Development of a nanoparticulate formulation of diminazene to treat African trypanosomiasis.

There is a real need to develop new therapeutic strategies for African trypanosomiasis infections. In our study, we developed a new drug delivery system of diminazene (DMZ), a trypanocidal drug registered for veterinary use. This drug candidate presents a limited efficacy, a poor affinity for brain tissue and instability. The development of colloidal formulations based on a porous cationic nanoparticle with an oily core ((70)DGNP(+)), has potentially two advantages: stabilization of the drug and potential targeting of the parasite. We analyzed two processes of drug loading: in process (DMZ was added during the preparation of (70)DGNP(+) at 80 °C) and post-loading (DMZ was mixed with a (70)DGNP(+) solution at room temperature). Poor stability of the drug was observed using the in process technique. When using the post-loading technique over 80% drug entrapment efficiency was obtained at a ratio of DMZ:phospholipids (wt:wt) < 5%. Moreover, DMZ loaded into (70)DGNP(+) was found to be protected against oxidation and was stable for at least six months at 4 °C. Finally, in vitro tests on T.b. brucei showed an increased efficacy of DMZ loaded in (70)DGNP(+).

Characterization of endocytosis of transferrin-coated PLGA nanoparticles by the blood-brain barrier.

Many studies showed that transferrin increases brain delivery of nanoparticles (NPs) in vivo, however the mechanisms implied in their brain uptake are not yet clearly elucidated. In this study we evaluated the endocytosis of PLGA NPs coated with transferrin on an in vitro model of the blood-brain barrier (BBB) made of a co-culture of brain endothelial cells and astrocytes. PLGA NPs were prepared using DiI as a fluorescent marker and coated with Tween 20, BSA and transferrin (Tf). Blank and BSA-NPs served as controls. The cellular toxicity on BBB of the different samples was evaluated following tight junction aperture and due to high toxicity NPs prepared with Tween 20 were discarded. The size of the NPs prepared by the solvent diffusion method, varied from 63 to 90 nm depending on DiI incorporation and surface coating. Proteins adsorption on the surface of the NPs was found to be stable for at least 12 days at 37 degrees C. Contrary to Blank or BSA-NPs, Tf-NPs were found to be highly adsorbed by the cells and endocytosed using an energy-dependent process. Studies in presence of inhibitors suggest that Tf-NPs interact with the cells in a specific manner and enter the cells via the caveolae pathway.

Chapter 1 - Drug delivery to the brain using colloidal carriers.

Many neurodegenerative diseases, cancer, and infections of the brain become more prevalent as populations become older. Despite major advances in neuroscience, the blood-brain barrier (BBB) ensures that many potential therapeutics cannot reach the central nervous system (CNS). The BBB is formed by the complex tight junctions between the endothelial cells of the brain capillaries and their low endocytic activity. It results in the capillary wall that behaves as a continuous lipid bilayer and prevents the passage of polar substances. Drug delivery to the brain has remained one of the most vexing problems in translational neuroscience research, because of the difficulties posed by the BBB. Several strategies for delivering drugs to the CNS have been developed. This review rationalizes the strategies to target drugs to the brain by using different colloids.

Influence of surface charge and inner composition of porous nanoparticles to cross blood-brain barrier in vitro.

The aim of these studies was to evaluate the binding, uptake and transcytosis of 60 nm porous nanoparticles (NPs) that differed in their surface charge and inner composition on the blood-brain barrier (BBB). They were prepared from maltodextrins derived with or without a cationic ligand. In the cationic NPs an anionic lipid was inserted in their core to give DPPG-NPs. The data showed that at 4 degrees C the three NPs bind in different areas on endothelial cells: cationic NPs were found mainly around the paracellular area, while neutral NPs were mainly on the cell surface and DPPG-NPs binding was found at both paracellular areas and on the surface of the cells. At 37 degrees C neutral and cationic NPs had similar degrees of binding and uptake and were transcytosed. Filipin treatment increased their binding and uptake suggesting that sterols are implied in their efflux. Neutral NPs transcytosis was also inhibited by filipin. This inhibition shows that neutral NPs, like LDL in this model, use the caveolae pathway. Neutral and cationic 60 nm porous NPs are potential candidates for drug delivery to the brain.