Micro-evaporators for kinetic exploration of phase diagrams

We use pervaporation-based microfluidic devices to concentrate species in aqueous solutions with spatial and temporal control of the process. Using experiments and modelling, we quantitatively describe the advection-diffusion behavior of the concentration field of various solutions (electrolytes, colloids, etc) and demonstrate the potential of these devices as universal tools for the kinetic exploration of the phases and textures that form upon concentration

Anion Effects on Calixarene Monolayers: A Hofmeister Series Study

Due to their amphiphilic structure, calixarenes adsorb at the air/water interface and form stable Langmuir films. We have explored the effect of salts on calix[6]- and calix[8]arene spreading isotherms at the air/water interface. A wide range of different potassium salts was used in the subphase: KCl, KI, KBr, KSCN, KNO3, CH3COOK, K2SO4, and K3PO4. The differences in Langmuir isotherms are due to the presence of different anions in the subphase, to the different conformations of the ligands at the interface, and to the different complexing affinities of calix[6]- and calix[8]arene for potassium ions. The two systems show a significant specific ion effect that can be discussed in terms of Hofmeister series. Characteristic monolayer parameters, e.g., limiting area (A lim), collapse pressure (πcoll), modulus of compressibility (Cs-1), and surface potential (ΔV), are discussed in terms of some physicochemical parameters that reflect dispersion forces: in particular, anion polarizabilities, lyotropic number (N), molar surface tension increment (σ), and partial molar volume (v s)

Why pH Titration in Protein Solutions Follows a Hofmeister Series

Measurements of pH in single-phase cytochrome c suspensions are reported. The pH, as determined by a glass electrode, has a fixed value. With the addition of salt, the supposedly fixed pH changes strongly. The pH depends on salt type and concentration and follows a Hofmeister series. A theoretical interpretation is given that provides insights into such Hofmeister effects. These occur generally in protein solutions. While classical electrostatic models provide partial understanding of such trends in protein solutions, they fail to explain the observed ion specificity. Such models neglect electrodynamic fluctuation (dispersion) forces acting between ions and proteins. We use a Poisson-Boltzmann cell model that takes these ionic dispersion potentials between ions and proteins into account. The observed ion specificity can then be accounted for. Proteins act as buffers that display similar salt-dependent pH trends not previously explained

Organized Hybrid Molecular Films from Natural Phospholipids and Synthetic Block Copolymers: A Physicochemical Investigation

International audienceIn the last few years, hybrid lipid-copolymer assemblies have attracted increasing attention as possible two-dimensional (2D) membrane platforms, combining the biorelevance of the lipid building blocks with the stability and chemical tunability of copolymers. The relevance of these systems varies from fundamental studies on biological membrane-related phenomena to the construction of 2D complex devices for material science and biosensor technology. Both the fundamental understanding and the application of hybrid lipid-copolymer-supported bilayers require thorough physicochemical comprehension and structural control. Herein, we report a comprehensive physicochemical and structural characterization of hybrid monolayers at the air/water interface and of solid-supported hybrid membranes constituted by 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and the block copolymer poly(butadiene-b-ethyleneoxide) (PBD-b-PEO). Hybrid lipid-copolymer supported bilayers (HSLBs) with variable copolymer contents were prepared through spontaneous rupture and fusion of hybrid vesicles onto a hydrophilic substrate. The properties of the thin films and the parent vesicles were probed through dynamic light scattering (DLS), differential scanning calorimetry (DSC), optical ellipsometry, quartz crystal microbalance with dissipation monitoring (QCM-D), and confocal scanning laser microscopy (CSLM). Stable, hybrid lipid/copolymer systems were obtained for a copolymer content of 10−65 mol %. In particular, DSC and CSLM show lateral phase separation in these hybrid systems. These results improve our fundamental understanding of HSLBs, which is necessary for future applications of hybrid systems as biomimetic membranes or as drug delivery systems, with additional properties with respect to phospholipid liposomes

Encapsulation of a cationic antimicrobial peptide into self-assembled polyion complex nano-objects enhances its antitumor properties

International audienceAntimicrobial peptides, a large class of molecules synthetized by various organisms as an innate defense against pathogens are more and more used for their anticancer properties as well. In order to overcome some of their limitations and to enhance their therapeutic efficiency, the use of delivery systems was taken into consideration. In this study we describe an original delivery system for antimicrobial peptides based on its physico-chemical properties, namely the selfassembled polyion complexes (PIC) based on electrostatic interactions of cationic antimicrobial peptide P6 with negatively charged double hydrophilic block copolymers, the poly(ethylene oxide)-poly(acrylic acid) (PEO-PAA) in our study. The drug delivery system was tested on 3D human tumor HCT-116 spheroids. The spheroid evolution and cell viability were monitored at 24 and 48 h after the treatment was applied. Our study demonstrates for the first time the feasibility of forming a polyion complex PIC with an antimicrobial peptide and that this self-assembled organisation provides added value in terms of anti-tumour therapeutic efficacy compared to the free form of the antimicrobial peptide

Rational design of block copolymer self-assemblies in photodynamic therapy

International audiencePhotodynamic therapy is a technique already used in ophthalmology or oncology. It is based on the local production of reactive oxygen species through an energy transfer from an excited photosensitizer to oxygen present in the biological tissue. This review first presents an update, mainly covering the last five years, regarding the block copolymers used as nanovectors for the delivery of the photosensitizer. In particular, we describe the chemical nature and structure of the block copolymers showing a very large range of existing systems, spanning from natural polymers such as proteins or polysaccharides to synthetic ones such as polyesters or polyacrylates. A second part focuses on important parameters for their design and the improvement of their efficiency. Finally, particular attention has been paid to the question of nanocarrier internalization and interaction with membranes (both biomimetic and cellular), and the importance of intracellular targeting has been addressed