Kinds Of Microcapsules Research Articles

Preparation and characterization of SiO2-coated 2,4-hexadiyn-1,6-bis(ethylurea) microcapsules

A novel kind of time-temperature indicator, SiO2-coated 2,4-hexadiyn-1,6-bis(ethylurea) microcapsules, has been fabricated by coating SiO2 on 2,4-hexadiyn-1,6-bis(ethylurea). This kind of microcapsules is a model hydrophilic indicator, its stability is improved. And temperature-induced color change is irreversible even under varying irradiation. The influences of ammonia, tetraethyl orthosilicate(TEOS) and temperature on the product have been investigated. 2,4-Hexadiyn-1,6-bis(ethylurea) and the coated particles have been characterized by means of elemental analysis, mass spectrum, FTIR and Raman spectra and DSC, SEM, TEM and DLS analyses. The results indicate that 2,4-hexadiyn-1,6-bis(ethylurea)/SiO2 ratios, ammonia concentration and temperature could modulate the monodispersity and size of the microcapsules. The experiments indicate that when the molar ratio of 2,4-hexadiyn-1,6-bis(ethylurea)/SiO2/ammonia is 1:3:3.5 and temperature is 40 °C, the obtained microcapsules are well coated with the best monodispersity. Such sustained-release and hydrophilic microcapsules have very good prospects as a novel time-temperature chromatic indicator.

Development of smart gypsum composites by incorporating thermoregulating microcapsules

Abstract Smart gypsum composites were manufactured by adding different kinds of microcapsules containing phase change materials (PCMs) in order to develop building materials with high thermal energy storage (TES) capacity useful for being applied in high comfort constructive systems. The physical, thermal and mechanical properties of these composites such as density, porosity, thermal stability, thermal conductivity (k), equivalent heat capacity (cp), the accumulated heat power (qacc) and the maximum compressive strength were studied. Results showed that the higher the microcapsules content, the lower the density and k and the higher the cp and qacc, due to the PCM action. Besides, the addition of 15 wt% of microcapsules respect to the hemihydrate would allow to save 4.5 kWh of energy per operating cycle in a standard room covered with 1 m3 of this gypsum. This energy is equivalent to the energy spent by three incandescent light bulbs of 60-W kept on all the day and a reduction of 1.395 kg of CO2 emissions to the atmosphere. The addition of these thermoregulating materials to gypsum decreases their compressive strength but all the developed materials satisfied the Spanish mechanical regulations for gypsum as building material, being possible to increase the total amount of added microcapsules.

Flame Retardation of SBS Composites Containing Ammounium Polyphosphate and its Microcapsules

Flame retardant properties of ammonium polyphosphate (APP) and its two kinds of microcapsules, MFAPP with a shell of MF resin and EPAPP with a shell of epoxy resin, were studied in styrene-butadiene-styrene rubber (SBS). The results indicate that the microencapsulation of APP leads to an increase in LOI in SBS compared with APP. When dipentaerythritol is incorporated into the SBS composites containing APP microcapsules, a further improvement in flame retardancy of the composites is observed. Moreover, thermal decomposition behavior and mechanical properties of the SBS composites are investigated.

Preparation of Infrared Stealthy Coatings

Two kinds of microcapsules were synthesized with paraffin and the mixture of n-butyl stearate and n-tetradecyl alcohol as the core material, and the melamine-formaldehyde (MF) resin as shell material, respectively. In this way, the infrared stealthy coatings were prepared by using the as-synthesized microcapsules, the hollow glass microspheres and other auxiliaries. The surface morphology of the microcapsules were investigated by using scanning electron microscopy (SEM). By using the contactless infrared thermometer measurement and radiation rate test device, the radiation exitances of coatings were determined. The radiation exitance of infrared stealthy coatings is lower than the common coatings, which improved the performance of infrared stealthy of destination.

Preparation and Characterization of Microencapsulated n-octadecane as Phase Change Materials

In this paper, a kind of microcapsule containing phase change material of n-octadecane was successfully synthesized based on in situ polymerization where trimethylol melamine and hexamethylol melamine were shell materials. We used difierent emulsiflcation time, reaction time and difierent treatment to improve the quality of the microcapsules. The microcapsule and coated fabric were characterized by the optical microscope, Scanning Electronic Microscope (SEM), laser diameter distribution machine and Difierential Scanning Calorimeter (DSC). The optical microscope and SEM pictures showed that this microcapsule has good surface conflguration. Particle size with laser diameter distribution machine displayed that grains of the microcapsule were distributed evenly. The DSC results revealed the phasechanging temperature and enthalpy of the microcapsule.

Development of novel flurbiprofen-loaded solid self-microemulsifying drug delivery system using gelatin as solid carrier

To develop a novel flurbiprofen-loaded solid self-microemulsifying drug delivery system (solid SMEDDS) with improved oral bioavailability using gelatin as a solid carrier, the solid SMEDDS formulation was prepared by spray-drying the solutions containing liquid SMEDDS and gelatin. The liquid SMEDDS, composed of Labrafil M 1944 CS/Labrasol/Transcutol HP (12.5/80/7.5%) with 2% w/v flurbiprofen, gave a z-average diameter of about 100 nm. The flurbiprofen-loaded solid SMEDDS formulation gave a larger emulsion droplet size compared to liquid SMEDDS. Unlike conventional solid SMEDDS, it produced a kind of microcapsule in which liquid SMEDDS was not absorbed onto the surfaces of carrier but formed together with carrier in it. However, the drug was in an amorphous state in it like conventional solid SMEDDS. It greatly improved the oral bioavailability of flurbiprofen in rats. Thus, gelatin could be used as a carrier in the development of solid SMEDDS with improved oral bioavailability of poorly water-soluble drug.

液晶微胶囊制备宽波反射凝胶

Chiral nematic(N*) liquid crystal can reflect incident light selectively,and the reflective bandwidth is less than 150 nm commonly.Five N* liquid crystals were prepared from a nematic liquid crystal with negative dielectric anisotropy SLC10V513-200 and chiral compounds R1011,CB15.Their reflective spectra could cover with the entire visible spectrum.Polyurea microcapsules containing above N* liquid crystals were prepared by interfacial polymerization of isophorone diisocyanate(IPDI).By mixing same weight of five kinds of microcapsules together in surfactant OP-10 and IPDI,a gel was obtained.Applying an alternating electric field to an 80.0 μm gel film,the liquid crystal molecules in microcapsules would align parallel with the substrates.Curing monomer in the microcapsules with UV light and planar texture can be fixed,so the gel film which could reflect entire visible light wavelength range was prepared.

Preparation of coated thermo‐regulating textiles using Rubitherm‐RT31 microcapsules

AbstractSpherical microcapsules with a 49 wt % of Rubitherm® RT31 were successfully synthesized by means of suspension‐like polymerization to be used for textile applications in summer conditions. Microcapsules were fixed into seven fabric substrates for different textile applications by a coating technique without deteriorating original functionalities of the textiles. Thermal performance of different coated textiles with 35 wt % of microcapsules was evaluated by differential scanning calorimetry (DSC) and infrared thermography (IR) techniques and the physical characteristics of textiles with thermo‐regulating properties were examined by environmental scanning electron microscopy (ESEM). It was observed that all treated textile substrates allow to obtain thermo‐regulating properties with acceptable latent heat storage capacities. Results also indicated that the presence of microcapsules containing Rubitherm® RT31 produces a significant thermal insulation effect during a cold to warm transition (20–45°C). Thus, this kind of microcapsules can be used to obtain textiles with thermal comfort‐related properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Effect of molecular weight of chitosan on microcapsules and hypatocytes in microcapsules

Objective To study the influence of molecular weight of chitosan on microcapsules and hepatocytes in microcapsules. Methods The mechanical strength, permeability to fluoresceine isothiocyanate-bovine serum albumin (FITC-BSA) and activity of hepatocytes in microcapsules were compared between two kinds of microcapsules made by low and middle molecular weight chitosan. Results After 100 min of stirring microcapsules, all middle molecular weight chitosan microcapsules were damaged, 5% low molecular weight chitosan microcapsules were damaged. There was significant difference in breakage rate of the mechanical strength between two microcapsules (P ＜ 0. 05). Fifteen min after addition of FITCBSA into microcapsule solution, fluorescence intensity in the low molecular weight chitosan microcapsules was 4 AU, and that in middle molecular weight of chitosan microcapsules was 1. 5 AU, suggesting there was significant difference in permeability to FITC-BSA between two kinds of microcapsules (P ＜ 0. 05).One week after culture of microencapsulated hepatocytes, staining test showed that 100% of liver cells in low molecular weight chitosan microcapsules were alive, while the number was about 40% in middle molecular weight chitosan microcapsules (P ＜ 0. 05). Conclusion Low molecular weight chitosan is more suitable as materials of microcapsules than molecular weight chitosan. Key words: Hepatocyte; Microcapsules; Chitosan

Preparation and release kinetics of microencapsulated cisplatin with ethylcellulose.

Several kinds of microcapsules containing cisplatin were prepared by the ethylcellulose coacervation process in an attempt to administer cisplatin with chemoembolization. Microcapsules made either with mechanical stirring or with sonication showed similar properties; the chemical structure of cisplatin was not affected by the micro-encapsulation process. The release kinetics of cisplatin from ethylcellulose-walled microcapsules followed different patterns, according to the wall thickness. In each case, the release kinetics did not depend on the stirring rate of the surrounding medium. Only microcapsules with a cisplatin release ratio from 80 to 100% within 24 h were selected for later clinical use.

PREPARATION OF HOLLOW POLYELECTROLYTE MICROCAPSULES AND THEIR FLUORESCENT PROTEINS LOADING

Hollow polyelectrolyte microcapsules with size around 4 ～ 5 μm,have been prepared by layer-by- layer ( LbL) adsorption technique,based on template of weakly crosslinked melamine formaldehyde ( MF) latex microspheres. In the presence of aqueous HCl solution ( pH = 1. 0),the MF cores are decomposed and hollow polyelectrolyte microcapsules are acquired. This kind of microcapsules can be utilized in many fields such as biosensor,drug release. Therefore,understandings on loading,penetrability of biomelocules on cell size microcapsules and their interaction with capsules are important,which are definitely favorable to their employment in real industry. In this study,R-phycoerythrins( R-PE) are used as a model to examine protein load behaviors and protein-capsules interaction. The R-PE is a kind of phycobiliprotein,which is found in red algae. It plays a crucial role in efficiently harvesting sunlight and then transfers this energy via a series of energy transfer mechanisms to chrolophyll in the membranes of photosynthetic organisms. The fluorescent intensity of R-phycoerythrin is compared before and after mixing with microcapsules where the pH value ranges at 3 ～ 10. It shows a maximum protein loading at pH 4 ～ 5. Moreover,the pH dependent protein loading of microcapsules is analyzed on laser scanning confocal microscope. The further results indicate some R- phycoerythrin is entrapped into capsules at pH 4 ～ 5. However,the R-phycoerythrin mainly adsorbs at the surface of the microspheres at a pH range of 6 ～ 10 and has a constant amount. It attributes microcapsules to have porous structure and high surface free energy. The capsules have a very poor protein loading amount at pH 3.

Microencapsulation of a probiotic bacteria with alginate–gelatin and its properties

Lactobacillus casei ATCC 393-loaded microcapsules based on alginate and gelatin had been prepared by extrusion method and the product could increase the cell numbers of L. casei ATCC 393 to be 107 CFU g−1 in the dry state of microcapsules. The microparticles homogeneously distributed with size of 1.1 ± 0.2 mm. Four kinds of microcapsules (S1, S2, S3 and S4) exhibited swelling in simulated gastric fluid (SGF) while the beads eroded and disintegrated rapidly in simulated intestinal fluid (SIF). Cells of L. casei ATCC 393 could be continuously released from the microcapsules during simulated gastrointestinal tract (GIT) and the release amounts and speeds in SIF were much higher and faster than that in SGF. Encapsulation in alginate–gelatin microcapsules successfully improved the survival of L. casei ATCC 393 and this approach might be useful in delivery of probiotic cultures as a functional food.

Sustainment of hepatocyte function with mixed cellular co-encapsulation

To evaluate the effects of mixed microcapsules of hepatocytes mixed with hepatocytes, transgenic hepatic stellate cell strain (HGF/CFSC), and/or bone marrow derived Thy-1(+) beta(2)M(-) cells (BDTCs) to sustain liver function. Three kinds of microcapsules containing hepatocytes, hepatocytes + CFSC/HGFs, or hepatocyte + CFSC/HGF + BDTC were prepared and cultured in conditioned culture fluids. The morphology of the microcapsules and the encapsulated cells were observed by microscopy. The supernatant was collected regularly to detect the secretion of albumin and urea. Forty Wistar rats underwent 90% hepatectomization to establish acute liver failure model. Six hours after the operation the rats were randomly divided into 4 groups to be intraperitoneally injected with one of the 3 kinds of microcapsules containing 3.5 x 10(7) hepatocytes as experimental groups (Groups II, III, and IV) or injected with blank microcapsule as control group. The behaviors of the rats were observed daily. Blood was collected from the eyeball at different time points to detect relevant biochemical indicators. Twenty-one and 42 days after the operation the rats were killed. Abdominal lavage was performed to collect the microcapsules to undergo microscopy. Liver specimens were colleted to undergo pathological examination. Severe liver failure occurred in the rats transplanted with blank microcapsules. Most of the rats in Groups II, III, and IV began to eat within 20 hours after hepatectomization. Nine of the 10 rats in the control group died within 48 hours after hepatectomization. Nine of the 10 rats of Group II survived a long time. All the rats in Groups III and IV survived till the end of experiment. In comparison with the supernatant of Group II, the contents of albumin and urea in the supernatants of Groups III and IV were significantly higher (all P < 0.01). The liver function indicators, ALT, AST, lactic dehydrogenase, and albumin worsened since one day after the operation. Five days after the transplantation of microcapsule, the above indicators showed remarkable improvement, and recovered to normal 7 days after. Twenty-one and 42 days after the transplantation regeneration was seen and edema was reduced in the livers in Groups II, III, and IV. Twenty-one days after the transplantation most of the microcapsules were still free in the peritoneal cavity in Group II. In Group III, most of the microcapsules aggregated around the portal vein, fibrosis at the surface of microcapsule to a certain degree was seen and surviving hepatocytes could be found inside the capsules 21 days after. Forty-two days after, vascularization of microcapsules was seen in Groups III and IV, especially in the latter group. Mature hepatocyte, transgenic liver nonparenchymal cells and/or BMSCs co-encapsulate transplantation effectively improve acute liver failure. The microenvironment created by CFSC/HGF and/or BDTC is propitious to the maintenance of capsulated hepatocytes' function and longevity.

Conceptual Design of Super Environment-Conscious Intelligent Composites Incorporated with Life-Cycle Program of Self-Repair and Self-Collapse and Application for Environment-Conscious Interior Planning in Buildings

Super environment-conscious intelligent composite materials incorporated with life-cycle program of self-repair during in service and self-collapse after designed service life are proposed. One example is carbon short-cut fiber reinforced composites (CFRC) incorporated into matrix mortar with numerous two kinds of micro capsules imbedded with two smaller capsules containing nanometer-size reacting particle (calcium oxide (CaO) or cement) and initiating one (highly water-containing resin particle). These double capsules are incorporated during mixing mortar and fiber as chemical admixture, but they are stably dispersed, not breaking during in service of composites. By triggering these double capsules by external electromagnetic wave having two different frequencies, these capsules are broken, and chemical reaction occurs. As the results, self-repair is made to occur in the crack part during in service by the rather mild hydration reaction of cement, and self-collapse after designed service life by the rapid expansive hydration reaction of CaO. These cement composites are intelligent due to the appropriate response to the controlled external electromagnetic trigger, and environment-friendly due to the elongation of service life by self-repair, and the easiness of demolition and recycling by self-collapse. The same concept is also applied to carbon continuous fiber reinforced plastic reinforced concrete (CFRPRC). Other than double microcapsules, glass optical fibers are also imbedded into matrix resin of FRP. By detecting the change of electric resistance of CFRP, we can predict the collapse. By triggering the embedded double capsules, self-repair and self-collapse are made to occur. These pseudo-biological functions of self-repair and self-collapse are also incorporated into base concrete. These CFRPRC are enough to become intelligent and environment-friendly. By using well designed these super environment-conscious intelligent composites, I try to realize environment-conscious interior planning in which non-adhesive, but joint or set-in type interior construction are considered.

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 N 2 adsorption/desorption. The comparison of the extractabilities and the stripping of Cu(II) into the various kind of microcapsules were examined.

Diffusion of Disperse Dye from Capsules Containing Ferromagnetic Substance into PET Film.

Sublimation/diffusion behavior of a microencapsuled dye (1-aminoanthraquinone(AAQ), C.I. Solvent Blue 35 and C.I. Disperse Red 50) into poly (ethylene terephthalate)(PET) film was evaluated applying the film roll method. Eight kinds of microcapsules (smaller than 15 μm in diameter) containing both dyestuff and ferromagnetic substance or only the dyestuff were prepared by using acrylate resin as capsul material. Fickian diffusion profiles of three kinds of dye were obtained both from free state and from microcapsules in the temperature range from 170 to 200°C. Hence, the diffusion coefficients D could be calculated using the equation (ln C=A−(χ2/4t)·1/D), where C is the concentration at distance χ from surface after time t and A is a constant. From the temperature dependence of the D, the activation energy (ΔE) for diffusion was calculated. ΔE for diffusion from microcapsules was a little larger than from free state. It was also found that there is no influence of ferromagnetic substance on diffusion. This fact indicates that the capsule wall affected as “a very low diffusion barrier”.

大腸ターゲティング徐放性製剤技術

To determine the necessary technology by which sustained drug release is obtained after drug is delivered to the colon, two kinds of microcapsules were prepared and were filled in a pressure-controlled colon delivery capsule (PCDC). 5-aminosalicylic acid (5-ASA) was microencapsulated with a water-insoluble polymer, ethylcellulose (EC) or with pH-sensitive polymers, Eudragit™ L-100 or S-100 and encased in PCDC, After oral administration of the test preparations to beagle dogs, the first appearance time of 5-ASA into the systemic circulation were 3 hr for all the colon delivery preparations. These test preparations were thought to be delivered to the colon. Both EC microcapsules and Eudragit S/RS microcapsules in PCDC showed longer mean residence time MRT, 8.2±0.6 hr and 8.7±0.9 hr, than Eudragit L/RS microcapsules in PCDC of which MRT was 6.6±0.2 hr, Since PCDC containing 5-ASA powder exhibited a MRT of 7.0±1.0 hr, these two types of preparations have sustained release characteristics.

Technology to Obtain Sustained Release Characteristics of Drugs after Delivered to the Colon

To determine the necessary technology by which sustained drug release is obtained after drug is delivered to the colon, two kinds of microcapsules were prepared and were filled in a pressure-controlled colon delivery capsule (PCDC). As a model drug 5-aminosalicylic acid (5-ASA) was used, because the target site of 5-ASA is the entire large intestine. 5-ASA was microencapsulated using a water-insoluble polymer, ethylcellulose (EC) or with pH-sensitive polymers, Eudragit™ L-100 or S-100 and encased in PCDC. The particle size of these microcapsules was around 800 μm and the loading efficiencies of 5-ASA were approximately 90%. In vitro dissolution tests were performed with the prepared microcapsules. The release rate of 5-ASA from the microcapsules was significantly prolonged as compared to 5-ASA powder, although there were no significant differences in the release rates between these microcapsules. By incorporating the 5-ASA microcapsules into PCDC, sustained release PCDCs for colon delivery were prepared and in vivo evaluation was performed using beagle dogs. As a fast release colon delivery system, PCDCs were prepared with 5-ASA powder suspended in suppository base. After oral administration of the test preparations to beagle dogs, plasma 5-ASA concentrations were measured and sustained release characteristics of 5-ASA from the test preparations were evaluated from the plasma 5-ASA concentration-time profiles. The first appearance time of 5-ASA into the systemic circulation after oral administration were 3 h for all the colon delivery preparations and it was thought that these test preparations were delivered to the colon. Both EC microcapsules and Eudragit S-100/RS-100 microcapsules in PCDC showed longer the mean residence time MRT, 8.2 ± 0.6 h and 8.7 ± 0.9 h, than Eudragit L-100/RS-100 microcapsules in PCDC where the MRT was 6.6 ± 0.2 h. Since PCDCs containing 5-ASA powder exhibited a MRT of 7.0 ± 1.0 h, these two types of preparations have suggested sustained release characteristics.

Formulation Factors of the Fenitrothion Microcapsule Influencing the Residual Efficacy against the German Cockroach

The relationship between the formulation factors of microcapsule, particle size and wall thickness, and the residual contact efficacy against German cockroaches was studied using several kinds of polyurethane-walled microcapsules. All kinds of microcapsules were trampled by the contact with cockroaches, although the degrees of the trampling were different. Moreover the residual efficacy depended on the mass median diameter and the wall thickness. The D/T ratio (the ratio of mass median diameter (D) to wall thickness (T)) was proposed as a parameter of the strength of microcapsule; the higher the D/T ratio, the more the trampled microcapsule. The result led to a conclusion that the D/T ratio was closely related to the residual efficacy. The D/T ratio to optimize the initial and residual efficacy of microcapsule was around 150.

Studies on microcapsules to replace erythrocytes in the passive agglutination reaction

Two kinds of microcapsules were made from polyurethane and polyurea. Each capsule had a mean diameter of 6 μm, a specific gravity of 1.10, and was red in color. The capsules were coated with ovalbumin condensed with glutaraldehyde. The coated capsuls were agglutinated with anti-ovalbumin antibody. The polyurethane capsule (positive charge) bound more ovalbumin and showed a higher sensitivity than did the polyurea capsule (negative charge) or erythrocytes.