交联糊精-碘微球的制备及体外释放

目的用空白交联糊精微球作为载体制备交联糊精-碘微球,作为敷料用于慢性有渗出物伤口的治疗。方法使用吸附载药法,考察母液中乙醇含量、碘溶液浓度、微球吸水度对交联糊精-碘微球载药量和包封率的影响,以蒸馏水、生理盐水和模拟渗出液为释放介质,考察微球的体外释放,并对释放曲线进行方程拟合,预测释放机制。结果与结论在载药过程中,随着母液中乙醇含量的提高,载药量和包封率降低;乙醇含量一定的溶液中,碘浓度变大载药量提高,而包封率变化不大;吸水度高的微球载药量和包封率较吸水度低的微球高。交联糊精-碘微球体外释放符合Pep-pas方程(n=0.43),游离碘通过F ick扩散机制释放。在生理盐水和模拟渗出液中碘的释放进一步减缓,为交联糊精-碘微球作为敷料用于渗出性伤口的治疗时达到缓释作用奠定基础。     

交联β-环糊精-可溶性淀粉聚合物微球的合成及载药性质

目的用β-环糊精和可溶性淀粉作为原料合成不溶于水的微球,并对其吸附载药性质进行研究。方法使用反相悬浮交联法制备聚合物微球,对其乳化及交联过程的各个因素进行考察,并且以水杨酸为模型药物,考察了交联反应不同因素对水杨酸载药量的影响。探讨了药物的吸附动力学和吸附热力学。用傅立叶红外色谱仪、粉末X射线衍射、激光衍射粒度分析仪等手段对微球的性质进行研究。结果与结论β-环糊精与可溶性淀粉和环氧氯丙烷的用量比例为9 g∶1 g∶12 mL、氢氧化钠质量分数为40%、水相油相体积比为15∶120、乳化剂用量为7.0 g、搅拌速度为400 r.min-1、60℃下交联8 h可以获得粒径为100μm左右、粒径分布较窄、形状圆整的微球。红外光谱证明β-环糊精和可溶性淀粉在交联后结构和性质发生变化,交联后生成的三维网络结构使其具有较大的机械强度和吸附能力,可以作为药物载体。实验结果表明交联微球对水杨酸的吸附很快,1 h可达到平衡,平衡时包封率达到58.35%,载药质量分数为4.856%,而且主要为物理吸附过程。     

阿奇霉素羧甲基壳聚糖微球的处方优化及质量评价

目的 优化阿奇霉素羧甲基壳聚糖微球的处方工艺，对其进行表征和质量评价。方法 采用乳化交联法制备阿奇霉素羧甲基壳聚糖微球；在单因素试验的基础上，采用星点设计-效应面法优化其处方工艺；采用红外光谱分析法(fourier transform infrared spectrum, FTIR)、X-射线衍射法(X-ray diffraction, XRD)和扫描电镜对其结构形态进行分析；采用透析法考察其体外释放行为；通过测定微球在模拟唾液中的释放度评价其掩味能力。结果 最优处方工艺为油水体积比4.5,载体质量浓度为36 g·L^-1,固化时间为2.8 h,制得的微球包封率为(86.32±1.52)%,载药量为(12.08±0.14)%;微球表面光滑圆整，分布均匀；FTIR和XRD结果均证实阿奇霉素被包裹于羧甲基壳聚糖中；微球在pH 6.8磷酸盐缓冲液中8 h稳定释放；在模拟唾液中30 s的释放浓度低于其苦味阈值。结论 此制备工艺可行，制得的微球载药量和包封率较高，释药稳定，口感适宜。     

槐定碱微球的质量评价

目的:为确保制剂的质量、疗效和使用的安全性,在确定了槐定碱微球的最佳处方和工艺后,对微球的形态、粒径、红外以及体外释药等方面的制剂学性质进行考察和评价.方法:用乳化交联法制备槐定碱微球,用光学显微镜、扫描电镜、高效液相色谱仪、红外光谱法、差示扫描量热测定法等检测手段对槐定碱微球的理化性质进行考察.结果:槐定碱微球外观圆...     

交联淀粉微球对碘的吸附性能

目的以杀菌剂碘作为模型药物对交联淀粉微球的吸附性能进行初步研究。方法利用硫代硫酸钠滴定法测定了微球粒径、碘溶液的浓度、微球的溶胀能力、吸附时间和环境温度对微球吸附碘性能的影响。结果交联淀粉微球的粒径对其载药吸附性能影响不大;当碘母液的质量浓度在0～7 g.L-1之间时微球吸附碘的量随着溶液中碘浓度的升高而增大,吸附效率基本不变;微球吸附碘的量和微球的干基吸水质量分数和溶胀体积倍数呈现较好的正相关性;微球快吸附主要发生在0～5 h内,慢吸附主要发生在6～12 h内;若环境的温度不同,微球吸附碘的量随着温度的升高而降低。结论交联淀粉微球对碘具有良好的吸附性能,可以通过改变碘溶液的浓度,调节微球的溶胀能力以及吸附时间来改变交联淀粉微球吸附碘的含量,此微球可以作为吸附碘的良好载体。     

海洋多糖BTH缓释微球的制备及释放特性研究

目的 以海藻酸钠与壳聚糖为载体材料制备苯并[l,2,3]噻二唑-7-硫代羧酸甲酯(BTH)缓释微球并研究其释放特性。 方法 采用乳化-外源凝胶法制备BTH缓释微球,通过傅里叶变换红外光谱(FT-IR)验证BTH包封于微球当中,利用高效液相(HPLC)外标法测定微球的包封率、载药量以及不同pH溶液中的释放曲线。结果 BTH被均匀的分散在缓释微球当中,平均载药量为11.14%,平均包封率为81.52%,微球可持续释放12天,累计释放量达到61%。 结论 制备的BTH缓释微球形态圆整,表面光滑,成球性好,载药量与包封率较高,具有显著的缓释效果。     

鼻用氟脲嘧啶壳聚糖微球的体外释放及溶胀影响因素

目的考察壳聚糖脱乙酰度、壳聚糖浓度、固化剂用量、固化时间以及介质pH值对氟脲嘧啶壳聚糖微球的体外释放与溶胀的影响。方法乳化化学交联法制备氟脲嘧啶鼻用微球,动态透析法检测微球的体外释放特性;根据微球吸水前后质量变化测定微球的溶胀率。结果壳聚糖的脱乙酰度越高、固化剂用量越大、固化时间越长则微球的溶胀越慢,微球的体外释放越慢;壳聚糖浓度的增加则使微球的溶胀度增加,体外释放量减少;释放介质的pH值对微球的溶胀性能影响很大,在酸性条件下微球溶胀度高且释药加快。结论影响壳聚糖微球溶胀的因素顺序为介质的pH值>固化剂用量>固化时间>壳聚糖浓度≈壳聚糖脱乙酰度;影响壳聚糖微球体外释放的因素顺序为固化剂用量>壳聚糖脱乙酰度>壳聚糖浓度,而固化时间和介质的pH值对体外释放无显著性影响。     

可溶性甲壳素/海藻酸钠交联微球的制备及其表征和控释性能考察

目的制备可溶性甲壳素/海藻酸钠交联微球,表征微球的微观结构和形态。方法利用滴入法制备可溶性甲壳素/海藻酸钠交联微球,用红外光谱和扫描电镜表征微球的微观结构和形态,以牛血清蛋白为药物模型,研究微球的药物缓释性能。结果可溶性甲壳素与海藻酸钠进行了良好的混溶,并且在钙离子（Ca2+）溶剂环境下形成交联微球。该微球对药物的包封率及缓释性能与海藻酸钠微球相比都有较大改善,包封率从42%提高到74%,药物缓释时间从4 h上升到24 h。结论可溶性甲壳素/海藻酸钠微球的释药具有pH响应性,在pH为1.2的条件下释药慢,而在pH为7.0～7.4时释药快,可用于小肠或结肠定位缓释系统。     

戊二醛一步固化法制备氟尿嘧啶壳聚糖微球

以壳聚糖为载体,戊二醛为交联剂,氟尿嘧啶为模型药物,采用一步固化法制备氟尿嘧啶壳聚糖微球制剂.以外观和包封率为指标优化了处方,并考察了交联剂浓度和交联时间对微球体外释放行为及溶胀度的影响.采用扫描电镜和红外光谱对微球结构进行表征.所得载药微球的载药量和包封率为33.5%、51.2%,平均粒径为(6.8±1.8)μm,30 min 时突释量为33.5%.     

甲硝唑羧甲基壳聚糖缓释微球的制备及体外释放

目的:探讨乳化交联法制备甲硝唑羧甲基壳聚糖微球的最佳工艺,并了解微球体外释药规律.方法:按正交设计,考察不同羧甲基壳聚糖浓度、投药比、交联度、乳化转速等条件对质量指标的影响,选出最佳方案,并进一步检测微球的体外释放特性.结果:各因素对所制微球综合评分指标的影响大小依次为:乳化转速>投药比>交联度>羧甲基壳聚糖浓度,用优化的工艺制得微球50～200μm粒径分布百分数为48.86%,载药量为48.19%,包封率为37.46%,在pHI.2、6.8和7.6,3种缓冲液中的释放时间为6～8h.结论:本法所制微球工艺稳定.在体外具有缓释作用.     

Glutaraldehyde cross-linked chitosan microspheres for controlled delivery of zidovudine

Zidovudine-Chitosan microspheres were prepared by a suspension cross-linking method. The chitosan was dissolved in 2% acetic acid solution and this solution was dispersed in the light liquid paraffin. Span-80 was used as an emulsifier and glutaraldehyde as cross-linking agent. The prepared microspheres were slight yellow, free flowing and characterized by drug loading, infrared spectroscopy (IR), differential scanning colorimetry (DSC) and scanning electron microscopy (SEM). The in-vitro release studies are performed in pH 7.4 buffer solution. Microspheres produced are spherical and have smooth surfaces, with sizes ranging between 60-210 μm, as evidenced by SEM and particle size analysis. The drug loaded microspheres showed up to 60% of entrapment and release was extended up to 18-24 h. Among all the systems studied, the 35% Glutaraldehyde crosslinked, microspheres with 1 : 6 drug/chitosan ratio showed 75% release at 12 h. The infrared spectra and DSC thermograms showed stable character of zidovudine in the drug loaded microspheres and revealed the absence of drug-polymer interactions. Data obtained from in vitro release were fitted to various kinetic models and high correlation was obtained in the Higuchi model. The drug release was found to be diffusion controlled.     

Particle Size Studies for Subcutaneous Delivery of Poly(lactide-co-glycolide) Microspheres Containing Ovalbumin as Vaccine Formulation

The primary objectives of the present study were to produce poly(lactide-co-glycolide) (PLGA) microspheres with different diameters, to characterize these microspheres which were loaded with a model antigen, ovalbumin and to evaluate the effect of microsphere particle size on the serum antibody levels following administration to mice. Four kinds of ovalbumin-loaded PLGA microspheres with different diameters (1·2, 3·5, 7·0 and 14·3 μm as mean volume diameter) were manufactured by a w/o/w emulsion/solvent evaporation method. Low loading percent (0·08%-0·25%w/w) and efficiencies (8–25% w/w) were observed. Examination using scanning electron photomicrographs showed smooth spherical particles. The in-vitro release of ovalbumin from microspheres showed an expected burst release with all batches and the extent of the burst release increased with decreasing diameters of spheres; PLGA microspheres with the smallest diameter (1·2/μm) showed an 80% burst release within one day. Approximately 10–60% of ovalbumin remained unreleased 30 days later. The single subcutaneous administrations of ovalbumin-loaded PLGA microspheres with different diameters to mice induced good antibody responses above ovalbumin saline negative controls at 3, 6, 9, and 12 weeks after inoculation. Especially, 0·16% ovalbumin-loaded PLGA microspheres having mean volume diameter of 3·5 /μm exhibited the best immune responses with values greater than those obtained after inoculation with adjuvants such as complete Freund's adjuvant or alum as positive control. The strong adjuvant activity of PLGA microspheres as vaccine formulation was suggested.     

Microencapsulation of ovalbumin in poly(lactide-co-glycolide) by an oil-in-oil (o/o) solvent evaporation method

Abstract

The objective of this study was to produce biodegradable poly(lactide-co-glycolide) (PLGA; 50/50) microspheres by an oil-in-oil (o/o) solvent evaporation method to prolong the in vitro release of ovalbumin (OVA) as a model protein. The effects, on loading efficiency, microsphere yield, morphology and drug release, of two dispersing agents, aluminum tristearate and Span 80, in mineral oil were examined. PLGA 50/50 microspheres containing OVA powder (sieved through a 53 μm mesh) were prepared using an o/o solvent evaporation method. When aluminum tristearate was employed as a dispersing agent, the loading efficiency and yield of OVA had maximum values of 89 and 72% at 0·15% (w/v) aluminum tristearate, respectively. Morphology studies suggested that the obtained microspheres were spherical, and had a smooth surface. The diameters of the microspheres ranged between 100 and 200 μm. The loading efficiency, or yield, for microspheres decreased significantly above or below 0·15% (w/v) aluminum tristearate, and microspheres wkh irregular shapes were observed. The minimum sedimentation volume ratio (F) was obtained at a dispersity of carbon black particles in ethanol containing 0·15% (w/v) aluminum tristearate by a sedimentation study, and the cloudy supernatant suggested a defiocculated suspension. However, on the contrary, when Span 80 was added into the mineral oil as a dispersing agent, the concentration of Span 80 had little or no effect on the characteristics of the prepared microspheres. Drug loadings (60–70%) were obtained within the Span 80 concentrations employed in the present study (0·05–1·0% (w/v)). The yields were also in the same levels. The microspheres prepared in mineral oil containing Span 80 had an average diameter less than 50 μm in all cases. Sustained-release characteristics were demonstrated for PLGA microspheres prepared in mineral oil containing aluminum tristearate as a dispersing agent, even though a burst release at the initial phase was observed. This initial burst release from PLGA microspheres was reduced to some extent by micronization of the OVA powder using a planetary-type ball mill. However, PLGA microspheres prepared in mineral oil containing Span 80 as a dispersing agent, exhibited a large initial burst release. This burst release seems to be due to the smaller size of microspheres and the OVA powder adhering to the surface of PLGA microspheres (confirmed by scanning electron microscope (SEM) study).     

Trehalose-hydroxyethylcellulose microspheres containing vancomycin for topical drug delivery.

A new formulation, in which vancomycin is entrapped into trehalose and hydroxyethylcellulose (Natrosol) spherical matrices, is described. Microspheres were produced by the solvent evaporation method. The entrapped drug was fully recovered following microspheres dissolution. Differential scanning calorimetry analyses proved that Natrosol maintains trehalose in its amorphous form. The stabilizing effects of trehalose on vancomycin were evaluated even after long storage and heating of microspheres. Calorimetric data indicated no decomposition of the entrapped drug. In vitro drug release, already performed by using a general two-compartment linear time-invariant open model, suggests that the new delivery system is suitable for topical application on extensive and purulent or burn wounds, when the skin is heavily damaged and the barrier disrupted. The system activation is determined by osmotic phenomena. The prepared new delivery system seems to have characteristics suitable for topical applications on extensive and purulent wounds. The system is able to take away serous exudates from wounds, thus letting the matrix to swell and form a viscous gel-like dispersion that, in turn, enables drug diffusion.     

Bioavailability of cyclosporin A dispersed in sodium lauryl sulfate-dextrin based solid microspheres

The purpose of this work was to develop a solid dispersion system containing cyclosporin A (CsA) in order to improve the bioavailability of poorly water-soluble CsA. Solid dispersion systems that are spherical in shape (CsA-microspheres) were prepared with varying ratios of CsA/sodium lauryl sulfate/dextrin using a spray-drying technique. The effects of sodium lauryl sulfate (SLS) and dextrin on the dissolution of CsA dispersed in SLS-dextrin based solid microspheres were investigated. The bioavailability of CsA-microspheres was compared with CsA powder alone and commercial Sandimmun in dogs. SLS significantly enhanced the dissolution of CsA from microspheres, while dextrin did not affect this. The CsA-microspheres at the CsA/SLS/dextrin ratio of 1/3/1, which gave the highest dissolution rate of CsA among the formula treated, was selected as an optimal formula for oral delivery. This formula gave significantly higher blood levels, area under the drug concentration-time curve (AUC) and maximum blood concentration of drug (Cmax) of CsA in dogs compared with the CsA powder alone. The AUC, Cmax and time to reach maximum blood concentration (Tmax) of CsA with CsA-microspheres was not significantly different from those after oral administration of Sandimmun, suggesting the similar bioavailability to Sandimmun in dogs. Our study demonstrates that the CsA-microspheres prepared with SLS and dextrin, with improved bioavailability of CsA, would be useful to deliver a poorly water-soluble CsA and could be applicable to other poorly water-soluble drugs.     

Crosslinked chitosan microspheres for encapsulation of diclofenac sodium: effect of crosslinking agent

Microspheres of chitosan crosslinked with three different crosslinking agents viz, glutaraldehyde, sulphuric acid and heat treatment have been prepared to encapsulate diclofenac sodium (DS). Chitosan microspheres are produced in a w/o emulsion followed by crosslinking in the water phase by one of the crosslinking methods. Encapsulation of DS has been carried out by soaking the already swollen crosslinked microspheres in a saturated solution of DS. Microspheres are further characterized by FTIR, x-RD and SEM. The in-vitro release studies are performed in 7.4 pH buffer solution. Microspheres produced are spherical and have smooth surfaces, with sizes ranging between 40-230 #181;m, as evidenced by SEM. The crosslinking of chitosan takes place at the free amino group in all the cases, as evidenced by FTIR. This leads to the formation of imine groups or ionic bonds. Polymer crystallinity increases after crosslinking, as determined by x-RD. The method adopted for drug loading into the microspheres is satisfactory, and up to 28-30% w/w loading is observed for the sulphuric acid-crosslinked microspheres, whereas 23-29 and 15-23% of loadings are obtained for the glutaraldehyde (GA)- and heat-crosslinked microspheres, respectively. Among all the systems studied, the 32% GA crosslinked microspheres have shown the slowest release i.e. 41% at 420 min, and a fastest release of 81% at 500 min is shown by heat crosslinking for 3 h. Drug release from the matrices deviates slightly from the Fickian process.     

Chitosan microspheres for encapsulation of alpha-lipoic acid

Encapsulation of alpha-lipoic acid (LA) was carried out using chitosan as an encapsulant matrix. Placebo and LA-loaded chitosan microspheres were prepared by a spray-drying process. Scanning electron microscopy (SEM) studies confirmed the spherical particle geometry and the smooth surface morphology of LA-loaded particles. The particle size distribution (PSD) analysis of the placebo and LA-loaded microspheres has shown that 50% of the microspheres were less than 3.53 and 7.89 microm, respectively. The structural interactions of the chitosan matrix with the encapsulated LA were studied by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) which revealed structural interactions of lipoic acid with the encapsulant matrix. The antioxidant activity of encapsulated lipoic acid was studied using the free-radical scavenging assay. This study demonstrated significant retention of antioxidant activity of lipoic acid (75%) after encapsulation in the chitosan matrix. Encapsulation efficiency of lipoic acid obtained in this study was 55.2% when ethanol and acetic acid (1:1 v/v) was used as incubation/extraction medium.