乳酸-羟基乙酸共聚物(PLGA)微球控释系统的突释

目的介绍近年来国内外对乳酸-羟基乙酸共聚物(PLGA)微球控释系统的突释的研究。方法分析有关文献资料,对产生突释的原因、影响突释的因素以及减少突释的方法进行详细介绍。结果和结论突释通常是不受欢迎的,随着对突释原因的深入了解,突释问题应能得到解决和控制。     

PLGA微球控释系统的突释及其控制

针对目前限制PLGA微球控释系统临床应用的突释问题，重点介绍了近年来国内外有关的研究进展，包括突释现象、突释原因、影响因素和控制突释的方法和技术。     

乳酸-羟基乙酸共聚物微球的研究进展

通过整理和归纳国内外文献,介绍乳酸-羟基乙酸(PLGA)载药微球的制备方法和作为药物载体的应用。     

替莫唑胺乳酸-羟基乙酸共聚物微球的制备及表征

采用乳化-溶剂挥发法制备替莫唑胺微球,考察了制备工艺中影响微球粒径、载药量和包封率的主要因素,筛选处方工艺.按优化工艺制得的微球形态圆整,表面光滑,平均粒径62.2μm,载药量7.5%,包封率83.5%,体外试验表明该载药微球有明显的缓释效果.     

蛋白质/多肽药物聚乳酸/乳酸-羟基乙酸共聚物微球研究进展

缓释微粒给药系统是蛋白质/多肽药物传输系统的一个重要研究方向，聚乳酸和乳酸-羟基乙酸共聚物是制备缓释微球最常用的载体材料。蛋白质/多肽药物聚乳酸/乳酸-羟基乙酸共聚物微球常用的制备方法包括溶剂萃取/挥发法(复乳法)、相分离法和喷雾干燥法。本文总结了微球制备中面临的难点如蛋白质/多肽药物稳定性、包封率、药物突释和药物吸附等问题，并综述了保持药物结构稳定性和生物活性、提高包封率、改善药物释放曲线等微球制备方法和进展。     

超氧化物歧化酶乳酸-羟乙酸共聚物微球的制备及其性质

利用复乳溶剂挥发法制备了超氧化物歧化酶（SOD）的乳酸－羟乙酸共聚物（PLGA）微球，考察了各工艺因素对微球粒径、包封率等的影响，通过扫描电子显微镜（SEM）、差示扫描量热分析（DSC）初步研究了其性质，结果表明，通过调整内水相的体积及浓度，分散相体积及PH值，可得到较高包封率，粒径在20－30μm，形态圆整，表面多孔的SOD微球，DSC表明SOD被有效地包入了PLGA微球中。     

乳酸/羟基乙酸共聚物分子量对艾塞那肽微球性质的影响

目的:制备艾塞那肽一乳酸/羟基乙酸共聚物(PLGA)微球,并研究PLGA分子量对微球性质的影响.方法:选用不同分子量的PLGA,采用复乳法制备艾塞那肽PLGA微球;对微球的粒径、载药量、包封率和体外释放等指标进行测定.结果:PLGA分子量对艾塞那肽PLGA微球的性质有明显影响.结论:可通过调节PLGA分子量调控微球的性质.     

乳酸-羟基乙酸共聚物微球、纳米粒载药体系的研究进展

目的:扩大乳酸-羟基乙酸共聚物微球、纳米粒载药体系的适用范围,并为其他缓控释剂型研发提供参考。方法:查阅文献,综述乳酸-羟基乙酸共聚物(PLGA)微球、纳米粒的表面修饰,PLGA与其他聚合物聚合作为药物载体改变释药行为,PLGA与其他聚合物制备双层微球及修饰特异标记用于疾病诊断的研究进展。结果与结论:PLGA微球、纳米粒经过适当的修饰,可以扩大其应用范围,更好地用作药物特别是基因、疫苗及抗原等某些特殊药物的载体,但有待进一步临床研究考察。     

乳酸-羟基乙酸共聚物在控释制剂研究中的应用与进展

目的 综述乳酸-羟基乙酸共聚物(PLGA)在药物控释制剂中的应用与进展。     

聚乳酸或乳酸／羟乙酸共聚物微球的制备方法 …

综述了微球的制备方法,包括乳化－溶剂挥发法喷雾干燥法,相分离法等。对现有制备法的优缺点和放大生产的可能性进行讨论。     

Control of encapsulation efficiency and initial burst in polymeric microparticle systems

Initial burst is one of the major challenges in protein-encapsulated microparticle systems. Since protein release during the initial stage depends mostly on the diffusional escape of the protein, major approaches to prevent the initial burst have focused on efficient encapsulation of the protein within the microparticles. For this reason, control of encapsulation efficiency and the extent of initial burst are based on common formulation parameters. The present article provides a literature review of the formulation parameters that are known to influence the two properties in the emulsion-solvent evaporation/extraction method. Physical and chemical properties of encapsulating polymers, solvent systems, polymer-drug interactions, and properties of the continuous phase are some of the influential variables. Most parameters affect encapsulation efficiency and initial burst by modifying solidification rate of the dispersed phase. In order to prevent many unfavorable events such as pore formation, drug loss, and drug migration that occur while the dispersed phase is in the semi-solid state, it is important to understand and optimize these variables.     

高效液相色谱法测定吉非替尼PLGA微球吉非替尼的含量

目的建立吉非替尼PLGA微球中吉非替尼含量测定的方法。方法色谱柱为Cosmosil C18（250 mm×4.6mm,5μm）,流动相为甲醇-0.1 mol L-1磷酸二氢钾溶液（37：63）,流速为1.0mL min-1,检测波长为250nm,柱温为30℃。结果吉非替尼线性范围为10.04～60.24μg mL-1（r=0.999 9）;平均回收率为98.6%,RSD=1.0%（n=9）。结论该方法操作简便、灵敏度高、重复性好,可作为该剂型质量控制的方法。     

多孔利福平 PLGA 微球的制备工艺研究

目的：以利福平为模型药物,研究多孔聚乳酸—羟基乙酸共聚物（poly（lactic-co-glycolic acid）,PLGA）微球的最佳制备工艺。方法乳化溶剂扩散法制备多孔微球,采用扫描电镜观察微球形态,HPLC 法测定微球包封率。通过单因素考察实验,筛选影响微球形态和包封率的主要因素并优选条件。结果制备过程中 PLGA 种类、PLGA 浓度、致孔剂浓度、均质速度、外水相 PVA 浓度等影响微球的粒径、多孔结构和包封率。按优化工艺制备的微球平均粒径为8．6μm,密度为0．1 g·cm －3,易于吸入并提高肺部的沉积率。结论低密度多孔微球具有适宜的吸入特性和肺部沉积率,或可成为递送抗结核药物的新载体。     

Kinetics of solvent extraction/evaporation process for PLGA microparticle fabrication

Organic solvent extraction/evaporation from an o/w-dispersion has been widely used for the fabrication of PLGA microparticles. The purpose of this work was to elucidate the kinetics of the solvent extraction/evaporation process. A mathematical diffusion model was developed and applied to predict the duration of the solvent extraction. As the diffusion coefficient, D(p), plays a major role in the modeled process, a new and experimentally simple method for estimating D(p) was developed. Both the experimental method and the mathematical model were validated through PLGA microparticle fabrication experiments. For microparticles of mode diameters of 2 and 20 microm, the solvent was extracted in approximately 10 s. Sufficient hardening of the microparticles required, however, the evaporation of solvent from the extraction phase. Residual solvent in extraction phase exerted a strong effect on the morphology of the final product as demonstrated by scanning electron microscopy. Only if most solvent was removed from the aqueous extraction phase, a powdery product of individual microparticles was obtained. At residual organic solvent concentration of above 0.2% in the extraction phase, the microparticles strongly aggregated during collection on a membrane filter and final drying. The presented methods may be useful for better controlling microparticle fabrication processes by solvent extraction/evaporation.     

Analysis of initial burst in PLGA microparticles

BACKGROUND: This review addresses recent advances in the understanding of the mechanisms that underlie burst release and strategies developed to control burst from poly(lactide-co-glycolide) (PLGA) microparticle formulations. While the initial burst release of drug is not always detrimental, excessive drug release in the burst phase may be toxic, and irregularity in the amount of drug released (e.g., from batch to batch) is not acceptable. Many drugs that are good candidates for sustained release treatments are not miscible in PLGA and common microparticle processing solvents, and, as a result, suffer from excessive initial burst release. OBJECTIVE: The aim of this review is to provide an update on research to understand the mechanisms that underlie burst release of drugs from PLGA microparticles, and strategies developed to control burst. METHODS: This review focuses on literature published since 2004. RESULTS: Strategies to control burst release fall into two general categories. First are efforts to improve the miscibility of drug and polymer by altering the composition of the formulation, for example by altering the salt form of the drug. Secondly, processing methods may be altered (increasing the rate of solvent removal, for example) to prevent drug-polymer separation. The goal of most strategies is to reduce or eliminate burst release, so that the encapsulated drug may be maximally retained in the delivery system for long-term delivery.     

Reduction in burst release of PLGA microparticles by incorporation into cubic phase-forming systems

A high initial burst release of an phosphorothioate oligonucleotide drug from poly(lactide-co-glycolide) (PLGA) microparticles prepared by the w/o/w solvent extraction/evaporation was reduced by incorporating the microparticles into the following glycerol monooleate (GMO) formulations: 1) pure molten GMO, 2) preformed cubic phase (GMO + water) or 3) low viscosity in situ cubic phase-forming formulations (GMO + water + cosolvent). The in situ cubic phase-forming formulations had a low viscosity in contrast to the first two formulations resulting in good dispersability of the microparticles and good syringability/injectability. Upon contact with an aqueous phase, a highly viscous cubic phase formed immediately entrapping the microparticles. A low initial burst and a continuous extended release over several weeks was obtained with all investigated formulations. The drug release profile could be well controlled by the cosolvent composition with the in situ systems.     

Microencapsulation of PEGylated Adenovirus within PLGA Microspheres for Enhanced Stability and Gene Transfection Efficiency

Purpose Green fluorescent protein (GFP) encoding adenovirus (ADV) was surface modified with polyethylene glycol (PEG) for microencapsulation within poly(lactic-co-glycolic acid) (PLGA) microspheres with the aim of improving stability and gene transfection activity. Methods A series of PEGylated ADV (PEG-ADV) with different PEG seeding densities on the viral surface was prepared and the GFP expression efficiency of each PEG-ADV in the series determined. The physical stabilities of naked ADV and PEG-ADV were comparatively evaluated by exerting a high shear homogenization process or by exposure to low pH. Naked ADV or PEG-ADV was microencapsulated within PLGA microspheres using a water-in-oil-in-water (W/O/W) double emulsion and solvent evaporation method. In vitro cumulative ADV and PEG-ADV release profiles from PLGA microspheres were determined over a 10-day period. GFP transfection efficiencies into HeLa cells were quantified, and the relative extent of the immune response for ADV and PEG-ADV encapsulated within PLGA microspheres was analyzed using macrophage cells. Results The physical stability of PEGylated ADV was greatly enhanced relative to that of naked ADV under the simulated W/O/W formulation conditions, such as exposure to an aqueous/organic interface during high shear-stressed homogenization. PEG-ADV was also more stable than ADV at low pH. ADV and PEG-AD were both released from PLGA microspheres similarly in a sustained fashion. However, when the ADV and PEG-ADV encapsulated microspheres transfected into HeLa cells, PEG-ADV microspheres demonstrated a higher GFP gene transfection efficiency than ADV microspheres. The PEG-ADV microspheres also exhibited a reduced extent of innate immune response for macrophage cells. Conclusions PEGylated ADV could be more safely microencapsulated within PLGA microspheres than naked ADV due to their enhanced physical stability under the harsh formulation conditions and acidic microenvironmental conditions of the microsphere, thereby increasing gene transfection efficiency.     

影响聚酯微球中药物释放的因素

聚酯材料因其原料易得、容易加工、生物相容性好、具有可生物降解性等优点,已经成为当今药物载体材料中的一大研究热点。现综合国内外的有关报道对可生物降解聚酯材料作为药物载体制备微球制剂的研究进展进行了综述。针对目前限制聚酯材料微球制剂临床应用存在的问题,从聚合物、药物、制备工艺、附加剂、辐射灭菌5个方面对影响聚乳酸(PLA)和聚乳酸乙醇酸共聚物(PLGA)缓释微球中药物释放的因素进行了重点介绍,为研究聚酯微球中药物的释放提供思路。     

不同PLGA型号对奥曲肽微球的包封率和体外释放行为的影响

考察了不同型号聚乳酸-羟基乙酸共聚物(PLGA)作为水溶性药物奥曲肽微球载体对载药量、包封率和体外释放行为的影响.结果表明,PLGA中丙交酯含量降低,载药量和包封率降低,而突释量增大.PLGA型号相同时,黏度较大的PLGA微球载药量和包封率较高,突释量较小.采用PLGA与聚乳酸(PLA)混合材料制备的微球比单用PLGA材料微球的突释量小、载药量和包封率高、缓释效果好.     

Enhanced targeting efficiency of PLGA microspheres loaded with Lornoxicam for intra-articular administration

Owing to its rationale of targeting the drug to the site of action and minimizing systemic toxic effects of the drug, intra-articular drug delivery system has gained growing interests. In this study, emphasis was placed on intra-articular Lornoxicam -loaded PLGA microspheres (Lnxc-PLGA-MS) preparation and improving the targeting of lornoxicam (Lnxc) in knee joint. The microspheres were prepared by a process involving solid-in-oil-in-water(S/O/W) emulsion, and evaluated for physicochemical properties. Joint cavity′s drug leakage into systemic circulation in rabbits was examined to define the drug stagnation. Meanwhile, drug retention in synovial fluid in rats was investigated to further validate the drug targeting. The microspheres were spherical as evidenced by the SEM photographs with mean size of 7.47μm, and encapsulation efficiency was observed 82.22% along with drug loading 12.17%. DSC revealed that the drug in the microspheres existed in the phase of uncrystallization. The formulated microspheres could prolong the drug release up to 32 days in vitro. Comparing with animals injected with lornoxicam solution, the plasma drug concentration decreased in rabbits and retention time increased in rats’ synovial fluid with intra-articular injections of microspheres, revealing good targeting efficiency. In conclusion, PLGA microspheres could be used to deliver lornoxicam following intra-articular administration for enhancing targeting efficiency.