Retrovirus budding may constitute a port of entry for drug carriers

Nanotechnology: intelligent design to treat complex disease

The purpose of this expert review is to discuss the impact of nanotechnology in the treatment of the major health threats including cancer, infections, metabolic diseases, autoimmune diseases, and inflammations. Indeed, during the past 30 years, the explosive growth of nanotechnology has burst into challenging innovations in pharmacology, the main input being the ability to perform temporal and spatial site-specific delivery. This has led to some marketed compounds through the last decade. Although the introduction of nanotechnology obviously permitted to step over numerous milestones toward the development of the "magic bullet" proposed a century ago by the immunologist Paul Ehrlich, there are, however, unresolved delivery problems to be still addressed. These scientific and technological locks are discussed along this review together with an analysis of the current situation concerning the industrial development.

Characterization of a synthetic anionic vector for oligonucleotide delivery using in vivo whole body dynamic imaging

PURPOSE

To compare the pharmacokinetics and bioavailability of an oligonucleotide delivered in a free form or using cationic or anionic synthetic carrier systems.

METHODS

Whole body dynamic quantitative imaging and metabolism of a HIV antisense oligonucleotide intravenously administered either free or incorporated into synthetic carriers were compared in baboons. using non invasive positron emission tomography and an enzyme-based competitive hybridization assay, respectively.

RESULTS

In its free form, the oligonucleotide showed high liver and kidney concentration, rapid plasmatic degradation and elimination from the body. Use of a cationic vector slightly protected the oligonucleotide against degradation and enhanced uptake by the reticulo-endothelial system. In contrast, the anionic vector dramatically enhanced the uptake in several organs, including the lungs, spleen and brain, with a prolonged accumulation of radioactivity in the brain. Using this vector, intact oligonucleotide was detected in plasma for up to two hours after injection. and the T 1/2beta and distribution volume increased by 4- and 7-fold, respectively. No evidence of toxicity was found after a single dose administration.

CONCLUSIONS

The anionic vector improves significantly the bioavailability and the pharmacokinetics of the oligonucleotide, and is a promising delivery system for in vivo administration of therapeutic nucleic acids.

Inhibition of inositol uptake in astrocytes by antisense oligonucleotides delivered by pH-sensitive liposomes

An oligonucleotide of 20 bases, complementary to a region of the sodium/myo-inositol cotransporter (SMIT) mRNA, was used to investigate the uptake efficiency and activity of transferred antisense oligonucleotides with regard to substrate uptake. We compared the efficiency of oligonucleotide delivery after application of either free or liposome-encapsulated material. Delivery of liposome-encapsulated material (marker or oligonucleotides) into astrocytoma cells and primary astrocyte cultures was more effective with pH-sensitive liposomes [dioleoylphosphatidylethanolamine (DOPE)/cholesteryl hemisuccinate (CHEMS)] than with non-pH-sensitive liposomes (soy lecithin) or free material in solution. Antisense activity was evaluated by determination of myo-inositol uptake and detection of SMIT transcripts by RT-PCR. Encapsulation of oligonucleotides in pH-sensitive liposomes increased the inhibition of inositol uptake at least 50-fold compared with application of free oligonucleotides in solution.

Cytosolic drug delivery using pH- and light-sensitive liposomes

A growing body of literature describes the development and applications of novel targeting and/or contents release triggering schemes to improve the therapeutic index of drugs encapsulated within liposomes. This review focuses on literature appearing between January 1995-December 1997 that report 1) antibody and receptor-mediated targeting approaches for improving drug localization and 2) acid, enzymatic, thermal or photochemical triggering processes that destabilize membranes and improve drug bioavailability via cytoplasmic delivery of liposomal contents.

pH-sensitive liposomes as a carrier for oligonucleotides: a physico-chemical study of the interaction between DOPE and a 15-mer oligonucleotide in quasi-anhydrous samples

pH-sensitive liposomes made of dioleoylphosphatidylethanolamine (DOPE)/oleic acid (OA)/cholesterol (CHOL) mixtures were shown to be very promising carriers for oligonucleotides (ON). However, it appeared necessary to clarify the structural consequence of the interactions of ON with the liposome, and especially on DOPE, the lipid responsible for the pH sensitivity. The present study was carried out by differential scanning calorimetry and X-ray diffraction, at low hydration. In such a case, DOPE generally adopt a hexagonal phase. It could be shown that ON increased DOPE transition temperature and increased v/al, as a result of electrostatic interactions between ON and DOPE headgroups. OA was found to have exactly opposite effects, its presence between DOPE molecules inhibiting the formation of hydrogen bonds. The presence of both ON and OA allowed the system to organize in a lamellar phase below the solid/liquid transition, whereas above this temperature ON preferably interacted with DOPE in a hexagonal phase and led OA to separate.