Calcium alginate microparticles for oral administration: I: effect of sodium alginate type on drug release and drug entrapment efficiency

The natural polymers alginate and chitosan were used for the preparation of controlled release nicardipine HCl gel microparticles. The effect of the mannuronic/guluronic acid content and the alginate viscosity on the prolonged action of the microparticles, which were prepared with different types of alginates, were investigated. The mean particle sizes and the swelling ratios of the microparticles were also determined. The in vitro release studies were carried out with a flow-through cell apparatus in different media (pH 1.2, 2.5, 4.5, 7 and 7.5 buffer solutions). The release of nicardipine was extended with the alginate gel microparticles prepared with guluronic acid rich alginate. After the determination of the most appropriate alginate type, the effect of alginatechitosan complex formation was studied on the release pattern of drug incorporated. It was observed that the alginate-chitosan complex formation reduced the erosion of the alginate-chitosan matrix at pH 7-7.5. The release of drug from the chitosan-alginate gel microparticles took place by both diffusion through the swollen matrix and relaxation of the polymer at pH 1.2-4.5     

Formation of alginate microspheres produced using emulsification technique

This study investigated the formative process of alginate microspheres produced using an emulsification technique. The alginate microspheres were produced by cross-linking alginate globules dispersed in a continuous organic phase using various calcium salts: calcium chloride, calcium acetate, calcium lactate and calcium gluconate. The size, shape, drug content and Ca²⁺ content of the microspheres were evaluated. The tack, viscosity and pH of the calcium salt solution and percentage of Ca²⁺ partitioned into the organic phase were determined. Microscopic examination of the test emulsion at various stages of the emulsification process was also carried out. The propensity of cross-linking reaction was found to be dependent on successful collision between alginate and calcium salt globules. Examination of the characteristics of microspheres indicated that the formed microsphere was a resultant product of alginate globule clustering. The growth propensity of microspheres was promoted by the higher rate and extent of cross-linkage which was governed by the pH, tack and/or Ca²⁺ content of the cross-linking solution, as well as the dissociation constant and diffusivity of the calcium salt. Overall, the amount of free Ca²⁺ cross-linked with alginate in the formed microspheres was in the following order: calcium acetate > calcium chloride + calcium acetate > calcium chloride + calcium gluconate; calcium chloride + calcium lactate > calcium chloride. In microencapsulation by emulsification, the mean size of the microspheres produced can be modified by varying the tack, pH and Ca²⁺ content of the cross-linking solution and through the use of a combination of calcium salts. The shape of the microspheres produced was, nonetheless, unaffected by the physicochemical properties of the cross-linking solution.     

Fabrication of microparticle protein delivery systems based on calcium alginate

Microparticle protein delivery systems based on calcium alginate were fabricated using a very convenient method, i.e. directly shredding the protein-loaded calcium alginate beads into microparticles in a commercial food processor for 3 min. Bovine serum albumin (BSA) as a model protein was encapsulated in the calcium alginate microparticles. The obtained protein-loaded microparticles were then coated with chitosan. This fabrication method offered high encapsulation efficiency and a high particle yield. Compared with beads, the microparticles exhibited a faster release rate in the initial release stage. By comparing the release profiles of uncoated beads/microparticles and chitosan-coated beads/microparticles, it was found that the releases from chitosan-coated beads/microparticles were slower. To examine whether the loaded protein denatured during the microparticle fabrication, trypsin was encapsulated in the calcium alginate microparticles and the bioactivity of trypsin released from the microparticles was measured.     

Sustained release properties of alginate microspheres and tabletted microspheres of diclofenac sodium

This study focused on the properties of diclofenac sodium (DNa) alginate (alg) microspheres and tabletted DNa alg microspheres using different polymers as additives. DNa alginate microspheres were prepared by the emulsification method and different polymers such as Eudragit (Eud) NE 30 D, Eudragit (Eud) RS 30 D and Aquacoat, which were incorporated into alg gel to control the release rate of drug. The release properties of DNa alg microspheres (1:1) were affected by the size, drug load of microspheres and also by the incorporated polymers, pH and ionic strength of dissolution medium. Tabletting of alg microspheres using carrageenan (carr), alg, pectin, NaCMC, tragacanth (trgh) and HPMC as additives in a (50:50) ratio produced tablets with good physical properties and also better controlled release of DNa. Dissolution studies were carried out in pH7.2 phosphate buffer and phosphate buffers whose pH values were gradually changed from pH 3 to 7.4. The rank order of DNa release from tablets was carr<alg<pectin<NaCMC<trgh<HPMC which relates to the viscosity and swelling properties of polymers. The drug release was very slow from trgh and HPMC based tablets, but addition of carr or alg in different ratios could adjust the release rate of drug.     

Designing improved poly lactic-co-glycolic acid microspheres for a malarial vaccine: incorporation of alginate and polyinosinic–polycytidilic acid

Abstract

Vaccination using proteins and peptides is currently gaining importance. One of the major drawbacks of this approach is the lack of an efficient immune response when the antigens are administered without adjuvants. In this study, we have taken the advantage of a combined adjuvant system in order to improve the immunogenicity of the SPf66 malarial antigen. For that purpose, we have combined poly (lactic-co-glycolic) acid microspheres, alginate, and polyinosinic polycytidilic acid. Our results show that microspheres can enhance the IgG production obtained with Freund’s complete adjuvant. We have attributed this improvement to the presence of polyinosinic polycytidilic acid, since formulations comprising this adjuvant overcame the immune response from the others. In addition, our microspheres produced both IgG1 and IgG2a, leading to mixed Th1/Th2 activation, optimal for malaria vaccination. In conclusion, we have designed a preliminary formulation with a high potential for the treatment of malaria.     

Wheat germ agglutinin-conjugated chitosan–Ca–alginate microparticles for local colon delivery of 5-FU: Development and in vitro characterization

The aim of this work was to prepare lectin-conjugated chitosan–Ca–alginate microparticles (MPs) loaded with acid-resistant particles of 5-fluorouracil (5-FU) for efficient local treatment of colon cancer. MPs were prepared by a novel one-step spray-drying technique and after wheat germ agglutinin (WGA) conjugation, they were characterized for size, swelling behavior, surface charge, entrapment efficiency and in vitro drug release. Prepared particles were spherical, with 6.73 μg/mg of WGA conjugated onto their surface. The size and zeta potential increased after conjugation, from 6.6 to 14.7 μm and from 9.6 to 15.3 mV, while drug encapsulation was 75.6 and 72.8%, respectively after conjugation. The swelling behavior of beads was mainly determined by properties of the cross-linked chitosan–alginate network. In vitro drug release studies carried out in simulated in vivo conditions with respect to pH, confirmed the potential of the particles to release the drug in a controlled manner. Also, the drug release was not significantly affected by WGA conjugation. The retention of biorecognitive activity of WGA after covalent coupling to MPs was confirmed by haemagglutination test. Functionalized MPs showed excessive mucoadhesiveness in vitro, due to the positive surface charge, pH-dependent swelling of the matrix and lectin–sugar recognition.     

紫外线对印模表面消毒效果的观察

目的 探讨紫外线对印模的消毒效果.方法 分别制取藻酸盐和硅橡胶印模,108个/ml的菌液0.1 ml均匀涂布在印模上,用波长为253.7 nm的紫外线对印模进行消毒,照射强度分别为1 000 μW/cm2和7 000 μW/cm2,消毒时间分别为:1 000 μW/cm2为0、10、15、20、30 s;7 000 μW/cm2为0、5、10、15、20 s.根据残留的细菌数进行消毒效果的判定,并进行统计学分析.结果 ①照射强度为7 000 μW/cm2的紫外线比强度为1 000 μW/cm2的具有更稳定的消毒作用.②使用1 000 μW/cm2的紫外线照射30 s,硅橡胶印模上试剂的细菌数明显少于藻酸盐印模(P＜0.01).③使用7 000 μW/cm2的紫外线分别照射5 s、10 s、15 s和20 s,硅橡胶印模上的细菌数明显少于藻酸盐印模(P＜0.01).结论 用紫外线对印模消毒是一个值得在临床推荐的方法,其效果在使用硅橡胶印模材料时更显著.     

Dimensional change over time of extended-storage alginate impression materials

Objectives:To evaluate the dimensional change over time of two extended-storage alginate impression materials.Methods:Impressions were made of stainless steel dies in accordance with ADA Specification No. 18 using three alginates: two extended-storage alginates and one conventional alginate. The impressions were stored for 30 minutes, 48 hours, or 100 hours (n  =  10 impressions/material/storage time). Following the respective storage times, dimensional change was measured by comparing the length of the middle horizontal line in the impression with the same line on the die and computing percent difference.Results:Significant differences in dimensional change were noted between materials across time (P < .05). All materials exhibited shrinkage after 30 minutes, with the conventional alginate continuing to shrink over time and the extended-storage alginates expanding with increased storage time. The conventional alginate was most accurate after 30 minutes. In contrast, one extended-storage alginate demonstrated minimal dimensional change at all storage times, and another was most accurate after 100-hour storage.Conclusions:Evidence suggests that delayed pouring with dental gypsum should not adversely affect dimensional accuracy of the generated casts with both extended-storage alginates. However, only one of the extended-storage materials appears suitable for both short-term and extended-storage applications.     

藻酸钠微球培养对兔髓核细胞生物学特性的影响

目的探讨藻酸钠微球培养对兔椎间盘髓核细胞（NPCs）体外生物学特性的影响。方法4月龄健康新西兰大耳白兔6只,取髓核细胞原代培养,传代后分为实验组（藻酸钠微球培养）和对照组（平面培养）,通过倒置相差显微镜对髓核细胞进行形态学观察,MTT法测定两组髓核细胞增殖情况,运用RT-PCR技术检测两组髓核细胞中Ⅱ型胶原和聚集蛋白聚糖的表达。结果经过2周的培养,两组髓核细胞增殖率无明显差异;藻酸钠微球培养组在Ⅱ型胶原和聚集蛋白聚糖的表达上均高于平面培养组（P〈0.01或P〈0.05）。结论藻酸钠微球培养法能促进髓核细胞中Ⅱ型胶原和聚集蛋白聚糖的表达,在维持其表型稳定方面优于平面培养法。     

Improving the therapeutic efficiency of ginger extract for treatment of colon cancer using a suitably designed multiparticulate system

Abstract

Ginger extract (GE), a potential natural anticancer agent, has compromised therapeutic utilization due to poor bioavailability and physicochemical properties. Present study aimed at assigning GE with a pharmaceutical couture so as to improve its biopharmaceutical performance by monitoring its localized (though prolonged) delivery in the distal parts of gastrointestinal tract for the treatment of colon cancer. Alginate beads entrapping 85.9?±?1.78% GE were subjected to Eudragit S100 coating. Latter is insoluble at acidic and near neutral (6.8) pH of stomach and upper part of small intestine and it led to 50% retardation (upto 12?h) in release of GE. However, it was solubilised at pH?>?7.0 resulting in colon targeted system. Developed beads were free flowing, showed a particle size of 0.9?±?0.006?mm and super class-II release controlled by swelling and polymer relaxation. Preclinical evaluation using 1,2-dimethylhydrazine-induced colon cancer, in male Wistar rats, in terms of histopathology, oxidative stress, mitochondrial complex activity, β-glucuronidase and ammonia concentration determinations indicated GE loaded beads (50?mg/kg) to be significantly better (p?<?0.05) than free GE. Highlight of the study was that GE loaded coated alginate beads were administered after the induction of colon cancer and significant recession of the cancers was observed after 4 weeks of treatment.