In vitro and in vivo studies evaluating a liposome system for drug solubilization

In Vitro and Ex Vivo Evaluations of Lipid Anti-Cancer Nanoformulations: Insights and Assessment of Bioavailability Enhancement

Lipid-based nanoformulations have been extensively investigated for improving oral efficacy of plethora of drugs. Chemotherapeutic agents remain a preferred option for effective management of cancer; however, most chemotherapeutic agents suffer from limitation of poor oral bioavailability that is associated with their physicochemical properties. Drug delivery via lipid-based nanosystems possesses strong rational and potential for improving oral bioavailability of such anti-cancer molecules through various mechanisms, viz. improving their gut solubilisation owing to micellization, improving mucosal permeation, improving lymphatic uptake, inhibiting intestinal metabolism and/or inhibiting P-glycoprotein efflux of molecules in the gastrointestinal tract. Various in vitro characterization techniques have been reported in literature that aid in getting insights into mechanisms of lipid-based nanodevices in improving oral efficacy of anti-cancer drugs. The review focuses on different characterization techniques that can be employed for evaluation of lipid-based nanosystems and their role in effective anti-cancer drug delivery.

"Evolving nanoparticle gene delivery vectors for the liver: What has been learned in 30 years"

Nonviral gene delivery to the liver has been under evolution for nearly 30years. Early demonstrations established relatively simple nonviral vectors could mediate gene expression in HepG2 cells which understandably led to speculation that these same vectors would be immediately successful at transfecting primary hepatocytes in vivo. However, it was soon recognized that the properties of a nonviral vector resulting in efficient transfection in vitro were uncorrelated with those needed to achieve efficient nonviral transfection in vivo. The discovery of major barriers to liver gene transfer has set the field on a course to design biocompatible vectors that demonstrate increased DNA stability in the circulation with correlating expression in liver. The improved understanding of what limits nonviral vector gene transfer efficiency in vivo has resulted in more sophisticated, low molecular weight vectors that allow systematic optimization of nanoparticle size, charge and ligand presentation. While the field has evolved DNA nanoparticles that are stable in the circulation, target hepatocytes, and deliver DNA to the cytosol, breaching the nucleus remains the last major barrier to a fully successful nonviral gene transfer system for the liver. The lessons learned along the way are fundamentally important to the design of all systemically delivered nanoparticle nonviral gene delivery systems.

Lipophilic drug transfer between liposomal and biological membranes: what does it mean for parenteral and oral drug delivery?

This review presents the current knowledge on the interaction of lipophilic, poorly water soluble drugs with liposomal and biological membranes. The center of attention will be on drugs having the potential to dissolve in a lipid membrane without perturbing them too much. The degree of interaction is described as solubility of a drug in phospholipid membranes and the kinetics of transfer of a lipophilic drug between membranes. Finally, the consequences of these two factors on the design of lipid-based carriers for oral, as well as parenteral use, for lipophilic drugs and lead selection of oral lipophilic drugs is described. Since liposomes serve as model-membranes for natural membranes, the assessment of lipid solubility and transfer kinetics of lipophilic drug using liposome formulations may additionally have predictive value for bioavailability and biodistribution and the pharmacokinetics of lipophilic drugs after parenteral as well as oral administration.

Transfer of lipophilic drugs between liposomal membranes and biological interfaces: Consequences for drug delivery

This review paper describes the present knowledge on the interaction of lipophilic, poorly water soluble, drugs with liposomal membranes and the reversibility of this interaction. This interaction is discussed in the context of equilibrium and spontaneous transfer kinetics of the drug, when the liposomes are brought in co-dispersion with other artificial or natural phospholipid membranes in an aqueous medium. The focus is on drugs, which have the potential to partition (dissolve) in a lipid membrane but do not perturb membranes. The degree of interaction is described as solubility of a drug in phospholipid membranes and the kinetics of transfer of a lipophilic drug between membranes. Finally, the consequences of these two factors on the design of lipid based carriers for oral, as well as parenteral use, for lipophilic drugs and lead selection of oral lipophilic drugs is described. Since liposomes serve as model-membranes for natural membranes, the assessment of lipid solubility and transfer kinetics of lipophilic drug using liposome formulations may additionally have predictive value for bioavailability and biodistribution and the pharmacokinetics of lipophilic drugs after parenteral as well as oral administration.

Phosphonocationic lipids in protein delivery to mice lungs

Cationic liposomes constitute one of the main approaches currently investigated to introduce a gene with therapeutic properties into a cell. Another alternative consists in directly introducing the normal protein of concern to, for example, restore the deleted function. We report here on in vitro and in vivo results obtained with GLB73, one of the phosphonolipids investigated as gene transfer agents. In previous studies this cationic lipid had shown its DNA-transfer efficacy in vitro and in vivo. We also confirmed the feasibility of protein/cationic lipid delivery in epithelial cells of mice lungs after intratracheal administration by use of a reporter gene (beta-galactosidase). Two quantitative tests (i.e., a chemiluminescent assay and a flow cytometry assay) were used to determine the amount of beta-galactosidase found in the lungs and the percentage of transfected cells. They showed that 50% of the cells of mice lungs were still positive at day 4 after protein/GLB73 delivery. Immunohistochemistry and electron microscopy studies allowed us to determine the spatial distribution and visualize the penetration of our complex into the lungs.

Spectroscopic studies of tin ethyl etiopurpurin in homogeneous and heterogeneous systems

Tin ethyl etiopurpurin is a promising second generation photosensitizer for photodynamic treatment of cancer. This compound is only poorly soluble in aqueous media and, therefore, needs a delivery system for administration to animals. Successful tumor eradication has previously been reported, following light exposure of rats previously administered with the purpurin formulated as a Cremophor El emulsion, in dipalmitoyl-phosphatidyl-choline liposomes or with gamma cyclodextrins. In this paper, we describe some absorbance and fluorescence studies of tin ethyl etiopurpurin in homogeneous and heterogeneous systems. In general, absorption and emission maxima were found to be red shifted as the environment changed from polar to non-polar. The viscosity and dielectric constant of the medium affected the purpurin fluorescence intensity. The liposome preparations were characterized by particle size determination, differential scanning calorimetry and by sensitizer fluorescence quenching studies. Photobleaching studies also showed variation owing to changes in the environment in which the dye was located.