Preparation of genipin cross-linked chitosan-gelatin microcapsules for encapsulation of Zanthoxylum limonella oil (ZLO) using salting-out method

Zanthoxylum limonella oil (ZLO) containing chitosan-gelatin complex microcapsules cross-linked with genipin, a cross-linker of natural origin, have been prepared by a complex coacervation process using the salting-out method. The effects of various parameters such as oil loading, degree of cross-linking, ratio of chitosan to gelatin, etc. on oil content, encapsulation efficiency and the release rate of ZLO have been studied. FT-IR spectroscopy has been used to understand the interaction between the polymers and oil. Scanning electron microscopy (SEM) has been employed to study the morphology of the prepared microcapsules.     

Polysulphone microcapsules containing silicone oil for the removal of toxic volatile organics from water

Removal of volatile organic contaminants (VOCs) from water is an important task for environmental protection. Silicone oil has many merits but can not be directly applied in extraction of VOCs due to its high viscosity, which can negatively affect the mass transfer. Therefore a new purification method with extractant microcapsules has been developed in this work. Polysulphone microcapsules containing silicone oil were prepared successfully using a solvent evaporation method. The mass transfer performance was determined with toluene as the recovered component and with the prepared microcapsules as the separation agent. Extraction equilibrium could be reached in approximately 60 min. The maximum uptake of toluene was 24.5 mg g(-1) microcapsules. Microcapsules were reused four times and showed very good stability. Using microcapsules containing silicone oil as the separation agent, high and stable extraction capacity has been successfully achieved, especially without any phase dispersion and phase separation processes. It may be concluded that low energy will be required in the new separation process.     

Preparation and stability of agarose microcapsules containing BCG

An emulsification/internal gelation method of preparing small-sized agarose microcapsules containing Bacillus Calmette-Guérin (BCG) is reported. Agarose microcapsules have been prepared by the emulsification of the hydrogel within a vegetable oil followed by its gelation due to the cooling of the system. Four different oils (sesame, sweet almonds, camomile and jojoba) were assayed. The rheological analysis of the oils showed a Newtonian behaviour, with viscosity values of 37.7, 51.2, 59.3 and 67.1 mPa s for jojoba, camomile, sesame and sweet almonds oil, respectively. The particle size of the microcapsules obtained ranged from 23.1 #181;m for the microcapsules prepared with sweet almonds oil to 42.6 #181;m for those prepared with jojoba. The microcapsule particle size was found to be dependent on the viscosity of the oil used in the emulsification step. The encapsulated BCG was identified by the Difco TB stain set K, followed by observation under optical microscopy. Once prepared, microcapsules were freeze-dried using 5% trehalose as cryoprotectant and the stability of the microcapsules was assayed during 12 months storage at room temperature, observing that agarose microcapsules were stable after 12 months storage, since there was no evidence of alteration in the freeze-dried appearance, resuspension rate, observation under microscope, or particle size.     

Preparation and stability of agarose microcapsules containing BCG

An emulsification/internal gelation method of preparing small-sized agarose microcapsules containing Bacillus Calmette-Guerin (BCG) is reported. Agarose microcapsules have been prepared by the emulsification of the hydrogel within a vegetable oil followed by its gelation due to the cooling of the system. Four different oils (sesame, sweet almonds, camomile and jojoba) were assayed. The rheological analysis of the oils showed a Newtonian behaviour, with viscosity values of 37.7, 51.2, 59.3 and 67.1 mPa s for jojoba, camomile, sesame and sweet almonds oil, respectively. The particle size of the microcapsules obtained ranged from 23.1 microm for the microcapsules prepared with sweet almonds oil to 42.6 microm for those prepared with jojoba. The microcapsule particle size was found to be dependent on the viscosity of the oil used in the emulsification step. The encapsulated BCG was identified by the Difco TB stain set K, followed by observation under optical microscopy. Once prepared, microcapsules were freeze-dried using 5% trehalose as cryoprotectant and the stability of the microcapsules was assayed during 12 months storage at room temperature, observing that agarose microcapsules were stable after 12 months storage, since there was no evidence of alteration in the freeze-dried appearance, resuspension rate, observation under microscope, or particle size.     

Polysulphone microcapsules containing silicone oil for the removal of toxic volatile organics from water

Removal of volatile organic contaminants (VOCs) from water is an important task for environmental protection. Silicone oil has many merits but can not be directly applied in extraction of VOCs due to its high viscosity, which can negatively affect the mass transfer. Therefore a new purification method with extractant microcapsules has been developed in this work. Polysulphone microcapsules containing silicone oil were prepared successfully using a solvent evaporation method. The mass transfer performance was determined with toluene as the recovered component and with the prepared microcapsules as the separation agent. Extraction equilibrium could be reached in ～ 60 min. The maximum uptake of toluene was 24.5 mg g^?1 microcapsules. Microcapsules were reused four times and showed very good stability. Using microcapsules containing silicone oil as the separation agent, high and stable extraction capacity has been successfully achieved, especially without any phase dispersion and phase separation processes. It may be concluded that low energy will be required in the new separation process.     

Preparation of uniform microcapsules with silicone oil as continuous phase in a micro-dispersion process

This paper presents an improved solvent evaporation method with silicone oil (PDMS) as the continuous phase for preparation of microcapsules to make more polymer solvents available. A microchannel device was used to produce emulsions instead of mechanical stirring to prepare the mono-dispersed microcapsules. Under the conditions of lower evaporation temperature and shorter evaporation time, uniform polyacrylonitrile (PAN) microcapsules containing Aliquat 336 (ALQ) have been successfully prepared. N,N-dimethylformamide (DMF) with lower evaporation ability was applied as the polymer solvent. The prepared microcapsules have rough surfaces and homogeneously internal structures. By changing the two-phase flow rate, the mean size of microcapsules can be easily controlled. When more ALQ was added in polymer solution, the loading ratio of microcapsules increased. The mass transfer performance and stability were determined by extraction of Cr (VI) ions from its aqueous solution. The mass transfer rate was fast enough. After three times of repeated extraction and stripping, the microcapsules kept almost the same extraction ability, which indicated that the microcapsules have very good stability.     

Preparation of uniform microcapsules with silicone oil as continuous phase in a micro-dispersion process

This paper presents an improved solvent evaporation method with silicone oil (PDMS) as the continuous phase for preparation of microcapsules to make more polymer solvents available. A microchannel device was used to produce emulsions instead of mechanical stirring to prepare the mono-dispersed microcapsules. Under the conditions of lower evaporation temperature and shorter evaporation time, uniform polyacrylonitrile (PAN) microcapsules containing Aliquat 336 (ALQ) have been successfully prepared. N,N-dimethylformamide (DMF) with lower evaporation ability was applied as the polymer solvent. The prepared microcapsules have rough surfaces and homogeneously internal structures. By changing the two-phase flow rate, the mean size of microcapsules can be easily controlled. When more ALQ was added in polymer solution, the loading ratio of microcapsules increased. The mass transfer performance and stability were determined by extraction of Cr (VI) ions from its aqueous solution. The mass transfer rate was fast enough. After three times of repeated extraction and stripping, the microcapsules kept almost the same extraction ability, which indicated that the microcapsules have very good stability.     

The influence of HLB on the encapsulation of oils by complex coacervation

Abstract

Microcapsules are used for the formulation of drug controlled release and drug targeting dosage forms. Encapsulated hydrophobic drugs are often applied as their solutions in plant oils. The uptake of the oils in the complex coacervate microcapsules can be improved by the addition of surfactants. In this study, soybean, olive and peanut oils were chosen as the representatives of plant oils. The well characterized complex coacervation of gelatin and acacia has been used to produce the microcapsules. The amount of encapsulated oil has been determined gravimetrically. The encapsulation of the oils was high (75–80%). When the surfactants with HLB values from 1.8 to 6.7 were used, the amount of encapsulated oil was high (65–85%). A significant decrease of the oil content in the microcapsules was found when Tween 61 with HLB = 9.6 had been added into the mixture. No oil was found inside the microcapsules from the coacervate emulsion mixture containing Tween 81 (HLB = 10) and Tween 80 (HLB = 15), respectively. The results of the experiment confirm the dependence of hydrophobic substance encapsulation on the HLB published recently for Squalan     

Preparation of high thermal stability polysulfone microcapsules containing lubricant oil and its tribological properties of epoxy composites

Polysulfone (PSF) microcapsules containing lubricant oil have been successfully prepared using solvent evaporation method. The results show that lubricant oil was successfully encapsulated and the encapsulation capacity of about 56.0?wt.% was achieved. The uniform microcapsules have nearly spherical shape and quite smooth outer surface. The mean diameter is approximately 156 and 169?μm by using different dispersant solutions. The wall material is porous in structure with wall thickness of about 20?μm. The initial decomposition temperature of PSF is 480?°C. It is higher than traditional poly(urea-formaldehyde) (PUF) and poly(melamine-formaldehyde) (PMF) wall materials with 245?°C and 260?°C initial decomposition temperature, respectively. High thermal stability of PSF microcapsules can be considered as additives in high temperature resistant polymer materials. The frictional coefficient and wear rate of epoxy composites decreased significantly by incorporating microcapsules containing lubricant oil into epoxy. When the concentration of microcapsules was 25?wt.%, the frictional coefficient and specific wear rate were reduced by 2.3 and 18.3 times, respectively, as compared to the neat epoxy.     

Microencapsulation of eugenol by gelatin-sodium alginate complex coacervation

Present study describes microencapsulation of eugenol using gelatin-sodium alginate complex coacervation. The effects of core to coat ratio and drying method on properties of the eugenol microcapsules were investigated. The eugenol microcapsules were evaluated for surface characteristics, micromeritic properties, oil loading and encapsulation efficiency. Eugenol microcapsules possessed good flow properties, thus improved handling. The scanning electron photomicrographs showed globular surface of microcapsules prepared with core: coat ratio1:1.The treatment with dehydrating agent isopropanol lead to shrinking of microcapsule wall with cracks on it. The percent oil loading and encapsulation efficiency increased with increase in core: coat ratio whereas treatment with dehydrating agent resulted in reduction in loading and percent encapsulation efficiency of eugenol microcapsules.     

Impact of the type of emulsifier on the physicochemical characteristics of the prepared fish oil-loaded microcapsules

Fish oil microcapsules were successfully prepared from fish oil-in-water emulsions using chitosan as shell material and anionic surfactants sodium dodecyl sulphate (SDS), sodium dodecylbenzenesulfonate (SDBS), sodium cholate (cholate), and sodium deoxycholate (DOC) as emulsifiers. The type of emulsifier influenced the physicochemical characteristics of the prepared microcapsules to different extents. The microcapsules formed with DOC showed the least mean effective diameter (MED) of 500?nm. Emulsion formed with DOC exhibited the smallest MED of 100?nm. The emulsions showed negative zeta potential values which became positive after encapsulation with chitosan. The surfactants showed little influence on thermal stability. Microcapsule suspensions showed creaming over storage. Fish oil at higher loading in SDS microcapsules showed higher primary and secondary oxidation. All microcapsules showed sustained release but the values varied depending upon the surfactants. The emulsion and microcapsules formed with DOC showed better morphology and stability despite its lower loading and encapsulation efficiency.     

番茄红素-橄榄油微囊的制备及稳定性研究

目的：利用微囊化技术提高番茄红素的稳定性。方法：以明胶和阿拉伯胶为混合壁材,用复凝聚法制备番茄红素-橄榄油微囊,通过电镜扫描和粒径测定法评价微囊的体外特征,并在光照和热破坏条件下考察其稳定性。结果：初步确定微囊制备的最佳工艺：以橄榄油为油相,囊材溶液质量浓度为0．05g·mL^-1,成囊时体系pH值为4．0、温度为45℃;选用高剪切乳化机进行乳化,转速为3000r·min^-1,乳化时间为5min;以冷冻干燥法进行微囊干燥。由此制得的微囊圆整度好,平均粒径约7μm,均匀度为0．0899,包封率为81．8％;在强光（4500h）或高温（60℃）下放置10天,其含量基本稳定。结论：番茄红素-橄榄油微囊制备工艺简易,成品稳定性好,值得进一步研究开发。     

复凝聚法制备桃金娘油肠溶微囊

目的采用复凝聚法制备桃金娘油肠溶微囊,并对其体外性质进行评价。方法选用海藻酸钠、氯化钙、壳聚糖为囊材采用复凝聚法制备桃金娘油微囊,用扫描电子显微镜(scanning electron microscope,SEM),Beckman Coulter LS 230激光粒度仪表征了微囊表面形态及粒径,采用顶空进样-GC色谱法测定了载药量和包封率。结果正交设计优化处方和工艺如下:海藻酸钠质量浓度为25g.L-1、壳聚糖质量浓度为3 g.L-1、凝聚速度为5 mL.min-1和凝聚时间为60 min,所得微囊粒径为(14.23±1.45)μm,载药质量分数为(11.3±0.4)%,包封率为(73.6±2.5)%。微囊具有耐酸和肠溶性能,表面褶皱,粒径分布均匀。结论复凝聚法可用于桃金娘油肠溶微囊的制备。     

The Influence of Surface Properties on Uptake of Oil into Complex Coacervate Microcapsules

Abstract— A range of surfactants with different hydrophile-lipophile balance (HLB) values was selected to investigate the influence of interfacial properties on the uptake of oil droplets into complex coacervate microcapsules. The well characterized gelatin/acacia complex coacervate system was used in this study and the encapsulation of squalane, and oleic acid was investigated. The surfactants investigated were Span 85, Span 80, Span 40, egg yolk lecithin, and Tween 80. Combinations of surfactants were utilized to obtain intermediate HLB values. The percentage oil encapsulated was determined gravimetrically, based on the initial concentration and the amount extracted from the microcapsules. The aqueous interfacial tension values of the oils and oil/surfactant systems were measured using the Wilhelmy plate method. The interfacial properties were correlated to the percentage oil uptake by the coacervate phase. The relative hydrophobicity/lipophilicity of the oil influenced its uptake by complex coacervate droplets. The presence of surfactant affected oil uptake, depending on the HLB value of the surfactant or surfactant mixture. Uptake of squalane by the gelatin/acacia coacervates was found to be optimized by the addition of surfactants with HLB values in the range 2·5–6. The percentage uptake of oil decreased rapidly for systems prepared containing surfactants with HLB values outside this range. No correlation was observed between oil uptake by the coacervate phase and the interfacial tension of the oil and oil/surfactant systems with double-distilled deionized water.     

An evaluation of albumin microcapsules prepared using a multiple emulsion technique

Albumin microcapsules containing sulphadiazine were prepared using a multiple emulsion technique. Heat was utilized to denature the albumin and form the capsule shell. Albumin microcapsules prepared using this technique were free-flowing, spherical in shape, and had varying degrees of vacuolation. The effects of drug: polymer ratio and concentration of cross-linking agent on the percentage of drug retained in the microcapsules and release of drug from the microcapsules were studied. Also, the effect of viscosity of the innermost oil layer, of the multiple emulsion, upon the mean diameter of the microcapsules and release of drug from the microcapsules was investigated.     

Preparation of a copoly (dl-lactic/glycolic acid)-zinc oxide complex and its utilization to microcapsules containing recombinant human growth hormone

A procedure to prepare a complex of copoly (dl-lactic/glycolic acid) and zinc oxide (PLGA-zinc oxide complex) was developed. Out of sparingly water-soluble zinc compounds, zinc oxide was most remarkably soluble in a PLGA/dichloromethane solution and the dissolution rates became faster as the water contents in the PLGA/dichloromethane solutions increased. Since the solubility of zinc oxide was saturated at approximately 0.5-fold molar ratio to PLGA and water was generated with dissolution of zinc oxide in the PLGA/dichloromethane solutions, it is suggested that zinc oxide interacts with the terminal carboxyl group of PLGA. In addition, the glass-transition temperature of a solid material obtained by vacuum-drying the PLGA/dichloromethane solution dissolving zinc oxide became higher as the zinc content increased, suggesting that the formation of a PLGA-zinc oxide complex. Microcapsules were prepared with the PLGA-zinc oxide complex using recombinant human growth hormone (rhGH) in order to evaluate an effect of the complex on protein release and stability of protein in the microcapsules. Released rhGH amount from the microcapsules prepared with the PLGA-zinc oxide complex after subcutaneous administration in rats was significantly larger than that from microcapsules prepared with PLGA alone, indicating that rhGH molecules in the microcapsules was stabilized by the PLGA-zinc oxide complex.     

Encapsulation of a lipid precursor,the eicosapentaenoic acid,to study the development of the Crassostrea gigas oyster flavours

The present study is part of a larger project whose aim is to understand how the oyster Crassostrea gigas develops its aromas from a lipid precursor, the eicosapentaenoic acid (EPA), in glyceride form. The objective of this study is, therefore, to prepare an encapsulation process that will enable the bivalve to be supplied with this lipid precursor. The complex coacervation method was chosen as it gave the best compatible microcapsules with respect to the nutritional aspects of oyster (i.e. digestibility) and the environmental constraints (i.e. behaviour and stability in seawater). The aim of this study is to manufacture and optimize a process of complex coacervation, to obtain capsules made of gelatin and acacia gum with a size under 100 microm in diameter and containing very small drops of cod liver oil (rich in EPA). The preservation of these microcapsules in seawater has been confirmed.     

Layer-By-Layer Synthesis of the pH-Responsive Hollow Microcapsule and Investigation of Its Drug Delivery and Anticancer Properties

Multilayered pH-responsive hollow microcapsules with non-toxicity and biological specificity advantages were prepared from two kinds of polymers i.e., chitosan (CH) and poly (ethylene glycol dimethacrylate-co-methacrylic acid) (PE) via layer-by-layer (LbL) method, which is followed by subsequent removal of silica core. The hollow nature of obtained spherical microcapsules was found by transmission electron microscopy (TEM). The microcapsules were prepared as gemcitabine (GM) and curcumin (CR) carriers. The drugs have been loaded within the microcapsules during or after the synthetic procedure. Although acceptable loading efficiencies (LE) were obtained in both methods, the amount of drug loaded during the synthesis method is relatively higher. Values above 78% and 87%, for releasing efficiency (RE%) and encapsulation efficiency (EE%), respectively, demonstrate the high potential of the prepared microcapsules for drug delivery. In addition, the difference between the amount of drug released in acidic and neutral pH indicates the pH-responsivity of the prepared microcapsules. Moreover, the dose-dependent high cytotoxicity effect of the prepared microcapsules was observed on the HCT116 colorectal carcinoma cells.     

Sustained-release dosage forms of microencapsulated isoniazid

The preparation and release characteristics of microcapsules of isoniazid have been studied. The differing techniques of microencapsulation are assessed and the dissolution of drug from suspended and tableted microcapsules prepared using the chosen technique has been monitored for in vitro release.     

Sustained-release dosage forms of microencapsulated isoniazid

The preparation and release characteristics of microcapsules of isoniazid have been studied. The differing techniques of microencapsulation are assessed and the dissolution of drug from suspended and tableted microcapsules prepared using the chosen technique has been monitored for in vitro release.