A novel approach to the pulmonary delivery of liposomes in dry powder form to eliminate the deleterious effects of milling

The effect of lyophilization and jet-milling on liposome integrity was investigated as a function of their ability to retain the encapsulated model drug on reconstitution of the dry products. The encapsulation efficiencies of the lyophilized and jet-milled formulations were determined at various concentrations of lactose. Lyophilization resulted in considerable leakage of the model drug at lower concentrations of lactose, and jet-milling further augmented the leakage for all the lyophilized formulations, with optimum retention obtained for formulations containing at least 10:1 molar ratio of lactose/lipid. In an attempt to overcome the deleterious effects of lyophilization and jet-milling, the feasibility of formulating phospholipid-based powders that result in spontaneous formation of liposomes in an aqueous environment has been investigated. Partitioning of three model drugs (viz., ciprofloxacin, CM3 peptide, and salbutamol sulfate) between the aqueous phase and spontaneously formed liposomes was determined in terms of encapsulation efficiency. The effects of several parameters, including lactose concentration, lipid composition, and lipid concentration on the encapsulation efficiency of these model drugs were investigated. The spontaneous formation of liposomes on dispersion of phospholipid-based powder formulations was further evidenced by freeze-fracture scanning electron microscopy. This novel approach for the delivery of liposomes in dry powder form appears promising because lyophilization is not involved and jet-milling of these powder formulations did not impact encapsulation efficiency. Jet-milled phospholipid-based powder formulations showed high encapsulation efficiencies of 96.2 +/- 1.4% for ciprofloxacin, 100% for CM3 peptide, and 45.3 +/- 3.1% for salbutamol sulfate compared with a high amount of leakage (> 50%) observed due to jet-milling of lyophilized liposome formulations encapsulating ciprofloxacin.     

Comparative study of liposomes,transfersomes and ethosomes as carriers for improving topical delivery of celecoxib

Topical administration of celecoxib proved to be an effective mean of preventing skin cancer development and improving anticancer drugs effectiveness in skin tumors treatment. The aim of this study was the development of an effective topical formulation of celecoxib, able to promote drug skin delivery, providing its in depth penetration through the skin layers. Three kinds of vesicular formulations have been investigated as drug carriers: liposomes containing a surfactant, or transfersomes and ethosomes, containing suitable edge activators. Firstly, the effect of membrane composition variations on the system performance has been evaluated for each vesicle type. Selected formulations were characterized for particle size, polydispersity index and encapsulation efficiency. The best formulations were subjected to ex vivo permeation studies through excised human skin. All vesicular formulations markedly (p < 0.001) improved the drug amount penetrated into the skin with respect to an aqueous suspension, from 2.0 to 6.5, up to 9.0 folds for liposomes, transfersomes and ethosomes, respectively. In particular, ethosomes containing Tween 20 as edge activator not only showed the best vesicle dimensions and homogeneity, and the highest encapsulation efficacy (54.4%), but also enabled the highest increase in drug penetration through the skin, probably due to the simultaneous presence in their composition of ethanol and Tween 20, both acting as permeation enhancers. Therefore, among the various vesicular formulations examined in the study, Tween 20-ethosomes can be considered the most promising one as carrier for topical celecoxib applications aimed to prevent skin cancer development and increase the anticancer drugs effectiveness against skin tumors.     

Relationship between surface concentration of l-leucine and bulk powder properties in spray dried formulations

The amino acid l-leucine has been demonstrated to act as a lubricant and improve the dispersibility of otherwise cohesive fine particles. It was hypothesized that optimum surface l-leucine concentration is necessary to achieve optimal surface and bulk powder properties. Polyvinylpyrrolidone was spray dried with different concentration of l-leucine and the change in surface composition of the formulations was determined using X-ray photoelectron spectroscopy (XPS) and time of flight-secondary ion mass spectrometry (ToF-SIMS). The formulations were also subjected to powder X-ray diffraction analysis in order to understand the relationship between surface concentration and solid-state properties of l-leucine. In addition, the morphology, surface energy and bulk cohesion of spray dried formulations were also assessed to understand the relation between surface l-leucine concentration and surface and bulk properties. The surface concentration of l-leucine increased with higher feed concentrations and plateaued at about 10% l-leucine. Higher surface l-leucine concentration also resulted in the formation of larger l-leucine crystals and not much change in crystal size was noted above 10% l-leucine. A change in surface morphology of particles from spherical to increasingly corrugated was also observed with increasing surface l-leucine concentration. Specific collapsed/folded over particles were only seen in formulations with 10% or higher l-leucine feed concentration suggesting a change in particle surface formation process. In addition, bulk cohesion also reduced and approached a minimum with 10% l-leucine concentration. Thus, the surface concentration of l-leucine governs particle formation and optimum surface l-leucine concentration results in optimum surface and bulk powder properties.     

Formulation optimization and characterization of spray dried microparticles for inhalation delivery of doxycycline hyclate

The local delivery of antibiotics in the treatment of infectious respiratory diseases is an attractive alternative to deliver high concentration of antimicrobials directly to the lungs and minimize systemic side effects. In this study, inhalable microparticles containing doxycycline hyclate, sodium carboxymethylcellulose, leucine and lactose were prepared by spray drying of aqueous ethanol formulations. Box-Behnken design was used to study the influence of various independent variables such as polymer concentration, leucine concentration, ethanol concentration and inlet temperature of the spray dryer on microparticle characteristics. The microparticles were characterized in terms of particle morphology, drug excipient interaction, yield, entrapment efficiency, Carr's index, moisture content, thermal properties, X-ray powder diffraction, aerosolization performance and in vitro drug release. The effect of independent variables on spray dryer outlet temperature was also studied. The overall shape of the particles was found to be spherical like doughnuts in the size range of 1.16-5.2 μm. The optimized formulation (sodium carboxymethylcellulose concentration 14% w/v, leucine concentration 33% w/v, ethanol concentration 36% v/v, inlet temperature of 140°C) exhibited the following properties: yield 56.69%, moisture content 3.86%, encapsulation efficiency 61.74%, theoretical aerodynamic diameter 3.11 μm and Carr's index 23.5% at an outlet temperature 77°C. The powders generated were of a suitable mass median aerodynamic diameter (4.89 μm) with 49.3% fine particle fraction and exhibited a sustained drug release profile in vitro.     

Nanocluster budesonide formulations enhance drug delivery through endotracheal tubes

The pulmonary system is an attractive route for drug delivery because the lungs have a large accessible surface area for treatment. For ventilated patients, an endotracheal tube is required for delivering drugs into the lungs. Such tubes are generally poor conduits for delivering traditional aerosol formulations. Both the formulation and the properties of the endotracheal tube are important effectors of delivery efficiency. In this study, agglomerates of budesonide nanoparticles (NanoClusters) were formulated with or without l-leucine or lactose. Teflon tubing was compared with commercial endotracheal tubes as a conduit for delivering budesonide powders into a cascade impactor. The effects of volumetric flow rate, tube size, and humidity were also investigated. NanoCluster budesonide (NC-Bud) formulations had a considerably higher emitted dose and fine particle fraction compared with stock budesonide and the commercial Flexhaler powder when applied through endotracheal tubes. Tubing material did not significantly affect powder performance, but decreasing tubing diameter or increasing volumetric flow rates yielded a smaller mass median aerodynamic diameter for NC-Bud. Engineered NC-Bud powders may dramatically improve drug delivery through endotracheal tubes when using proper ventilator settings.     

去氢骆驼蓬碱脂质体的制备和体外释放特性

目的：研究去氢骆驼蓬碱（harmine,HM）脂质体的制备工艺和体外释放特性。方法：运用薄膜分散-pH值梯度法制备HM．脂质体以及高速离心法分离脂质体与游离药物,并测定其包封率;借助综合评分法,评价其粒径、多分散系数、包封率、载药量指标;运用正交优化实验法考察磷脂-胆固醇与药-脂比、超声时间、外相pH值对脂质体的影响,述选最优工艺处方,评价脂质体与原料药的体外释放情况。结果：最优处方因素为磷脂-胆固醇比值为4：1,超声时间为300S,药-脂比值为1：5,外相pH值为6,8,即X13X23X32X43,经实验验证其粒径为（155.0±14．5）nm,多分散系数为（0．148±0．011）,包封率为（80．90±0．01）％,载药量为（11．16±0．01）％;其原料药0．5h累积释放百分比大于50％,不到2h已全部释放,而优化后的脂质体在1h内其累积释放百分比大于50％,4h后释放完成。结论：采用薄膜分散-pH值梯度法,以最优处方制得HM-脂质体,其粒径大小适中、形态均匀,包封率和载药量相对较高,体外释放显示具有较好的缓释特性。     

Development and Evaluation of Sustained-Release Ibuprofen–Wax Microspheres. II. In Vitro Dissolution Studies

A modified USP paddle method using minibaskets was used to study the effects of various formulations on in vitro dissolution of ibuprofen microspheres. Formulations containing waxes such as paraffin or ceresine wax without modifiers exhibited very slow dissolution profiles and incomplete release, which did not improve with increased drug loading or the preparation of smaller microspheres. The addition of modifiers such as stearyl alcohol and glyceryl mono-stearate greatly increased the dissolution rate, with 20% (w/w) near the optimum for predictable dissolution. Higher drug loading and decreased microsphere size increased the dissolution rate from microspheres containing modifier. Optimum formulations contained ceresine wax or microcrystalline wax and stearyl alcohol as a modifier, with a drug content of 17%. An increase in the encapsulation dispersant concentration had little effect on the dissolution profiles. The dissolution data from narrow size fractions of microspheres indicated spherical matrix drug release kinetics; the 50% dissolution time decreased with the square of the microsphere diameter. With appropriate modifiers, wax microsphere formulations of drugs with solubility characteristics similar to those of ibuprofen can offer a starting basis for predictable sustained release dosage forms.     

结肠癌细胞及线粒体双级靶向脂质体的处方工艺筛选研究

目的：研究结肠癌细胞及线粒体双级靶向脂质体（HA/TPP-TPGS LP/DOX）的最佳处方工艺。方法：用薄膜分散法结合微孔滤膜法制备;以细胞抑制率为指标,用MTT法筛选最佳聚脂比;以包封率为指标,用正交试验筛选最佳胆脂比、药脂比和超声时间;以粒径为指标,筛选最佳透聚比;以复溶后粒径和包封率为指标,筛选冻干保护剂的品种;用荧光显微镜和流式细胞术考察脂质体的靶向性;用透析法考察体外释药行为。结果：最佳处方是聚脂比1∶7、胆脂比1∶10、药脂比1∶15、超声时间15 min、透聚比2∶1,冻干保护剂为蔗糖。制备的脂质体呈类球形,粒径（142.20±0.54）nm,Zeta电位-（24.06±0.25）mV,包封率（98.20±0.18）%,稳定性高,有双级靶向性和体外药物缓释性。结论：本研究制备的脂质体有包封率高、粒径小、双级靶向性和缓释性等优点,为进一步研究奠定了基础。     

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.     

Sodium pantoprazole-loaded enteric microparticles prepared by spray drying: effect of the scale of production and process validation

Pantoprazole is a prodrug used in the treatment of acid related disorders and Helicobacter pylori infections. It is activated inside gastric parietal cells binding irreversibly to the H(+)/K(+)-ATPase. In this way, pantoprazole must be absorbed intact in the intestinal tract, which indicates that enteric drug delivery systems are required for its oral administration. The purpose of this study was to investigate the physical characteristics of enteric pantoprazole-loaded microparticles prepared by spray drying using a blend of Eudragit S100 and HPMC. The microparticles were produced in different spray dryers and operational conditions at laboratory and pilot scales. Microparticles produced with two fluid nozzle atomizer and air pressure of 196 kPa presented satisfactory encapsulation efficiency and gastro-resistance. Microparticles produced with the same atomizer but using 49 kPa of air pressure presented strings in the powder. The microparticles produced in mixed flow presented very high polydispersity and the ones produced with rotating disc atomizer presented drug crystals adsorbed on the particle surfaces. The microparticles produced with two fluid nozzle atomizer and 196 kPa were prepared in three consecutive days for the process validation. The powders showed reproducible diameter, polydispersity, densities, encapsulation efficiency and gastro-resistance profile.     

Proniosomal powder of captopril: formulation and evaluation

The aim of the present study was to design a proniosomal drug delivery system of captopril to overcome the limitations of conventional dosage form and to optimize encapsulation parameters to achieve a delivery system suitable for in vitro investigations. Proniosomes are dry powders, which makes richer processing and packing possible. A surfactant coated carrier method was utilized to formulate proniosomal powder containing captopril as a model drug. This system was evaluated in vitro for drug loading, vesicle size, angle of repose, encapsulation efficiency, and stability studies. This method of proniosome loading resulted in 54.16-70.10% of encapsulation. This study examined critical parameters such as type and composition of surfactant. Proniosomes were investigated by transmission electron microscopy for characterization. Four week stability data for proniosomal powder is reported, and at all sampling points significantly higher drug retention was observed. Thus, it can be concluded that the encapsulation of captopril in proniosomes facilitates the controlled release and constitutes a good choice.     

Formulation development of smart gel periodontal drug delivery system for local delivery of chemotherapeutic agents with application of experimental design

Smart gel periodontal drug delivery systems (SGPDDS) containing gellan gum (0.1–0.8% w/v), lutrol F127 (14, 16, and 18% w/v), and ornidazole (1% w/v) were designed for the treatment of periodontal diseases. Each formulation was characterized in terms of in vitro gelling capacity, viscosity, rheology, content uniformity, in vitro drug release, and syringeability. In vitro gelation time and the nature of the gel formed in simulated saliva for prepared formulations showed polymeric concentration dependency. Drug release data from all formulations was fitted to different kinetic models and the Korsemeyer-Peppas model was the best fit model. Drug release was significantly decreased as the concentration of each polymer component was increased. Increasing the concentration of each polymeric component significantly increased viscosity, syringeability, and time for 50%, 70%, and 90% drug release. In conclusion, the formulations described offer a wide range of physical and drug release characteristics. The formulation containing 0.8% w/v of gellan gum and 16% w/v of lutrol F127 exhibited superior physical characteristics.     

Development and Characterization of a Liposome Preparation by a pH-Gradient Method

Abstract— A pH gradient across liposome bilayers was established in order to load a model drug (orciprenaline sulphate) into liposome vesicles. This method of liposome loading resulted in yields as high as 80–85% encapsulation. An eight-step process was designed to scale-up the process and was evaluated. In this process a diafiltration technique was successfully used to remove the excess orciprenaline sulphate present in the external medium. Finally, drug-loaded liposomes were lyophilized using lactose as an internal and external liposomal cryoprotectant. Five-month stability data for the liposomes is reported. An HPLC technique was used to determine the drug concentration and a laser light-scattering technique was employed to determine the liposome vesicle size and polydispersity factor. Liposomes prepared by the pH-gradient method showed high encapsulation efficiency. Upon storage at 2–8°C the vesicle size increased and encapsulation efficiency decreased with time. These phenomena are attributed to gradual fusion of liposomes and loss of drug to the extra-liposomal media.     

替诺福韦阳离子脂质体的制备及其对人体肝细胞SMMC-7721摄取和细胞毒性研究

目的:研究替诺福韦阳离子脂质体的制备及其促进肝实质细胞摄取的情况和细胞毒性作用。方法:采用叔丁醇冻干法制备替诺福韦阳离子脂质体,测定其包封率及理化性质;以SMMC-7721细胞为模型,研究脂质体对肝实质细胞摄取替诺福韦的促进作用,MTT法检测不同条件下载药脂质体对细胞的毒性情况。结果:制备的脂质体包封率为(88.3±1.6)%,粒径为(278.4±67.6)nm,Zeta电势为(31±5)mV;经半乳糖基及PEG修饰的脂质体较游离药物进入肝实质细胞的浓度明显升高,且时间延长;当替诺福韦脂质体、脂质浓度分别为7.5、30μg·mL-1时,细胞存活率在80%以上,毒性较小。结论:所制备的阳离子脂质体具有显著增加细胞摄取替诺福韦和保护替诺福韦的作用,有望成为抗病毒药物如替诺福韦等的高效传递系统。     

冻干工艺及保护剂对羟基喜树碱脂质体质量的影响

用薄膜水化-高压均质法制备羟基喜树碱脂质体,以葡聚糖凝胶色谱法分离脂质体和游离药物,采用HPLC法测定包封率。通过差示扫描量热法测定含不同保护剂的脂质体的最低共熔点和玻璃化转变温度,并比较冻干品外观、冻干前后脂质体包封率和粒径的变化,优选出最佳的冻干工艺、冻干保护剂种类及比例。结果表明,以6%蔗糖为冻干保护剂,经4℃、1 h,-18℃、12 h和-35℃、5 h逐步预冻,然后于-54℃冷冻干燥24 h,制得的冻干品外观良好,脂质体复溶后粒径变化小,包封率达(87.0±2.7)%。     

Design and synthesis of novel galactosylated polymers for liposomes as gene drug carriers targeting the hepatic asialoglycoprotein receptor

The 18-mer oligodeoxynucleotides (ODNs) that can inhibit survivin gene expression were selected as a model gene drug to study hepatic-targeting drug delivery system. Novel galactosylated polymers (cholesteryloxycarbonylamino) ethylamine-alpha,beta-polyasparthydrazied (CHE-PAHy-Lacs), which target asialoglycoprotein receptor on hepatic parenchymal cells (PC), were designed and synthesized as non-toxic, non-antigenic and non-teratogenic ligands for liposomes. The liposomes incorporating different CHE-PAHy-Lacs were prepared and characterized by zeta potential and particle size analyzer. The drug encapsulation efficiency was measured by gel filtration method. 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate was used as a marker for all the liposome preparations in the in vivo experiments. The CHE-PAHy-Lac liposomes produced a significant improvement in the encapsulation efficiency of ODNs (28.73-51.37%) compared with conventional liposomes (9.88%). The in vivo results showed that the liposomes incorporating CHE-PAHy-Lac, which contained about 30% (w/w) galactosyl residues, exhibited marked accumulation in the liver and hepatic PC. These results suggest that the novel galactosylated polymers used for liposomes have a great potential as a gene delivery system for hepatic targeting.     

Development of liposome gel based formulations for intravaginal delivery of the recombinant HIV-1 envelope protein CN54gp140

Mucosally-administered vaccine strategies are widely investigated as a promising means of preventing HIV infection. This study describes the development of liposomal gel formulations, and novel lyophilised variants, comprising HIV-1 envelope glycoprotein, CN54gp140, encapsulated within neutral, positively charged or negatively charged liposomes. The CN54gp140 liposomes were evaluated for mean vesicle diameter, polydispersity, morphology, zeta potential and antigen encapsulation efficiency before being incorporated into hydroxyethyl cellulose (HEC) aqueous gel and subsequently lyophilised to produce a rod-shaped solid dosage form for practical vaginal application. The lyophilised liposome-HEC rods were evaluated for moisture content and redispersibility in simulated vaginal fluid. Since these rods are designed to revert to gel form following intravaginal application, mucoadhesive, mechanical (compressibility and hardness) and rheological properties of the reformed gels were evaluated. The liposomes exhibited good encapsulation efficiency and the gels demonstrated suitable mucoadhesive strength. The freeze-dried liposome-HEC formulations represent a novel formulation strategy that could offer potential as stable and practical dosage form.     

Encapsulation enhancement and stabilization of insulin in cationic liposomes

The purpose of this study was to enhance encapsulation efficiency and sustained-release delivery for parenteral administration of a protein drug. To reduce the administration frequency of protein drugs, it is necessary to develop sustained delivery systems. In this study, protein drug-loaded cationic liposomes were formulated with dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), dioleoyl-3-trimethylammonium-propane (DOTAP), and cholesterol (CH) at a molar ratio of DOPE/DOTAP/CH of 2/1.5/2. Five mol% of distearoylphosphatidyl ethanolamine polyethylene glycol (DSPE-PEG) was added prior to encapsulation of the drug into liposomes. Insulin was chosen as a model protein drug and encapsulation efficiency was evaluated in various liposomes with and without DSPE-PEG. Scanning electron microscopy was used to examine the insulin-loaded cationic liposomes. Structural analysis was performed using spectropolarimetry. Additionally, the stability and cytotoxicity of insulin-loaded cationic liposomes were evaluated. Liposomes coated with DSPE-PEG showed higher insulin encapsulation efficiency than did those without DSPE-PEG, but not significantly. Moreover, among the liposomes coated with DSPE-PEG, those hydrated with 10% sucrose showed higher encapsulation efficiency than did liposomes hydrated in either phosphate-buffered saline or 5% dextrose. In vitro release of insulin was prolonged by cationic liposomes. Our findings suggest that cationic liposomes may be a potential sustained-release delivery system for parenteral administration of protein and peptide drugs to prolong efficacy and improve bioavailability.