Kinetic control of liposome size by direct lipid transfer.

Spontaneous lipid vesiculation and related size distribution are traditionally studied in the framework of equilibrium thermodynamics and continuum mechanics, overlooking the kinetic aspects of the process. In the scenario of liposomes consisting of different lipid molecules dispersed in the same medium - a non-equilibrium situation -, the system evolves driven by lipid monomer transfer among the different liposomes. This process encompasses time-dependent changes in liposome size and size distribution, thus predicting size and composition at a given time would entail the control of the size of liposomes by kinetic means, an asset in the framework of diagnostics and synthetic biology.

Asymmetric Lipid Transfer between Zwitterionic Vesicles by Nanoviscosity Measurements.

The interest in nano-sized lipid vesicles in nano-biotechnology relies on their use as mimics for endosomes, exosomes, and nanocarriers for drug delivery. The interactions between nanoscale size lipid vesicles and cell membranes involve spontaneous interbilayer lipid transfer by several mechanisms, such as monomer transfer or hemifusion. Experimental approaches toward monitoring lipid transfer between nanoscale-sized vesicles typically consist of transfer assays by fluorescence microscopy requiring the use of labels or calorimetric measurements, which in turn require a large amount of sample.

Coarse-grained modelling of surface nanobubbles.

Surface nanobubbles are nanoscale gaseous objects that form on hydrophobic surfaces in contact with water. Understanding nanobubble formation and stability remains challenging due to the lack of appropriate theoretical framework and adequate modelling. Here we present a non-equilibrium coarse-grained model for nanobubbles at hydrophobic surfaces.

Low-density/high-density liquid phase transition for model globular proteins.

The effect of molecule size (excluded volume) and the range of interaction on the surface tension, phase diagram, and nucleation properties of a model globular protein is investigated using a combination of Monte Carlo simulations and finite temperature classical density functional theory calculations. We use a parametrized potential that can vary smoothly from the standard Lennard-Jones interaction characteristic of simple fluids to the ten Wolde-Frenkel model for the effective interaction of globular proteins in solution. We find that the large excluded volume characteristic of large macromolecules such as proteins is the dominant effect in determining the liquid-vapor surface tension and nucleation properties.

Phase behavior of a confined nanodroplet in the grand-canonical ensemble: the reverse liquid-vapor transition.

The equilibrium density distribution and thermodynamic properties of a Lennard-Jones fluid confined to nanosized spherical cavities at a constant chemical potential was determined using Monte Carlo simulations. The results describe both a single cavity with semi-permeable walls as well as a collection of closed cavities formed at the constant chemical potential. The results are compared to calculations using classical density functional theory (DFT).

Dependence of the liquid-vapor surface tension on the range of interaction: a test of the law of corresponding states.

The validity of the principle of corresponding states is investigated for the case of a potential with more than one intrinsic length scale. The planar surface tension of coexisting liquid and vapor phases of a fluid of Lennard-Jones atoms is studied as a function of the range of the potential using both Monte Carlo simulations and density functional theory (DFT). The interaction range is varied from r(c)(*) = 2.

Dark-field digital holographic microscopy to investigate objects that are nanosized or smaller than the optical resolution.

We describe a transmission dark-field digital holographic microscope based on a Mach-Zehnder configuration for the detection of nanosize objects or objects smaller than the optical resolution limit. An optical stop adequately placed in the object beam removes the nondiffracted beam while keeping the light scattered by the object. This configuration combines an improved detection of objects smaller than the optical resolution with the refocusing capability yielded by digital holography.

Structural and dynamical characterization of Hele-Shaw viscous fingering.

Viscous fingering occurs in the interfacial zone between two fluids confined between two plates with a narrow gap (Hele-Shaw geometry) when a highly viscous fluid is displaced by a fluid with relatively low viscosity. Using a mesoscopic approach--the lattice Boltzmann method--we investigate the dynamics of spatially extended Hele-Shaw flow under conditions corresponding to various experimental systems by tuning the 'surface tension' and the reactivity between the two fluids. We discuss the onset of the fingering instability (dispersion relation), analyse the structural properties (characterization of the interface) and the dynamical properties (growth of the mixing zone) of the Hele-Shaw systems, and show the effect of reactive processes on the structure of the interfacial zone.