紫杉醇PLGA微球制备及体外性质评估

目的：以乳酸-羟基乙酸共聚物（PLGA）为材料,制备用于肿瘤内注射的紫杉醇PLGA长效缓释微球.方法：采用改良溶剂蒸发法制备,对微球的体外性质以及不同剂量（10,15,25 kGy）60Coγ射线对微球性质的影响进行考察.结果：制得的微球形态圆整,载药量、包封率、平均粒径和跨距分别为1.53%,97.29%,42.72μm和0.95.药物体外释放30 d累计释放达到56.19%,体外降解30 d后微球失去完整结构,表面粗糙.3个剂量60Coγ射线的灭菌效果均良好,且对微球的体外性质均无明显影响.微球中二氯甲烷的残留量低于药典规定的限度.结论：紫舷杉醇PLGA微球满足缓释长效的要求,对恶性肿瘤的间质化疗具有一定前景.     

Formulation and in-vitro characterization of retinoic acid loaded poly (lactic-co-glycolic acid) microspheres

Poly (lactic-co-glycolic acid) (PLGA) microspheres containing all-trans retinoic acid (atRA) were prepared by emulsion/solvent evaporation technique. PLGA (50:50) with inherent viscosities of 0.17 and 0.39 dL g(-1) was used. Polyvinyl alcohol (PVA) or PVA and sodium oleate (SO) combinations (4:1) were used to stabilize the emulsions. The effect of polymer viscosity, emulsifier type and concentration on the in vitro release of atRA from the microspheres was investigated. The stability of the microparticles was also tested at the temperatures of 4, 25 and 40 degrees C. The particle size ranged between 1-2 microm. Microspheres were smooth and spherical in shape, as determined by scanning electron microscope (SEM) photographs. The yield of microspheres ranged from 50-75% and the encapsulation efficiency was determined between 45-75%. In vitro release studies showed that atRA release from microspheres lasted for 11 days.     

Preparation and characterization of poly(lactic-co-glycolic acid) microspheres loaded with a labile antiparkinson prodrug

L-dopa-α-lipoic acid (LD-LA) is a new multifunctional prodrug for the treatment of Parkinson's disease. In human plasma, LD-LA catechol esters and amide bonds are chemically and enzymatically cleaved, respectively, resulting in a half-life time of about fifty minutes. In the present work, the unstable LD-LA was entrapped into biodegradable poly(lactic-co-glycolic acid) (PLGA) microspheres designed as depot systems to protect this prodrug against degradation and to obtain a sustained release of the intact compound. The microspheres were prepared by an oil-in-water emulsion/solvent evaporation technique and the effect of formulation and processing parameters (polymer concentration in the organic solvent, volumes ratio of the phases, rate of the organic solvent evaporation) on microspheres characteristics (size, loading, morphology, release) was investigated. Also emphasis was given on the stability of the drug before and after release as well as on the underlying mass transport mechanisms controlling LD-LA release. Interestingly, when encapsulated in appropriate conditions into PLGA microspheres, the labile prodrug was stabilized and released via Fickian diffusion up to more than one week.     

紫杉醇PLGA微球制备及工艺优化

目的：以乳酸-羟基醋酸共聚物[-poly（lactic-co-glycolic acid），PLGA3为材料，制备用于肿瘤内注射的紫杉醇PLGA长效缓释微球。方法：采用改良溶剂蒸发法制备，使用星点设计一效应面法优化处方，并对药物体外释放进行评估。结果：以投药比（％）和聚乙烯醇（PVA）浓度为自变量，载药量、包封率、粒径和跨距为因变量进行多元线形回归和二次多项式拟合，结果表明二次多项式拟合的效果较好，较优工艺条件为投药比1．6％、PVA浓度2％。照优化工艺制得的微球形态圆整，载药量、包封率、平均粒径和跨距分别为1．53％，97．29％，42．72胛和0．95，与方程预测值的偏差分别为4．08％，1．91％，6．48％和-4．9HD％。微球体外释放30d累计释放率达56．19％。结论：本实验所得的紫杉醇PLGA微球满足缓释长效的要求，所建立的模型预测性良好。     

Pharmacokinetics and in vitro and in vivo correlation of huperzine A loaded poly(lactic-co-glycolic acid) microspheres in dogs

The purpose of this study was to investigate the pharmacokinetics and in vitro/in vivo correlation (IVIVC) of huperzine A loaded poly(lactic-co-glycolic acid) (PLGA) microspheres in dogs. Several huperzine A loaded PLGA microspheres were prepared by an O/W method and three of them (single dose) were injected intramuscularly (i.m.) or subcutaneously (s.c.) to five beagle dogs, respectively. With the increase of the molecular weight of PLGA and the particle size of microspheres, the in vitro and in vivo release periods of huperzine A were prolonged. After s.c. injection, the release of huperzine A from microspheres was faster than that after i.m. injection. The IVIVC models of huperzine A loaded PLGA microspheres were established successfully and after i.m. administration the linear relationship between the in vitro and the in vivo releases was better than that after s.c. administration. It was also found when the particle size of the microspheres was smaller; the values of correlation coefficient were higher.     

Development and characterization of poly(lactic-co-glycolic) acid nanoparticles loaded with copaiba oleoresin

Abstract

Copaiba oleoresin (CPO), obtained from Copaifera landgroffii, is described as active to a large number of diseases and more recently in the endometriosis treatment. In this work, poly(lactic-co-glycolic acid) (PLGA) nanoparticles containing CPO were obtained using the design of experiments (DOE) as a tool to optimize the production process. The nanoparticles optimized by means of DOE presented an activity in relation to the cellular viability of endometrial cells. The DOE showed that higher amounts of CPO combined with higher surfactant concentrations resulted in better encapsulation efficiency and size distribution along with good stability after freeze drying. The encapsulation efficiency was over 80% for all produced nanoparticles, which also presented sizes below 300?nm and spherical shape. A decrease in viability of endometrial stromal cells from ectopic endometrium of patients with endometriosis and from eutopic endometriotic lesions was demonstrated after 48?h of incubation with the CPO nanoparticles. The nanoparticles without CPO were not able to alter the cell viability of the same cells, indicating that this material was not cytotoxic to the tested cells and suggesting that the effect was specific to CPO. The results indicate that the use of CPO nanoparticles may represent a promising alternative for the treatment of endometriosis.     

In vitro characteristics of poly（lactic-co-glycolic acid） microspheres incorporating gelatin particles loading basic fibroblast growth factor

AIM: To construct a sustained drug release system for basic fibroblast growth factor (bFGF). With this special system, bFGF can be used to repair an injured peripheral nerve, injured spinal cord, or as a carrier for other drugs that need to be released over a long time. METHODS: Microsphere composite was prepared by encapsulating bFGF into gelatin particles with poly(lactic-co-glycolic acid) (PLGA) as its outer-coating. The encapsulation was conducted by a phase separation method. RESULTS: The average diameter of the gelatin particle-PLGA microsphere composite was 5-18 mum, and bFGF-loading efficiency was up to 80.5%. The bFGF releasing experiment indicated that this new composite system could release bFGF continuously and protect bFGF from denaturation. CONCLUSION: A modified approach was successfully employed to develop a biodegradable system for sustained release of the drug of bFGF in vitro.     

Pharmacokinetic study of methotrexate following intra-articular injection of methotrexate loaded poly(L-lactic acid) microspheres in rabbits

The pharmacokinetics and tissue distribution of methotrexate (MTX) were investigated following intra-articular injection of either MTX solution or controlled release MTX loaded microspheres in healthy rabbit joints. MTX solution or MTX loaded microspheres (size 30-100 mum) (10 mg MTX) was injected into the right knee joint cavity of rabbits. Blood samples were taken at predetermined times from the jugular vein. Urine samples were also collected over time periods up to 24 h. The major organs and synovial tissues were removed for analysis 6 and 24 h post-injection (n = 4). MTX and 7-OH-MTX concentrations in the plasma and major organs were determined by HPLC. The MTX plasma area under the concentration-time curve (AUC) for rabbits injected with MTX solution was seven fold higher than that of the rabbits injected with MTX microspheres, while t(1/2) and mean residence time (MRT) were not significantly different between two treatment groups. Four fold more MTX was excreted in the urine from rabbits injected with MTX solution compared to those injected with MTX loaded microspheres 24 h following intra-articular injection. The concentration of MTX in the synovial tissues following intra-articular injection was significantly higher in the rabbits injected with microspheres than in the rabbits injected with MTX solution. MTX solution was rapidly cleared from the joint cavity while MTX encapsulated microspheres retained MTX in the joint cavity.     

188Rhenium(V)-dimercaptosuccinic acid loaded poly(lactic-co-glycolic)acid microspheres for targeted radiotherapy: production and effectivity

Poly(lactic-co glycolic)acid (75:25) (PLGA) microspheres for the delivery of a radiation dose to tumors were synthesized after loading the 188Re(V) labeled DMSA. The 188ReO4- in place of 99mTcO4- was replaced to label DMSA, because of their structural and chemical similarities and to make the molecule site specific for radiotherapy. The radiolabeling efficiency of DMSA was more than 97% as confirmed by ITLC. A solvent evaporation technique was used to encapsulate DMSA in PLGA microspheres. Electron microscopy demonstrated the microspheres size ranged between 0.4-1.8 microm. As demonstrated by DSC, DMSA was encapsulated (20-30%) within the microspheres in solid solution, metastable molecular dispersion or crystallization forms. In vitro release studies confirmed the stability of DMSA.     

白藜芦醇PLGA长效注射微球的制备及工艺考察

目的采用乳化溶剂挥发法制备白藜芦醇聚乳酸羟基乙酸[poly(lactic-co-glycolic acid),PL-GA]长效微球,评价各因素对微球性质的影响。方法以微球的包封率、载药量、突释和粒径作为微球的质量评价指标,研究分散相与连续相的体积比、PLGA浓度、聚乙烯醇(polyvinyl alcohol,PVA)浓度、搅拌速度对微球性质的影响,并优化白藜芦醇PLGA微球的制备工艺。结果分散相与连续相的体积比为1∶50时,包封率高,但4 h突释量达到76%,当分散相与连续相体积比由1∶50提升到1∶150时,突释降低了22%;随着聚合物浓度的增加粒径明显增大,突释显著降低;理论载药量对粒径影响不大,在高载药量时突释显著减少;搅拌速度的增加使粒径减小,突释增加;PVA浓度的增加对粒径没有明显的影响,但当PVA的质量浓度从1 g.L-1增加到5 g.L-1时,包封率从93.57%降低到80.31%。结论分散相与连续相的体积比、PLGA浓度、PVA浓度、搅拌速度对微球性质有很大的影响。优化条件下制备的微球形态完整,载药量为(27.86±1.00)%,包封率为(93.57±2.87)%,平均粒径约为21.12μm。白藜芦醇PLGA微球体外释放25 d的累积释药率达(94.04±4.94)%,有望研制成1个月给药1次的给药系统。     

Methotrexate loaded poly(L-lactic acid) microspheres for intra-articular delivery of methotrexate to the joint

A controlled release delivery system that localizes methotrexate (MTX) in the synovial joint is needed to treat inflammation in rheumatoid arthritis (RA). The purpose of this work was to develop and characterize MTX loaded poly(l-lactic acid) (PLLA) microspheres and evaluate in vivo tolerability and MTX plasma concentrations following intra-articular injection into healthy rabbits. MTX loaded PLLA (2 kg/mole) microspheres were prepared using the solvent evaporation method and characterized in terms of size, molecular weight, thermal properties, and release rates into phosphate buffered saline (PBS) (pH 7.4) at 37 degrees C. Biocompatibility was evaluated by observing the swelling of the joints of the rabbits and histological analysis following the injection of the microspheres. MTX concentrations in the plasma and urine samples of rabbits were evaluated by high-performance liquid chromatography (HPLC). MTX loaded microspheres showed a rapid burst phase followed by a slow release phase. MTX loaded and control microspheres were biocompatible and plasma concentrations of MTX were tenfold higher in rabbits injected intra-articularly with free MTX than MTX microspheres. MTX microspheres may retain the drug in the joint by reducing clearance from the joint into the blood.     

高效液相色谱法测定乳酸羟醋酸共聚物微球中纳美芬的含量

目的：建立高效液相色谱法测定纳美芬缓释微球载药量的方法。方法：色谱柱为C18柱，流动相为甲醇-0．02mol·L^-1，磷酸缓冲液（pH4．0）-三乙胺（40：60：0．2），检测波长为284mm。结果：在5．24～83．84mg·L^-1范围内，峰面积对质量浓度有良好的线性关系，日内RSD≤0．77％，日间RSD≤1．10％，回收率为92．8％。结论：HPLC法专属性强，结果准确。     

Release mechanisms from gentamicin loaded poly(lactic-co-glycolic acid) (PLGA) microparticles

To provide local gentamicin delivery for 1 week based on a biodegradable system, poly(lactic-co-glycolic acid) (PLGA) microparticles were developed utilizing a 50/50 blend of Resomer RG 502H, an uncapped variety of 13.5 kD, and Resomer RG 503, an endcapped polymer of 36.2 kD. The liberation mechanism was investigated by analysis of morphological changes and thermal analysis focusing on the polymer glass transition temperature (T(g)) and the mechanical properties. The release of gentamicin was related to a structural breakdown of the particles reaching a critical molecular weight. A T(g) of < 37 degrees C in the hydrated state was not indicative of collapse and agglomeration of the particles because the mechanical strength of the polymer structures in the rubbery state may still render sufficient support. As the gap between incubation temperature and T(g) widened, the mechanical stability of the PLGA microparticles decreased and became decisive. Particles prepared with RG 502H show a lower ability to bear mechanical stress than RG 503 and 50/50 RG 502H/RG 503 microparticles.     

Studies on the poly(lactic-co-glycolic) acid microspheres of cisplatin for lung-targeting

Lung-targeting cisplatin-loaded poly(lactic-co-glycolic) acid microspheres (CDDP-PLGA-MS) were prepared by a solvent evaporation method. The uniform design was used to optimize the technology of preparation, the appearance and size distribution were examined by scanning electron microscope, and the aspects such as in vitro release characteristics, stability, drug loading, loading efficiency, pharmacokinetics and tissue distribution in rabbit were studied. The experimental results showed that the microspheres were globular in appearance and dispersed well. The average particle size was 12.8 microm with 98% of the microspheres being in the range of 5-30 microm. The drug loading and loading efficiency were 17.68 and 53.2%, respectively. The in vitro release behavior could be expressed by the following equation: 1-Q=0.424e(-0.360t)+0.474e(-0.001t). After i.v. administration (15 min), the drug concentration of microspheres group in lung in rabbits was 212 microg/g, while that of controlled group was 1.37 microg/g. CDDP-PLGA-MS showed a combination of lung-targeting and sustained drug release in experiments on rabbits.     

不同表面活性剂修饰的汉防己甲素PLGA纳米粒制备表征及体外评价

目的:基于纳米粒的递送系统,以改善天然化合物汉防己甲素对肺癌的功效。方法:选取聚乙烯醇、普朗尼克-F127和双十二烷基二甲基溴化铵3种不同的稳定剂,采用单乳化扩散溶剂挥发法制备载汉防己甲素的PLGA纳米粒,考察不同稳定剂对载药纳米粒粒径、ζ电位以及对肺癌A549细胞摄取的影响。结果:2%,1%和0.1%浓度的PVA、PF127和DMAB制备的纳米粒呈表面光滑、大小均一的球形,粒径范围均控制在180~200nm;药物包封率为50%~60%;体外释放实验显示,在pH 7.4的PBS溶液中3组载药纳米粒均呈现缓慢持续释药;细胞学实验结果表明3组纳米粒给药系统均表现出比药物更强的抗肿瘤活性。结论:对PLGA进行表面修饰制备的纳米载体能使汉防己甲素的给药效率得到明显提升。     

Formulation and release characteristics of poly(lactic-co-glycolic acid) microspheres containing chemically modified protein

Chemical modification of proteins may influence their formulation into and release from polymeric microspheres. Three chemical modifications of rat serum albumin (RSA) were effected on the amine groups of this protein: conjugation with a polyanion using 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide, intermolecular cross-linking using glutaraldehyde, and reductive alkylation using propyl aldehyde. The modified proteins had different physicochemical properties as well as improved encapsulation efficiencies compared with native RSA microspheres. The microspheres were incubated at 37 degrees C for over one month to investigate the influence of protein modification on the release profiles. Microsphere degradation accelerated from the ninth day of the release studies and this coincided with an increase in the release rates. The degradation rates of poly(lactic-co-glycolic acid) microspheres containing either native or cross-linked RSA were more rapid than those containing either heparin conjugated or propylated RSA. This was in agreement with the release data, since the release of the native and cross-linked RSA were more rapid than those of the other modified proteins. The release profiles of the RSA-heparin conjugates and the propylated RSA were approximately zero rather than first order between the tenth and thirtieth day of study. Chemical modification of protein may be a useful method to increase encapsulation efficiency and to decrease release rates of proteins that are to be used in microsphere formulations of potent therapeutic proteins.     

Encapsulation and stabilization of nerve growth factor into poly(lactic-co-glycolic) acid microspheres.

The development of a stable sustained-release formulation of recombinant human nerve growth factor (rhNGF) for the treatment of neuronal diseases is described. The protein was encapsulated into poly(lactic-co-glycolic) acid (PLGA) microspheres using a spray freeze drying technique. Liquid nitrogen and cold ethanol were used to spray-freeze-dry solid rhNGF that had been suspended in a solution of PLGA dissolved in ethyl acetate. When excipients such as sugar (trehalose), surfactant (pluronic F68), and poly(ethylene glycol) (PEG) were added to the PLGA formulation to protect rhNGF from degradation during spray freeze drying, the protein degraded via aggregation during in vitro release. The formation of an insoluble rhNGF-zinc complex prior to encapsulation into PLGA microspheres stabilized the protein during both microencapsulation and release. In this study, we have demonstrated that the addition of zinc acetate in a 1:12 rhNGF-to-zinc acetate molar ratio in a solid rhNGF formulation (4 mM sodium bicarbonate at pH 7.4) improves stability of rhNGF during release at 37 degrees C (physiological temperature). The stabilization may be due to rhNGF complexation with zinc to form stable aggregates. The PLGA formulation consisting of 10% rhNGF encapsulated in 12 kDa PLGA (50:50 lactide/glycolide) provided a continuous release of 14 days. The low initial burst (approximately 1%) and controlled-release rate were achieved by the addition of 3 or 6% solid zinc carbonate to the polymer phase during microencapsulation.     

Pharmacokinetic and pharmacodynamic profiles of recombinant human erythropoietin-loaded poly(lactic-co-glycolic acid) microspheres in rats

Aim:

To characterize the pharmacokinetic and pharmacodynamic profiles of the recombinant human erythropoietin (rhEPO)-loaded poly(lactic-co-glycolic acid) (PLGA) microspheres in rats.

Methods:

The rhEPO-loaded microspheres were prepared using a solid-in-oil-in-water emulsion method. Pharmacokinetics and pharmacodynamics of the rhEPO-loaded microspheres were evaluated in male Sprague-Dawley rats. The serum rhEPO level was determined with ELISA. The level of anti-rhEPO antibody in the serum was measured to assess the immunogenicity of rhEPO released from the microspheres.

Results:

rhEPO was almost completely released from the PLGA microspheres in vitro, following zero-order release kinetics over approximately 30 d. After intramuscular injection (10 000 or 30 000 IU rhEPO/kg) in the rats, the serum rhEPO concentration reached maximum levels on d 1, then decreased gradually and was maintained at nearly steady levels for approximately 4 weeks. Furthermore, the release of rhEPO from the PLGA microspheres was found to be controlled mainly by a dissolution/diffusion mechanism. A good linear correlation (R²=0.98) was obtained between the in vitro and in vivo release data. A single intramuscular injection of the rhEPO-loaded PLGA microspheres (10 000 or 30 000 IU rhEPO/kg) in the rats resulted in elevated hemoglobin and red blood cell concentrations for more than 28 d. Moreover, the immunogenicity of rhEPO released from the PLGA microspheres was comparable with that of the unencapsulated rhEPO.

Conclusion:

The results prove the feasibility of using the PLGA-based microspheres to deliver rhEPO for approximately 1 month.