Mannosylated liposomes bearing Amphotericin B for effective management of visceral Leishmaniasis

The cationic and mannosylated liposomes were prepared using the cast film method and compared for their antileishmaniasis activity. The surface of the Amphotericin B (Amp B)-bearing cationic multilamellar liposomes was covalently coupled with p-aminophenyl-α-D-mannoside using glutaraldehyde as a coupling agent, which was confirmed by agglutination of the vesicles with concanavalin A. The prepared liposomes were characterized for shape, size, percent drug entrapment, vesicle count, zeta potential, and in vitro drug release. Vesicle sizes of cationic and mannosylated liposomes were found to be 2.32?±?0.23 and 2.69?±?0.13?µm, respectively. Zeta potential of cationic liposomes was higher (30.38?±?0.3 mV), as compared to mannosylated liposomes (17.7?±?0.8 mV). Percentage drug release from cationic and mannose-coupled liposomes was found to be 45.7%?±?3.1 and 41.9%?±?2.8, respectively, after 24 hours. The in vivo antileishmanial activity was performed on Leishmania donovani–infected golden hamster, and results revealed that Amp B solution was reduced by 42.5?±?1.8% in the parasite load, whereas the placebo cationic liposomes and drug-containing cationic liposomes showed a reduced parasite load (i.e., 28.1?±?1.5 and 61.2?±?3.2%, respectively). The mannose-coupled liposomes showed a maximum reduction in parasite load (i.e., 78.8?±?3.9%). The biodistribution study clearly showed the higher uptake of mannosylated liposomes in the liver and spleen and hence the active targeting to the reticular endothelial system, which, in turn, would provide a direct attack of the drug to the site where the pathogen resides, rendering the other organs free and safe from the toxic manifestations of the drug.     

Development of Mannosylated Liposomes Using Synthesized N-Octadecyl-d-Mannopyranosylamine to Enhance Gastrointestinal Permeability for Protein Delivery

The lysozyme (LZ)-entrapped mannosylated liposomes were prepared in this study by the use of N-octadecyl-D-mannopyranosylamine (SAMAN), which had been synthesized in-house and confirmed by characterization with FTIR and NMR. The reactant residues of synthesized SAMAN were found to be less than 1%. The mean sizes, zeta potentials, drug entrapment efficiencies, and loading capacities of all liposomal formulations were in the ranges of 234.7 to 431.0 nm, -10.97 to -25.80 mV, 7.52 to 14.10%, and 1.44 to 2.77%, respectively. The permeability of mannosylated LZ liposomes across Caco-2 cell monolayers was significantly enhanced to about 2.5- and 7-folds over those of conventional liposomes and solution, respectively, which might be due to the role of mannose receptor or mannose-binding protein on the intestinal enterocytes.     

Double-liposome - based dual-drug delivery system as vectors for effective management of peptic ulcer

The aim of the present investigation was to prepare and evaluate a vesicular dual-drug delivery system for effective management of the mucosal ulcer. Inner encapsulating and double liposomes were prepared by the glass-bead and reverse-phase evaporation methods, respectively. The formulation consisted of inner liposomes bearing ranitidine bismuth citrate (RBC) and outer liposomes encapsulating amoxicillin trihydrate (AMOX). The optimized inner liposomes and double liposomes were extensively characterized for vesicle size, morphology, zeta potential, vesicles count, entrapment efficiency, and in vitro drug release. In vitro, the double liposomes demonstrated a sustained release of AMOX and RBC of 93.6 ± 1.9 and 84.1 ± 0.9%, respectively, at the end of 144 hours. Ex vivo studies were conducted on Helicobacter pylori (ATCC26695) bacterial cell lines. Double liposomes showed a more enhanced percent H. pylori growth inhibition than the plain drug combination. Further, in vivo studies illustrated enhanced antisecretory and ulcer-protective activity of double liposomes, as compared to the plain drug combination. Microscopic studies also supported the ulcer-protective action of the formulation. Thus, it may be concluded that double liposomes are instrumental in reducing gastric secretions and targeting ulcer sites with the interception of minimal side effects, thus suggesting their potential in ulcer therapy.     

Delivery in vivo of 14-deoxy-11-oxoandrographolide, an antileishmanial agent, by different drug carriers

An antileishmanial compound, 14-deoxy-11-oxo-andrographolide, a derivative of andrographlide, isolated from the Indian medicinal plant Andrographis paniculata was evaluated for efficacy in free form and in different vesicular delivery modes on hamster model of Leishmaniasis. The subcutaneous injection of free drug reduced the spleen parasite load by 39%, whereas for drug incorporated in liposomes, niosomes and microspheres, reductions in the parasite load were 78%, 91% and 59%, respectively. Moreover, the drug in various delivery modes, particularly in liposomal and niosomal forms, showed no apparent immediate toxicity. Although an inverse linear relationship between the size of carriers and per cent efficacy in reduction of spleen parasite load was established, involvement of other factors such as drug release profiles or rates remains an open question. Because of greater efficacy and lesser toxicity, liposomal, niosomal and possibly microsphere-incorporated 14-deoxy-11-oxo-andrographolide might have clinical application to combat visceral Leishmaniasis.     

Targeting of piperine intercalated in mannose-coated liposomes in experimental leishmaniasis

The leishmanicidal property of piperine intercalated in liposomes and in mannose-coated liposomes was tested in experimental visceral leishmaniasis in hamsters. Mannose-coated liposomal piperine eliminated intracellular amastigotes of Leishmania donovani in splenic macrophages much more efficiently than did the liposomal piperine or free piperine. At a dose equivalent to 6 mg/kg body wt every 4th day for a total of 4 doses in 12 days, the mannose-coated liposomal piperine was found to reduce spleen parasite load to the extent of 90% in comparison to that achieved by liposomal piperine (77%) or free piperine (29%). Histological examination of spleen and liver function tests showed that the toxicity of piperine was reduced when mannosylated liposomal piperine was administered.     

Surface-Modified Liposomal Formulation of Amphotericin B: <Emphasis Type="Italic">In vitro</Emphasis> Evaluation of Potential Against Visceral Leishmaniasis

Surface modification of liposomes with targeting ligands is known to improve the efficacy with reduced untoward effects in treating infective diseases like visceral leishmaniasis (VL). In the present study, modified ligand (ML), designed by modifying polysaccharide with a long chain lipid was incorporated in liposomes with the objective to target amphotericin B (Amp B) to reticuloendothelial system and macrophages. Conventional liposomes (CL) and surface modified liposomes (SML) were characterized for size, shape, and entrapment efficiency (E.E.). Amp B SML with 3% w/w of ML retained the vesicular nature with particle size of ～205 nm, E.E. of ～95% and good stability. SML showed increased cellular uptake in RAW 264.7 cells which could be attributed to receptor-mediated endocytosis. Compared to Amp B solution, Amp B liposomes exhibited tenfold increased safety in vitro in RAW 264.7 and J774A.1 cell lines. Pharmacokinetics and biodistribution studies revealed high t _1/2, area under the curve (AUC)_0–24, reduced clearance and prolonged retention in liver and spleen with Amp B SML compared to other formulations. In promastigote and amastigote models, Amp B SML showed enhanced performance with low 50% inhibitory concentration (IC₅₀) compared to Amp B solution and Amp B CL. Thus, due to the targeting ability of ML, SML has the potential to achieve enhanced efficacy in treating VL.     

Potential effect of cationic liposomes on interactions with oral bacterial cells and biofilms

Context: Although oral infectious diseases have been attributed to bacteria, drug treatments remain ineffective because bacteria and their products exist as biofilms. Cationic liposomes have been suggested to electrostatically interact with the negative charge on the bacterial surface, thereby improving the effects of conventional drug therapies. However, the electrostatic interaction between oral bacteria and cationic liposomes has not yet been examined in detail.

Objective: The aim of the present study was to examine the behavior of cationic liposomes and Streptococcus mutans in planktonic cells and biofilms.

Materials and methods: Liposomes with or without cationic lipid were prepared using a reverse-phase evaporation method. The zeta potentials of conventional liposomes (without cationic lipid) and cationic liposomes were ?13 and 8?mV, respectively, and both had a mean particle size of approximately 180?nm. We first assessed the interaction between liposomes and planktonic bacterial cells with a flow cytometer. We then used a surface plasmon resonance method to examine the binding of liposomes to biofilms. We confirmed the binding behavior of liposomes with biofilms using confocal laser scanning microscopy.

Results: The interactions between cationic liposomes and S. mutans cells and biofilms were stronger than those of conventional liposomes. Microscopic observations revealed that many cationic liposomes interacted with the bacterial mass and penetrated the deep layers of biofilms.

Discussion and conclusion: In this study, we demonstrated that cationic liposomes had higher affinity not only to oral bacterial cells, but also biofilms than conventional liposomes. This electrostatic interaction may be useful as a potential drug delivery system to biofilms.     

Investigations on feasibility of in situ development of amphotericin B liposomes for industrial applications

Amphotericin B (AmB) liposome formulations are very successful in the treatment of fungal infections and leishmaniasis. But higher cost limits its widespread use among people in developing countries. Therefore, we have developed a modified ethanol-injection method for the preparation of AmB liposomes. Two liposomal formulations were developed with dimyristoyl phosphatidylcholine [F-1a] and soya phosphatidylcholine [F-2a], along with egg phosphatidyl glycerol and cholesterol. AmB was dissolved in acidified dimethyl acetamide and mixed with ethanolic lipid solution and rapidly injected in 5% dextrose to prepare liposomes. Liposomes were characterized on the basis of size (~100?nm), zeta (-43.3?±?2.8 mV) and percent entrapment efficiency (>95%). The in vitro release study showed an insignificant difference (P?≥?0.05) for 24-hour release between marketed AmB liposomes (AmBisome) and F-1a and F-2a. Proliposome concentrate, used for the preparation of in situ liposomes, was physically stable for more than 3 months at experimental conditions. Similarly, AmB showed no sign of degradation in reconstituted liposomes stored at 2-8°C for more than 3 months. IC(50) value of Ambisome (0.18 μg/mL) was comparatively similar to F-1a (0.17 μg/mL) and F-2a (0.16 μg/mL) against intramacrophagic amastigotes. Under experimental conditions, a novel modified method for AmB liposomes is a great success and generates interest for development as a platform technology for many therapeutic drug products.     

Ketorolac Tromethamine Liposomes: Encapsulation and Release Studies

Liposomes loaded with ketorolac tromethamine salt were prepared by using a thin layer evaporation method. The physical properties of liposomes were studied by using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The relationship between lipid composition, encapsulation efficiency, vesicle size, and the release of ketorolac tromethamine-loaded liposomes was studied. The drug content was found to be dependent on the lipidic composition used in the preparations and, in particular, vesicles containing both cationic lipids (dimethyldioctadecylammonium bromide and N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium chloride), and phosphatidylcholine had a higher entrapped efficiency than liposomes with phosphatidylcholine alone or in the presence of cholesterol. Finally, the cationic liposomes appear to be useful as carriers for ketorolac tromethamine to control its in vitro release.     

盐酸洛拉曲克脂质体的制备及其质量考察

目的：制备盐酸洛拉曲克脂质体并考察其理化特性。方法：采用薄膜挤压-硫酸铵梯度法制备盐酸洛拉曲克脂质体,透射电镜及激光粒度分析仪分别观察和检测其粒径大小及分布,通过紫外分光光度法测定包封率及评估体外释药试验。结果：制备的盐酸洛拉曲克脂质体包封率达83.6%±2.37%,粒径103.5±26nm且分布均匀。24h体外释放实验结果提示约有66.5%的盐酸洛拉曲克从脂质体释放出来。结论：新制备的盐酸洛拉曲克脂质体粒径大小均匀,包封率尚有提高空间,具有体外缓慢释药的特性。     

Ketorolac tromethamine liposomes: encapsulation and release studies

Liposomes loaded with ketorolac tromethamine salt were prepared by using a thin layer evaporation method. The physical properties of liposomes were studied by using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The relationship between lipid composition, encapsulation efficiency, vesicle size, and the release of ketorolac tromethamine-loaded liposomes was studied. The drug content was found to be dependent on the lipidic composition used in the preparations and, in particular, vesicles containing both cationic lipids (dimethyldioctadecylammonium bromide and N-[1-(2,3-dioleoyloxy)propyl]-N,N,N-trimethylammonium chloride), and phosphatidylcholine had a higher entrapped efficiency than liposomes with phosphatidylcholine alone or in the presence of cholesterol. Finally, the cationic liposomes appear to be useful as carriers for ketorolac tromethamine to control its in vitro release.     

Hydrogen peroxide production from reactive liposomes encapsulating enzymes.

Reactive cationic and anionic liposomes have been prepared from mixtures of dimyristoylphosphatidylcholine (DMPC) and cholesterol incorporating dimethyldioctadecylammonium bromide and DMPC incorporating phosphatidylinositol, respectively. The liposomes were prepared by the vesicle extrusion technique and had the enzymes glucose oxidase (GO) encapsulated in combination with horseradish peroxidase (HRP) or lactoperoxidase (LPO). The generation of hydrogen peroxide from the liposomes in response to externally added D-glucose substrate was monitored using a Rank electrode system polarised to +650 mV, relative to a standard silver-silver chloride electrode. The effects of encapsulated enzyme concentration, enzyme combinations (GO+HRP, GO+LPO), substrate concentration, electron donor and temperature on the production of hydrogen peroxide have been investigated. The electrode signal (peroxide production) was found to increase linearly with GO incorporation, was reduced on addition of HRP and an electron donor (o-dianisidine) and showed a maximum at the lipid chain-melting temperature from the anionic liposomes containing no cholesterol. To aid interpretation of the results, the permeability of the non-reactive substrate (methyl glucoside) across the bilayer membranes was measured. It was found that the encapsulation of the enzymes effected the permeability coefficients of methyl glucoside, increasing them in the case of anionic liposomes and decreasing them in the case of cationic liposomes. These observations are discussed in terms of enzyme bilayer interactions.     

Targeting of urea stibamine encapsulated in liposomes to reticuloendothelial system for the treatment of experimental leishmaniasis

The antileishmanial antimonial drug urea stibamine was encapsulated in mannosylated and nonmannosylated liposomes and was tested against experimental leishmanial infection in hamsters. The study demonstrated that liposome encapsulation of urea stibamine enhanced its effectiveness, an effect which was greater when mannosylated liposomes were used.     

Assembly of Plasmid DNA into Liposomes After Condensation by Cationic Lipid in Anionic Detergent Solution

A novel strategy to prepare negatively charged and small DNA-containing liposomes after condensation of plasmid DNA by a cationic lipid in deoxycholate micelle environment is described. The average diameter of resulting complexes was 62±8 nm. DNA-containing liposomes were then prepared by dialysis. The shape of the resulting liposomes was spherical. The average diameter and the surface charge of the liposomes were 86±6 nm and −24±3 mV, respectively. The plasmid DNA inside liposomes remained in a supercoiled form after incubation with DNase.     

Enhanced permeability across Caco-2 cell monolayers by specific mannosylating ligand of buserelin acetate proliposomes

Context: Oral delivery of peptide and protein drugs still remains the area of challenges due to their low stability and permeability across GI tract. Among numerous attempts, the receptor-mediated drug targeting is a promising approach to enhance GI permeability.

Objective: The aim of this study was to prepare mannosylated buserelin acetate (MANS-BA) proliposome powders grafted with N-octadecyl-d-mannopyranosylamine (SAMAN) as targeting moiety and evaluate their permeability across Caco-2 cell monolayers.

Materials and methods: The MANS-BA proliposome powders were prepared by coprecipitation method. The targeting moiety SAMAN was synthesized in-house and confirmed by characterization using Fourier transform infrared (FTIR) and differential scanning calorimeter (DSC).

Results: The MANS-BA liposomes reconstituted from proliposome powders exhibited the oligolamellar vesicular structure of phospholipid bilayer. Their size, zeta potential and entrapment efficiency were in the ranges of 93.11–218.95?nm, ?24.03 to ?37.15?mV and 21.12–33.80%, respectively. The permeability of reconstituted MANS-BA liposomes across Caco-2 cell monolayers was significantly enhanced to about 1.2- and 2.2-fold over those of conventional BA liposomes and solution, respectively.

Discussion: Increase in dicetylphosphate, cholesterol and SAMAN contents resulted in significant increase in size and zeta potential of reconstituted MAN-BA liposomes. The entrapment efficiency was increased with increasing dicetylphosphate and mannitol contents in liposomes containing cholesterol.

Conclusions: The significantly enhanced permeability across Caco-2 cell monolayers of MANS-BA liposomes might be due to the role of mannose receptor on intestinal enterocytes.     

Surface modified liposomes by mannosylated conjugates anchored via the adamantyl moiety in the lipid bilayer

The aim of the present study was to encapsulate mannosylated 1-aminoadamantane and mannosylated adamantyltripeptides, namely [(2R)-N-(adamant-1-yl)-3-(α,β-d-mannopyranosyloxy)-2-methylpropanamide and (2R)-N-[3-(α-d-mannopyranosyloxy)-2-methylpropanoyl]-d,l-(adamant-2-yl)glycyl-l-alanyl-d-isoglutamine] in liposomes. The characterization of liposomes, size and surface morphology was performed using dynamic light scattering (DLS) and atomic force microscopy (AFM). The results have revealed that the encapsulation of examined compounds changes the size and surface of liposomes. After the concanavalin A (ConA) was added to the liposome preparation, increase in liposome size and their aggregation has been observed. The enlargement of liposomes was ascribed to the specific binding of the ConA to the mannose present on the surface of the prepared liposomes. Thus, it has been shown that the adamantyl moiety from mannosylated 1-aminoadamantane and mannosylated adamantyltripeptides can be used as an anchor in the lipid bilayer for carbohydrate moiety exposed on the liposome surface.     

Triggered release of doxorubicin following mixing of cationic and anionic liposomes

In many applications, an ability of liposomes to retain drug and then rapidly release it at some later time would be of benefit. In this work, we investigate the ability of cationic large unilamellar vesicles (LUV) to promote rapid release of doxorubicin from anionic LUV. It is shown that the addition of cationic liposomes containing cholesterol, dioleoylphosphatidylethanolamine (DOPE), distearoylphosphatidylcholine (DSPC) and the cationic lipid N,N-dioleyl-N,N-dimethylammonium chloride (DODAC) to doxorubicin-containing LUV composed of cholesterol, DOPE, DSPC and the anionic lipid dioleoyphosphatidylglycerol (DOPG) can result in release of more than 90% of the drug in times of 30 s or less. Further, it is shown that these release characteristics are exquisitely dependent on the presence of DOPE and cholesterol. In the absence of DOPE, much slower release rates are observed, with maximum release levels of 50% after a 2-h incubation at 20 degrees C. Remarkably, threshold levels of more than 10 mol% cholesterol are required before any appreciable release is observed. [31P]NMR spectroscopy and freeze-fracture electron microscopy studies reveal that systems giving rise to rapid release of doxorubicin exhibit limited formation of inverted hexagonal (H(II)) phase, suggesting that these lipids facilitate drug release by formation of local regions of non-bilayer structure. It is concluded that drug release triggered by mixing anionic and cationic liposomes could be of utility in drug delivery applications.     

Triggered release of doxorubicin following mixing of cationic and anionic liposomes

In many applications, an ability of liposomes to retain drug and then rapidly release it at some later time would be of benefit. In this work, we investigate the ability of cationic large unilamellar vesicles (LUV) to promote rapid release of doxorubicin from anionic LUV. It is shown that the addition of cationic liposomes containing cholesterol, dioleoylphosphatidylethanolamine (DOPE), distearoylphosphatidylcholine (DSPC) and the cationic lipid N,N-dioleyl-N,N-dimethylammonium chloride (DODAC) to doxorubicin-containing LUV composed of cholesterol, DOPE, DSPC and the anionic lipid dioleoyphosphatidylglycerol (DOPG) can result in release of more than 90% of the drug in times of 30 s or less. Further, it is shown that these release characteristics are exquisitely dependent on the presence of DOPE and cholesterol. In the absence of DOPE, much slower release rates are observed, with maximum release levels of 50% after a 2-h incubation at 20 °C. Remarkably, threshold levels of more than 10 mol% cholesterol are required before any appreciable release is observed. [³¹P]NMR spectroscopy and freeze-fracture electron microscopy studies reveal that systems giving rise to rapid release of doxorubicin exhibit limited formation of inverted hexagonal (H_II) phase, suggesting that these lipids facilitate drug release by formation of local regions of non-bilayer structure. It is concluded that drug release triggered by mixing anionic and cationic liposomes could be of utility in drug delivery applications.     

Preparation and quality evaluation of coenzyme Q10 long-circulating liposomes

The aim of this work was to prepare coenzyme Q10 (CoQ10) long-circulating liposomes, and establish the quality standard to determine the content and entrapment efficiency. CoQ10 long-circulating liposomes were prepared by the film dispersion method, HPLC assay for the determination of CoQ10 was developed. Free drugs and liposomes were separated using the protamine aggregation method and entrapment efficiency was determined. The liposomes were homogeneous and the mean diameter was 166.0 nm, Zeta potential was −22.2 mV. The content and entrapment efficiency of CoQ10 were 98.2% and 93.2% for three batches of liposomes, respectively. The lyophilized form of liposomes prepared by freeze-drying showed stable quality characteristics during storage. The formulation and preparative method can be used to prepare CoQ10 long-circulating liposomes with high entrapment efficiency and high quality, the determination method of drug content and entrapment efficiency were effective and rapid and can be used for quality evaluation of liposomes.     

青藤碱磷脂复合物纳米结构脂质载体的制备、表征及药动学研究

为制备青藤碱磷脂复合物纳米结构脂质载体,并进行体外和SD大鼠体内评价。实验采用溶剂挥发法制备青藤碱磷脂复合物,乳化超声法制备青藤碱磷脂复合物纳米结构脂质载体。考察其粒径分布、Zeta电位,包封率,载药量及体外释药等基本理化性质。SD大鼠分别灌胃给予青藤碱混悬液和青藤碱磷脂复合物纳米结构脂质载体,比较药动学行为及生物利用度。结果显示,青藤碱磷脂复合物纳米结构脂质载体的平均粒径为201.32±5.05 nm,Zeta电位为-22.2±1.5 mV,包封率为80.31±1.01%,载药量为4.42±0.28%,体外释药具有明显的缓释特征,体外释药模型符合Weibull释药模型,拟合方程为:LnLn(1/1-Mt/M∞)=0.576 6Lnt-1.478 1(r=0.988 8)。体内药动学研究结果表明,磷脂复合物纳米结构脂质载体改变了青藤碱的药动学行为,增强了体内吸收,延长了青藤碱在体内滞留时间,相对生物利用度提高到了1.75倍。因此,青藤碱磷脂复合物纳米结构脂质载体可显著促进青藤碱体内吸收,提高其口服生物利用度。