Towards a clinical application of freeze-dried squalene-based nanomedicines.

Squalene-adenosine (SQAd) nanoparticles (NPs) were found to display promising pharmacological activity similar to many other nanomedicines, but their long-term stability was still limited, and their preparation required specific know-how and material. These drawbacks represented important restrictions for their potential use in the clinic. Freeze-drying nanoparticles is commonly presented as a solution to allow colloidal stability, but this process needs to be adapted to each nanoformulation. Hence, we aimed at developing a specific protocol for freeze-drying SQAd NPs while preserving their structural features. NPs were lyophilised, resuspended and analysed by dynamic light scattering, atomic force microscopy and small-angle scattering. Among four different cryoprotectants, trehalose was found to be the most efficient in preserving NPs physico-chemical characteristics. Interestingly, we identified residual ethanol in NP suspensions as a key parameter which could severely affect the freeze-drying outcome, leading to NPs aggregation. Long-term stability was also assessed. No significant change in size distribution or zeta potential could be detected after three-month storage at 4 °C. Finally, freeze-dried NPs innocuity was checked in vitro on cultured hepatocytes and in vivo on mice. In conclusion, optimisation of freeze-drying conditions resulted in safe lyophilised SQAd NPs that can be easily stored, shipped and simply reconstituted into an injectable form.

Design, Preparation and Characterization of Modular Squalene-based Nanosystems for Controlled Drug Release.

This article reviews the innovative and original concept the "squalenoylation", a technology allowing the formulation of a wide range of drug molecules (both hydrophilic and lipophilic) as nanoparticles. The "squalenoylation" approach is based on the covalent linkage between the squalene, a natural and biocompatible lipid belonging to the terpenoid family, and a drug, in order to increase its pharmacological efficacy. Fundamentally, the dynamically folded conformation of squalene triggers the resulting squalene-drug bioconjugates to self-assemble as nanoparticles of 100-300 nm. In general, these nanoparticles showed long blood circulation times after intravenous administration and improved pharmacological activity with reduced side effects and toxicity. This flexible and generic technique opens exciting perspectives in the drug delivery field.

Influence of the nanoprecipitation conditions on the supramolecular structure of squalenoyled nanoparticles.

Hydrophobic organic compounds dissolved in a polar solvent can self-assemble into nanoparticles (NPs) upon nanoprecipitation into water. In the present study, we have investigated the structure of squalenacetyl-adenosine (SQAc-Ad) nanoparticles which were previously found to exhibit impressive neuroprotective activity. When obtained by nanoprecipitation of a SQAc-Ad ethanolic solution into water, two different supramolecular organizations of SQAc-Ad NPs were evidenced, depending on the water-to-ethanol volume ratio. It has been shown that a fraction of the solvent remained associated with the NPs, despite prolonged evaporation under reduced pressure after nanoprecipitation, and that this residual solvent dramatically affected their structure. This study points to the importance of being in the "Ouzo" region to minimize the amount and effect of residual solvent and to control the structure of NPs.

"Squalenoylcurcumin" nanoassemblies as water-dispersible drug candidates with antileishmanial activity.

Curcumin, a natural polyphenolic compound, showed antiparasitic potential, including trypanocidal and leishmanicidal activity, in several in vitro and in vivo models. The molecule is well tolerated in humans. However, it is insoluble in water and displays poor oral bioavailability as a result of low absorption. New derivatives of curcumin were prepared by esterification of one or two of its phenolic groups with 1,1',2-tris-norsqualenic acid. These "squalenoylcurcumins" were formulated as water-dispersible nanoassemblies of homogeneous size, and they proved to be stable. Squalenoylcurcumins were inactive against Trypanosoma brucei brucei trypomastigotes, even as nanoassemblies, in contrast with curcumin. However, against Leishmania donovani promastigotes, the activities of the squalenoylcurcumins and their nanoassemblies were enhanced relative to that of curcumin. In L. donovani axenic and intramacrophagic amastigotes, they showed activity in the range of miltefosine, with good selectivity indexes. In regard to their dispersibility in water and to the safety of curcumin, these nanoassemblies are promising candidates for preclinical study toward the treatment of visceral leishmaniasis.

Patrick Couvreur: inspiring pharmaceutical innovation.

Patrick Couvreur speaks to Hannah Stanwix, Managing Comissioning Editor: Professor Patrick Couvreur received his pharmacy degree from the Université Catholique de Louvain (Louvain-la-Neuve, Belgium) in 1972. He holds a PhD in pharmaceutical technology from the same university and completed a postdoctoral fellowship at the Eidgenössische Technische Hochschule (Zürich, Switzerland). Since 1984, Professor Couvreur has been Full Professor of Pharmacy at the Paris-Sud University (Paris, France) and was holder of the Chair of Innovation Technologique at the prestigious Collège de France (Paris, France). He has published more than 450 peer-reviewed articles and has an H-index of 73, with over 19,000 citations. Professor Coureur has been recognized by numerous national and international awards, including the 2004 Pharmaceutical Sciences World Congress Award, the prestigious Host Madsen Medal, the Prix Galien, the European Pharmaceutical Scientist Award 2011 from the European Federation of Pharmaceutical Sciences, the Médaille de l'Innovation from the Centre National de la Recherche Scientifique, and recently the European Inventor Award 2013 from the European Patent Office.

Nanoprecipitation and the "Ouzo effect": Application to drug delivery devices.

Biodegradable nanocarriers such as lipid- or polymer-based nanoparticles can be designed to improve the efficacy and reduce the toxic side effects of drugs. Under appropriate conditions, nanoprecipitation of a hydrophobic compound solution in a non-solvent can generate a dispersion of nanoparticles with a narrow distribution of sizes without the use of surfactant ("Ouzo" effect). The aim of this review is to present the main parameters controlling the nucleation and growth of aggregates in a supersaturated solution and the characteristics of the obtained nanoparticles. The importance of the kinetics of mixing of the solution containing the hydrophobic compound and the non-solvent is highlighted. Illustrative examples of polymeric nanoparticles for drug delivery or terpenoid-based nanoprodrugs obtained by nanoprecipitation are reported.