Encapsulation of Enrofloxacin in Liposomes I: Preparation and In Vitro Characterization of LUV

Cholesterol-Conjugate as a New Strategy to Improve the Cytotoxic Effect of 5-Fluorouracil on Liver Cancer: Impact of Liposomal Composition

Purpose:

Hepatocellular carcinoma (HCC) is a common liver malignancy, which has a low survival rate of all cancers. 5-fluorouracil (5-FU) is clinically recognized to treat HCC. However, the success of this therapy is highly limited due to rapid clearance and non- selective distribution. Cholesterol- conjugate (5-FUC) loaded liposomes proposed to facilitate the transport of 5-FUC into tumor cells via Low-Density Lipoprotein receptor (LDL receptor) that overexpressed in HCC. Thus, the aim of this study was to use 5-FUC loaded liposome as a promising strategy to combat HCC and improve the response of HCC to chemotherapy.

Methods:

5-FUC and 5-FU loaded liposomes were optimized based on Cholesterol (CHO) ratio and type of phospholipid to achieve a potential effect on HCC. Liposomes were prepared by the thin-film hydration method, and evaluated in terms of particle size, polydispersity, zeta potential, Entrapment Efficiency (EE), morphology, drug release and cytotoxicity.

Results:

The obtained liposomes had a suitable nano-range particle size with negative zeta potential, and acceptable EE%. In vitro drug release of 5-FUC loaded liposomes showed a lower cumulative release over 24 h as compared to 5-FU loaded liposomes. 5-FUC loaded liposomes exhibited a higher in vitro cytotoxic effect as compared to the free drug and 5-FU loaded liposomes against HepG2 cell lines after 48 h via MTT assay.

Conclusion:

These results concluded that 5-FUC loaded liposomes could be used as an alternative tactic to increase the therapeutic index of 5-FU and pave the way for potential clinical applications.

A pre-formulation strategy for the liposome encapsulation of new thioctic acid conjugates for enhanced chemical stability and use as an efficient drug carrier for MPO-mediated atherosclerotic CVD treatment

Lipoyl-apocynin and lipoyl-sesamol are bio-active conjugates of thioctic acid, synthesized using a benign chemical approachviathe combination of thioctic acid and the powerful bio-phytonutrients, apocynin and sesamol, respectively.

Recent advances in testing of microsphere drug delivery systems

INTRODUCTION

This review discusses advances in the field of microsphere testing.

AREAS COVERED

In vitro release-testing methods such as sample and separate, dialysis membrane sacs and USP apparatus IV have been used for microspheres. Based on comparisons of these methods, USP apparatus IV is currently the method of choice. Accelerated in vitro release tests have been developed to shorten the testing time for quality control purposes. In vitro-in vivo correlations using real-time and accelerated release data have been developed, to minimize the need to conduct in vivo performance evaluation. Storage stability studies have been conducted to investigate the influence of various environmental factors on microsphere quality throughout the product shelf life. New tests such as the floating test and the in vitro wash-off test have been developed along with advancement in characterization techniques for other physico-chemical parameters such as particle size, drug content, and thermal properties.

EXPERT OPINION

Although significant developments have been made in microsphere release testing, there is still a lack of guidance in this area. Microsphere storage stability studies should be extended to include microspheres containing large molecules. An agreement needs to be reached on the use of particle sizing techniques to avoid inconsistent data. An approach needs to be developed to determine total moisture content of microspheres.

PEGylated liposomes of anastrozole for long-term treatment of breast cancer: in vitro and in vivo evaluation

The aim of present study was to develop conventional and PEGylated (long circulating), liposomes containing anastrozole (ANS) for effective treatment of breast cancer. ANS is a third-generation non-steroidal aromatase inhibitor of the triazole class used for the treatment of advanced and late-stage breast cancer in post-menopausal women. Under such disease conditions the median duration of therapy should be prolonged until tumor regression ends (>31 months). Liposomes were prepared by the thin film hydration method by using ANS and various lipids such as soyaphosphatidyl choline, cholesterol and methoxy polyethylene glycol distearoyl ethanolamine in different concentration ratios and evaluated for physical characteristics, in vitro drug release and stability. Optimized formulations of liposome were studied for in vitro cytotoxic activity against the BT-549 and MCF-7 cell lines and in vivo behavior in Wistar rats. Preformulation studies, both Fourier transform infrared study and differential scanning calorimetry analysis showed no interaction between the drug and the excipients used in the formulations. The optimized formulations AL-07 and AL-09 liposomes showed encapsulation efficiencies in the range 65.12 ± 1.05% to 69.85 ± 3.2% with desired mean particle size distribution of 101.1 ± 5.9 and 120.2 ± 2.8 nm and zeta potentials of -43.7 ± 4.7 and -62.9 ± 3.5 mV. All the optimized formulations followed Higuchi-matrix release kinetics and when plotted in accordance with the Korsemeyer-Peppas method, the n-value 0.5 < n < 1.0 suggests an anomalous (non-Fickian) transport. Likewise, the PEGylated liposomes showed greater tumor growth inhibition on BT-549 and MCF-7 cell lines from in vitro cytotoxicity studies (p < 0.05). Pharmacokinetic study of conventional and PEGylated liposomes in Wistar rats demonstrated a 3.33- and 20.28-fold increase in AUC(0-∞) values when compared to pure drug (p < 0.001). Among the formulations, PEGylated liposomes showed encouraging results by way of their long circulation and sustained delivery properties for effective treatment of breast cancer.

Effective topical delivery systems for corticosteroids: dermatological and histological evaluations

Atopic dermatitis (AD) is a chronic and relapsing skin disease with severe eczematous lesions. Long-term topical corticosteroid treatment can induce skin atrophy, hypopigmentation and transepidermal water loss (TEWL) increase. A new treatment approach was needed to reduce the risk by dermal targeting. For this purpose, Betamethasone valerate (BMV)/Diflucortolone valerate (DFV)-loaded liposomes (220-350 nm) were prepared and incorporated into chitosan gel to obtain adequate viscosity (∼13 000 cps). Drugs were localized in stratum corneum + epidermis of rat skin in ex-vivo permeation studies. The toxicity was assessed on human fibroblast cells. In point of in-vivo studies, pharmacodynamic responses, treatment efficacy and skin irritation were evaluated and compared with previously prepared nanoparticles. Liposome/nanoparticle in gel formulations produced higher paw edema inhibition in rats with respect to the commercial cream. Similar skin blanching effect with commercial creams was obtained via liposome in gels although they contain 10 times less drug. Dermatological scoring results, prognostic histological parameters and suppression of mast cell numbers showed higher treatment efficiency of liposome/nanoparticle in gel formulations in AD-induced rats. TEWL and erythema measurements confirmed these results. Overview of obtained results showed that liposomes might be an effective and safe carrier for corticosteroids in skin disease treatment.

Preparation of nanobubbles for ultrasound imaging and intracelluar drug delivery

Echogenic bubble formulations have wide applications in both disease diagnosis and therapy. In the current study, nanobubbles were prepared and the contrast agent function was evaluated in order to study the nanosized bubble's property for ultrasonic imaging. Coumarin-6 as a model drug was loaded into nanobubbles to investigate the drug delivery potential to cells. The results showed that the nanobubbles composed of 1% of Tween 80, and 3 mg/ml of lipid worked well as an ultrasonic contrast agent by presenting a contrast effect in the liver region in vivo. The drug-loaded nanobubbles could enhance drug delivery to cells significantly, and the process was analyzed by sigmoidally fitting the pharmacokinetic curve. It can be concluded that the nanobubble formulation is a promising approach for both ultrasound imaging and drug delivery enhancing.

In Vitro Evaluation of Enrofloxacin-Loaded MLV Liposomes

Fluoroquinolones are broad-spectrum antimicrobial agents that seem to reach their intracellular target site (DNA gyrase) in Escherichia coli by means of an uptake process through the outer and inner membranes. Delivery of quinolones with liposomes has many advantages than the free form of the drug. Liposomes may represent an excellent device for improving the selective transport of antibiotics in these respects. In this study, enrofloxacin-loaded multilamellar vesicles (MLVs) were prepared and the effects of formulation variables on the liposome characteristics were investigated. Liposomes were prepared by using the dry lipid film method. A number of variables, such as phospholipid (DL-alpha -phosphatidylcholine dipalmitoyl), cholesterol, enrofloxacin (ENF), stearylamine, and dicetyl phosphate molar ratios and alpha -tocopherol amounts, were studied. The liposome size, encapsulation capacity, drug release, stability, and electrophoretic mobility of ENF-loaded liposomes were determined. Using this method, spherical MLVs with high drug content could be produced. Particle size of liposomes changed between 1.63 and 3.31 micro m and liposome size was affected by all formulation variables (p < 0.05) except molar ratio of ENF. MLVs can be used as a carrier system for the controlled release of ENF. The highest encapsulation of ENF amount can be obtained using positively charged SA in the formulation and changing the formulation parameters can vary drug release patterns.

Mesoporous silica nanomaterial-based biotechnological and biomedical delivery systems

This review details the recent advancements in the design of mesoporous silica nanomaterials for controlled release drug, gene and neurotransmitter delivery applications. The high surface area (>900 m2/g), tunable pore diameter (2–20 nm) and uniform mesoporous structure (hexagonal channels or cubic pores) of the mesoporous silicas offer a unique advantage for loading and releasing large quantities of biomedical agents. Recent breakthroughs in controlling the particle size and shape of these materials have greatly improved the biocompatibility and the cellular uptake efficiency. The strategy of using various removable capping moieties, such as photo- or redox-responsive organic groups, inorganic nanoparticles, dendrimers and polymers, to encapsulate guest biomolecules inside the porous matrices further enables the utilization of these surface-functionalized mesoporous silica nanomaterials for stimuli-responsive controlled release in vitro and in vivo. In addition to the reviewed studies, many new and exciting applications of these novel materials will soon be realized.

Spectroscopic studies of D-alpha-tocopherol concentration-induced transformation in egg phosphatidylcholine vesicles

The effects of embedding up to 60 mol% of α-tocopherol (α-Toc) on the morphology and structure of the egg phosphatidylcholine (PC) membrane were studied using spectroscopic techniques. The resulting vesicles were subjected to turbidometric and dynamic light scattering measurements to evaluate their size distribution. The α-Toc intrinsic fluorescence and its quenching was used to estimate the tocopherol position in the membrane. Optical microscopy was used to visualize morphological changes in the vesicles during the inclusion of tocopherol into the 2 mg/ml PC membrane. The incorporation of up to 15 mol% of tocopherol molecules into PC vesicles is accompanied by a linear increase in the fluorescence intensity and the simultaneous formation of larger, multilamellar vesicles. Increasing the tocopherol concentration above 20 mol% induced structural and morphological changes leading to the disappearance of micrometer-sized vesicles and the formation of small unilamellar vesicles of size ranging from 30 to 120 nm, mixed micelles and non-lamellar structures.

Lipid vesicles in capillary electrophoretic techniques: characterization of structural properties and associated membrane-molecule interactions

This paper reviews the use of lipid vesicles as model membranes in capillary electrophoresis (CE). The history and utility of CE in the characterization of microparticles is summarized, focusing on the application of colloidal electromigration theories to lipid vesicles. For instance, CE experiments have been used to characterize the size, surface properties, enclosed volumes, and electrophoretic mobilities of lipid vesicles and of lipoprotein particles. Several techniques involving small molecules or macromolecules separated in the presence of lipid vesicles are discussed. Interactions between the analytes and the lipid vesicles - acting as a pseudostationary phase or coated stationary phase in electrokinetic chromatography (EKC) - can be used to obtain additional information on the characteristics of the vesicles and analytes, and to study the biophysical properties of membrane-molecule interactions in lipid vesicles and lipoproteins. Different methods of determining binding constants by EKC are reviewed, along with the relevant binding constant calculations and a discussion of the application and limitations of these techniques as they apply to lipid vesicle systems.