this communication, a method for encapsulation of a polymeric resin using radiation technology is reported. The quaternary ammonium resin, polydiallyldimethylammonium chloride (PDADMAC) was incorporated in the core of a preformed hollow polyethersulfone microcapsule, using radiation technology, for the extraction of anions from aqueous solutions. The idea was to introduce the monomer into the porous microcapsules and initiate polymerization by radiation to trap the polymer formed inside the capsule. The resultant capsule was able to take up and exchange some anions (F −, Cl −, Br −, NO 3 2− and SO 4 2−) at relatively low concentrations.

Microfluidic Synthesis of Reversibly Swelling Porous Polymeric Microcapsules with Controlled Morphology

Microfluidic Synthesis of Reversibly Swelling Porous Polymeric Microcapsules with Controlled Morphology

Preparation of Surface Porous Microcapsules Templated by Self-assembly of Nonionic Surfactant Micelles

Microcapsules with controllable porous surface morphology and good monodispersity were prepared using the one-step synthetic strategy by employing the self-assembly template of nonionic surfactant micelles above its cloud point. Both the pore size (from 100 to 400 nm) and pore density are tunable by changing the amount of core materials or the ratio of core material to shell material. This methodology provides a versatile and effective route for preparation of porous microsphere materials, which can encapsulate lipophilic functional compounds.

The application of corrugated parallel bundle model to immobilized cells in porous microcapsule membranes

To describe immobilized cells in porous microcapsule membranes with straight pores, a novel model called corrugated parallel bundle model (CPBM) was utilized. In this model, a network was developed with 10 main pores each composing 10 pore elements. Cell growth kinetic in the network was examined using non-structural models. Effectiveness factor and pore plugging time were calculated by solving reaction-diffusion equation set via finite difference method. The findings revealed that diffusion coefficient for lower order reactions will create a lesser impact on the reduction of effectiveness factor. These findings also indicated that the use of such supporting carrier for cell immobilization could enhance the operational life of the system.

New PVDF microcapsules for application in catalysis

Novel polyvinylidene fluoride (PVDF) porous microcapsule membranes were successfully prepared with non-solvent induced phase inversion method for the immobilization of catalyst ammonium molybdate tetrahydrate ((NH4)6Mo7O24·4H2O).The chemical–physical analysis of the new PVDF catalytic microcapsules was carried out by means of SEM, EDX, IR, DSC and XRD techniques.Catalytic activity of the PVDF catalytic microcapsules has been evaluated in the oxidation of benzyl alcohol to benzaldehyde in solvent free conditions. The polymeric microcapsules “keep in contact” the two phases: the organic phase, containing the substrate and the product, and the aqueous phase with the oxidant, H2O2. In literature, ((NH4)6Mo7O24·4H2O) was reported to be effective in the oxidation of alcohols with H2O2 in combination with a phase transfer catalyst in chlorinated solvents.The effect of reaction temperature, substrate:oxidant ratio, swelling of polymeric microcapsules on the reaction progress was investigated.PVDF catalytic microcapsules have given proof of their complete stability under oxidation conditions and their good recycle.

Effects of preparation conditions on the microstructure of porous microcapsule membranes with straight open pores

Experimental investigations on the effects of preparation conditions on the microstructure of porous microcapsule membranes with straight open pores were carried out systematically. The polyethersulfone (PES) hollow microcapsules with straight open pores across the whole membrane thickness were prepared by a gel–sol phase inversion method together with an accompanying process for peeling off the surface dense layer. The results showed that, with increasing the PES polymer concentration, the membrane thickness of the microcapsules increased simply and the average pore size of the microcapsule membranes decreased to some extent. With increasing the concentration of inorganic additive lithium chloride, the straight pores across the microcapsule membrane became more compact and symmetrical, and the pore diameter decreased significantly; meanwhile, the membrane thickness increased to some extent. With increasing the dosages of organic additives polyvinyl pyrrolidone and polyethylene glycol, the average pore diameter of the straight pores across the microcapsule membranes decreased simply, the membrane thickness also decreased significantly. With increasing the temperature of coagulation bath in the preparation of microcapsule membranes, the average pore size of the microcapsule membranes became smaller simply, the membrane thickness also decreased gradually. With increasing the dissolution time, the average pore size of the microcapsule membranes increased slightly, and the membrane thickness of the hollow microcapsules also decreased to some extent. The results provided some guidance for the structurally controllable preparation of the hollow microcapsules with straight open pores across the membranes.

薬物を内包した多孔性無機微粒子の設計とその評価

In the present study, to develop controlled-release dosage forms, interfacial reaction method was used to design of the porous inorganic microcapsule of drug. First, the inorganic microspheres with sharp size distribution were produced by using interfacial reaction method. Second, pore volume of porous shell, the route of drug release, was tried to increase. Third, impregnation method or suspension method was used to design of the porous inorganic microcapsules of water soluble drug and the porous inorganic microcapsules of poor solubility drug.1) The inorganic microspheres with under 5μm size and sharp size distribution could be produced by using interfacial reaction method. The agitation speed preparing W/O emulsion was important in producing microspheres with sharp size distribution.2) Pore volume of porous microspheres increased with the volume of the pore formations generated by adding NaOH and K(OH)2. The addition of hydroxide was effective in the porous microspheres.3) The porous inorganic microspheres could be loaded with water soluble drug and poor solubility drug by using impregnation method or suspension method. The dissolution test results showed the amount of drug release could be controlled with pore of the porous inorganic microcapsule.

Structural Control of Porous Microcapsules Prepared by in-situ Polymerization in W/O/W Emulsion System

Structural Control of Porous Microcapsules Prepared by in-situ Polymerization in W/O/W Emulsion System

A porous microcapsule membrane with straight pores for the immobilization of microbial cells

A novel type of polyethersulfone porous microcapsule membranes with straight pores across the whole thickness was successfully prepared with a gel–sol phase inversion method for the immobilization of microbial cells. The mean diameter of the microcapsules was about 2 mm, and the microcapsule membranes were full of straight finger pores. The pore size distribution was from 3.5 to 53.6 μm and the median pore diameter was 13.6 μm. The prepared microcapsules had large total pore volume, and total pore area and porosity (as large as 91.7%). The prepared porous microcapsules were used as carriers for the immobilization of microbial cells in the anaerobic wastewater biotreatment process. Immobilized anaerobic microbial cells were found both inside the membrane pores and in the inner spaces of microcapsules. The prepared porous microcapsules were proven to be efficient for the microbial immobilization under anaerobic conditions.