Confocal and probe microscopy to study gene transfection mediated by cationic liposomes with a cationic cholesterol derivative.

A novel cationic cholesterol derivative with a hydroxyethyl amino head group (I) has been synthesized and used for liposome-mediated gene transfection. Cationic liposomes with derivative (I) greatly facilitated gene transfection into various cultured cells. The efficiency of transfection by liposomes with derivative (I) was much higher than that using liposomes with DC-chol (II) or lipofectine. Atomic force microscopy and confocal laser scanning microscopy revealed the molecular mechanism of gene transfection by cationic liposomes. The results showed that at least two steps were involved in gene transfection mediated by cationic liposomes. One was endocytosis, where the liposome-DNA complex was internalized into target cells, and the other was membrane fusion between the liposome vectors and endosomes, where DNA transferred from the liposome to the nucleus. In addition we found that microtubules were involved in the intracellular dynamics of gene transfection.     

脂质体包裹的反义寡核苷酸逆转耐甲氧西林金黄色葡萄球菌耐药性的研究

目的：用人工合成磷脂二棕榈酰磷脂酰胆碱（dipalmitoyl phosphatidylcholine，DPPC），二肉豆蔻酰磷脂酰甘油（dimyristoyl phosphatidylglycerol，DMPG）制备反义寡核苷酸阴离子脂质体并研究脂质体包裹的抑制耐甲氧西林金黄色葡萄球菌（methicillin resistant staphylococcus aureus，MRSA）耐药基因表达信号传导通路中BlaRlmRNA表达的反义寡核苷酸（antisense phosphothioate oligodeoxynucleotides，AS-ODNs）对MRSA耐药性的影响。方法：设计合成AS-ODNs；薄膜分散冻干法制备其脂质体；透射电镜观察脂质体的形态；离心纯化脂质体并用紫外分光光度计测定包封率、渗漏率；振荡法检测体外释放度；平板克隆形成实验计数菌落数CFU；微量法测定细菌生长曲线。结果：反义寡核苷酸阴离子脂质体大小均匀，为圆球体，包封率为77．38％，冷冻条件下保存1月后渗漏率为0．18％，体外释放度实验表明24h后约60％的药物从脂质体中释放，反义寡核苷酸脂质体可显著抑制MRSA生长，脂质体包裹的不同剂量的AS-ODNs中MRSA的菌落形成单位（CFU）与空白对照组比较明显减少，具有剂量依赖性，且效果明显优于未被脂质体包裹的AS-ODNs。结论：采用薄膜分散冻干法制备反义寡核苷酸阴离子脂质体，包封率较高，质量稳定，反义寡核苷酸脂质体能逆转MRSA的耐药性，效果明显优于单用AS-ODNs，可作为反义寡核苷酸进入细菌的载体。     

A diglyceride derivative of methotrexate: Synthesis and cytotoxic activity in addressed liposomes

A synthesis of a lipophilic derivative of methotrexate was devised, this being suitable for insertion into the membranes of carrier liposomes. The conjugate consisted of a rac-1,2-dioleoylglycerol residue attached via an ester bond to methotrexate via the β-alanyl-N-carbonylmethylene linker. A liposomal formulation of the derivative showed cytotoxic activity in cultures of M3 melanoma cells; this activity depended on the structure of the carbohydrate ligands on the liposome surface. As compared with a control liposome preparation carrying a diglyceride derivative of methotrexate and bearing an inactive pentaol aminoglucitol ligand, the cytotoxicity of liposomes carrying trisaccharide A residues was 1.5 times greater and that of liposome carrying tetrasaccharide sialyl-Lewis X was three times greater. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 41, No. 6, pp. 10–14, June, 2007.     

Interaction of colistin and colistin methanesulfonate with liposomes: colloidal aspects and implications for formulation

Interaction of colistin and colistin methanesulfonate (CMS) with liposomes has been studied with the view to understanding the limitations to the use of liposomes as a more effective delivery system for pulmonary inhalation of this important class of antibiotic. Thus, in this study, liposomes containing colistin or CMS were prepared and characterized with respect to colloidal behavior and drug encapsulation and release. Association of anionic CMS with liposomes induced negative charge on the particles. However, degradation of the CMS to form cationic colistin over time was directly correlated with charge reversal and particle aggregation. The rate of degradation of CMS was significantly more rapid when associated with the liposome bilayer than when compared with the same concentration in aqueous solution. Colistin liposomes carried positive charge and were stable. Encapsulation efficiency for colistin was approximately 50%, decreasing with increasing concentration of colistin. Colistin was rapidly released from liposomes on dilution. Although the studies indicate limited utility of colistin or CMS liposomes for long duration controlled-release applications, colistin liposomes were highly stable and may present a potential opportunity for coformulation of colistin with a second antibiotic to colocalize the two drugs after pulmonary delivery.     

Liposomes from hydrogenated soya lecithin formed in sintered glass pores

Possible complete closure of hydrophilic drug solutions in liposomes with required dimensions is the aim of variety liposome techniques. The ease of separating medication-loaded liposomes from liposome suspension to achieve an appropriate drug concentration in the final preparation is also desired. This paper describes the use of liposome preparation method, called reverse-phase evaporation, which leads to practical achievement of the earlier mentioned objectives. Preparation process is performed in an appropriately designed device. In optimal conditions of liposome preparation the final encapsulation efficiency of hydrophilic drug solution amounted to 50% in liposomes with a diameter in the range of a few micrometers up to 250 nm. The diameter of terminal liposomes is a simple function of relative amount of the lipid used and the degree of emulsion emulsification w/o at the beginning of liposome preparation. The density of the concentrated drug solution trapped in liposomes is usually higher than that of the buffer. Therefore, the loaded liposomes may be easily separated from non-trapped material by using of a simple sedimentation at 30000 x g. Density of aqueous drug solution insufficient to effective centrifugation can be magnified with an appropriate quantity of sucrose solution before encapsulation.     

LC-MS法研究尼莫地平脂质体原位凝胶在家兔体内的药动学

目的研究尼莫地平脂质体原位凝胶在家兔体内的药动学。方法单剂量(尼莫地平0.5 mg·kg~(-1))于家兔后腿股四头肌肌内注射尼莫地平溶液剂、尼莫地平脂质体、泊洛沙姆188(P188)修饰的尼莫地平脂质体和尼莫地平脂质体原位凝胶,建立高效液相色谱-质谱(LC-MS)法测定血浆中尼莫地平的浓度。结果尼莫地平在0.8～800μg·L~(-1)范围内线性关系良好(r=0.999 2),提取回收率大于90%,日内、日问精密度RSD<15%。尼莫地平脂质体原位凝胶和脂质体的c_(max)分别为(88±s 18)和(224±64)μg·L~(-1);t_(max)分别为(2.0±0.7)和(0.29±0.14)h;AUC_(0-∞)分别为(402±15)和(273±28)μg·h·L~(-1)。尼莫地平脂质体原位凝胶的c_(max)、t_(max)、AUC_(0-∞)等药动学参数与尼莫地平脂质体和P188修饰的尼莫地平脂质体均有显著或极显著差异。结论尼莫地平脂质体原位凝胶经肌内注射后可延长药物在体内的驻留时间,具有一定的缓释作用并提高了尼莫地平的生物利用度。     

Liposome–skin interactions and their effects on the skin permeation of drugs

The aim of the study was to evaluate the interaction of phospholipid liposomes with skin and stratum corneum lipid liposomes (SCLLs). The influence of phospholipid liposomes on the skin permeability of model drugs was also studied. The transdermal flux of the drugs applied in various phospholipid containing formulations through human epidermis was studied in diffusion chambers. Liposomes in water solutions did not enhance the skin permeability of the drugs, but when ethanol (32% w/v) was present in the donor with EPC (egg yolk lecithin), permeabilities of some model drugs were substantially increased. Confocal microscopy studies revealed that EPC do not penetrate into the skin from water solutions, while from ethanol solutions, EPC penetrates deeply into the stratum corneum. Also, resonance energy transfer between different liposome compositions and the release of calcein from SCLLs showed that interactions between phospholipid liposomes and SCLLs increased with increasing ethanol concentration in the liposome solutions.     

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.     

Degradation Kinetics of Water-Insoluble Lauroyl-lndapamide in Aqueous Solutions: Prediction of the Stabilities of the Drug in Liposomes

The aim of this study was to explore the degradation kinetics of water-insoluble lauroyl-indapamide in solutions and predict the stabilities of lauroyl-indapamide encapsulated in liposomes. Buffer-acetone (9:1) was used as the reaction solution and the reaction temperature was maintained at 60 degrees C. The correlation of the apparent degradation constants (k(obs)) of lauroyl-indapamide in liposomes and in buffer-acetone solutions at different pH has been explored. The degradation of lauroyl-indapamide in solutions was found to follow pseudo-first-order kinetics and was significantly dependent on the pH values. Lauroyl-indapamide was the most stable at pH 6.8, increasing or decreasing the pH of the solutions would decrease its stabilities. Buffer concentration had some effects on the stabilities of lauroyl-indapamide. The degradation active energies Ea were 68.19 kJ x mol(-1), 131.75 kJ x mol(-1) and 107.72 kJ x mol(-1) at pH3.6, 6.8 and 12 respectively in acetone-free buffer solutions (0.05M) calculated according to the Arrhenius equation with the extrapolation method. The apparent degradation constants (kobs) of lauroyl-indapamide in liposome and in buffer-acetone (9:1) solutions showed a good correlation at different pH levels, which indicates that the stabilities of the drug that dissolved in acetone-buffer mixture solutions can be used to predict the stabilities of the drug in liposomes as well.     

Determination of partition coefficients of diazepam and flurazepam between phosphatidylcholine bilayer vesicles and water by second derivative spectrophotometric method

Second derivative spectrophotometry allowed the establishment of a simple and accurate method for the determination of partition coefficients of benzodiazepine drugs in a liposome/water system. The absorption spectra of diazepam (DZ) and flurazepam (FZ) in phosphatidylcholine (egg yolk) bilayer vesicle suspensions showed small spectral changes depending on the concentration of phosphatidylcholine vesicles. However, the intense background signals caused by the light scattering of the phosphatidylcholine vesicles made it difficult to yield a correct base line, thus the quantitative spectral data could not be obtained. In the second derivative spectra, the spectral changes were enhanced and three derivative isosbestic points were observed for each drug indicating the entire elimination of the residual background signal effects. The derivative intensity change of each drug (DeltaD) induced by its interaction with phosphatidylcholine bilayers was measured at a specific wavelength. From the relationship between the DeltaD value and the lipid concentration, the molar partition coefficients (K(p)s) of DZ and FZ were calculated and obtained with a good precision of R.S.D below 10%. The fractions of the partitioned DZ and FZ calculated by using the obtained K(p) values agreed well with the experimental values. The results prove that the derivative method can be usefully and easily applied to the determination of partition coefficients of benzodiazepines in the liposomes/water system without any separation procedures.     

Synthesis of cholesterol modified cationic lipids for liposomal drug delivery of antisense oligonucleotides.

The paper describes a novel synthesis of cholest-5-en-3 beta-yl-6-aminohexyl ether (AH-Chol). AH-Chol was used to prepare positively charged liposomes. The liposomes consisted of phospholipon 90H and the cationic cholesterol derivative in an equimolar ratio. Liposome preparation was achieved by membrane homogenization after rehydration of a dry lipid film. Oligonucleotides (ODN) were adsorbed to the cationic liposomes very efficiently. At an ODN/liposome ratio of 1:5 (10:50 micrograms/ml) 84.2 +/- 5.4% of the ODNs were bound to the liposomal membrane. Within the range of 1:40 and 1:100 charge neutralization occurred and the liposome dispersion showed an increase in particle size due to aggregation. Below or above this range of charge neutralization the ODN loaded liposome preparation was physically stable, no sedimentation, increase of vesicle size or vesicle aggregation occurred.     

Liposomal diclofenac eye drop formulations targeting the retina: Formulation stability improvement using surface modification of liposomes

An efficient liposomal formulation for targeting the retina was produced as an optimal means of distributing therapeutic agents to the retina. Diclofenac was used as a model compound for liposome encapsulation, and the release rate and distribution to the retina were investigated. The calcium acetate gradient method was found to be the optimal method for encapsulating diclofenac into liposomes. Entrapment efficiency using this method was greater than 97%, whereas conventional hydration method achieved 51.3%. The resultant formulation obtained with the gradient method caused aggregation and/or fusion of liposomes. To avoid inhibition of retinal delivery due to the aggregation of the carrier, surface modification was performed simultaneously with the gradient method. The increase in particle size of the liposomal formulation clearly was inhibited for a long time in the presence of polyvinyl alcohol or its derivative. This observation may be explained by surface modification of the liposomes by physisorption or anchoring effect of polymers on the surface of the lipid bilayer. Furthermore, the sustained release profile of the diclofenac formulation was retained after modification. An in vivo animal study revealed that concentration of the accumulated diclofenac in the retina-choroid was enhanced 1.8-fold by surface-modified liposome entrapment compared to that of the unaltered diclofenac solution.     

Effects of lipid composition and preparation conditions on physical-chemical properties, technological parameters and in vitro biological activity of gemcitabine-loaded liposomes

The effects of lipid composition and preparation conditions on the physicochemical and technological properties of gemcitabine-loaded liposomes, as well as the in vitro anti-tumoral activity of various liposome formulations were investigated. Three liposome formulations were investigated: DPPC/Chol/Oleic acid (8:3:1 molar ratio, liposomes A), DPPC/Chol/DPPS (6:3:1 molar ratio, liposomes B) and DPPC/Chol/DSPE-MPEG (6:3:1 molar ratio, liposomes C). Multilamellar liposomes were prepared by using the TLE, FAT and DRV methods, while small unilamellar liposomes were obtained by extrusion through polycarbonate filters. Light scattering techniques were used to characterize liposome formulations. Loading capacity and release profiles of gemcitabine from various liposome formulations were also investigated. Caco-2 cells were used to evaluate in vitro the antitumoral activity of gemcitabine-loaded liposomes with respect to the free drug and also the intracellular drug uptake. Preparation methods and liposome lipid composition influenced both physicochemical parameters and drug delivery features. Liposomes with a size ranging from 200 nm to 7 microm were obtained. The gemcitabine entrapment was higher than that expected probably due to an interaction with the liposome lipid components. The following decreasing loading capacity order was observed: liposome B>liposome C>liposome A. Gemcitabine release from various liposome formulations is modulated by two different processes, i.e. desorption from and permeation through liposomal bilayers. MTT assay showed a greater cytotoxic effect of gemcitabine-loaded liposomes with respect to the free drug. The following decreasing anticancer activity order was observed between the various liposome formulations: liposome C>liposome A>liposome B. The increased anticancer activity is correlated to the ability of the colloidal carrier to increase the intracellular drug uptake. Due to the encouraging results and to the high liposome modularity various applications of potential therapeutic relevance can be envisaged for liposomes.     

Polyethylene glycol-coated liposomes for oral delivery of recombinant human epidermal growth factor

The present study was to investigate the feasibility of oral delivery of recombinant human epidermal growth factor (rhEGF). Polyethylene glycol (PEG)-coated liposomes containing rhEGF was prepared and evaluated for their stability and permeability in Caco-2 cells. In the animal study, we also determined plasma concentration and gastric ulcer healing effect after oral administration of rhEGF liposomes or the solution. Encapsulation of rhEGF into liposomes, suppressed the degradation in Caco-2 cell homogenate compared with the solution. The flux of rhEGF from dipalmitoylphosphatidylcholine (DPPC) liposome across Caco-2 cell monolayer from the apical to basolateral side was three times greater than that from phosphatidylcholine (PC) liposome or the solution. After oral administration of rhEGF liposomes or the solution in rats, the area under the concentration-time curve (AUC) of rhEGF increased 1.7- and 2.5-fold for PC and DPPC liposomes, respectively. The gastric ulcer healing effect was significantly increased in DPPC liposome compared with PC liposome and the solution. The enhanced curative ratio of rhEGF encapsulated into DPPC liposome may be due to the resistance to enzyme degradation, higher permeability and increased plasma AUC. Therefore, PEG-coated liposomes containing rhEGF could be used as an oral delivery formulation with enhanced encapsulation efficiency.     

粒径和质量浓度对辅酶Q_(10)脂质体光解动力学的影响

目的为辅酶Q10脂质体的进一步研究提供参考。方法制备不同粒径和不同质量浓度的辅酶Q10脂质体,进行光照加速试验,考察脂质体中辅酶Q10的光解规律。结果辅酶Q10脂质体的光解符合一级降解动力学。平均粒径为309.4、125.9、64.8 nm的1.0 g.L-1辅酶Q10脂质体的光解半衰期分别为55.4、45.3、34.3 h;药物质量浓度为1.0、0.5、0.1 g.L-1辅酶Q10脂质体(309.4 nm)的光解半衰期分别为55.4、31.1、19.3 h。结论辅酶Q10脂质体的光解具有一定的粒径和质量浓度依赖性,粒径越大,起始质量浓度越高,光解半衰期越长,光保护效果越明显。     

Development of a novel one-step production system for injectable liposomes under GMP

Abstract

There are few methods available for injectable liposome production under good manufacturing practices (GMP). Injectable liposome production processes under GMP generally consist of liposome formation, size homogenization, organic solvent removal, liposome concentration control and sterilization. However, these complicated and separate processes make it difficult to maintain scalability, reproducibility and sterility. To overcome these limitations, we developed a novel one-step in-line closed liposome production system that integrated all production processes by combining the in-line thermal mixing device with modified counterflow dialysis. To validate the system, we produced liposomal cyclosporine A (Lipo-CsA) and lyophilized the liposomes. The three independent pilot batches were highly reproducible and passed the quality specifications for injectable drugs, demonstrating that this system could be used under GMP. The accelerated stability test suggested that the liposomes would be stable in long-term storage. This one-step system facilitates a fully automated and unattended production of injectable liposomes under GMP.     

Monosialoganglioside containing cationic liposomes with a cationic cholesterol derivative promote the efficiency of gene transfection in mammalian culture cells

We have studied the effects of monosialoganglioside (GM1)-containing cationic liposomes with a cationic cholesterol on the liposome-mediated gene transfection into mammalian culture cells. The results showed that both cationic liposomes with either a cationic cholesterol derivative of a hydrophobic amino head group (I) and a hydrophilic amino head group (II) promoted the transfection of luciferase plasmids (pGL3) into HeLa and CHO-K1 cells more than the control cationic liposomes without GM1. In addition, we found that cationic liposomes with a cationic cholesterol derivative (II) were about ten times as effective as that by commercially available cationic liposome Lipofectin. Confocal fluorescence microscopy showed that the liposome/DNA complex was transferred more efficiently into the target cells by the GM1-containing liposomes than by the liposomes without GM1. In proportion to the above results, free antisense DNAs were also more efficiently transferred into the nucleus of the target cells by the GM1-containing liposomes. When there was 100 mM galactose in the transfection medium, the luciferase activity by the GM1-containing liposomes was reduced to the level of the control liposomes. The results suggest that GM1-containing cationic liposomes with a cationic cholesterol derivative of a hydrophobic amino head group or a hydrophilic amino head group should significantly increase the transfection efficiency of plasmid DNAs and antisense DNAs by galactose receptor-mediated endocytosis. This means that the GM1-containing liposomes described here should be very promising for gene transfection in vitro.     

支链淀粉修饰双嘧达莫脂质体的制备及其在小鼠体内的组织分布

目的研究支链淀粉修饰双嘧达莫(DIP)脂质体的制备方法并考察其在小鼠体内的组织分布。方法 采用薄膜-分散法制备普通DIP脂质体；合成两亲性的棕榈酰化支链淀粉并用其修饰DIP脂质体；比较修饰前后包封率、zeta电位、平均粒径和径距的变化；采用反相高效液相法测定小鼠组织中的DIP浓度。结果修饰后DIP脂质体的包封率降低，zeta电位增加，平均粒径和径距无明显变化；普通脂质体可以增强DIP在肺部、肝脏和脾脏的分布，而较之普通脂质体，支链淀粉修饰的脂质体可以进一步增加肺部DIP水平，同时减少DIP在肝脏和脾脏的分布，并延长在肺部的滞留时间。结论与普通脂质体和注射液比较，支链淀粉修饰的脂质体可以改变DIP在小鼠体内的组织分布，具有显著的肺靶向性。     

Characterization of endotoxin and cationic liposome interaction

The objective of this study was to characterize the interaction of endotoxin with cationic liposomes used in nonviral gene delivery. Endotoxin-cationic liposome interaction was characterized using fluorescent anisotropy, and the Limulus amebocyte lysate (LAL) assay. Cellular toxicity of endotoxin-cationic liposome complex was examined using a dimethylthiazol diphenyltetrazolium bromide (MTT) assay. The effect of endotoxin on the lipid-DNA complex and subsequent transfection into COS-1 cells was also examined. A competitive interaction occurred between fluoroscein isothiocyanate (FITC)-labeled endotoxin and plasmid DNA for binding dioleoyl glycero trimethylammonium propane:dioleoyl glycero phosphoethanolamine (DOTAP:DOPE) liposomes using fluorescent anisotropy techniques. The LAL assay demonstrated no change in endotoxin activity upon interaction with liposomes. No loss of COS cell viability was detected via the MTT assay during a 5-hr exposure to endotoxin. Transient transfection studies indicate that increasing levels of endotoxin lowered activity more than 90% at 50,000 endotoxin units (EU)/ml. Endotoxin and cationic liposomes interact mainly by an electrostatic attraction. Endotoxin contamination can potentially impact transfection efficiency via competition with plasmid DNA for cationic liposome binding by increasing transfection variability at 50 EU/ml, a concentration of endotoxin contamination that can occur with small-scale plasmid preparations used for in vitro cell transfections, but would not be expected with typical GLP or GMP preparations used in clinical studies.     

Body distributioin of RGD-mediated liposome in brain-targeting drug delivery

RGD conjugation liposomes (RGD-liposomes) were evaluated for brain-targeting drug delivery. The flow cytometric in vitro study demonstrated that RGD-liposomes could bind to monocytes and neutrophils effectively. Ferulic acid (4-hydroxy-3-methoxycinnamic, FA) was loaded into liposomes. Rats were subjected to intrastriatal microinjections of 100 units of human recombinant IL-1beta to produce brain inflammation and caudal vein injection of three formulations (FA solution, FA liposome and RGD-coated FA liposome). Animals were sacrificed 15, 30, 60 and 120 min after administration to study the body distribution of the FA in the three formulations. HPLC was used to determine the concentration of FA in vivo with salicylic acid as internal standard. The results of body distribution indicated that RGD-coated liposomes could be mediated into the brain with a 6-fold FA concentration compared to FA solution and 3-fold in comparison to uncoated liposome. Brain targeted delivery was achieved and a reduction in dosage might be allowed.