海藻酸钙凝胶微球的制备和pH依赖性溶胀

利用海藻酸钠溶液与氯化钙溶液发生胶凝反应，本文用滴制的方法制备了海藻酸钙凝胶微球，并对制备的处方和工艺进行了探讨，同时考察了海藻酸钙凝胶微球的特征和溶胀特性。干燥的凝胶微球在不同pH的水性介质中溶胀特性不同。海藻酸钙凝胶微球的这种溶胀的pH敏感性，使其能成为口服药物缓释制剂的载体。     

阿霉素海藻酸钙凝胶微丸的释放性

以阿霉素为阳离子模型药物，研究了不同初始浓度海藻酸钠（ＳｏｄｉｕｍＡｌｇｉｎａｔｅ，ＮａＡｌｇ）制备的空白微丸对药物的摄取作用和不同介质中药物的释放过程     

双氯芬酸钠海藻酸钙凝胶微球的制备及其性质分析

目的制备双氯芬酸钠海藻酸钙凝胶微球，并对凝胶微球的性质进行分析。方法采用滴制法制备双氯芬酸钠海藻酸钙凝胶微球，紫外分光光度法测定药物的含量，对凝胶微球的粒度、圆整度、休止角和堆密度进行测定，并用扫描电镜观察凝胶微球的形态。结果制备的双氯芬酸钠海藻酸钙凝胶微球包封率较高，粉体学性质良好，球形均匀圆整。结论该方法适用于双氯芬酸钠海藻酸钙凝胶微球的制备。     

硝苯地平海藻酸钙凝胶缓释微丸处方及工艺的优化

目的制备硝苯地平 海藻酸钙凝胶缓释微丸。方法采用滴制法。用单因素考察及均匀设计实验优化处方及工艺。结果优化得到的微丸在体外累计释放硝苯地平百分率 ,2h为 2 0 %～ 3 0 % ,6h为 60 %～ 80 % ,1 2h>85 %。结论在体外释放度实验中 ,硝苯地平海藻酸钙凝胶微丸具有良好的缓释作用     

海藻酸钙凝胶微丸作为口服缓释给药载体的研究

将海藻酸钠溶液滴入胶凝剂氯化钙溶液中制备了海藻酸钙凝胶微丸。以胶凝过程中凝胶微丸重量变化 (失水量 )研究了胶凝速率及不同浓度海藻酸钠溶液 ( 1 %～ 4 % )与氯化钙溶液 ( 0 0 5～0 2 0mol/L)对胶凝速率的影响 ,结果是 6h前胶凝速率快 ,随后减慢 ,约 70h胶凝完全 ,氯化钙溶液的浓度≥ 0 1mol/L对胶凝速率无明显影响。干燥的凝胶微丸在不同水性介质中溶胀试验结果表明 :在温度约 37℃时 ,微丸在蒸馏水和 0 1mol/L盐酸 ( pH1 0 )中几乎不溶胀 ,而在磷酸盐缓冲溶液( pH6 8)中1h溶胀 ,溶胀后的微丸直径是干燥前湿微丸直径的 1 80 %。海藻酸钙凝胶微丸这种溶胀的 pH敏感性 ,使它能成为口服药物缓释制剂的载体。以硝苯地平为模型药物制备的海藻酸钙凝胶微丸 ,其体外释放试验结果 ,2h累积释放量为 2 0 %～ 30 % ,6h为 6 0 %～ 80 % ,1 2h时大于85 %。药物从微丸中的释放是以扩散和骨架溶蚀相结合的方式。由此可见 ,硝苯地平的海藻酸钙凝胶微丸具有缓释作用     

避蚊胺-海藻酸钙微球的试制

采用溶剂挥发法制备避蚊胺-海藻酸钙微球。所得微球外观圆整,平均粒径47.2μm,载药量（26.33±1.17）%,包封率（87.41±3.21）%。考察了将其加至空白霜剂后对大鼠离体皮肤累积渗透量的影响,并与微粉硅胶载药霜剂和原药霜剂比较。结果表明,海藻酸钙微球可减少避蚊胺的累积渗透量。     

阿西美辛海藻酸钙凝胶微丸释药影响因素考察

目的:考察阿西美辛海藻酸钙凝胶微丸的释药机制。方法:采用滴制法制备阿西美辛海藻酸钙微丸,考察海藻酸钠浓度,钙离子浓度,投药量,滴头直径大小对药物释放的影响。结果:海藻酸钠浓度增加,钙离子浓度增加,滴头直径增加,释药速率减慢。结论:在体外释放度实验中,阿西美辛海藻酸钙凝胶微丸具有良好的缓释作用,海藻酸钙凝胶微丸是一种非常有潜力的药物载体。     

避蚊胺-海藻酸钙微球的制备及其体外透皮吸收研究

目的 制备海藻酸钙空白微球,减少避蚊胺(DEET)的透皮吸收,延长其作用时间.方法采用溶剂挥发法制备海藻酸钙微球,采用光学显微镜和激光粒度仪考察微球特性;吸附DEET后制成霜荆,通过Franz扩散池,用气相色谱法考察含药微球的透皮吸收.结果所得微球外观圆整,平均粒径42.5μm,吸附量为1.2177 g·g-1.透皮试验结果表明,海藻酸钙空白微球能延长DEET的释放,减少皮肤渗透.结论 海藻酸钙微球具有显著的缓释效果,并减少DEET对人体及皮肤的不良反应.     

肺靶向海藻酸钙微球体内外溶蚀行为的探讨

采用乳化法制备肺靶向海藻酸钙微球,制品平均粒径(12.2±8.9)μm,在注射用水中的溶胀率约150%,在生理盐水中24h累积溶蚀率约60%.小鼠尾静脉注射微球后肺靶向效果显著,5min时肺组织中充斥微球,6h时可见微球溶蚀.     

pH值调节法制备壳聚糖空白微球

目的：介绍一种壳聚糖空白微球的制备方法。方法：将溶有氨水的异丙醇加入到壳聚糖乳液中，使得壳聚糖液滴由酸性变为碱性，壳聚糖凝固析出。结果：制得了粒径在3～8μm左右，粒径分布均匀的壳聚糖微球。结论：使用改变pH值的方法来制备壳聚糖微球，避免了传统固化剂的使用及其缺点。     

Evaluation of drug release kinetics and physico-chemical characteristics of metronidazole floating beads based on calcium silicate and gas-forming agents

In the present investigation metronidazole-loaded alginate beads consisting of calcium silicate as a porous carrier or NaHCO₃ as a gas-forming agent were prepared for local eradication of Helicobacter Pylori. Gelation method was used for preparation of conventional sodium alginate beads. Drug entrapment efficiency, drug loading, floating properties, drug release, crystallinity and release kinetic as well as morphology of the prepared beads were assessed. The silicate based beads showed slower release pattern, compared to the gas-forming beads due to network structure strengthening effect of the calcium silicate. Furthermore, the gas-forming-based beads had shorter initial buoyancy lag time, owing to the fact that the NaHCO₃ produced larger pores than those of silicate treated ones. Drug entrapment efficiency ranged between 61.7 and 93.1% for the prepared formulations. The maximum value of drug loading for gas-forming and silicate-based beads were 66.64% and 34.97%, respectively. Kinetically, release pattern of metronidazole in simulated gastric fluid from the beads fitted best to Reciprocal powered time, Weibull and log-probability models with the respect overall mean percentage error values of 4.50, 5.30 and 7.76. By and large, these systems can float in the gastric condition and control the drug release from the beads.     

pH-dependent release property of alginate beads containing calcium carbonate particles

Alginate bead containing calcium carbonate particle were prepared by dropping the suspension of alginate/calcium carbonate (4/1, w/w) into aqueous solution of CaCl₂ (0.1?M). The pH-dependent release property of the bead was observed for 12?h using blue dextran as a model drug. The release increased up to 4?h in a saturation manner. When no calcium carbonate was contained, the release exhibited no marked variation with pH and the values were 27–39%. On the other hand, in case calcium carbonate was included in the matrix of alginate beads, intensive release(40–50%) was achieved in acidic and neutral conditions and the degrees of release were suppressed in alkali conditions and the values were ～20%. The pH-sensitive release property is possibly because the particles of calcium carbonate embedded in the matrix of beads were leached out in acidic and neutral conditions, leaving cavities in the matrix. The cavities are likely to be main pathways for the release of blue dextran.     

Biphasic release characteristics of dual drug-loaded alginate beads

The dual drug-loaded alginate beads simultaneously containing drug in inner and outer layers were prepared by dropping plain (single-layered) alginate beads into CaCl₂ solution. The release characteristics were evaluated in simulated gastric fluid for 2 h followed by intestinal fluids thereafter for 12 h. The surface morphology and cross section of dual drug-loaded alginate beads was also investigated using scanning electron microscope (SEM). The poorly water-soluble ibuprofen was chosen as a model drug. The surface of single-layered and dual drug-loaded alginate beads showed very crude and roughness, showing aggregated particles, surface cracks and rough crystals. The thickness of dual drug-loaded alginate beads surrounded by outer layer was ranged from about 57 to 329μm. The distinct chasm between inner and outer layers was also observed. In case of single-layered alginate beads, the drug was not released in gastric fluid but was largely released in intestinal fluid. However, the release rate decreased as the reinforcing Eudragit^® polymer contents increased. When the plasticizers were added into polymer, the release rate largely decreased. The release rate of dual drug-loaded alginate beads was stable in gastric fluid for 2 h but largely increased when switched in intestinal fluid. The drug linearly released for 4 h followed by another linear release thereafter, showing a distinct biphasic release characteristics. There was a difference in the release profiles between single-layered and dual drug-loaded alginate beads due to their structural shape. However, this biphasic release profiles were modified by varying formulation compositions of inner and outer layer of alginate beads. The release rate of dual drug-loaded alginate beads slightly decreased when the outer layer was reinforced with Eudragit^® RS100 polymers. In case of dual drug-loaded alginate beads with polymer-reinforced outer layer only, the initial amount of drug released was low but the initial release rate (slope) was higher due to more swellable inner cores when compared to polymer-reinforced inner cores. The current dual drug-loaded alginate beads may be used to deliver the drugs in a time dependent manner.     

Morphology and buoyancy of oil-entrapped calcium pectinate gel beads

A new emulsion-gelation method to prepare oil-entrapped calcium pectinate gel (CaPG) beads capable of floating in the gastric condition was designed and tested. The gel beads containing edible oil were prepared by either being gently mixed or homogenized an oil phase and a water phase containing pectin, and then extruded into calcium chloride solution with gentle agitation at room temperature. The gel beads formed were then separated, washed with distilled water, and dried at 37 degrees C for 12 hours. A model of the emulsion-gelation process to illustrate the formation of oil-entrapped CaPG beads was proposed. The effect of selected factors, such as type of oil, percentage of oil, and type of pectin on morphology and floating properties was investigated. The oil-entrapped calcium pectinate gel beads floated if a sufficient amount of oil was used. Scanning electron photomicrographs demonstrated very small pores, ranging between 5 and 40 microm, dispersed all over the beads. The type and percentage of oil play an important role in controlling the floating of oil-entrapped CaPG beads. The results suggested that oil-entrapped CaPG beads were promising as a carrier for intragastric floating drug delivery.     

加替沙星pH敏感眼用原位凝胶体外释放的研究

目的研究加替沙星pH敏感眼用原位凝胶的体外释药特性与机制。方法采用改良桨法考察加替沙星pH敏感眼用原位凝胶的释药规律,并用无膜溶出法研究其释放机制。结果凝胶溶蚀和药物释放随着振荡频率和释放面积的增加而加快。其溶蚀度与释放度有明显相关性。结论体外的溶蚀行为与释放行为遵循零级动力学方程,凝胶溶蚀是决定药物释放的主要因素。     

Development and evaluation of polyethyleneimine-treated calcium alginate beads for sustained release of diltiazem

The objective of this investigation is to develop a multi-unit sustained release dosage form of a water soluble drug from a completely aqueous environment avoiding the use of any organic solvent. The drug was complexed with resin and calcium alginate or polyethyleneimine-treated calcium alginate beads loaded with the resinate were prepared by a ionic/polyelectrolyte complexation method. The effect of different formulation variables on the characteristics of the beads was investigated. Although the drug release from spherical and smooth-surfaced calcium alginate beads in both acidic and alkaline dissolution media were slower than those obtained from plain resinate, none of the variables were found to prolong the drug release considerably due to rapid swelling and disintegration of calcium alginate beads in alkaline medium. On the other hand, drug release from polyethyleneimine-treated calcium alginate beads in acidic medium did not increase appreciably following a burst release. However, in alkaline medium, the drug release was found to increase gradually and extend over a different period of time depending on the intensity of polyethyleneimine treatment. Scanning electron micrographs revealed the formation of a dense membrane around the resinate-loaded calcium alginate matrix. The membrane appeared to be responsible for reduced swelling and protracted disintegration of the beads resulting in slow release of the drug. The results indicate that sustained release of a water soluble drug from polyethyleneimine-treated calcium alginate beads could be achieved by adjusting the formulation variables.