The Effect of Different Lipid Components on the In Vitro Stability and Release Kinetics of Liposome Formulations

Liposomes are colloidal carriers that form when certain (phospho)lipid molecules are hydrated in an aqueous media with some energy input. The ideal liposome formulation with optimum stability will improve drug delivery by decreasing the required dose and increasing the efficacy of the entrapped drug at the target organ or tissue. The most important parameter of interest in this article was to compare the efficacy of three different liposomes formulated with DSPC, DMPC, and DPPC, all saturated neutral phospholipids with different acyl chain lengths and transition temperatures. DMPC has a phase transition temperature (Tc) below 37°C, whereas the other two phospholipids possess Tcs above the physiological temperature. These lipids were then added to a cholesterol concentration of 21% to optimize the stability of the vesicles. The liposomes were prepared by a sonication and incubated in phosphate buffered saline (PBS) at 4°C and 37°C. The encapsulation efficiency, initial size, and drug retention of the vesicles were tested over a 48-hr period employing radiolabeled inulin as a model drug. The phase transition temperature of liposomes, which depends on the Tc of the constituent lipids, was an important factor in liposome stability. Of all the liposomes tested, the greatest encapsulation efficiency was found for the DSPC liposomes (2.95%) that also had the greatest drug retention over 48 hr at both 4°C (87.1 ± 6.8%) and 37°C (85.2 ± 10.1%), none of these values being significantly different from time zero. The lowest drug retention was found for DMPC liposomes for which a significant difference in drug retention was seen after only 15 min at both 4°C (47.3 ± 6.9%) and 37°C (53.8 ± 4.3%). The DPPC liposomes showed a significant difference in drug retention after 3 hr at 4°C (62.1 ± 8.2%) and after 24 hr at 37°C (60.8 ± 8.9%). Following the initial drop at certain time intervals a plateau was reached for all of the liposome formulations after which no significant difference in drug retention was observed. In conclusion, liposomes with higher transition temperatures appear to be more stable in PBS either at 4°C or 37°C, indicating that the increase in acyl chain length (and therefore transition temperature) is directly proportional to stability.     

The effect of dimyristoylphosphatidylethanol on the lateral and rotational mobilities of liposome lipid bilayers

The aim of this study was to provide the basis to further examine the mode of action of ethanol. Fluorescent probes reported to have different membrane mobilities were used to evaluate the effect of dimyristoylphosphatidylethanol (DMPEt) on the lateral and rotational mobilities of liposome lipid bilayers. An experimental procedure, based on the selective quenching of 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1,3-di(1-pyrenyl)propane (Py-3-Py) by trinitrophenyl groups, was used. DMPEt increased the bulk lateral and rotational mobilities, and had a greater fluidizing effect on the outer than the inner monolayer. These effects of DMPEt on liposomes may be responsible for some, but not all, of the general anesthetic actions of ethanol.     

Dexamethasone incorporating liposomes: effect of lipid composition on drug trapping efficiency and vesicle stability

Effect of lipid composition on encapsulation and stability of dexamethasone (DXM) incorporating multilamellar vesicles (MLV) is studied. MLVs composed of phosphatidylcholine (PC) or distearoyl-glycero-PC (DSPC), with or without cholesterol (Chol), are prepared and the release of DXM during vesicle incubation in buffer or plasma proteins is evaluated. Incorporation of DXM is slightly higher in DSPC liposomes compared with PC, whereas the drug is displaced from liposomes, as the Chol content of liposome membranes increases. Plain lipid and Chol-containing liposomes lose similar fractions of vesicle-incorporated DXM during incubation in buffer or serum, whereas DXM release kinetics are similar (for each liposome type studied), implying that drug release is due mainly to dilution of liposome dispersions that leads to repartitioning of DXM.     

Effect of drug stability on the analysis of release data from controlled release microspheres

The objective of this study was to determine the effect of drug stability on the analysis of in vitro release data from controlled release microspheres. Amoxicillin was chosen as a model drug and its stability in various media determined. The in vitro release of amoxicillin from PLGA microspheres was investigated in phosphate buffered saline (PBS) containing either Tween-80 or Tween-80 + Na-azide. Drug concentration in the media and the amount remaining inside the microspheres were analysed using HPLC. Amoxicillin degraded rapidly in PBS. The rate of degradation was reduced in the presence of Tween 80 and Na-azide. Drug release from the microspheres was analysed with and without considering the drug degradation rate. Mass balance between released drug, drug remaining in the microspheres and initial drug loading was only achieved when drug degradation was accounted for. Drug stability should be considered in analysis of in vitro extended release data, since released drug may degrade with time. These results have implications for in vitro release studies for controlled release products that include drugs and other compounds which are susceptible to degradation during the course of the release study.     

Kinetic modelling of liposome degradation in serum: Effect of size and concentration of liposomes in vitro

The purpose of this study is to propose a new method for quantitative evaluation of liposome degradation in serum. The time course of liposome degradation in rat serum was monitored continuously, using 6(5)-carboxyfluorescein as an aqueous phase marker. The degradation curves exhibited three characteristic phases: lag time, degradation, and plateau. This curve was described by a kinetic model with three parameters: lag time (τ), first-order degradation rate constant (k), and maximum degradation (α). The rate and extent of the degradation of liposomes were evaluated separately in terms of k and α, respectively. The effects of size and concentration of liposomes on their degradation kinetics were examined using this method. Both k and α increased with increasing liposomal size. The increased affinity of larger liposomes for complement was suggested to increase both k and α. On the other hand, α decreased with increasing liposomal concentration without altering k. The decreased extent of degradation was considered to result from the depletion of complement components. There was no significant effect of size and concentration of liposomes on τ. Quantitative evaluation of the rate and extent of degradation of liposomes will provide deeper insights into the interaction between liposomes and serum components, and basic information on liposomes as potential drug carriers.     

青蒿油多相脂质体体外抗肿瘤实验研究

目的 研究青蒿油多相脂质体对不同肿瘤细胞株的生长抑制作用.方法 采用四甲基偶氮唑盐(MTT)法检测青蒿油多相脂质体对4种不同肿瘤细胞株的生长抑制作用.结果 青蒿油多相脂质体对人白血病HL-60及人红白血病K562、小鼠黑色素瘤B-16、人肝癌BEL-7402细胞的半抑制浓度(IC50)分别为124.00、390.14、391.94、854.01μg/mL,在浓度为520μg/mL时,对四种细胞株的抑制率分别为93.09％、70.56％、77.55％、40.00％.结论 青蒿油多相脂质体在体外对4种肿瘤细胞株均具有明显的抑制作用,具有开发成抗癌新药的潜力.     

The effect of lipid composition and liposome size on the release properties of liposomes-in-hydrogel

To study the release of liposome-associated drugs into hydrogels, we designed and synthesized two pH-sensitive rhodamine derivatives to use as model compounds of different lipophilicities. The dyes were fluorescent when in the free form released from liposomes into the chitosan hydrogel, but not when incorporated within liposomes. The effect of liposomal composition, surface charge and vesicle size on the release of those incorporated dyes was evaluated. The lipophilicity of the rhodamine derivatives affected both the amount and rate of release. While liposome size had only a minor effect on the release of dyes into the hydrogel, the surface charge affected the release to a greater extent. By optimizing the characteristics of liposomes we could develop a liposomes-in-hydrogel system for application in wound therapy. We further characterized liposomes-in-hydrogel for their rheological properties, textures and moisture handling, as well as their potential to achieve a controlled release of the dye. The polymer-dependent changes in the hydrogel properties were observed upon addition of liposomes. The charged liposomes exhibited stronger effects on the textures of the chitosan hydrogels than the neutral ones. In respect to the ability of the system to handle wound exudates, chitosan-based hydrogels were found to be superior to Carbopol-based hydrogels.     

不同表面活性剂对伊文思蓝脂质体体内外性质的影响

目的　寻找与二硬脂酰磷脂酰乙醇胺 聚乙二醇 (DSPE PEG)功能相似的表面活性剂 ,以增加脂质体的稳定性 ,改善其体内分布 ,提高靶向性。方法　制备伊文思蓝 (EB)脂质体 ,考察胆固醇与磷脂的比例对伊文思蓝脂质体包封率的影响 ;比较用DSPE PEG、吐温 80 (Tween 80 )和苄泽 3 5 (Brij 3 5 )修饰后的EB脂质体的包封率和在大鼠体内组织分布状况的变化。结果　EB脂质体的包封率最高为 2 5 3 0 %。用DSPE PEG、Tween 80和Brij 3 5修饰后使EB脂质体的包封率略有下降 ,但差别不显著 ;体内分布实验结果显示 :修饰后的脂质体在肝、脾和肾中EB的浓度均有不同程度的降低 ,脑中EB的浓度有所提高 ,而且以Tween 80修饰组最显著。结论　DSPE PEG、Tween 80和Brij 3 5对EB脂质体的包封率影响较小。Brij 3 5对EB脂质体的作用与DSPE PEG相似 ,能提高脂质体逃避网状内皮系统吞噬的能力 ;Tween 80主要能增加EB脂质体在大鼠脑组织中的分布 ,为脑靶向脂质体的研究提供了有益信息     

Stability and in vitro release profile of enalapril maleate from different commercially available tablets: possible therapeutic implications

Stability of enalapril maleate formulations can be affected when the product is exposed to higher temperature and humidity, with the formation of two main degradation products: enalaprilat and a diketopiperazine derivative. In this work, stability and drug release profiles of 20 mg enalapril maleate tablets (reference, generic and similar products) were evaluated. After 180 days of the accelerated stability testing, most products did not exhibit the specified amount of drug. Additionally, drug release profiles were markedly different from that of the reference product, mainly due to drug degradation. Changes in drug concentration and drug release profile of enalapril formulations are strong indicators of a compromised bioavailability, with possible interferences on the therapeutic response for this drug.     

Vehicle effects on in vitro release of tiaprofenic acid from different topical formulations

The aim of the present study was to investigate the in vitro release properties of tiaprofenic acid (TA) from different topical vehicles. Carbopol 940 gel, chitosan gel, two types of emulsion-based ointment formulations (o/w and w/o) and hydrophilic petrolatum USP were prepared with 2% drug content. Drug release from all vehicles through a standard cellophane membrane was evaluated by using Franz-type diffusion cells. In vitro release study results showed that the diffusion coefficients of the drug from vehicles rank according to the following order: Carbopol 940 gel (D = 3.11 x 10(-7) +/- 0.54 cm(2)/s) > chitosan gel (D = 0.27 x 10(-7) +/- 0.08 cm(2)/s) > emulsion-based ointment (o/w) (D = 0.18 x 10(-7) +/- 0.05 cm(2)/s) > emulsion-based ointment (w/o) (D = 0.13 x 10(-7) +/- 0.02 cm(2)/s) > hydrophilic petrolatum USP (D = 0.02 x 10(-7) +/- 0.01 cm(2)/s). Carbopol 940 gel base showed significantly higher drug release than other vehicles (P < 0.001). These results indicated that Carbopol 940 gel base is a good candidate for the topical delivery of TA, giving significantly higher drug release than the other vehicles.     

西咪替丁注射液与丹参注射液配伍在不同时段的稳定性

目的 采用高效液相色谱技术研究分析西咪替丁注射液与丹参注射液配伍的稳定性情况.方法 分别制备西咪替丁注射液与丹参注射液混合液的待检样品,进行高效液相色谱分析,观察西咪替丁注射液与丹参注射液配伍溶液外观、pH值变化及不溶性微粒数情况,检测配伍溶液的回收率及质量浓度变化情况.结果 西咪替丁注射液与丹参注射液配伍的溶液0～2...     

氨苯砜脂质体的制备及其体外释放考察

目的:制备氨苯砜脂质体,并进行体外释放考察。方法:采用不同方法制备氨苯砜脂质体,以包封率为指标,确定合适的制备方法,并对制备的脂质体进行质量考察及体外释放考察。结果:薄膜-超声法制备脂质体方便简单,包封率较高。与混悬液相比,其体外释放有明显缓释特征。结论:薄膜-超声法适于制备氨苯砜脂质体,所得制剂体外释放有明显缓释特征。     

Cytotoxic effect of different camptothecin formulations on human colon carcinoma in vitro

Two innovative 20-S-camptothecin (CPT) formulations, previously found suitable to achieve therapeutically relevant CPT concentrations, were assessed for their in vitro cytotoxic potential as compared to an aqueous CPT solution, using the MTT assay. The formulations, cationic CPT-containing liposomes (CPT-Lip), hydroxypropyl-beta-cyclodextrin (HP-beta-CD) complexed CPT (CPT-CD) and a saturated aqueous CPT solution (CPT-Sol), were diluted in culture medium to appropriate CPT concentrations (4.7-300 ng/ml), and incubated with HT-29 and SW-480 human colon carcinoma cell lines. IC50 values were calculated after 48 and 72 h incubation for the HT-29 and SW-480 cell lines, respectively, and were found to be of the same magnitude for all formulations, with only a slight difference (CPT-Sol相似文献   

pH敏感多肽修饰载紫杉醇脂质体的制备及评价

目的制备p H敏感多肽修饰载紫杉醇脂质体(p HS-LP-PTX),并评价其体外性质。方法采用薄膜分散法制备PHS-LP-PTX,MTT实验考察脂质体对MCF-7细胞和Hep G2细胞的毒性,通过细胞摄取实验考察脂质体与肿瘤细胞的结合能力。结果所制备的p HS-LP-PTX在p H6.4时平均粒径为125.5±13.4 nm,Zeta电位为10.47±2.53 m V,24 h内具有良好的血清稳定性。MTT结果显示:p H6.4时,p HS-LP-PTX的细胞毒性优于各对照组。体外细胞摄取实验表明:p H6.4时,MCF-7细胞和Hep G2细胞对p HS-LP-PTX的摄取效率优于p H7.4时和普通脂质体。结论紫杉醇脂质体经过p H敏感多肽修饰后,能增强脂质体在酸性环境下的细胞穿透能力,是一种良好的p H敏感型肿瘤靶向给药系统。     

Investigation of the effect of different adjuvants on felodipine release kinetics from sustained release monolithic films

A transdermal film was developed employing a calcium channel blocker, felodipine, with two acrylic resin polymers of varying permeability (Eudragit RL 100 and RS 100). The drug and two acrylic co-polymers of different permeabilities at ratio 1:1, with and without adjuvants were used to form films. Adjuvants, including polyethylene glycols (PEG 200, 400, 600, 1000), glycerol, ethoxydiglycol and propylene glycol were incorporated into films. The effect of these adjuvants on the release of drug from the films was investigated by the USP Method Apparatus II. The release data were evaluated kinetically using a computer programme (DISSOL). Drug release from the formulations containing 10% adjuvants showed zero order kinetics. The release profiles of the films which contained 10% glycerol and ethoxydiglycol were in most agreement with the target profile that was plotted based on the pharmacokinetic parameters. The relationship between the in vitro drug release data and moisture permeation constant and glass transition temperature was investigated. The in vitro release rate of drug increased with increasing water vapor transmission. No relationship was established between glass transition temperature values of the films and in vitro release of drug.     

总姜黄素脂质体的包封率和体外释药测定

目的:研究总姜黄素脂质体的包封率测定方法,初步考察其体外释放规律。方法:用乙醇注入法制备了总姜黄素脂质体,葡聚糖凝胶 G-50柱分离方法测定脂质体的包封率,并用溶出度第三法考察脂质体的体外释放过程。分析柱为岛津 C_(18)色谱柱(150 mm×4.6 mm,5μm),乙腈-水-冰醋酸(45:55:2)为流动相,流速1mL·min~(-1),检测波长430nm。结果:总姜黄素脂质体的平均包封率为64.4%,体外释放符合一室模型。结论:该方法简便、易操作,可作为总姜黄素脂质体包封率和体外释药的研究。     

In vitro release,rheological, and stability studies of mefenamic acid coprecipitates in topical formulations

A suitable topical formulation of mefenamic acid was developed in order to eliminate the gastrointestinal disorders associated with its oral administration. Drug coprecipitates prepared with different polymers at various drug-to-polymer ratios improved drug solubility and dissolution compared to pure drug and physical mixtures. PVP polymers (ratio 1:4) produced the best results. Aqueous ionic cream, ointments of absorption and water soluble bases and gels of methylcellulose, carboxymethylcellulose sodium, HPMC, Carbopol^® 934 and 940, and Pluronic^® F127 bases containing 1–10% drug as coprecipitates of PVP polymers (1:4) were prepared. The highest drug release was achieved at 1% drug concentration from water soluble base and methylcellulose among cream/ointment and gel bases, respectively. Gels, in general yielded better release than creams/ointments. All tested medicated creams/ointments exhibited plastic flow while all gels conformed to pseudoplasticity. Most of them showed thixotropy, a desired property of topical preparations. Stability studies revealed that HPMC and methylcellulose had the smallest changes in drug content, viscosity, and pH among the formulations. Considering drug release, rheological properties, and stability, methylcellulose gel containing 1% drug as coprecipitates of PVP K90 was the best among the studied formulations, was promising for improving bioavailability of mefenamic acid and can be used in future studies.     

异维A酸固体脂质纳米粒的制备和稳定性考察

目的采用固体脂质纳米粒作为异维A酸载体,以提高其稳定性。方法采用纳米乳法制备异维A酸固体脂质纳米粒。结果制得的固体脂质纳米粒为球形粒子,平均粒径为53．23nm,包封率〉97％。25℃和40℃避光贮存6个月,含量和包封率均无明显变化。     

Effect of polymeric stabilizers on the size and stability of PLGA paclitaxel nanoparticles

The aim of this study is to formulate polymeric paclitaxel nanoparticles with various stabilizers to improve solubility, enhance stability, maximize therapeutic efficacy and minimize detrimental toxicities of paclitaxel. In this study, trastuzumab-guided poly lactic-co-glycolic acid (PLGA)-loaded paclitaxel nanoparticles were formulated with pluronic F-127, polyvinyl alcohol (PVA), poloxamer 407, Tween-80, span 20, sodium dodecyl sulfate (SDS), and sodium lauryl sulfate (SLS) at different concentrations (0.5, 1, 1.5 and 2%) using the solvent evaporation method. The nanoparticles were evaluated for physicochemical characteristics and short and long-term stability. The optimum particle size (190 nm ± 12.42 to 350 nm ± 11.1), PDI (0.13 ± 0.02 to 0.2 ± 0.01), surface charge (-19.1mv ± 1.5 to −40.4mv ± 1.6), drug loading (2.43 to 9.5 %) and encapsulation efficiency (greater than 80 %) were obtained with these stabilizers while keeping the polymer concentration, temperature, probe size, amplitude and sonication time constant. The nanoformulations were stably stored at 4 °C. The nanoformulations of paclitaxel with pluronic F-127, polyvinyl alcohol (PVA), and poloxamer 407 were found to be more soluble, stable, uniform in physicochemical properties, and efficient in drug loading and encapsulation for improved therapeutic effects.     

In vitro evaluation of quercetin cutaneous absorption from topical formulations and its functional stability by antioxidant activity

Recently, it was demonstrated that two different formulations containing quercetin inhibit the UVB-induced cutaneous oxidative stress and inflammation. Therefore, in the present study it was evaluated the functional stability of those formulations by the antioxidant activity, the release of quercetin from the formulations, and its skin retention using modified Franz diffusion cells. Both formulations tested ((1) non-ionic emulsion with high lipid content and (2) anionic emulsion with low lipid content) remained functionally (hydrogen-donating ability) stable during 180 days. Furthermore, quercetin was released from both formulations as determined using nitrocellulose membrane. In vitro antioxidant activity of retained quercetin into the skin was observed for both formulations as detected by the inhibition of malondialdehyde formation. The effect of quercetin retention was time-dependent for formulation 1. Concluding, this study demonstrates that quercetin remains functionally stable in formulations, and measuring the antioxidant activity is an efficient approach to evaluate quercetin skin retention with minimal interference of the tissue products. Furthermore, the present results on skin retention explain the previous study on quercetin in vivo activities, and together, these data suggest that formulations containing quercetin may be used as topical active products to control UVB-mediated oxidative damage of the skin.