Immune Augmentation of Injectable PLGA – Dextran (PLDEX) a Double Polymeric Microspheres as an Adjuvant for Hepatitis B Vaccine

A new method has been developed to prepare microspheres by blending PLGA and dextran polymers (PLDEX) using solvent evaporation technique. Recombinant hepatitis B vaccine (HBsAg) was incorporated in to the double polymeric system. The objective of this study was to investigate the feasibility of PLDEX polymeric microspheres as an adjuvant for hepatitis B vaccine (HBsAg). The present study demonstrates the immunogenicity profile of HBsAg encapsulated in PLDEX and compared their efficacy with alum adsorbed HBsAg. The single intramuscular injection of HBsAg loaded PLDEX microspheres in Wistar rats resulted satisfactory antibody titers. Based on in vivo findings PLDEX microspheres were able induce satisfactory immune response.

A method of elevated temperatures coupled with magnetic stirring to predict real time release from long acting progesterone PLGA microspheres

The object of the study was to develop a quick and reproducible accelerated in vitro release method to predict and deduce the function of the real time(37 °C) release for long acting PLGA microspheres. The method could be described in several steps. First, the release of the microspheres were studied using the sample and separate method at 37 °C with normal orbital shaking and elevated temperatures with magnetic stirring to further accelerate the release. Second, the most similar profile at elevated temperatures with the real time release was chosen with the help of the n value in the fitted Korsmeyer-Peppas Function. Third,the Weibull function and conversion ratio were used to deduce the function of real time release according to the chosen profile at elevated temperatures. The key point in this study was to provide a quick and precise method to predict the real time release for long acting progesterone PLGA microspheres. So the elevated temperatures coupled with magnetic stirring were used to accelerate the release further, and when there have many similar release profiles with the real time release at elevated temperatures, releasing time at elevated temperatures and the R2 of the final deduced function will be used to help choosing the most similar release profile with the real time release. Four different types of progesterone PLGA microspheres were used to verify the method, and all the deduced function correlated well with the real time releases, for R2 = 0.9912, 0.9781, 0.9918 and 0.9972, respectively.

Development of composite PLGA microspheres containing exenatide-encapsulated lecithin nanoparticles for sustained drug release

This study aimed to prepare poly(D, L-lactic-co-glycolic acid) microspheres(PLGA-Ms)by a modified solid-in-oil-in-water(S/O/W) multi-emulsion technique in order to achieve sustained release with reduced initial burst and maintain efficient drug concentration for a prolonged period of time. Composite PLGA microspheres containing exenatideencapsulated lecithin nanoparticles(Ex-NPs-PLGA-Ms) were obtained by initial fabrication of exenatide-loaded lecithin nanoparticles(Ex-NPs) via the alcohol injection method,followed by encapsulation of Ex-NPs into PLGA microspheres. Compared to Ms prepared by the conventional water-in-oil-in-water(W/O/W) technique(Ex-PLGA-Ms), Ex-NPs-PLGAMs showed a more uniform particle size distribution, reduced initial burst release, and sustained release for over 60 d in vitro. Cytotoxicity studies showed that Ms prepared by both techniques had superior biocompatibility without causing any detectable cytotoxicity.In pharmacokinetic studies, the effective drug concentration was maintained for over 30 d following a single subcutaneous injection of two types of Ms formulation in rats, potentially prolonging the therapeutic action of Ex. In addition, administration of Ex-NPs-PLGA-Ms resulted in a more smooth plasma concentration-time profile with a higher area under the curve(AUC) compared to that of Ex-PLGA-Ms. Overall, Ex-NPs-PLGA-Ms prepared by the novel S/O/W method could be a promising sustained drug release system with reduced initial burst release and prolonged therapeutic efficacy.

PREPARATION AND ADSORBABILITY OF DEXTRAN MICROSPHERES WITH UNIFORM DIAMETER

The method of preparing uniform dextran microspheres with a narrow diameter distribution was introduced and the adsorbability of these microspheres was evaluated.The microspheres were prepared in W/O microemulsion using 0.5% dextran solution as the aqueous phase and n-hexane as the oil phase.Characteristics of the prepared dextran microspheres were examined with laser light blocking technique,optical microscope and ultraviolet spectrometer.The results show that the prepared dextran microspheres have uniform morphology and narrow diameter distribution,nearly 92% of them having a diameter of 56.6 μm.In vitro evaluation of adsorbability,wet dextran microspheres have good adsorption of 98.32 mg/g of model drug methylene blue in 20.86 mg/L methylene blue solution at 25℃.The adsorption of dried dextran microspheres under the same condition is 132.15 mg/g,which is even higher.And the adsorbability of dextran microspheres has significant relationship with the concentration of methylene blue and temperature.The adsorbability is better at lower temperature and higher concentration of methylene blue.

Sustained release donepezil loaded PLGA microspheres for injection:Preparation,in vitro and in vivo study

The purpose of this study was to develop a PLGA microspheres-based donepezil(DP)formulation which was expected to sustain release of DP for one week with high encapsulation efficiency(EE).DP derived from donepezil hydrochloride was encapsulated in PLGA microspheres by the O/W emulsion-solvent evaporation method.The optimized formulation which avoided the crushing of microspheres during the preparation process was characterized in terms of particle size,morphology,drug loading and EE,physical state of DP in the matrix and in vitro and in vivo release behavior.DP microspheres were prepared successfully with average diameter of 30m,drug loading of 15.92±0.31%and EE up to 78.79±2.56%.Scanning electron microscope image showed it has integrated spherical shape with no drug crystal and porous on its surface.Differential scanning calorimetry and X-ray diffraction results suggested DP was in amorphous state or molecularly dispersed in microspheres.The Tg of PLGA was increased with the addition of DP.The release profile in vitro was characterized with slow but continuous release that lasted for about one week and fitted well with first-order model,which suggested the diffusion governing release mechanism.After single-dose administration of DP microspheres via subcutaneous injection in rats,the plasma concentration of DP reached peak concentration at 0.50 d,and then declined gradually,but was still detectable at 15 d.A good correlation between in vitro and in vivo data was obtained.The results suggest the potential use of DP microspheres for treatment of Alzheimer’s disease over long periods.

Preparation of PLA or PLGA Microspheres with Estradiol the Effects of THF—adding on the Properties of MS

Aim Polylactic acid (PLA) or polylactide-co-glycolide (PLGA) was used asbiodegradable and biocom-patible carriers to achieve sustained release ofestradial-PLGA/PLA-Microspheres (E_2-PLGA/PLA-MS). THF was added in the organic phase to study itseffects on the properties of MS. Methods MS were formed by an emulsification-solvent extractionmethod with mixture of ethyl acetate (EtoAc) and tetrahydrofuran (THF) as the organic solvents, andthen the properties and in vitro drug release behavior were examined. Results The results indicatedthat the drug loading efficiency decreased when THF added, but when the ratio of EtoAc was more than50% , there was no obvious effect of THF ratio, but the particle size increased accordingly. Thecarriers' properties and the drug contents were the main factors influencing the in vitro drugrelease. Conclusions By controlling the technology and formulation, we can get sustained-release E_2biodegradable microsperes with proper particle size, drug content and low burst-release, althoughTHF with readily solubility in water was used in the organic phase.

外水相组成对醋酸戈舍瑞林PLGA微球理化性质的影响

目的 采用W/O/W和O/W乳化溶剂挥发法制备醋酸戈舍瑞林PLGA微球,考察在外部水相中加入不同浓度的氯化钠和甘露醇对所制备微球理化性质的影响。方法 醋酸戈舍瑞林PLGA微球采用W/O/W和O/W乳化溶剂挥发法制备,以微球的表面形态、内部形态、粒径、载药量、体外累计释放行为、结构和晶型来评价不同浓度的添加剂对两种制备方法所制得微球的影响。结果 采用W/O/W制备的微球增加外水相中氯化钠的浓度,微球载药量增加、粒径减小、突释量降低、微球表面及内部孔洞减少;增加外水相中甘露醇的浓度,微球载药量增加、粒径减小,突释量降低、微球表面孔洞减少,内部孔洞未减少;O/W法制备的微球增加水相中氯化钠和甘露醇的浓度,微球载药量增加、粒径减小、突释量降低、微球表面及内部孔洞减少。结论 通过增加外部水相中添加剂的浓度,有效改善了醋酸戈舍瑞林PLGA微球的结构和性质。

NMR relaxation and diffusion studies to probe the motional dynamics of risperidone within PLGA microsphere

The present study aims to investigate the motional dynamics of risperidone within polylactic co-glycolic acid(PLGA)microsphere by employing solution state'H and 19F nuclear magnetic resonance(NMR)measurements.Risperidone,a second-generation fluorinated antipsychotic drug used for the treatment of schizophrenia is commercially marketed as PLGA microsphere formulation resulting in prolonged release of the drug in solution.Although the current trend in the pharmaceutical market is to develop drug formulation with long-acting release(LAR)products,complete physicochemical characterization of such formulations are scarce.Especially the effects of microsphere encapsulation on the motional properties and diffusion behavior of the drugs are not discussed adequately in any of the earlier reports.We therefore,have employed NMR relaxation and diffusion measurements to decipher the interaction of PLGA cavity water with risperidone.A detailed analysis of NMR relaxation rates confirmed the event of encapsulation and the presence of local motion in the non-fluorinated end of risperidone.Further,the relaxation data indicated a significant alteration in 19F chemical shift anisotropy(CSA)and CSA/dipole-dipole(DD)cross-correlated relaxation mechanism and decreased effect of solvent relaxation pointing out reduced water concentration within the microsphere cavity.'H and 19F diffusion coefficients of risperidone led to the information about hydrodynamic radius of risperidone in free and encapsulated states.Measurement of hydrodynamic radius supported the presence of limited water in PLGA cavity allowing higher translational mobility of risperidone after the encapsulation.

BCNU/PLGA microspheres:a promising strategy for the treatment of gliomas in mice

Objective：To investigate the effects of BCNU/PLGA microspheres on tumor growth,apoptosis and chemotherapy resistance in a C57BL/6 mice orthotopic brain glioma model using GL261 cell line.Methods：BCNU/PLGA sustained-release microspheres were prepared by the water-in-oil-in-water emulsion technique.GL261 cells were intracranially injected into C57BL/6 mouse by using the stereotactic technology.A total of 60 tumor-bearing mice were randomly and equally divided into three groups：untreated control,PLGA treated,BCNU/PLGA treated.Magnetic resonance imaging （MRI） was taken to evaluate tumor volume.BCNU/PLGA sustained-release wafers were implanted in the treatment group two weeks after inoculation.Survival time and quality were observed.Specimens were harvested,and immunohistochemical staining was used to check the expression of Bax,Bcl-2,and O6-methylguanine-DNA methyltransferase （MGMT）.Statistical methods was used for analysis of relevant data.Results：BCNU/PLGA sustained-release wafers were fabricated and implanted successfully.There is statistical difference of survival time between the BCNU/PLGA treated group and control groups （P＜0.05）.MRIscan showed inhibitory effect of BCNU/PLGA on tumor growth.Compared to the group A and B,BCNU/PLGA decreased the expression of apoptosis related gene Bcl-2 （P＜0.05）,but did not elevate the expression level of Bax （P＞0.05）,with the ratio of Bax/Bcl-2 increased.For MGMT protein expression,no statistically significant change was found in treated group （P＞0.05）.Conclusions：Local implantation of BCNU/PLGA microspheres improved the survival quality and time of GL261 glioma-bearing mice significandy,inhibited the tumor proliferation,induced more cell apoptosis,and did not increase the chemotherapy resistance.

Effect of Excipients on Stability and Structure of rhCuZn-SOD Encapsulated in PLGA Microspheres

When a protein is encapsulated into poly( DL -lactide-co-glycolide)(PLGA) microspheres by means of the double-emulsion method,the harsh microspheres formation process including ultrasonification,exposure to an organic solvent and a polymer may cause the denaturation of the protein. In this study,we investigated the enzymatic activity change and the effect of the excipients on the stability of recombinant human Cu,Zn-superoxide dismutase(rhCu,Zn-SOD) during the emulsification. The specific activity recovery was found to be concentration dependent and the excipients involved such as PEG 600 and Tween 20,and trehalose were shown to increase the stability of rhCu,Zn-SOD. The protein structural integrity within the microspheres was analyzed by FTIR. The structure of rhCu,Zn-SOD within PLGA microspheres containing trehalose was found to be similar to that of the native solid state,whereas the protein encapsulated during the preparation in the absence of any excipient changed due to the possible hydrophobic interaction with the polymer. The results suggest that a rational stability strategy for protein to be encapsulated into microspheres should aim at different processes.

Preparation and Characterization of Lung-targeting Cefquinome-loaded PLGA Microspheres

We developed poly lactic-co-glycolic acid（PLGA） microspheres loaded with cefquinome and tested their effectiveness in a mouse model. The microspheres were prepared by optimizing several key parameters such as PLGA molecular weight, drug/polymer ratio, internal water volume and ethyl acetate. Drug loading efficiency, stability, in vitro release and tissue distribution in mouse were evaluated. The average particle size of the microspheres was 27.84 μm. The drug loading efficiency was 64.57%. The in vitro release of cefquinome from microspheres after 4 h was about 40% compared with over 90% for the drug alone. The concentration of cefquinome in lung reached 25 μg/g 0.25 h after injection, and kept at 10 μg/g 4 h after injection. However, the concentration of cefquinome was very low in other organs even 0.25 h after injection. In conclusion, Cefquinome-loaded PLGA microspheres are compatible as an effective lung-targeting drug delivery system and have a good sustained release efficacy.

Dexamethasone-Loaded PLGA Microspheres Incorporated PLLA/PLGA/PCL Composite Scaffold for Bone Tissue Engineering

The combination of micro-carriers and polymer scaffolds as promising bone grafts have attracted considerable interest in recent decades.The poly(L-lactic acid)/poly(lactic-co-glycolic acid)/polycaprolactone(PLLA/PLGA/PCL)composite scaffold with porous structure was fabricated by thermally induced phase separation(TIPS).Dexamethasone(DEX)was incorporated into PLGA microspheres and then loaded on the PLLA/PLGA/PCL scaffoldtopreparethedesiredcompositescaffold.The physicochemical properties of the prepared composite scaffold were characterized.The morphology of rat bone marrow mesenchymal stem cells(BMSCs)grown on scaffolds was observed using scanning electron microscope(SEM)and fluorescence microscope.The resultsshowedthatthePLLA/PLGA/PCLscaffoldhad interconnected macropores and biomimetic nanofibrous structure.In addition,DEX can be released from scaffold in a sustained manner.More importantly,DEX loaded composite scaffold can effectively support the proliferation of BMSCs as indicated by fluorescence observation and cell proliferation assay.The results suggested that the prepared PLLA/PLGA/PCL composite scaffold incorporating drug-loaded PLGA microspheres could hold great potential for bone tissue engineering applications.

An accelerated method to evaluate thymopentin release from microspheres in vitro

To design an accelerated method to evaluate thymopentin release from PLGA microspheres in vitro. Microspheres were prepared by double emulsion technique, using poly（lactide-co-glycolide） （PLGA） as carrier. At higher medium temperature （45℃, 50℃ and 55℃）, an accelerated release testing in short time was studied and correlated with the conventional release （37℃） in vitro. The release in vitro of thymopentin from PLGA microspheres at 45 ℃, 50℃ and 55℃ was significantly accelerated （P 〈 0.05）. In particular, at 50℃, an accelerated release （30 h） of the hydrophilic peptide from the PLGA matrix was achieved and correlated well with the conventional release （30 d）. An accelerated release testing in vitro at higher temperature could be used to monitor thymopentin release from PLGA microspheres.

Intra-articular delivery of tetramethylpyrazine microspheres with enhanced articular cavity retention for treating osteoarthritis

Tetramethylpyrazine(TMP) is a traditional Chinese herbal medicine with strong antiinflammatory and cartilage protection activities, and thus a promising candidate for treating osteoarthritis. However, TMP is rapidly cleared from the joint cavity after intra-articular injection and requires multiple injections to maintain efficacy. The aim of this study was to encapsulate TMP into poly(lactic-co-glycolic acid)(PLGA) microspheres to enhance the TMP retention in the joint, reducing injection frequencies and decreasing dosage. TMP microspheres were prepared by emulsion/solvent evaporation method. The intra-articular retention of the drug was assessed by detecting the drug concentration distributed in the joint tissue at different time points. The therapeutic effect of TMP microspheres was evaluated by the swelling of knee joints and histologic analysis in papain-induced OA rat model. The prepared freezedried microspheres with a particle size of about 10 μm can effectively prolong the retention time of the drug in the articular cavity to 30 d, which is 4.7 times that of the TMP solution.Intra-articular injection of TMP microspheres efficiently relieved inflammatory symptoms,improved joint lesions and decreased the depletion of proteoglycan. In conclusion, intraarticular injection of TMP loaded microspheres was a promising therapeutic method in the treatment of OA.

Preparation of PLGA Ceftiofur Hydrochlorate Lung- targeted Microsphere with Spray Drying Process

To explore the preparation of PLGA ceftiofur hydrochlorate lung-targeted microsphere with spray drying process, the preparation technics was optimized by orthogonal experiments. Appearance, particle size, drug-loaded properties and medicine dissolution rate of the microsphere were evaluated. The experimental results show that the prepared PLGA microspheres loaded with ceftiofur hydrochlorate have good appearance, good encapsulate rate and dissolution. The drug loading capacity of ceftiofur-hydrochlorate-loaded PLGA microsphere prepared with spray drying process is 23.06%, i e, when the dosing ratio is 1：3, the encapsulate rate is 92.23% at maximum, and the release percentage of medicine is at 0.5 h. The medicine is released almost completely at 20 h and the accumulated medicine release is 98.12%.

Development and Validation of a Reverse-phase High Performance Liquid Chromatography Method for Determination of Exenatide in Poly(lactic-co-glycolic acid) Microspheres

Exenatide（synthetic exendin-4）, which has been approved by the Food and Drug Administration（FDA） for the adjunctive treatment of patients with type 2 diabetes, is an incretin mimetic agent. The development and validation of a RP-HPLC method for the quantification of the exenatide in poly（lactic-co-glycolic acid）（PLGA） microspheres is described. Separation was performed on a C4 column via a mobile phase consisting of ACN：KH2PO4（0.02 tool/L, pH=2.5） gradient elution from 30：70 to 45：55（volume ratio） in 30 min. Multi-diode array detection（DAD） appears to be most appropriate to evaluate the spectral purity of exenatide. The limits of detection and quantification of exenatide were 0.4 and 1.2 μg/mL, respectively. The calibration curve of exenatide was linear in a range of 0.025--0.2 mg/mL with a correlation coefficient of 0.9995. The results of validation study show that this method is specific, accurate（recovery〉95%）, precise（RSD〈2.0%） and robust.

姜黄素肺靶向PLGA微球的制备及工艺优化

以乳化-溶剂挥发法制备姜黄素PLGA微球,以载药量为响应指标,以乳化时间、姜黄素浓度、PLGA质量分数为变量,通过星点设计-响应面法优化微球制备工艺。微球最优处方为:乳化时间64 s,姜黄素浓度为0.52%,PLGA质量分数为1.91%,该工艺条件下制得的微球平均载药量为7.85%,与预测值相比,偏差为1.5%;微球平均粒径为10.25μm,具有被动肺靶向性。

体内外环境对PLGA微球形态的影响

为了解聚乳酸-羟基乙酸共聚物(PLGA)微球在体内外环境中形态的差异,进一步解析PLGA微球体内外环境对药物释放的影响,本试验采用乳化法制备PLGA微球,荧光标记后,采用光学显微镜、荧光分光光度计、激光共聚焦显微镜和苏木精-伊红染色法分别观察PLGA微球在不同介质、体外细胞环境和小鼠体内环境中形态的变化。结果显示,制备的PLGA微球为透明且表面光滑的球形,在水、PBS和血清中保持球形,膨胀率分别为23.7%、13.1%和0.5%;在0、24、48和72 h时,PLGA微球在血清中泄露分别是PBS中的6.54倍、8.66倍、4.67倍和3.61倍;PLGA微球在体外细胞环境中为半透明球形;PLGA微球在小鼠体内环境条件下前2天保持球形,第3天PLGA微球的形态发生变化。PLGA微球表面和内部结构在体外和体内环境中的差异表明PLGA微球中的药物在体外和体内环境中释放也存在差异。本试验发现体外和体内环境条件下PLGA微球形态会发生变化,可作为合理设计静脉注射用PLGA微球的参考,为进一步改善PLGA微球中药物释放提供数据支持。

Dextran Microsphere Hepatic Artery Embolization for Hepatoma: Pathological Assessment of Its Efficacy in Resected Cases

Objective To evaluate the therapeutic effect and the mechanism of dextran microsphere hepatic artery embolization for hepatoma. Methods Partial hepatectomy was performed in 11 patients with hepatoma pretreated with dextran microsphere hepatic artery embolization. All specimens were for histopathologic studies in order to observe the destiny of dextran microspheres and necrotic degree of the tumor. Results complete necrosis of the tumor was found in seven cases and incomplete necrosis of the tumor in the rest 4. Tumors in the later were near to areas rich in arterial collateral anastomoses. The extent of tumor necrosis was unrelated to the presence and thickness of tumor capsule and capsular invasions. Dextran microspheres could cause permanent embolization of distal arterioles. The microspheres were very biocompatible and cause little foreign body reaction. No inflammatory changes were seen both inside and outside of the embolized artery 191 days after embolization. Dextran microspheres were not absorbed and the vessel recanalization was also not seen. Dextran microsphere was not found in portal veins. Conclusion Some hepatomas distant from the collateral circulation of arteries could be cured with dextran microsphere hepatic artery embolization alone.