Formulation and characterization of the microencapsulated entomopathogenic fungus Metarhizium anisopliae MA126

Bioinsecticides are expected to be used for controlling major species of aphids. The present study explored a liquid phase coating technique for the formulation of microencapsulated conidia of the entomopathogenic fungus Metarhizium anisopliae MA126. Various parameters for microencapsulation were investigated. The biopolymers sodium alginate, hydroxypropyl methyl cellulose (HPMC) and chitosan were tested as coating materials. Calcium chloride was used as the cross-linking agent for converting soluble sodium alginate into an insoluble form. To improve the efficiency of microencapsulation, the additives of HPMC, dextrin, chitosan or HPMC/chitosan in various ratios (1 : 1, 1 : 3 and 3 : 1) were used as the coating materials. The particle size of a bare microcapsule was less than 30 microm. Larger size microcapsules were produced using vortex method by comparison with that using homogenization method. The latter method, however, was easy to scale up. The effect of coating materials on the morphology and encapsulation efficiency of the microcapsules was also studied. The best encapsulation efficiency (78%) was using HPMC as the additive of the coating material. The next was dextrin (70%). By measuring the germination rate, the results showed that the activity was approximately 80% of the initial after 6 months of storage at 4 degrees C, while that of the bare conidia was less than 50% stored in identical conditions.     

Encapsulation of olive leaf antioxidants in microbeads: Application of alginate and chitosan as wall materials

Edible microcapsule technology has been declared as a newly developed technology in 21st century by some certain authorities in order to preserve food products. Encapsulation of the bioactive materials in edible coatings is a blessing that can eliminate many undesirable situations that might arise when it is used as additive. In this study, olive leaf extract has been evaluated as active material to prepare microcapsules by using alginate as coating. Ionic gelation was used to produce microbeads. The experimental design of the encapsulation system, the effects of the process parameters, the modeling of the experimental data and the optimization of the conditions were carried out with Box-Behnken design of response surface method (Box-Behnken-RSM). Box-Behnken-RSM produced 17 experimental runs. Calcium chloride (2–15%, w/v) and sodium alginate concentrations (1–2%, w/v), and hardening time (15–45 min) were selected as independent variables, while encapsulation efficiency (EE) of the capsules in terms of total phenolic content (TPC) and oleuropein concentration were responses. Impact of chitosan as coating layer was also investigated with three different ratios of chitosan (0.4%, 0.7%, 1% w/v). Accelerated oxidation test was employed to measure the stability of the microcapsules against oxidation by means of Rancimat method. Encapsulation of the olive leaf extract in alginate microbeads was satisfying with >70% and >90% efficiencies with respect to TPC and oleuropein under optimum conditions (2.34% calcium chloride concentration and 2% sodium alginate for 26 min of hardening time).     

Microencapsulation of hemoglobin in chitosan-coated alginate microspheres prepared by emulsification/internal gelation

Chitosan-coated alginate microspheres prepared by emulsification/internal gelation were chosen as carriers for a model protein, hemoglobin (Hb), owing to nontoxicity of the polymers and mild conditions of the method. The influence of process variables related to the emulsification step and microsphere recovering and formulation variables, such as alginate gelation and chitosan coating, on the size distribution and encapsulation efficiency was studied. The effect of microsphere coating as well its drying procedure on the Hb release profile was also evaluated. Chitosan coating was applied by either a continuous microencapsulation procedure or a 2-stage coating process. Microspheres with a mean diameter of less than 30 microm and an encapsulation efficiency above 90% were obtained. Calcium alginate cross-linking was optimized by using an acid/CaCO(3) molar ratio of 2.5, and microsphere-recovery with acetate buffer led to higher encapsulation efficiency. Hb release in gastric fluid was minimal for air-dried microspheres. Coating effect revealed a total release of 27% for 2-stage coated wet microspheres, while other formulations showed an Hb release above 50%. Lyophilized microspheres behaved similar to wet microspheres, although a higher total protein release was obtained with 2-stage coating. At pH 6.8, uncoated microspheres dissolved in less than 1 hour; however, Hb release from air-dried microspheres was incomplete. Chitosan coating decreased the release rate of Hb, but an incomplete release was obtained. The 2-stage coated microspheres showed no burst effect, whereas the 1-stage coated microspheres permitted a higher protein release.     

Encapsulation of ethanol by spray drying technique: effects of sodium lauryl sulfate.

Microcapsules composed of ethanol, water and dextrin as a water-soluble polymer can be used to encapsulate poorly water-soluble drugs by spray drying technique. For the encapsulation of a high dose of poorly water-soluble drugs, large amounts of ethanol and consequently large quantities of dextrin are needed for the dissolution of drug and the encapsulation of ethanol, respectively. In order to increase the ethanol content with the decreased amount of dextrin, sodium lauryl sulfate (SLS) was employed in the preparation of microcapsules without drug by a spray drying method. Phase diagrams were prepared to determine the region of microcapsule formation with a three-component system of ethanol, dextrin and water. The homogeneous phase indicated in the phase diagram was used to prepare the alcoholic microcapsules since this phase was not separated rapidly and not too viscous to be spray-dried. Interestingly, SLS at concentrations below 2% remarkably increased both the ethanol content and the encapsulation efficiency of ethanol. The maximum ethanol content and encapsulation efficiency were observed with 0.5-1% of SLS (35.4 and 67.6%, respectively). Furthermore, the increase by SLS was more pronounced at the low dextrin/water ratios than at the high dextrin/water ratios. In particular, the ethanol content and the encapsulation efficiency with the dextrin/ethanol/water ratio of 0.4/1/1, which had relatively small amounts of dextrin, were about ten times higher in the presence of SLS than those without SLS. In conclusion, this study shows that small amounts of SLS can increase the ethanol content and the encapsulation efficiency of ethanol, and allow the reduction in the amount of dextrin required to encapsulate ethanol in the preparation of microcapsules. These findings suggest that the use of SLS may permit the effective encapsulation of high dose of water-insoluble drug into microcapsules.     

Optimization and characterization of chitosan-coated alginate microcapsules containing albumin

In order to obtain small microcapsules with high protein encapsulation efficiency and extended release characteristics various processing factors were studied. Bovine serum albumin-loaded alginate microcapsules were prepared by an emulsion method and further incubated in chitosan. Many process factors were tested including the concentration and molecular weight of alginate, the concentration and pH of chitosan, and surfactants, etc. Microcapsules were achieved with diameters less than 2 microm, high encapsulation efficiency (> 80%) and high loading rate (> 10% w/w). The results also showed that the initial BSA amount of 20%-30% loaded alginate microcapsules coated with 0.2%-0.5% chitosan solutions at pH 4 by the two-stage procedure present the best sustained releasing characteristics.     

正交试验优选白藜芦醇微囊处方

目的：优选白藜芦醇微囊的处方。方法：采用滴制法制备白藜芦醇微囊,以海藻酸钠黏度、海藻酸钠与白藜芦醇质量比、海藻酸钠质量分数、氯化钙质量分数为考察因素,以白藜芦醇载药量和包封率的综合评分为评价指标,采用正交试验优选白藜芦醇微囊处方。结果：最优处方为海藻酸钠黏度为380cps、海藻酸钠与白藜芦醇的质量比为0．5：1、海藻酸钠质量分数为2．0％、氯化钙质量分数为3．0％。结论：所选白藜芦醇微囊处方合理,制得的白藜芦醇微囊裁药量和包封率较高。     

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.     

Immobilization and bioactivity of glucose oxidase in hydrogel microspheres formulated by an emulsification-internal gelation-adsorption-polyelectrolyte coating method

The purpose of this study was to develop a novel microsphere formulation of glucose oxidase (GOX) with high drug loading, encapsulation efficiency and bioactivity. GOX was encapsulated in alginate/chitosan microspheres (ACMS) using an emulsification-internal gelation, followed by GOX adsorption and polyelectrolyte coating method. The factors influencing GOX loading, encapsulation efficiency and activity of the loaded GOX were investigated. The resultant ACMS in wet state were spherical with a mean diameter of about 138 microm. GOX loading was found to be pH dependent. High GOX loading and encapsulation efficiency were achieved when the pH of the adsorption medium was lower than the isoelectric point (pI) of GOX. GOX loading and encapsulation efficiency increased with increasing GOX concentration in the loading solution, but decreased with increasing chitosan concentration in the coating solution. The activity of loaded GOX increased and then decreased with increasing chitosan concentration. The activity of GOX in ACMS was maintained and showed sustained production of H(2)O(2) as compared to free GOX. Around 90% of the original activity of immobilized GOX remained after lyophilization and storage at -20 degrees C for a month. These results suggest that the ACMS and the fabrication method are suitable for microencapsulation of proteins like GOX.     

壳聚糖-海藻酸钠微囊对干扰素-tau的控释作用

目的用壳聚糖和海藻酸钠为原料,制备干扰素-tau微囊,希望开发成为一种口服干扰素制剂。方法使用注射器手工滴制的方法,在滴加过程中,速度和距离是影响囊形的主要因素。结果壳聚糖-海藻酸钠微囊法应用于干扰素-tau药物的包封,其制备简单快速,干扰素-tau包封率很高,并且具有肠溶缓释作用。结论壳聚糖-海藻酸钠微囊有望用作干扰素-tau或其它肽类药物的口服制剂。     

干扰素-tau微囊的制备工艺优化

目的用壳聚糖和海藻酸钠为原料,制备干扰素-tau微囊。方法采用凝聚法制备了干扰素-tau壳聚糖-海藻酸钠微囊,以包封率、微囊强度为指标,设立总的评估指数,用L9(34)表进行正交实验优化制备工艺。结果最终的优化方案为:2.0%海藻酸钠、0.4%壳聚糖、0.3%干扰素-tau以及1.0%氯化钙溶液。结论该工艺简便、稳定,壳聚糖-海藻酸钠微囊有望用作干扰素-tau或其它蛋白质药物的口服制剂技术。     

Preparation and in vitro dissolution of salbutamol sulphate microcapsules and tabletted microcapsules

Abstract

Salbutamol sulphate is a sympathomimetic amine having a rather short plasma half-life. Aiming to achieve sustained release of this drug through microencapsu-lation, the coacervation method with a 1:1 core-shell ratio was used. In vitro release rate experiments were performed on the microcapsules prepared using ethyl cellulose as the coating agent and compared to the results of intact drug, the tabletted microcapsules and a commercial tablet. The release rate of salbutamol sulphate could be controlled through microencapsulation. The time for the 50% release of the drug was 15 and 90 min for the tabletted microcapsules and microcapsules respectively. The specific surface area of the intact drug was 0.35m²/cc while it reduced to 0.06m²/cc after encapsulation.     

对乙酰氨基酚/阿拉伯胶-壳聚糖多层微囊的制备及其体外释药研究

目的:制备对乙酰氨基酚多层微囊并考察其体外释药性能和机制。方法:以阿拉伯胶和壳聚糖为囊材,以戊二醛为交联剂,使用溶液干燥法(复合乳液法)制备载药(对乙酰氨基酚)多层(阿拉伯胶-壳聚糖-阿拉伯胶-壳聚糖)微囊。通过正交试验,以阿拉伯胶溶液-二氯甲烷体积比(A)、壳聚糖用量(B)、戊二醛-成壳材料总量比例(C)为因素,包封率为指标,优选制备工艺。通过测定其在盐酸溶液中的体外累积释药率并进行释放动力学模型拟合分析其释药机制。结果:最佳工艺条件为A4:3、B0.6g、C1:3。所制备的多层微囊球形完整、光滑,囊壁较厚;突释效果不明显,药物在12h内全部释放,其体外释药机制符合Ritger-Peppas模型。结论:所制载药多层微囊突释效应小、缓释效果较好。     

Effect of the shell-forming polymer ratio on the encapsulation of tea tree oil by complex coacervation as a natural biocide

Abstract

The aim of this study was to develop footwear materials with antimicrobial properties using microencapsulated Tea Tree oil (TTO) as a natural biocide. For that purpose, gelatine–carboxymethylcellulose based microcapsules containing TTO were synthesised by a complex coacervation process. Furthermore, the influence of the gelatine (G)/sodium carboxymethylmethyl cellulose (CMC) ratio (G/C) on the microcapsule properties, as well as in the microencapsulation oil efficiency, was evaluated. The microcapsules were characterised by different experimental techniques and applied to footwear materials (leather and textile) to evaluate their performance. The microcapsule durability under different conditions, such as rubbing and ironing, was analysed in order to simulate shoe manufacturing and shoe wearing. The properties of the microcapsules obtained by complex coacervation, using gelatine and sodium carboxymethylcellulose as shell-forming polymers, are determined by the ratio between those two polymers (G/C). The results obtained showed a notable effect of G/C ratio on the formation of the coacervate during the synthesis process and also on the encapsulation efficiency of the antimicrobial oil, with the optimal value for the G/C ratio being around 10.     

One-step microencapsulation and spraying of pesticide formulations for improved adhesion and sustained release

Abstract

Aim: To reduce the contamination arising from abuse of commercial pesticide formulations, the coaxial electrospray (CES) method was used for one-step microencapsulation and spraying of pesticides.

Methods: After optimisation of process parameters, polymeric microcapsules with different structures were fabricated as the carriers of azoxystrobin (AZS). For the resultant microcapsules, the sustained pesticide release was verified in vitro and the adhesion properties were investigated through a normalised rinsing test.

Results: The maximum encapsulation efficiency of the fabricated AZS-loaded microcapsules was 99.14%. Compared to commercial AZS aqueous suspension, the microcapsules fabricated by the CES method exhibited improved sustained release performance of AZS, which could be readily controlled by adjusting the shell thicknesses. Moreover, highly enhanced adhesion performance was observed for the AZS-loaded microcapsules directly sprayed in CES process.

Conclusions: The CES process is promising to be applied as a one-step microencapsulation and spraying technology for improving pesticide utilisation and reducing environmental pollution.     

Development of miconazole nitrate containing chitosan microcapsules and their anti-Aspergillus niger activity

In this article, we report the development of chitosan/miconazole nitrate microcapsules. Four miconazole nitrate ratios including 12.5, 25, 50 and 100?mg were performed in the chitosan-based microencapsulation system. Chitosan microcapsules with the drug input of 25?mg showed the highest encapsulation efficiency (52.47%) and acceptable mean particle size (5.65?µm) when compared with those of 12.5, 50 and 100?mg. Fourier transform infrared spectroscopic spectrum proved the entrapment of miconazole nitrate into chitosan microcapsules. The antifungal result demonstrated that microcapsules containing 75?µg miconazole nitrate possessed comparable anti-Aspergillus niger activity as the commercial ointment. The growth inhibition of miconazole nitrate containing chitosan microcapsules towards human skin keratinocytes was found to be dose dependent. A total of 75?µg of miconazole nitrate containing microcapsules revealed about 25% of growth inhibition while that of 150?µg showed approximately 70% of growth inhibition. Special monitoring should be taken if a higher dose of miconazole nitrate was used to develop the microcapsules.     

Chitosan-reinforced alginate microspheres obtained through the emulsification/internal gelation technique.

Alginate microspheres prepared by emulsification/internal gelation were chosen as carriers for a model protein, hemoglobin (Hb). Reinforced chitosan-coated microspheres were obtained by an uninterrupted method, in order to simplify the coating process, minimize protein losses during production and to avoid Hb escape under acidic conditions. Microspheres recovery was evaluated as well as its morphology by determination of Hb encapsulation efficiency and microscopic observation, respectively. The formation of chitosan membrane made of it interaction with alginate was assessed by DSC (differential scanning calorimetry) and FT-IR (Fourier-transform infrared spectrometry) studies. Spherical uncoated microspheres with a mean diameter of 20 microm and encapsulation efficiency above 89% were obtained. Coated microspheres provided similar encapsulation efficiency but a higher mean diameter was obtained due to microspheres clumping during the coating step. Protein loss occurred mainly during emulsification rather than recovery. FT-IR and DSC together indicated electrostatic interactions between alginate carboxylate and chitosan ammonium groups as the main forces for complex formation. Hb release from microspheres showed a pH-dependent profile and was affected by chitosan coating. Under simulated gastric conditions, a total Hb burst release from uncoated microspheres was decreased with one-stage and two-stage chitosan coatings (68% and 28%, respectively). At pH 6.8, the Hb release from coated microspheres was fast but incomplete. These results suggest an optimization of the coating method to protect Hb under acidic conditions and to permit a complete but sustained release of Hb.     

肝素微胶囊的制备及其性能研究

本研究利用壳聚糖与海藻酸钠为囊材,借助油包水(w/o)乳化交联技术制备了新型肝素微胶囊,并对其性能进行了系统性的研究。研究结果表明随着微胶囊中壳聚糖的含量的增加,肝素在胶囊里面的包封率增大,而释放速率则降低。当微囊中的壳聚糖含量达到20%(wt)时,肝素的包封率可以达到58%。     

红景天苷缓释微胶囊的制备及体外释放特性研究

目的:制备红景天苷微胶囊,测定其包封率,并考察其体外释药特性。方法:以生物相容性良好的壳聚糖和海藻酸钠为囊壁材料,红景天苷药物微粒为囊芯,采用静电吸引层层纳米自组装技术(LBL法)制备红景天苷微胶囊。结果:制备的微胶囊包封率较高,达到78.02±0.72%;不同包裹层数的微胶囊在体外释放速度不同。结论:用LBL法制备的红景天苷微胶囊具有较高的包封率和缓释特性,具有一定的应用前景。     

Development of miconazole nitrate containing chitosan microcapsules and their anti-Aspergillus niger activity

In this article, we report the development of chitosan/miconazole nitrate microcapsules. Four miconazole nitrate ratios including 12.5, 25, 50 and 100?mg were performed in the chitosan-based microencapsulation system. Chitosan microcapsules with the drug input of 25?mg showed the highest encapsulation efficiency (52.47%) and acceptable mean particle size (5.65?μm) when compared with those of 12.5, 50 and 100?mg. Fourier transform infrared spectroscopic spectrum proved the entrapment of miconazole nitrate into chitosan microcapsules. The antifungal result demonstrated that microcapsules containing 75?μg miconazole nitrate possessed comparable anti-Aspergillus niger activity as the commercial ointment. The growth inhibition of miconazole nitrate containing chitosan microcapsules towards human skin keratinocytes was found to be dose dependent. A total of 75?μg of miconazole nitrate containing microcapsules revealed about 25% of growth inhibition while that of 150?μg showed approximately 70% of growth inhibition. Special monitoring should be taken if a higher dose of miconazole nitrate was used to develop the microcapsules.     

Preparation of microencapsulated liposomes,II. Systems containing nylon-gelatin and nylon-gelatin-acacia walling material

Abstract

Liposome suspension was encapsulated and isolated in nylon-gelatin and nylon-gelatin-acacia walled microcapsules. the resulting liposomal microcapsules could be stored in the dry state as a free-flowing powder. Liposomes remained intact after the microencapsulation, and encapsulation efficiency was greater than 90 per cent. the release of drug from microcapsules was retarded in the presence of drug-loaded liposomes.