Partial least squares analysis and mixture design for the study of the influence of composition variables on lipidic nanoparticle characteristics.

Lipidic nanoparticles (NP), formulated from a phase inversion temperature process, have been studied with chemometric techniques to emphasize the influence of the four major components (Solutol®, Labrasol®, Labrafac®, water) on their average diameter and their distribution in size. Typically, these NP present a monodisperse size lower than 200 nm, as determined by dynamic light scattering measurements. From the application of the partial least squares (PLS) regression technique to the experimental data collected during definition of the feasibility zone, it was established that NP present a core-shell structure where Labrasol® is well encapsulated and contributes to the structuring of the NP. Even if this solubility enhancer is regarded as a pure surfactant in the literature, it appears that the oil moieties of this macrogolglyceride mixture significantly influence its properties. Furthermore, results have shown that PLS technique can be also used for predictions of sizes for given relative proportions of components and it was established that from a mixture design, the quantitative mixture composition to use in order to reach a targeted size and a targeted polydispersity index (PDI) can be easily predicted. Hence, statistical models can be a useful tool to control and optimize the characteristics in size of NP.

How to characterize the dynamics of cold atoms in non-dissipative optical lattices?

We examine here the classical dynamics of cold atoms in square optical lattices, i.e. lattices obtained with two orthogonal stationary plane waves. Contrary to many of the past studies in this domain, the potential here is time independent and non-dissipative. We show that, as a function of the experimental parameters, very different behaviours are obtained, both for the dynamics of atoms trapped inside individual sites and for atoms travelling between sites: inside the sites, chaos may be the main regime or, on the contrary, it may be negligible; outside the sites, chaos sometimes coexists with other regimes. We discuss the consequences of these differences on the macroscopic behaviour of the atoms in the lattice, and we propose experimental measurements able to characterize these dynamics and to distinguish between the different cases.

Influence of the introduction of a solubility enhancer on the formulation of lipidic nanoparticles with improved drug loading rates.

The objective of the present paper is to develop lipidic nanoparticles (NP) able to encapsulate drugs presenting limited solubility in both water and lipids, with high loading rates, and without using organic solvents. In this goal, a solubility enhancer, a macrogolglyceride (Labrasol), was incorporated in a formulation process based on a low-energy phase inversion temperature method. From electrical conductivity through the temperature scans, it appears that presence of Labrasol does not prevent the phase inversion, and it takes part in the microemulsion structuring, probably of bicontinuous type. After screening pseudo-ternary diagrams, the feasibility of NP was established. From results of a partial least square analysis, it appears that these NP present a core-shell structure where Labrasol is well encapsulated and contributes to the formation of the oily liquid core of the NP. The diameter of the NP, assessed by dynamic light scattering, remains kinetically stable. These NP, smaller than 200 nm, spherical in shape as attested by cryo-transmission electron micrographs, are able to encapsulate a tripentone, a new anticancer agent, with drug loading rates up to 6.5% (w/w). So highly drug-loaded lipidic nanocarriers were developed without using the slightest organic solvent trace, and making it easily possible dose adjustment.

Instabilities in a magneto-optical trap: noise-induced dynamics in an atomic system

The instabilities observed in the atomic cloud of a magneto-optical trap are experimentally studied through the dynamics of the center of mass location and the cloud population. Two dynamical components are identified: a slow, stochastic one affects both variables, and a fast, deterministic one affects only the center of mass location. A one-dimensional stochastic model taking into account the shadow effect is developed from these observations and reproduces the experimental behavior. It is shown that instabilities are driven by noise and present stochastic resonancelike characteristics.