Influence of Some Formulation Variables on the Optimization of pH-dependent,Colon-targeted,Sustained-release Mesalamine Microspheres

The aim of this work was to understand the influence of different formulation variables on the optimization of pH-dependent, colon-targeted, sustained-release mesalamine microspheres prepared by O/O emulsion solvent evaporation method, employing pH-dependent Eudragit S and hydrophobic pH-independent ethylcellulose polymers. Formulation variables studied included concentration of Eudragit S in the internal phase and the ratios between; internal to external phase, drug to Eudragit S and Eudragit S to ethylcellulose to mesalamine. Prepared microspheres were evaluated by carrying out in vitro release studies and determination of particle size, production yield, and encapsulation efficiency. In addition, morphology of microspheres was examined using optical and scanning electron microscopy. Emulsion solvent evaporation method was found to be sensitive to the studied formulation variables. Particle size and encapsulation efficiency increased by increasing Eudragit S concentration in the internal phase, ratio of internal to external phase, and ratio of Eudragit S to the drug. Employing Eudragit S alone in preparation of the microspheres is only successful in forming acid-resistant microspheres with pulsatile release pattern at high pH. Eudragit S and ethylcellulose blend microspheres were able to control release under acidic condition and to extend drug release at high pH. The stability studies carried out at 40°C/75% RH for 6 months proved the stability of the optimized formulation. From the results of this investigation, microencapsulation of mesalamine in microspheres using blend of Eudragit S and ethylcellulose could constitute a promising approach for site-specific and controlled delivery of drug in colon.     

Design of Methylprednisolone Biodegradable Microspheres Intended for Intra-articular Administration

This study aimed to design methyprednisolone (MP)-loaded poly(d,l lactide-co-glycolide) (PLGA) microspheres (MS) intended for intra-articular administration. MP was encapsulated in four different types of PLGA by using an S/O/W technique. The effects of β-irradiation at the dose of 25 kGy were evaluated on the chemical and physicochemical properties of MS and the drug release profiles. The S/O/W technique with hydroxypropylmethylcellulose (HPMC) as surfactant allowed obtaining MS in the tolerability size (7–50 μm) for intra-articular administration. The MP encapsulation efficiency ranged 56–60%. HPMC traces were evidenced in the loaded and placebo MS by attenuated total reflectance Fourier transform infrared spectroscopy. MS made of the capped PLGA DL5050 2M (MS 2M) and uncapped PLGA DL5050 3A (MS 3A) prolonged the release of MP over a 2- to 3-month period with a triphasic (burst release–dormant period–second release pulse) and biphasic release pattern, respectively. The β-irradiation did not significantly alter the morphology, chemical, and physicochemical properties of MS. The only variation was evidenced in the drug release for MS 2M in term of shorting of the dormant period. The minimal variations in the properties of irradiated PLGA MS, which are in disagreement with literature data, may be attributed to a radioprotecting effect exerted by HPMC.     

苄丝肼微球的体外释放行为

采用S/O/W和W/O/W法,和不同的苄丝肼载药量制作缓释微球,用HPLC考察其释放曲线、突释情况和包封率,实验表明S/O/W法制作的苄丝肼微球缓释效果更好,达到了6d,包封率能达到70%以上,突释情况可以接受,苄丝肼载药量低的微球能达到更高的包封率。     

装载于PLGA中的5-氟尿嘧啶缓释微球的制备及其体外释放的研究

目的：研究装载于不同分子量的PLGA中的5-氟尿嘧啶微球的制备方法及其在体外条件下的缓释行为。方法：以水包油包固复乳法将5-氟尿嘧啶包裹在高分子聚乳酸-聚羟基乙酸共聚物（PLGA）中,形成缓释微球,考察其大小,外观,包封率等理化性质,以紫外分光光度法为检测方法研究其体外释放行为。结果：经扫描电子显微镜观察,所制备的微球形态完整,大小较均匀。具有一定得包封率和载药量,体外释放研究表明其处方1和处方2的缓释时间为8天和23天。结论：以水包油包固复乳法制备的PLGA 5-氟尿嘧啶微球能够达到缓释的目的。     

重组人粒细胞集落刺激因子缓释微球的研究

目的：研究固体／油／水法制备重组人粒细胞集落刺激因子缓释微球,为开发其缓释剂型进行初步研究。方法：以聚乳酸．聚羟乙酸共聚物（PLGA）为载体材料：用固体／油／水法和水／油／水法制备载rhG-CSF缓释微球;考察粒径大小、外观、包封率等理化性质;用MieroBCA法考察微球的体外释药特性及影响因素;用SEC-HPLC和MTT比色法初步评价了微球制备工艺过程对rhG-CSF稳定性的影响。结果：两种方法制得的微球形态圆整、分散性良好,包封率均超过80％。固／油／水法制得的微球体外释放在2周内可超过90％,而水／油／水法制得的微球在相同的时间内仅释放30％。对于固／油／水法制备过程,SEC-HPLC法测定蛋白无明显聚集体出现,MTT法测定蛋白活性无明显损失。结论：实验证明了固／油／水法制备的PLGA微球可以实现2周以上的体外缓释。     

Investigation on Processing Variables for the Preparation of Fluconazole-Loaded Ethyl Cellulose Microspheres by Modified Multiple Emulsion Technique

Fluconazole-loaded ethyl cellulose microspheres were prepared by alginate facilitated (water-in-oil)-in-water emulsion technology and the effects of various processing variables on the properties of microspheres were investigated. Scanning electron microscopy revealed spherical nature and smooth surface morphology of the microspheres except those prepared at higher concentration of emulsifiers and higher stirring speeds. The size of microspheres varied between 228 and 592 μm, and as high as 80% drug entrapment efficiency was obtained depending upon the processing variables. When compared up to 2 h, the drug release in pH 1.2 HCl solution was slower than in pH 7.4 phosphate buffer saline solution. However, this trend was reversed at high shear conditions. The microspheres provided extended drug release in alkaline dissolution medium and the drug release was found to be controlled by Fickian-diffusion mechanism. However, the mechanism shifted to anomalous diffusion at high shear rates and emulsifier concentrations. The aging of microspheres did not influence the drug release kinetics. However, the physical interaction between drug and excipients affected the drug dissolution behaviors. X-ray diffractometry (X-RD) and differential scanning calorimetry (DSC) analysis revealed amorphous nature of drug in the microspheres. Fourier transform infrared (FTIR) spectroscopy indicated stable character of fluconazole in the microspheres. The stability testing data also supported the stable nature of fluconazole in the microspheres. The fluconazole extracted from 80% drug-loaded formulation showed good in vitro antifungal activity against Candida albicans. Thus, proper control of the processing variables involved in this modified multiple emulsion technology could allow effective incorporation of slightly water soluble drugs into ethyl cellulose microspheres without affecting drug stability.     

Effects of Piper cubeba L. essential oil on methicillin‐resistant Staphylococcus aureus: an AFM and TEM study

The increasing prevalence of antibiotic‐resistant bacteria is creating a real challenge for health care systems worldwide, making the development of novel antibiotics a necessity. In addition to the development of new antibiotics, there is an urgent need for in‐depth characterization of the mechanisms of bacterial resistance toward new drugs. Here, we used essential oils extracted in our laboratory from Piper cubeba against methicillin‐resistant Staphylococcus aureus ATCC 43300, one of the most prominent antibiotic‐resistant bacteria. Effects of the essential oils extracted from P cubeba on bacteria were mainly evaluated using 2 powerful microscopy techniques: atomic force microscopy and transmission electron microscopy. High‐resolution atomic force microscopy images of the cells were obtained close to their native environment by immobilizing the cells on porous Polyether sulfone membranes, which were prepared in our laboratory with a wide range and distribution of pore sizes and depth. Inhibition zones (mm) and minimum inhibitory concentrations were determined. Two different concentrations of the oil were used to treat the cells: 50 μg/mL minimum inhibitory concentration and 25 μg/mL. The 50 μg/mL oil solution caused severe damage to the bacterial cells at microscopic levels while the 25 μg/mL solution showed no effects compared to the control. However, at nanoscopic levels, the 25 μg/mL oil solution caused significant changes in the cell wall, which could potentially impair bacterial activities. These results were also confirmed by transmission electron microscopy micrographs. Our results indicate that the extract has a good biological activity against methicillin‐ and oxacillin‐resistant S aureus and that it acts on the cell wall and plasma (cytoplasmic) membrane.     

壳聚糖/有机累托石微球的合成及表征

目的:以牛血清白蛋白(BSA)作为模型药物,制备壳聚糖/有机累托石复合物微球,建立一种安全有效的药物控释传递系统。方法:壳聚糖(CS)/有机累托石(OREC)和海藻酸钠,按照不同的混合比例交联,在Ca2+水溶液中包裹BSA而形成壳核结构的微球。采用傅立叶红外光谱(FTIR)、动态光散射(DLS)、原子力显微镜(AFM)、X-衍射(XRD)、扫描电镜(SEM)和透射电镜(TEM)观察研究微球的形态、CS和OREC的插层结构、BSA的包封率和控释效果。结果:口光学显微镜和扫描电镜观察显示,形成了壳核结构的微球。傅里叶变换光谱和X-射线能量分散显示,OREC存在于微球中。小角X-射线衍射证实,CS链成功的插入OREC插层中。BSA的包封率和控释检测结果显示,与纯的CS/ALG形成的微球相比较,CO复合物所形成的微球药物释放率明显提高。结论:OREC-HTCC纳米粒子是良好的蛋白药物载体,具有包封率高、缓释效果好等优点,为CS-OREC作为潜在的药物给药系统的进一步应用提供科学依据。     

Cellulose-Based Matrix Microspheres of Prednisolone Inclusion Complex: Preparation and Characterization

The purpose of the present investigation was to encapsulate pure prednisolone (PRD) and PRD–hydroxypropyl-β-cyclodextrin (HPβCD) complex in cellulose-based matrix microspheres. The system simultaneously exploits complexation technique to enhance the solubility of low-solubility drug (pure PRD) and subsequent modulation of drug release from microspheres (MIC) at a predetermined time. The microspheres of various compositions were prepared by an oil-in-oil emulsion–solvent evaporation method. The effect of complexation and presence of cellulose polymers on entrapment efficiency, particle size, and drug release had been investigated. The solid-state characterization was performed by Fourier transform infrared spectroscopy, thermogravimetry, differential scanning calorimetry, and powder X-ray diffractometry. The morphology of MIC was examined by scanning electron microscopy. The in vitro drug release profiles from these microspheres showed the desired biphasic release behavior. After enhancing the solubility of prednisolone by inclusion into HPβCD, the drug release was easily modified in the microsphere formulation. It was also demonstrated that the CDs in these microspheres were able to modulate several properties such as morphology, drug loading, and release properties. The release kinetics of prednisolone from microspheres followed quasi-Fickian and first-order release mechanisms. In addition to this, the f ₂-metric technique was used to check the equivalency of dissolution profiles of the optimized formulation before and after stability studies, and it was found to be similar. A good outcome, matrix microspheres (coded as MIC5) containing PRD–HPβCD complex, showed sustained release of drug (95.81%) over a period of 24 h.     

Ethylcellulose-Based Matrix-Type Microspheres: Influence of Plasticizer RATIO as Pore-Forming Agent

In this study, ethylcellulose (EC)-based microsphere formulations were prepared without and with triethyl citrate (TEC) content of 10% and 30% by water-in-oil emulsion-solvent evaporation technique. Diltiazem hydrochloride (DH) was chosen as a hydrophilic model drug and used at different drug/polymer ratios in the microspheres. The aim of the work was to evaluate the influence of plasticizer ratio on the drug release rate and physicochemical characteristics of EC-based matrix-type microspheres. The resulting microspheres were evaluated for encapsulation efficiency, particle size and size distribution, surface morphology, total pore volume, thermal characteristics, drug release rates, and release mechanism. Results indicated that the physicochemical properties of microspheres were strongly affected by the drug/polymer ratio investigated and the concentration of TEC used in the production technique. The surface morphology and pore volume of microspheres significantly varied based on the plasticizer content in the formulation. DH release rate from EC-based matrix-type microspheres can be controlled by varying the DH to polymer and plasticizer ratios. Glass transition temperature values tended to decrease in conjunction with increasing amounts of TEC. Consequently, the various characteristics of the EC microspheres could be modified based on the plasticized ratio of TEC.     

Formulation optimization of chelerythrine loaded O-carboxymethylchitosan microspheres using response surface methodology

The aims of this investigation were to develop a procedure to prepare chelerythrine (CHE) loaded O-carboxymethylchitosan (O-CMCS) microspheres by emulsion cross-linking method and optimize the process and formulation variables using response surface methodology (RSM) with a three-level, three-factor Box-Behnken design (BBD). The independent variables studied were O-CMCS/CHE ratio, O/W phase ratio, and O-CMCS concentration, dependent variables (responses) were drug loading content and encapsulation efficiency. Mathematical equations and response surface plots were used to relate the dependent and independent variables. The process and formulation variables were optimized to achieve maximum drug loading content and entrapment efficiency by the desirability function. The optimized microsphere formulation was characterized for particle size, shape, morphology and in vitro drug release. Results for mean particle size, drug loading content, entrapment efficiency, and in vitro drug release of CHE-loaded O-CMCS microspheres were found to be of 12.18 μm, 4.16 ± 3.36%, 57.40 ± 2.30%, and 54.5% at pH 7.4 after 70 h, respectively. The combination use of RSM, BBD and desirability function could provide a promising application for O-CMCS as controlled drug delivery carrier and help to develop procedures for a lab-scale microemulsion process.     

Macrophage-Specific Targeting of Isoniazid Through Mannosylated Gelatin Microspheres

Active targeting of drug molecules can be achieved by effective attachment of suitable ligands to the surface of carriers. The present work was attempted to prepare mannosylated gelatin microspheres (m-GMs) so as to achieve targeted delivery of isoniazid (INH) to alveolar macrophages (AMs) and maintain its therapeutic concentration for prolonged period of time. Microspheres were prepared by emulsification solvent extraction method and evaluated for physicochemical characteristics, drug release, ex vivo drug uptake by AMs and pharmacokinetic characteristics. Fourier transform infrared spectroscopy and nuclear magnetic resonance spectral analysis confirmed that mannosylation took place through Schiff base formation between aldehyde and amino groups of mannose and gelatin, respectively. Prepared microspheres offered suitable physicochemical characteristics for their delivery to AMs. Their average size was about 4 μm and drug entrapment efficiency of 56% was achieved with them. Ex vivo uptake results indicated that in comparison to plain microspheres, m-GMs were selectively uptaken and were found to be associated with phago-lysosomal vesicles of AMs. Pharmacokinetic studies showed the formulation could maintain the therapeutic concentration of INH for prolonged period of time even with a reduced clinical dose. m-GMs were found to be stable in broncheo-alveolar lavage fluid. The study concluded that ligand decorated carriers could be a potential strategy to improve the therapeutic properties of INH.     

Prednisolone-Loaded PLGA Microspheres. <Emphasis Type="BoldItalic">In Vitro</Emphasis> Characterization and <Emphasis Type="BoldItalic">In Vivo</Emphasis> Application in Adjuvant-Induced Arthritis in Mice

This study aimed at preparation of a sustained-release steroidal treatment for chronic inflammatory conditions, such as rheumatoid arthritis. To achieve such a goal, biodegradable poly-lactide-co-glycolide prednisolone-loaded microspheres were prepared using o/w emulsion solvent evaporation method. Formulation parameters were adjusted so as to optimize the microsphere characteristics. The prepared microspheres exhibited smooth and intact surfaces, with average size range not exceeding 65 μm. The encapsulation efficiency percent of most microsphere formulations fell within the range of 25–68%. Drug release from these microspheres took place over 4 weeks, with near-to-zero-order patterns. Two successful formulations were chosen for the treatment of unilateral arthritis, induced in mice using Freund's complete adjuvant (FCA). Inflammatory signs of adjuvant arthritis included severe swelling of the FCA-injected limbs, in addition to many histopathological lesions. These included inflammatory cell infiltration, synovial hyperplasia, cartilage, and bone erosion. Parenteral administration of the selected formulae dramatically reduced the swelling of the FCA-injected limbs. In addition, histological examination revealed that the microsphere treatment protocol efficiently protected cartilages and bones of mice, injected with FCA initial and booster doses, from erosion. These results could not be achieved by a single prednisolone dose of 5 mg/kg.     

Preparation and optimization of rivastigmine-loaded tocopherol succinate-based solid lipid nanoparticles

Rivastigmine hydrogen tartrate (RHT) is a pseudo-irreversible inhibitor of cholinesterase and is used for the treatment of Alzheimer's. However, RHT delivery to the brain is limited by the blood–brain barrier (BBB). The purpose of this study was to improve the brain-targeting delivery of RHT by producing and optimizing rivastigmine hydrogen tartrate-loaded tocopherol succinate-based solid lipid nanoparticles (RHT-SLNs). RHT-SLNs were prepared using the microemulsion technique. The impact of significant variables, such as surfactant concentration and drug/lipid ratio, on the size of RHT-SLNs and their drug loading and encapsulation efficiency was analysed using a five-level central composite design (CCD). The minimum size of particles and the maximum efficiency of loading and encapsulation were defined according to models derived from a statistical analysis performed under optimal predicted conditions. The experimental results of optimized RHT-SLNs showed an appropriate particle size of 15.6?nm, 72.4% drug encapsulation efficiency and 6.8% loading efficiency, which revealed a good correlation between the experimental and predicted values. Furthermore, in vitro release studies showed a sustained release of RHT from RHT-SLNs.     

Influence of Rheology of Dispersion Media in the Preparation of Polymeric Microspheres through Emulsification Method

Chitosan microspheres as drug delivery system have attained importance and attracted the attention of researchers in last few years. This study was aimed toward the elucidation of the effect of viscosity of external oil phase on the properties of microspheres prepared by emulsification method. Chitosan microspheres were prepared utilizing oil phase of different viscosity viz. castor oil, heavy liquid paraffin, light liquid paraffin and mixture of light paraffin, and petroleum ether (1:1 v/v ratio). Microspheres prepared in highly viscous castor oil exhibited an average size of 11.52 ± 0.57 μm with a percentage drug entrapment of 43.12 ± 2.14. On the other hand, very small microspheres of 3.15 ± 0.04 μm and 68.87 ± 1.03% drug entrapment were obtained when mixture of liquid paraffin and petroleum ether was utilized as oil phase. Effect of viscosity on percent mucoadhesion, percent drug entrapment, zeta potential, percent process yield, etc. of microspheres has been observed. In vitro drug release in phosphate buffer pH 7.4 was determined for different batch of microspheres. The results revealed a difference in the drug release pattern of the different microspheres prepared as a function of viscosity of different oil phase. Use of low viscose oil resulted in the formulation of spherical and small size microspheres. This work was a part of our ongoing thrust and project to develop microparticulate drug delivery system.     

Preparation of 8-hydroxyquinoline derivatives as potential antibiotics against Staphylococcus aureus

This work describes the preparation of quinoline compounds as possible anti-bacterial agents. The synthesized quinoline derivatives show anti-bacterial activity towards Staphylococcus aureus. It is interesting to observe that the synthetic 5,7-dibromo-2-methylquinolin-8-ol (4) shows a similar minimum inhibitory concentration of 6.25 μg/mL as compared to that of methicillin (3.125 μg/mL) against Staphylococcus aureus.     

干扰素α缓释微球的制备及体外释放研究

目的:开发一种有效地长效缓释干扰素α微球制剂。方法:利用S/O/W乳剂-挥发法制备了包裹干扰素α多糖颗粒的PLAG微球,对其外观形态进行了考察,并用ELISA方法考察了微球体外释放效果。结果:制备的干扰素α微球圆整光滑,粒径均匀;经24天体外释放,累计释放率达到80%以上。结论:通过包封包裹干扰素α的多糖颗粒进PLGA微球,有效地保护了干扰素α在微球中的活性,实现了长效缓释,是一种可行的缓释方案。     

壳聚糖装载猪胸腺肽微球给药

目的：以猪胸腺肽为芯材、壳聚糖为壁材,采用乳化交联结合单凝聚法制备猪胸腺肽壳聚糖口服微球。方法：以壁材浓度、交联剂含量、油水比值、芯材壁材比值为四因素设计正交实验,确定微球最佳制备条件,并对其体外释放及稳定性进行研究。结果：制备微球最优化条件为壳聚糖浓度1％、25％戊二醛含量7％、油水比值2：1、壳聚糖与胸腺肽比值1：1;微球在pH1．5的HC1溶液中2h释放30％,在pH6．8及7．4的PBS缓冲液中最终释放度约80％,并在24h达到释放终点;微球30rain突释率约为10％,1h释放率约为20％,其后缓慢而持续地释放;猪胸腺肽壳聚糖微球在0℃保存8个月时微球外观及形态没有差异,药物剩余率约为91．8％。结论：采用乳化交联结合单凝聚法制备的猪胸腺肽壳聚糖口服微球为缓释给药系统的临床应用奠定了理论基础,具有重要的实际应用价值和社会意义。     

左旋多巴甲酯缓释微球的研究

目的：由于长期服用左旋多巴治疗帕金森病,其药物浓度波动刺激易引起异动症,本实验旨在制备突释小,药物释放浓度稳定的左旋多巴甲酯微球制剂。方法：将左旋多巴甲酯用复乳法包裹于PLGA微球内,采用C18反相色谱研究药物包封率和体外释放行为。结果：通过调节药物浓度和不同高分子组合筛选出突释小,包封率高且缓慢释放的处方。结论：左旋多巴甲酯包裹于PLGA能实现理想的缓释效果,降低药物浓度波动,为后期药效学实验提供基础。     

Repair effect of diabetic ulcers with recombinant human epidermal growth factor loaded by sustained-release microspheres

In this study the w/o/w extraction-evaporation technique was adopted to prepare poly(lactic-co-glycolic acid) (PLGA) microspheres loading recombinant human epidermal growth factor (rhEGF). The microspheres were characterized for morphology by transmission electron microscopy (TEM) and particle size distribution. The release performances, the proliferation effects and therapeutic effects of rhEGF-loaded PLGA microspheres were all studied. The results showed that these spherical microspheres had a narrow size distribution and a high drug encapsulation efficiency (85.6%). RhEGF-loaded microspheres enhanced the growth rate of fibroblasts and wound healing more efficiently than pure rhEGF. The number of the proliferating cell nuclear antigen (PCNA) in the epidermis layer with the microsphere treatment was significantly larger than those of the control groups. Overall locally sustained delivery of rhEGF from biodegradable PLGA microspheres may serve as a novel therapeutic strategy for diabetic ulcer repair.