Lipid microspheres as drug carriers: a pharmaceutical point of view

Glycosylated Sertraline-Loaded Liposomes for Brain Targeting: QbD Study of Formulation Variabilities and Brain Transport

Effectiveness of CNS-acting drugs depends on the localization, targeting, and capacity to be transported through the blood-brain barrier (BBB) which can be achieved by designing brain-targeting delivery vectors. Hence, the objective of this study was to screen the formulation and process variables affecting the performance of sertraline (Ser-HCl)-loaded pegylated and glycosylated liposomes. The prepared vectors were characterized for Ser-HCl entrapment, size, surface charge, release behavior, and in vitro transport through the BBB. Furthermore, the compatibility among liposomal components was assessed using SEM, FTIR, and DSC analysis. Through a thorough screening study, enhancement of Ser-HCl entrapment, nanosized liposomes with low skewness, maximized stability, and controlled drug leakage were attained. The solid-state characterization revealed remarkable interaction between Ser-HCl and the charging agent to determine drug entrapment and leakage. Moreover, results of liposomal transport through mouse brain endothelialpolyoma cells demonstrated greater capacity of the proposed glycosylated liposomes to target the cerebellar due to its higher density of GLUT1 and higher glucose utilization. This transport capacity was confirmed by the inhibiting action of both cytochalasin B and phenobarbital. Using C6 glioma cells model, flow cytometry, time-lapse live cell imaging, and in vivo NIR fluorescence imaging demonstrated that optimized glycosylated liposomes can be transported through the BBB by classical endocytosis, as well as by specific transcytosis. In conclusion, the current study proposed a thorough screening of important formulation and process variabilities affecting brain-targeting liposomes for further scale-up processes.

Assessment of simvastatin niosomes for pediatric transdermal drug delivery

The prevalence of childhood dyslipidemia increases and is considered as an important risk factor for the incidence of cardiovascular disease in the adulthood. To improve dosing accuracy and facilitate the determination of dosing regimens in function of the body weight, the proposed study aims at preparing transdermal niosomal gels of simvastatin as possible transdermal drug delivery system for pediatric applications. Twelve formulations were prepared to screen the influence of formulation and processing variables on critical niosomal characteristics. Nano-sized niosomes with 0.31 μm number-weighted size displayed highest simvastatin release rate with 8.5% entrapment capacity. The niosomal surface coverage by negative charges was calculated according to Langmuir isotherm with n = 0.42 to suggest that the surface association was site-independent, probably producing surface rearrangements. Hypolipidemic activities after transdermal administration of niosomal gels to rats showed significant reduction in cholesterol and triglyceride levels while increasing plasma high-density lipoproteins concentration. Bioavailability estimation in rats revealed an augmentation in simvastatin bioavailability by 3.35 and 2.9 folds from formulation F3 and F10, respectively, compared with oral drug suspension. Hence, this transdermal simvastatin niosomes not only exhibited remarkable potential to enhance its bioavailability and hypolipidemic activity but also considered a promising pediatric antihyperlipidemic formulation.

QbD approach to investigate product and process variabilities for brain targeting liposomes

Efficacy of central nervous system-acting medications is limited by its localization and ability to cross the blood-brain barrier (BBB); therefore, the crux is in designing delivery systems targeted to cross the BBB. Toward this objective, this study proposed pegylated and glycosylated citalopram hydrobromide (Cit-HBr) liposomes as a delivery approach for brain targeting. The multicomponent liposomes were evaluated for drug encapsulation, vesicular size, size distribution, conductivity and drug release characteristics. Moreover, the interaction among the employed components was evaluated by Fourier transform infrared, differential scanning calorimetric and X-ray diffraction analysis. Through a systematic screening design of formulation and process variables in the optimization phase, an improvement of Cit-HBr loading, fine vesicular size with narrow size distribution, greater stability and sustained release features were achieved. The compatibility studies unveiled a significant interaction between Cit-HBr and dicetyl phosphate to control drug encapsulation and release properties. The optimization process showed a minimal range of design space to achieve the preset desirability; more precisely dicetyl phosphate, polyethylene glycol, N-acetyl glucosamine and freeze-thaw cycles of 3%, 5%, 4% and 2 cycles, respectively, were used. Using brain endothelial cell models, the optimized formulations showed an acceptable cell viability with preserved monolayer integrity and an enhanced flux and permeability. Thus, this study has proposed an optimized pegylated and glycosylated vector that is a promising step for brain targeting.

Formulation, preparation and evaluation of flunarizine-loaded lipid microspheres

The aim of this study was to investigate the feasibility of preparing flunarizine-loaded lipid microspheres. Lipid microspheres (LMs) are excellent drug carriers for drug delivery systems (DDS) and are relatively stable and easily mass-produced. They have no particular adverse effects. LMs have been widely studied as drug carriers for water-soluble drugs, lipid-soluble drugs and inadequately soluble (in water or in lipid) drugs, in that they have a lipid layer, a water layer and an emulsifier layer. Flunarizine (FZ), a poorly water-soluble drug, was incorporated in lipid microspheres to reduce side effects by avoiding the use of supplementary agents, compared with solution injection. After investigation, the final formulation was as follows: 10% oil phase (long-chain triglyceride (LCT); medium-chain fatty acid (MCT) = 50:50); 1.2% egg lecithin; 0.2% Tween-80; 2.5% glycerin; 0.3% dl-α-tocopherol; 0.02% EDTA; 0.03% sodium oleate; 0.1% FZ and double-distilled water to give a total volume of 100 mL. Homogenization was the main method of preparation and the best conditions were a temperature of 40°C, a pressure of 700–800 bar and a suitable cycle frequency of about 10. The particle size distribution, zeta-potential and entrapment efficacy were found to be 198.7 ± 54.0 nm, −26.4mV and 96.2%, respectively. Its concentration in the preparation was 1.0mg mL−1. The lipid microspheres were stable during storage at 4°C, 25°C and 37°C for 3 months. Pharmacokinetic studies were performed in rats using a dose of 1.0 mg kg−1. The pharmacokinetic parameters were as follows: AUC0-t 6.13 μg h mL−1, t½ 5.32 h and Ke 0.16 Lh−1. The preparation data fitted a two-compartment model estimated by using 3p87 analysis software. From the observed data, FZ encapsulated in LMs did not significantly alter the pharmacokinetic characteristic compared with the FZ solution injection and did not produce a delayed release effect, when it was released in-vivo in rats. However, the availability of the drug was increased. These results suggested that this LM system is a promising option for the preparation of the liquid form of FZ for intravenous administration.

A novel drug carrier: lipophilic drug-loaded polyglutamate/polyelectrolyte nanocontainers

A novel lipophilic drug carrier, "oil-in-water" multifunctional composite nanocontainers, is developed by combining ultrasonic technique and layer-by-layer assembly. Polyglutamate/polyethyleneimine/poly(acrylic acid) nanocontainers loaded with the lipophilic drug, rifampicin, dissolved in soybean oil were fabricated. Raman confocal microscopy and scanning electron microscopy proved the successful incorporation of rifampicin into composite water-dispersible polyglutamate/polyelectrolyte nanocontainers. Transmission electron microscopy and confocal laser scanning microscopy indicated that the drug can be released by changing the pH value of the media due to the pH-responsive properties of the polyglutamate/polyelectrolyte shell.

The effect of oil components on the physicochemical properties and drug delivery of emulsions: Tocol emulsion versus lipid emulsion

An emulsion system composed of vitamin E, coconut oil, soybean phosphatidylcholine, non-ionic surfactants, and polyethylene glycol (PEG) derivatives (referred to as the tocol emulsion) was characterized in terms of its physicochemical properties, drug release, in vivo efficacy, toxicity, and stability. Systems without vitamin E (referred to as the lipid emulsion) and without any oils (referred to as the aqueous micelle system) were prepared for comparison. A lipophilic antioxidant, resveratrol, was used as the model drug for emulsion loading. The incorporation of Brij 35 and PEG derivatives reduced the vesicle diameter to <100nm. The inclusion of resveratrol into the emulsions and aqueous micelles retarded the drug release. The in vitro release rate showed a decrease in the order of aqueous micelle system>tocol emulsion>lipid emulsion. Treatment of resveratrol dramatically reduced the intimal hyperplasia of the injured vascular wall in rats. There was no significant difference in this reduction when resveratrol was delivered by either emulsion or the aqueous micelle system. The percentages of erythrocyte hemolysis by the emulsions and aqueous micelle system were approximately 0 and approximately 10%, respectively. Vitamin E prevented the aggregation of emulsion vesicles. The mean vesicle size of the tocol emulsion remained unchanged during 30 days at 37 degrees C. The lipid emulsion and aqueous micelle system, respectively, showed 11- and 16-fold increases in vesicle size after 30 days of storage.

Effect of liposome encapsulation of tea catechins on their accumulation in basal cell carcinomas

BACKGROUND

(-)-Epigallocatechin gallate (EGCG), the main active polyphenol in green tea, is associated with antioxidant and anticancer activities.

OBJECTIVE

The aim of this study was to evaluate the feasibility of using liposomes for intratumor distribution of EGCG and its derivative, (+)-catechin.

METHOD

Liposomes containing egg phosphatidylcholine, cholesterol, or anionic surfactant in the presence of 15% ethanol were prepared. The physicochemical characteristics including vesicle size, zeta potential, drug entrapment, and drug release of liposomal formulations were determined. The liposomes containing EGCG were injected into basal cell carcinomas (BCCs), melanomas, and colon tumors to examine the tumor uptake of the drug. Liposomes were also incubated with a given number of BCC cells, and the cell viability was estimated.

RESULT

Almost no drug molecules were observed when free EGCG was administered to BCCs. EGCG encapsulated in liposomes with deoxycholic acid (DA) and ethanol increased drug deposition by 20-fold as compared to the free form. The larger vesicle size of this formulation was suggested to be the predominant factor governing this enhancement. The liposomes without ethanol showed low or negligible enhancement on EGCG uptake in BCCs. Liposomes protected EGCG from degradation, resulting in the induction of greater BCC death compared to that by free EGCG at lower concentrations.

CONCLUSION

These results suggest that the intratumor injection of liposomes containing EGCG with moderate modification is an effective approach for increasing EGCG deposition in BCCs.

Enhancement of the transdermal delivery of catechins by liposomes incorporating anionic surfactants and ethanol

The aim of this study was to develop and evaluate liposomal formulations encapsulating tea catechins, which possess antioxidant and chemopreventive activities. Liposomes were characterized for size, zeta potential, and entrapment efficiency. Both in vitro and in vivo skin permeation were examined using nude mouse skin as a model. The results suggested that the liposomal composition plays an important role in affecting the efficiency of transdermal catechin delivery. Incorporation of anionic surfactants such as deoxycholic acid (DA) and dicetyl phosphate (DP) in the liposomes in the presence of 15% ethanol increased the (+)-catechin permeation by five to seven-fold as compared to the control. The flexibility of bilayers is suggested as an important factor governing the enhancing effect of liposomes. Intercellular spaces within the stratum corneum but not shunt routes are the major pathways for catechin delivery from liposomes. (+)-Catechin and (-)-epicatechin are isomers which showed similar encapsulation efficiencies and skin permeation in liposomes. (-)-Epigallocatechin-3-gallate showed the highest encapsulation rate and in vivo skin deposition level in liposomes among all catechins tested. The stability and in vitro tranepidermal water loss test indicated the safety of the practical use of liposomes developed in this study.

Pharmacokinetic Study of Ketoprofen Isopropyl Ester-Loaded Lipid Microspheres in Rat Blood Using Microdialysis

A blood microdialysis technique coupled with high-performance liquid chromatography was used to investigate the pharmacokinetics of unbound ketoprofen in rats after intravenous administration of a lipid-soluble ketoprofen derivate, ketoprofen isopropyl ester (KPI), loaded into lipid microspheres (LM) and ketoprofen solution. A microdialysis probe was inserted into the jugular vein of male Wistar rats. KPI-loaded LM or ketoprofen solution (24 mg/kg, i.v.) was then administrated via a femoral vein. Dialysate samples were analyzed using HPLC. The in vitro and in vivo recovery rate of the microdialysis probe was 30.42+/-0.74% (n=3) and 40.27+/-2.74% (n=3), respectively. The pharmacokinetic parameters for ketoprofen after intravenous administration of KPI-loaded LM and ketoprofen solution exhibited no statistically significant differences. The results of this pharmacokinetic study indicate that the microdialysis technique can be widely applicable to investigations of in vivo free-drug of microcarrier systems.

Properties of various phosphatidylcholines as emulsifiers or dispersing agents in microparticle preparations for drug carriers

We investigated characteristics of various phosphatidylcholines (PCs) used as dispersing agents and emulsifiers. Six PCs with different lengths of acyl hydrocarbon chains and different degrees of unsaturated acyl hydrocarbon chains were selected to examine influences of a lipophillic part of phosphatidylcholines in emulsion and dispersion systems. Vesicles and oil-in-water emulsions were prepared by sonication under several ambient temperature conditions. Mean diameters of vesicles and oil droplets in emulsions were measured by a submicron particle sizer. In vesicles that are generated by hydration of the PCs and have a bilayer form, particle size was influenced by length and degree of unsaturation of acyl hydrocarbon chains of a PC. PCs with shorter acyl hydrocarbon chains or unsaturated bonds are considered more potent dispersing agents. Preparation temperature of the PC is also a factor affecting potency of dispersion. In O/W emulsions in which PCs were absorbed at water-oil interfaces and which have a single layer form or liquid-crystal layer form, particle size was also influenced by length and degree of unsaturation of acyl hydrocarbon chains of a PC. PCs with shorter and saturated acyl hydrocarbon chains are considered more potent emulsifiers. Unsaturation of acyl hydrocarbon chains weaken the ability of emulsification due to vulnerable double bonds. For stable emulsions, it is considered beneficial for PCs to form small oil droplets and lamellae liquid-crystal phase. From this perspective, saturated PCs with short hydrocarbon chains, i.e., DLPC and DMPC, may have advantages in preparing a stable emulsion not only by giving a smaller droplet size but also by forming lamellae liquid-crystal phase. When considering characteristics of PCs as emulsifiers, their characteristics as dispersing agents is also useful information.

Toward development of a non-viral gene therapeutic

Gene therapy is an emerging field that has reached the early clinical stages of development for some disease states. However, the demonstration of safety in animals and the introduction of gene-based formulations in humans hides the fact that numerous developmental and basic research questions remain. This article highlights progress and emerging issues in the area of liposome-based non-viral gene delivery. The colloidal nature of these formulations render them complicated at the physico-chemical and biological levels. Instrumentation and methodologies need to be developed to better understand the subtleties of plasmid DNA, complexing agents, delivery mode and the route of entry into the cell and the nucleus. Major hurdles to entry include membrane binding, endosomal release, nuclear uptake and decomplexation. Each 'stage' is poorly understood but numerous approaches are being directed to increase cellular delivery. These research efforts, coupled with sensible formulation research and a multi-disciplinary, long-term effort, are necessary for success.