乳化法制备海藻酸钙/聚组氮酸微胶囊

采用乳化法制备海藻酸钙微球及海藻酸钙/聚组氨酸载药微胶囊,并考察不同海藻酸钠浓度、氯化钙浓度对微球表面形态、粒径分布、载药性能及微胶囊控制释放性能的影响。结果表明海藻酸钠浓度主要影响微球的粒径大小,氯化钙浓度主要影响微球的分散程度及粒径分布,微球载药量均随海藻酸钠浓度及氯化钙浓度的增加而减小,所制备的微胶囊均无明显的突释现象。     

高载药量海藻酸钙/几丁聚糖微胶囊的性能

采用乳化固化法制备了平均粒径为820nm海藻酸钙微球,并制备了海藻酸钙/几丁聚糖微胶囊。以牛血清白蛋白(BSA)为模型药物,考察投药浓度、几丁聚糖分子量和浓度等对微胶囊载药量和药物释放的影响,发现其载药量最大可达40%以上,结果还显示这种微胶囊具有很好的体外缓释性能。     

壳聚糖/海藻酸钙微胶囊的通透性能

以传统细胞培养的重要碳源葡萄糖与柠檬酸、氮源L-谷氨酸为小分子模型,以聚乙二醇为测定微囊膜截留相对分子质量的模型分子,研究了微胶囊通透性能,考察了制备条件对壳聚糖/海藻酸钙微胶囊通透性能的影响.结果说明:葡萄糖、柠檬酸和L-谷氨酸可以自由透过微囊膜扩散;采用20 mg/mL海藻酸钠溶液与相对分子质量5万、2 mg/mL壳聚糖溶液制备微胶囊,胶囊的截留相对分子质量为1500;降低成膜壳聚糖溶液浓度和壳聚糖分子量,增大微胶囊粒径均有利于提高壳聚糖/海藻酸钙微胶囊的通透性.     

载脂肪酶壳聚糖/海藻酸钙微胶囊的制备

针对固定化脂肪酶的研究背景,以壳聚糖、海藻酸钠为微载体制备材料,采用脉冲电场液滴工艺制备壳聚糖/海藻酸钙微胶囊。以脂肪酶为生物模型,系统考察了制备条件对载脂肪酶壳聚糖/海藻酸钙微胶囊酶活力的影响。结果表明:海藻酸钠质量浓度和酶与海藻酸钠载体配比是影响固定化酶活力的主要因素,载酶量为15mg/mL,海藻酸钠质量浓度为10mg/mL时载酶微胶囊酶活力最高,球形度好。通过改变壳聚糖质量浓度和相对分子质量,可以调控微胶囊膜的厚密程度进而影响固定化酶活力。成膜液pH值依次影响壳聚糖与海藻酸盐分子中官能团的电离状态、成膜反应静电络合程度、酶蛋白包封率,最终影响固定化酶活力。在载酶量为15mg/mL,海藻酸钠质量浓度为10mg/mL,壳聚糖相对分子质量、质量浓度和pH值依次为50kDa、1mg/mL和3.0的条件下,固定化酶活力为187IU/g。     

高压静电法制备载阿糖胞苷海藻酸钙-几丁聚糖微胶囊

采用海藻硅酸钠和几丁聚糖为原料制备海藻酸钙-几丁聚糖药物缓释微胶囊,初步考察了载阿糖胞苷微胶囊的制备以及不同分子量几丁聚糖、静/动态载药方式对阿糖胞苷释放性能的影响。     

阿维菌素海藻酸钙微球制备与表征

[目的]制备阿维菌素海藻酸钙微球,并评价其相关性能。[方法]采用内源乳化法制备阿维菌素海藻酸钙微球,以溶胀率、产率为考察指标,结合正交设计试验对微球的制备工艺进行优化,并利用光学显微镜和傅立叶变换红外光谱仪对微球进行了观察和表征。[结果]阿维菌素海藻酸钙微球最佳工艺为海藻酸钠和Span 80的质量浓度均为15 g/L、海藻酸钠与CaCO3质量比3∶1、水油两相体积比为1∶2。所制备的微球外观呈规则球形,载药率和包封率分别达到84.21%和20.16%。体外药物释放试验表明,阿维菌素海藻酸钙微球48 h累计释放率为78.61%。[结论]所制备的阿维菌素海藻酸钙微球具有良好的缓释性,提高了农药的利用率。     

海藻酸钙微胶囊制备方法及其在农药缓释中的应用

海藻酸钠与不同钙盐在不同溶剂中制备海藻酸钙微胶囊,并对腐霉利原药进行包埋.用扫描电子显微镜测定微胶囊粒径大小及其分布;高效液相色谱测定微胶囊中腐霉利的释放速度.结果表明:采用新方法制备的微胶囊粒径分布在1～20 μm之间,粒径分布范围较窄,在乙醇溶液中对腐霉利具有缓释作用.同时对不同方法制备的海藻酸钙微胶囊在腐霉利药物释放速度方面进行比较.     

海藻酸钠/壳聚糖/海藻酸钙微胶囊机械强度的研究

采用脱乙酰度≥95%的壳聚糖为原料,通过NaNO_2氧化法降解得到不同分子量的壳聚糖。通过单因素试验,考察不同反应条件对海藻酸钠/壳聚糖/海藻酸钙微胶囊机械强度的影响,再通过响应面试验优化微胶囊的制备工艺。研究结果表明,当成膜时间为32 min,壳聚糖浓度为6.1 g/L,壳聚糖分子量为58189,壳聚糖pH值为6.0时,海藻酸钠/壳聚糖/海藻酸钙微胶囊的机械强度最高。     

小粒径咖啡因微胶囊制备及其缓释研究

本文研究了以明胶为囊材,采用反相乳化法制备咖啡因微胶囊,考察不同的制备条件对微胶囊粒径与微胶囊载药量、包埋率的影响。结果表明,乳化剂用量、水油比例和搅拌速度对微胶囊粒径有较大影响,加入苯甲酸钠能有效地提高微胶囊的载药量,提高明胶浓度可增加咖啡因的包埋率,且所得的微胶囊有一定的缓释性能。     

海藻酸钠-壳聚糖微胶囊的制备

对海藻酸钠-壳聚糖交联法制备微胶囊的条件进行了研究,考察了海藻酸钠浓度、壳聚糖浓度、氯化钙浓度、p H值和温度对微胶囊粒径、形态和强度的影响,确定了实验室制备微胶囊的最佳条件为:海藻酸钠浓度1.5%,壳聚糖浓度0.75%,氯化钙浓度5.0%,壳聚糖溶液的p H值和温度分别为5.4和25℃。     

含微胶囊相变材料的海藻酸钙大胶囊的制备及其性能

采用原位聚合法合成了微胶囊相变材料,并通过锐孔法制备了海藻酸钙包覆多个微胶囊相变材料的大胶囊。用FTIR分析了大胶囊的化学结构,采用游标卡尺测量在不同质量分数的海藻酸钠水溶液和氯化钙水溶液中制备的大胶囊的平均粒径;用SEM和DSC对微胶囊相变材料的微观形貌和热性能进行了分析,对大胶囊的热性能进行了考察,讨论了在不同海藻酸钠质量分数下制备的大胶囊经甲苯萃取30 m in后的热性能。结果表明,微胶囊呈粒径均一,表面光滑,密封较好的球体;其相变温度为34.1℃,相变潜热为143.8 J/g。随着微胶囊相变材料加入量的增加,大胶囊的相变潜热逐渐增加;当w(CaC l2)=2%时,随着海藻酸钠质量分数的增加,大胶囊的粒径由1.36 mm逐渐增加至1.96 mm并趋于平缓,且海藻酸钠水溶液质量分数不宜超过3%;随着氯化钙质量分数的增加,大胶囊平均粒径逐渐增长,但幅度较其随海藻酸钠质量分数变化的幅度小;甲苯对大胶囊壳材的渗透能力随海藻酸钠质量分数的增加而减小。     

Controlled release of diclofenac sodium and ibuprofen through beads of sodium alginate and hydroxy ethyl cellulose blends

Controlled release of diclofenac sodium (DS) and ibuprofen (IB) drugs through sodium alginate (NaAlg)‐hydroxy ethyl cellulose (HEC) blend polymeric beads has been investigated. Beads were prepared by precipitating the viscous solution of NaAlg and HEC blend in alcohol followed by crosslinking with calcium chloride. Different formulations were developed in bead form by varying the amount of HEC, crosslinking agent, and drug concentration. Swelling studies in water, percent encapsulation of drugs, and release studies were carried out. The DS‐loaded beads have shown better release performance than the IB‐loaded beads. Diffusion parameters were evaluated from the Fickian diffusion theory. Mathematical modeling studies and drug release characteristics through bead matrices were studied by solving Fick's diffusion equation. The results are discussed in terms of drug release patterns and theoretical concentration profiles generated through matrices, considering spherical geometry of the beads. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5708–5718, 2006     

Poly(L‐histidine)‐chitosan/alginate complex microcapsule as a novel drug delivery agent

Novel poly(L ‐histidine)‐chitosan/alginate complex microcapsules were prepared from biodegradable polymers poly(L ‐histidine) (PLHis) in the presence of chitosan at acetate buffer solution pH 4.6. Microcapsules obtained are spherical and well‐dispersed with a smooth surface and a narrow size distribution. The microcapsules can encapsulate the protein model drug hemoglobin (Hb) efficiently. The results show that the complex microcapsules with low, medium, or high molecular weight of chitosan (0.05%, w/v), the highest encapsulation efficiencies obtained are 91.3%, 85.9%, and 94.2% with loading efficiencies of 47.8%, 44.3%, and 39.7%, respectively. The release profiles indicate that Hb‐loaded microcapsules conform to first‐order release kinetic in whole procedure, and 84.8%, 71.4%, and 87.3% of Hb were released during 72‐h incubation in PBS pH6.8 for microcapsules with low, medium, and high molecular weight chitosan (0.05%, w/v), respectively. The results also indicate that particle size and drug loading efficiency have a significant influence on the release profile and encapsulation efficiency. Our results reveal that the PLHis‐chitosan/alginate complex microcapsules are able to encapsulate and release Hb and are potential carriers for protein drugs. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Polyelectrolyte complexes of sodium alginate with chitosan or its derivatives for microcapsules

Chitosan, a cationic polysaccharide, was heterogeneously deacetylated with a 47% sodium hydroxide solution and followed by a homogeneous reacetylation with acetic anhydrides to control the N-acetyl content of the chitosan having a similar molecular weight. The chitosans having different degrees of N-acetylation were complexed with sodium alginate, an anionic polysaccharide, and the formation behavior of polyelectrolyte complexes (PECs) was examined by the viscometry in various pH ranges. The maximum mixing ratio (R_max) increased with a decrease in the degree of N-acetylation of the chitosan at the same pH, and with a decrease in pH at the same degree of N-acetylation. Similarly, N-acylated chitosans were also prepared. The N-acyl chitosans scarcely affected the formation behavior of PECs with sodium alginates. For the application of the PECs produced, the microencapsulation of a drug was performed and the release property of drug was tested. The microcapsules were prepared in one step by the extrusion of a solution of guaifenesin and sodium alginate into a solution containing calcium chloride and chitosan through interpolymeric ionic interactions. The drug release during the drug-loaded microcapsules storage in saline was found to depend on the pH where the microcapsules were formed and the kind of N-acyl groups introduced to the chitosan. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 425–432, 1997     

Preparation of polyethersulfone–alginate microcapsules for controlled release

In this study, polyethersulfone (PES)–alginate microcapsules were prepared for drug‐controlled release, and vitamin B₁₂ (VB₁₂), rifampicin (RFP), and bovine serum albumin (BSA) were used as model drugs. Different microcapsules were prepared by the variation of the crosslinking degree of alginate and the variation of the chemical components of the microcapsule membrane, including the PES and polyethylene glycol (PEG) contents. Systematic experiments were carried out to study their influences on the release profile of the model drugs. The results showed that with the increase of the crosslinking degree of the alginate, the drug release rate increased; whereas with the increase of the PES concentration used to prepare the microcapsule membrane, the drug release rate decreased. The contents of the PEG in the microcapsule membrane also affected the drug release. This study enriched the methodology of the fabrication of the microcapsules, and the microcapsules may have a potential use for controlled release. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Preparation and characterization of ciprofloxacin‐loaded alginate/chitosan sponge as a wound dressing material

The aim of this study is preparation and characterization of alginate/chitosan sponges including a model antibiotic (i.e., ciprofloxacin) to use in wound and/or burn treatment. Sponges were prepared firstly by the gelation of sodium alginate followed by lyophilization, crosslinking with calcium chloride, and finally coating with chitosan. Sponges were characterized with respect to morphology, water uptake, in vitro drug release behavior, and antimicrobial activity. Investigated and evaluated parameters in all of these studies were selected as the concentration of calcium chloride, alginate viscosity, drug content, and molecular weight of chitosan. Drug release and water uptake were found to be greatly influenced by these parameters. Water uptake and drug release rate were decreased by increasing the crosslinking density, chitosan molecular weight, and alginate viscosity. In the antimicrobial tests, it was obtained that the antimicrobial activity is directly proportional with the release rates and water uptake. Morphological studies showed a highly porous structure with interconnected pores. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1602–1609, 2006     

Chitosan/polyethylene glycol–alginate microcapsules for oral delivery of hirudin

A mild chitosan/calcium alginate microencapsulation process, as applied to encapsulation of biological macromolecules such as albumin and hirudin, was investigated. The polysaccharide chitosan was reacted with sodium alginate in the presence of calcium chloride to form microcapsules with a polyelectrolyte complex membrane. Hirudin-entrapped alginate beads were further surface coated with polyethylene glycol (PEG) via glutaraldehyde functionalities. It was observed that approximately 70% of the content is being released into Tris-HCl buffer, pH 7.4 within the initial 6 h and about 35% release of hirudin was also observed during treatment with 0.1 M HCl, pH 1.2 for 4 h. But acid-treated capsules had released almost all the entrapped hirudin into Tris-HCl, pH 7.4 media within 6 h. From scanning electron microscopic and swelling studies, it appears that the chitosan and PEG have modified the alginate microcapsules and subsequently the protein release. The microcapsules were also prepared by adding dropwise albumin-containing sodium alginate mixture into a PEG– CaCl₂ system. Increasing the PEG concentration resulted in a decrease rate of albumin release. The results indicate the possibility of modifying the formulation to obtain the desired controlled release of bioactive peptides (hirudin), for a convenient gastrointestinal tract delivery system. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2143–2153, 1998     

海藻酸钠微囊的制备及应用进展

微囊化技术作为一项发展迅速的新技术,具有精确给药、芯材控释等特点,在生物医药、食品、化工等领域均得到成功应用。海藻酸钠是从海洋藻类提取的功能独特的植物多糖,具有良好的溶解性、成膜性和凝胶性等优势,已被广泛用作微囊的包膜材料。但海藻酸钠微囊易受到基质材料、交联剂和生产工艺参数的影响,性质难以调控,所以微囊的生产仍存在配方不完善、制备工艺不稳定等问题。为解决上述问题,本综述对海藻酸钠的离子交换性、pH敏感性、凝胶特性等性质和微囊制备过程的影响因素进行了总结。论述了海藻酸钠微囊在包封细胞、药物以及精油方面的应用,指出今后的研究方向应集中于改进微囊的制备工艺,探明海藻酸钠成膜机理与机械性能的关系,提高海藻酸钠微囊强度与韧性,继续推进海藻酸钠与其他高分子材料的复配研究,以期扩大海藻酸钠微囊的应用范围,加快海藻酸钠微囊的工业化进程。     

Optimization of L-Asparaginase Immobilization onto Calcium Alginate Beads

In this study, anti-leukemic enzyme L-asparaginase (E.C.3.5.1.1) from Escherichia coli ATCC 11303 was modified by the microencapsulation technique onto calcium alginate beads. Using response surface methodology (RSM), a three-level full factorial design, the values of concentration of sodium alginate, concentration of calcium chloride, and enzyme loading were investigated to obtain the highest residual L-asparaginase (L-ASNase) activity % (immobilized enzyme activity/free enzyme activity). The effects of the studied factors on immobilization were evaluated The predicted values by the model were close to the experimental values, indicating suitability of the model. The results presented that an increase in sodium alginate concentration increased the percent of residual activity of L-ASNase at any given calcium chloride concentration and the moderate amount of enzyme loading increased the percent residual activity. The optimal immobilization conditions were as follows: sodium alginate 1.98% (w/v), calcium chloride concentration 3.70% (w/v), and enzyme load 46.91% (v/v). The highest residual L-ASNase activity % obtained was 34.49%.