Effect of process variables on particle size of gelatin microspheres containing lactic acid

Gelatin microspheres containing lactic acid were prepared by a polymerization technique using glutaraldehyde as the cross-linking agent. Because particle size distribution of microspheres is a vital factor in the characterization of microspheres, the present study was carried out to evaluate the effect of process variables on the microspheres size distribution. It was found that concentration of a gelatin solution is the most important parameter that influences the particle size of microspheres. By using different concentrations of gelatin solution, microspheres with different size ranges were prepared. Both the stirring rate of the system and the volume ratio of aqueous and oil phases exerted a great influence on microsphere-size distribution, whereas, cross-linking time and cross-linker concentration only affected the yield. Lower-phase volume ratios resulted in small uniform microspheres with smooth surfaces and a narrow size range. The effect of emulsifier concentration (span 80), below 1% (w/w, with respect to the weight of the oil phase), on particle size was appreciable. However, at higher concentrations, little effect was observed.     

莲心总碱-阿霉素明胶微球的制备研究

目的制备莲心总碱-阿霉素明胶微球。方法采用乳化交联法制备莲心总碱-阿霉素明胶微球,用均匀设计对其制备工艺进行优化。结果莲心总碱-阿霉素明胶微球的最优制备条件为：明胶浓度：22.5%,明胶与药物质量比为1∶20,油水相体积比为1∶17.5,搅拌速度：900 r.min-1,25%戊二醛溶液用量：50μL/0.6 g明胶,Span-80用量：2%。按优化工艺参数制得的载药微球呈圆球形,表面光滑,总载药量为：2.56%,包封率为：66.44%,90%的微球分布在10-100μm。结论采用优化工艺条件制备的莲心总碱-阿霉素明胶微球,载药量较大,包封率较高,粒径分布相对集中,形态较好。     

Cytotoxicity of 5-fluorouracil entrapped in gelatin microspheres

Gelatin microspheres were prepared by water/oil emulsion polymerization and by cross-linking with glutaraldehyde. For the microsphere preparation procedure, two different gelatin (5 or 10% w/v) and three different glutaraldehyde (5, 0.5 or 0.1% v/v) concentrations were used. The influence of preparation compositions on microsphere recovery, particle size and morphology, swelling and degradation, 5-fluorouracil loading and release, and cytotoxicity were investigated. The concentrations of gelatin and glutaraldehyde influenced the size and surface properties of microspheres. The decrease in gelatin concentration and the increase in glutaraldehyde concentration resulted in the formation of smaller (140.82-71.47 microm for gelatin microspheres with a 5% gelatin content; 297.67-97.44 microm for gelatin microspheres with a 10% gelatin content) microspheres with smoother surface properties. Swelling values were decreased as the amount of glutaraldehyde was increased. In particular, for microspheres with a high glutaraldehyde content (5% v/v), only about 15% were degraded in 12 days, whereas for those with 0.5% (v/v) glutaraldehyde, almost 97% degradation occurred in the same period. The most rapid 5-fluorouracil release was observed from uncross-linked microspheres (about 88% in 4 h), whereas a particular slower release (about 36% in 4 h) profile was obtained for the highly cross-linked ones. Cytotoxicity tests of free and entrapped 5-fluorouracil were carried out with MCF-7 breast cancer cell line. Free 5-fluorouracil produced an immediate effect, whereas entrapped 5-fluorouracil showed a prolonged cytotoxic effect.     

Preparation and characterization of drug‐loaded chitosan–tripolyphosphate microspheres by spray drying

The present study reports on the preparation of chitosan–tripolyphosphate (TPP) microspheres by the spray‐drying method using acetaminophen as a model drug substance. Chitosan–TPP microspheres were spherical and had a smooth surface. Perfectly spherical chitosan–TPP microparticles loaded with acetaminophen were obtained in the size range of 3.1–10.1 µm. Spray‐dried chitosan–TPP microspheres were positively charged (zeta potential ranged from +18.4 to +31.8). The encapsulation efficiency of these microspheres was in the range of 48.9–99.5%. The swelling capacity of chitosan–TPP microspheres increased with increases in the molecular weight of chitosan and decreases with increasing volume of 1% wt/vol TPP solution used for the cross‐linking reaction. The effect of chitosan concentration, drug loading, volume of TPP solution used for cross‐linking, and chitosan molecular weight on surface morphology and drug release rate was extensively investigated. Microparticles with spherical shape and slower release rates were obtained from chitosan–TPP microspheres prepared using a higher concentration of chitosan, higher volume of TPP solution, a higher molecular weight chitosan and/or a higher drug loading. Most importantly, the drug release rate was mainly controlled by the chitosan–TPP matrix density and, thus, by the degree of swelling of the hydrogel matrix. Drug release from chitosan–TPP microspheres occurred via diffusion as the best fit for drug release was obtained using the Higuchi equation. Drug Dev. Res. 64:114–128, 2005. © 2005 Wiley‐Liss, Inc.     

Preparation and characterization of ibuprofen microspheres

Ibuprofen was microencapsulated with Eudragit RS using an o/w emulsion solvent evaporation technique. The effects of three formulation variables including the drug:polymer ratio, emulsifier (polyvinyl alcohol) concentration and organic solvent (chloroform) volume on the entrapment efficiency and microspheres size distribution were examined. The drug release rate from prepared microspheres and the release kinetics were also studied. The results demonstrated that microspheres with good range of particle size can be prepared, depending on the formulation components. The drug:polymer ratio had a considerable effect on the entrapment efficiency. However, particle size distribution of microspheres was more dependent on the volume of chloroform and polyvinyl alcohol concentration rather than the drug:polymer ratio. The drug release pattern showed a burst effect for all prepared microspheres due to the presence of uncovered drug crystals on the surface. It was shown that the release profiles of all formulations showed good correlation with the Higuchi model of release.     

Preparation of magnetic gelatin microspheres for the targeting of drugs

Magnetically responsive gelatin microspheres for the targeting of drugs have been prepared using a water-in-oil emulsion technique with chemical cross-linking of the protein. The manufacturing variables affecting microsphere size, size distribution and surface characteristics have been examined as well as the magnetic responsivenessin vitro. Sesame oil was utilized for non-aqueous phase and magnetic gelatin microspheres of different size from 1.89 to 14.88 μm in mean diameter could be obtained with variation of HLB values of non-ionic surfactants. The content of magnetite which uniformly distributed throughout the microspheres was 26.7% (w/w). It was possible to control the localization of magnetic gelatin microspheres at specific sites within capillary models by using external magnetic field of under 5K gauss.     

丝素空白微球的制备

目的以丝素蛋白为载体,制备丝素空白微球,并对影响微球粒径的因素进行考察。方法以液状石蜡为油相,再生丝素溶液为水相,Span 80为乳化剂,戊二醛为交联剂,采用乳化-化学交联法制备丝素微球,采用显微镜测定法测定微球的平均粒径,采用单因素试验考察了Span 80、转速、戊二醛、水油比对微球平均粒径的影响。结果所制得的微球圆整,无粘连。结论以丝素为载体,采用乳化-化学交联法,制备了丝素空白微球。     

Preparation and characterization of ibuprofen microspheres

Ibuprofen was microencapsulated with Eudragit RS using an o/w emulsion solvent evaporation technique. The effects of three formulation variables including the drug:polymer ratio, emulsifier (polyvinyl alcohol) concentration and organic solvent (chloroform) volume on the entrapment efficiency and microspheres size distribution were examined. The drug release rate from prepared microspheres and the release kinetics were also studied. The results demonstrated that microspheres with good range of particle size can be prepared, depending on the formulation components. The drug:polymer ratio had a considerable effect on the entrapment efficiency. However, particle size distribution of microspheres was more dependent on the volume of chloroform and polyvinyl alcohol concentration rather than the drug:polymer ratio. The drug release pattern showed a burst effect for all prepared microspheres due to the presence of uncovered drug crystals on the surface. It was shown that the release profiles of all formulations showed good correlation with the Higuchi model of release.     

Gelatin microspheres crosslinked with D,L-glyceraldehyde as a potential drug delivery system: preparation, characterisation, in vitro and in vivo studies

To overcome the restriction in using crosslinked gelatin in the pharmaceutical field, D,L-glyceraldehyde (GAL), a non-toxic crosslinking agent, was proposed. Gelatin microspheres crosslinked with different concentrations of GAL (0.5, 1 or 2%, w/v) and for different time periods (1 or 24 h) were prepared. The effect of the preparation variables was evaluated analysing the extent of crosslinking, the morphological aspect, the particle size and the swelling behaviour. To evaluate the pharmaceutical properties, an antihypertensive drug, clonidine hydrochloride, was chosen as drug model and loaded into the microspheres. Either the increase of the crosslinker concentration or of the crosslinking time period decreased both the swelling and the in vitro drug release processes of the microspheres. After the subcutaneous injection, the loaded microspheres crosslinked with the lowest GAL concentration (0.5%, w/v) or for the shortest time period (1 h) showed a reduction of systolic blood pressure (SBP) similar to that recorded with a clonidine hydrochloride solution having the same drug concentration. Instead, the microspheres crosslinked for 24 h with concentrations of GAL higher than 0.5% (w/v) produced a more gradual and sustained SBP reduction and the antihypertensive effect was maintained until 52-72 h. The biocompatibility studies showed that the microspheres crosslinked with GAL are well tolerated in vivo. These results suggest the potential application of gelatin microspheres crosslinked with GAL as a suitable drug delivery system for the subcutaneous administration.     

Effects of formulation factors on encapsulation efficiency and release behaviour in vitro of huperzine A-PLGA microspheres

To develop a long-acting injectable huperzine A-PLGA microsphere for the chronic therapy of Alzheimer's disease, the microsphere was prepared by using an o/w emulsion solvent extraction evaporation method based on a series of formulation design of the emulsion. The dialysis method was used for release analysis. The encapsulation efficiency and release amount of the microspheres were determined by a UV/VIS spectrophotometer. The morphology of the microspheres was observed by scanning electron microscopy. The distribution of the drug within microspheres was observed by a confocal laser scanning microscope. The results indicated that the PLGA 15?000 microspheres possessed a smooth and round appearance with average particle size of 50?µm or so. The encapsulation percentages of microspheres prepared from PLGA 15?000, 20?000 and 30?000 were 62.75%, 27.52% and 16.63%, respectively. The drug release percentage during the first day decreased from 22.52% of PLGA 30?000 microspheres to 3.97% of PLGA 15?000 microspheres, the complete release could be prolonged to 3 weeks. The initial burst release of microspheres with higher molecular weight PLGA could be explained by the inhomogeneous distribution of drug within microspheres. The encapsulation efficiency of the microspheres improved as the polymer concentration increased in the oil phase and PVA concentration decreased in the aqueous phase. The burst release could be controlled by reducing the polymer concentration. Evaporation temperature had a large effect on the drug release profiles. It had better be controlled under 30°C. Within a certain range of particle size, encapsulation efficiency decreased and drug release rate increased with the reducing of the particle size.     

Effects of formulation factors on encapsulation efficiency and release behaviour in vitro of huperzine A-PLGA microspheres

To develop a long-acting injectable huperzine A-PLGA microsphere for the chronic therapy of Alzheimer's disease, the microsphere was prepared by using an o/w emulsion solvent extraction evaporation method based on a series of formulation design of the emulsion. The dialysis method was used for release analysis. The encapsulation efficiency and release amount of the microspheres were determined by a UV/VIS spectrophotometer. The morphology of the microspheres was observed by scanning electron microscopy. The distribution of the drug within microspheres was observed by a confocal laser scanning microscope. The results indicated that the PLGA 15,000 microspheres possessed a smooth and round appearance with average particle size of 50 microm or so. The encapsulation percentages of microspheres prepared from PLGA 15,000, 20,000 and 30,000 were 62.75%, 27.52% and 16.63%, respectively. The drug release percentage during the first day decreased from 22.52% of PLGA 30,000 microspheres to 3.97% of PLGA 15,000 microspheres, the complete release could be prolonged to 3 weeks. The initial burst release of microspheres with higher molecular weight PLGA could be explained by the inhomogeneous distribution of drug within microspheres. The encapsulation efficiency of the microspheres improved as the polymer concentration increased in the oil phase and PVA concentration decreased in the aqueous phase. The burst release could be controlled by reducing the polymer concentration. Evaporation temperature had a large effect on the drug release profiles. It had better be controlled under 30 degrees C. Within a certain range of particle size, encapsulation efficiency decreased and drug release rate increased with the reducing of the particle size.     

Biodegradable bromocryptine mesylate microspheres prepared by a solvent evaporation technique. I: Evaluation of formulation variables on microspheres characteristics for brain delivery

The aim of this study was to formulate biodegradable microspheres containing an anti-parkinsonian agent, bromocryptine mesylate, for brain delivery. The effect of formulation parameters (e.g. polymer, emulsifying agent type and concentration) on the characteristics of the microspheres produced, the efficiency of drug encapsulation, the particle size distribution and in vitro drug release rates from the bromocryptine mesylate microspheres were investigated using a 3 2 factorial design. Bromocryptine mesylate was encapsulated into biodegradable polymers using the following three different polymers; poly(L-lactide), poly(D,L-lactide) and poly(D,L-lactide-co-glycolide). The SEM photomicrographs showed that the morphology of the microspheres greatly depended on the polymer and emulsifying agent. The results indicate that, regardless of the polymer type, increase in emulsifying agent concentration from 0.25-0.75% w/v markedly decreases the particle size of the microspheres. Determination of particle size revealed that the use of 0.75% w/v of emulsifying agent concentration and a polymer solution concentration of 10% w/v resulted in optimum particle size. In order to prepare biodegradable microspheres with high drug content and small particle size, selection of polymer concentration as well as emulsifying agent concentration is critical. Polymer type has a less pronounced effect on the percentage encapsulation efficiency and particle size of microspheres than on the t 50% . The microspheres prepared by all three polymers, at a polymer concentration of 10% w/v and an emulsifying agent concentration of 0.75% w/v with NaCMC:SO (4:1, w/v) mixture was as the optimum formulation.     

Biodegradable bromocryptine mesylate microspheres prepared by a solvent evaporation technique. I: Evaluation of formulation variables on microspheres characteristics for brain delivery

The aim of this study was to formulate biodegradable microspheres containing an anti-parkinsonian agent, bromocryptine mesylate, for brain delivery. The effect of formulation parameters (e.g. polymer, emulsifying agent type and concentration) on the characteristics of the microspheres produced, the efficiency of drug encapsulation, the particle size distribution and in vitro drug release rates from the bromocryptine mesylate microspheres were investigated using a 3(2) factorial design. Bromocryptine mesylate was encapsulated into biodegradable polymers using the following three different polymers; poly(L-lactide), poly(D,L-lactide) and poly(D,L-lactide-co-glycolide). The SEM photomicrographs showed that the morphology of the microspheres greatly depended on the polymer and emulsifying agent. The results indicate that, regardless of the polymer type, increase in emulsifying agent concentration from 0.25-0.75% w/v markedly decreases the particle size of the microspheres. Determination of particle size revealed that the use of 0.75% w/v of emulsifying agent concentration and a polymer solution concentration of 10% w/v resulted in optimum particle size. In order to prepare biodegradable microspheres with high drug content and small particle size, selection of polymer concentration as well as emulsifying agent concentration is critical. Polymer type has a less pronounced effect on the percentage encapsulation efficiency and particle size of microspheres than on the t(50%). The microspheres prepared by all three polymers, at a polymer concentration of 10% w/v and an emulsifying agent concentration of 0.75% w/v with NaCMC:SO (4:1, w/v) mixture was as the optimum formulation.     

Effects of formulation factors on encapsulation efficiency and release behaviour in vitro of huperzine A-PLGA microspheres

To develop a long-acting injectable huperzine A-PLGA microsphere for the chronic therapy of Alzheimer's disease, the microsphere was prepared by using o/w emulsion solvent extraction evaporation method based on a series of formulation design of the emulsion. The dialysis method was used for release analysis. The encapsulation efficiency and release amount of the microspheres were determined by UV/VIS spectrophotometry. The morphology of the microspheres was observed by scanning electron microscopy. The distribution of the drug within microspheres was observed by a confocal laser scanning microscope. The results indicated that the PLGA 15 000 microspheres possessed a smooth and round appearance with average particle size of 50 microm or so. The encapsulation percentages of microspheres prepared from PLGA 15 000, 20 000 and 30 000 were 62.75, 27.52 and 16.63%, respectively. The drug release percentage during the first day decreased from 22.52% of PLGA 30 000 microspheres to 3.97% of PLGA 15 000 microspheres, the complete release could be prolonged to 3 weeks. The initial burst release of microspheres with higher molecular weight PLGA could be explained by the inhomogeneous distribution of drug within microspheres. The encapsulation efficiency of the microspheres improved as the polymer concentration increase in oil phase and PVA concentration decreased in aqueous phase. The burst release could be controlled by reducing the polymer concentration. Evaporation temperature had a large effect on the drug release profiles. It had better be controlled under 30 degrees C. Within a certain range of particle size, encapsulation efficiency decreased and drug release rate increased with the reducing of the particle size.     

长春西汀聚乳酸-聚乙醇酸缓释微球的研制

目的:制备长春西汀聚乳酸-聚乙醇酸(PLGA)缓释微球,并研究其药剂学性质。方法:采用改良O/W乳化-溶剂挥发法制备微球,以PLGA浓度、理论载药量、有机相与分散介质的比例和分散介质中明胶的浓度为4因素,每个因素选定3个水平,按L9(34)的正交设计方案,以载药量、包封率和粒径分布为指标,优化处方。用扫描电镜观察微球的形态,用光学显微镜观察并计算微球的粒径分布,用差示扫描量热(DSC)法研究药物在载体中的分散状态,用紫外分光光度法检测微球中长春西汀含量并计算载药量和包封率,用动态透析释药法进行微球的体外释放研究。结果:最佳处方为PLGA浓度16%,理论载药量20%,有机相与分散介质的比例1:10,分散介质中明胶的浓度1%;制备的长春西汀PLGA缓释微球的形态圆整、光滑,粒径分布均匀,平均粒径为(10.0±0.18)μm(n=500),DSC法分析药物确已被包裹于微球中,载药量为(18.46±0.26)%,包封率为(91.30±0.98)%(n=3),24h累积释药率约为18%。结论:长春西汀PLGA缓释微球制备工艺稳定,质量符合药剂学要求,缓释性好。     

褪黑激素明胶微球的鼻腔给药

目的　制备经鼻粘膜给药的褪黑激素明胶微球,以提高其生物利用度。方法　用乳化交联技术制备褪黑激素明胶微球,用放射性核素^99mTc标记,用γ射线闪烁显像技术考察微球在鼻粘膜滞留时间,用HPLC法测定药物的体内吸收。结果　褪黑激素明胶微球粒径在30～70 μm,平均粒径为50.2 μm,褪黑激素含量为13.48%。与滴鼻液相比,明胶微球在鼻粘膜滞留时间明显延长。褪黑激素明胶微球的绝对生物利用度为87.47%。结论　鼻粘膜给药明胶微球,能避免肝脏首过作用,延长药物在鼻粘膜滞留时间,提高药物吸收,有很好的应用前景。     

洛索洛芬钠缓释微球的制备及体外释药特性考察

目的延缓洛索洛芬钠在局部的作用时间,了解洛索洛芬钠缓释微球的体外释药特性。方法采用乳化-化学交联法制备明胶微球,采用正交试验优化明胶微球的处方和制备工艺;采用流化床包衣技术制备缓释微球;采用透析法考察体外释药特性。结果制备明胶微球最优处方和工艺为:洛索洛芬钠5.0 g,质量分数为20%的明胶溶液100 mL作为水相,含质量分数0.5%Span 80的液体石蜡混合液400 mL作为油相,55℃搅拌下将水相缓缓加入至油相中,500 r.min-1乳化20 min,冰水浴20 min,加入戊二醛使体积分数为50%,交联90 min,4000 r.min-1离心分离10 min,用丙酮、乙醚交替洗涤3次,40℃真空干燥12 h;制备的明胶微球平均粒径为18.25μm,载药量为19.37%,包封率为87.72%,包衣后质量增加25%;洛索洛芬钠缓释微球体外释药过程符合Higuchi方程。结论制备的洛索洛芬钠缓释微球具有明显的缓释作用。     

阿苯达唑-壳聚糖微球的制备及其质量指标的考察

目的:考察阿苯达唑-壳聚糖微球(ABZ-CS-MS)的载药量、包封率、表面形态及结果特性,以及微球在不同介质中的体外释放特性。方法:采用乳化-交联固化法,以液体石蜡为油相,Span-80为乳化剂,戊二醛为交联剂,壳聚糖(chitosan,CS)为载体,制备阿苯达唑-壳聚糖微球(ABZ-CS-MS);应用光学显微镜测量ABZ-CS-MS的的粒径大小及其分布;用扫描电镜(SEM)观察ABZ-CS-MS的表面形态;用红外光谱(fourier transform infraredspectrometer,FT-IR)、X-线粉末衍射法(X-ray power diffraction,X-RD)和差示扫描热量法(differential scanning calo-rimetry,DSC)检测ABZ-CS-MS的特性;用体外动态透析法测定ABZ-CS-MS在不同介质条件下的释药性能。结果:所制备的ABZ-CS-MS形态圆整,粒径分布较为均匀,平均粒径为(153±7)μm,载药量为(20.92±0.15)%,包封率为(25.37±0.22)%;ABZ-CS-MS分别在不同介质(0.1mol/L HCl液、PBS(pH=3.5)、PBS(pH=7.4)和0.9%氯化钠溶液)中的释放均遵循Weibull方程,其中在PBS(pH=3.5)中释放效果最佳。结论:该法制备的ABZ-CS-MS的质量与性能良好,具有较好的载药量,包封率高,形态圆整,缓释作用明显。     

尼莫地平明胶微球的制备及其性质研究

目的研究尼莫地平明胶微球的制备工艺,并考察其体外释药特性。方法以天然的可生物降解的明胶为载体,液体石蜡为油相,Span80为乳化剂,采用正交设计优化空白明胶微球的制备工艺,用乳化法制备尼莫地平明胶微球。结果优选所制尼莫地平明胶微球形态圆整,大小均匀,表面光滑,载药量为13.48%。体外释药结果表明,一级动力学方程能较好地对其进行拟合。结论制备工艺稳定可行,所得尼莫地平明胶微球具有良好的缓释效果。     

盐酸尼卡地平鼻粘膜用明胶微球的工艺研究

目的研究盐酸尼卡地平鼻粘膜用明胶微球的制备工艺。方法以天然可生物降解的明胶为载体材料 ,液体石蜡为油相 ,Span80为乳化剂 ,采用正交设计优化空白明胶微球制备工艺 ,用乳化法和吸附法制备了盐酸尼卡地平明胶微球。采用溶媒提取法利用HPLC测定微球中药物含量。结果所得明胶微球形态良好 ,粒径分布窄 ,所选择的HPLC法用于测定明胶微球中药物含量回收率及重现性均较好 ,乳化法制备明胶微球的包封率为 31 3% ,吸附法为 5 1 %。结论所优化制备工艺可用于盐酸尼卡地平鼻粘膜给药明胶微球的制备。