Influence of DNA condensation state on transfection efficiency in DNA/polymer complexes : an AFM and DLS comparative study

peer reviewedAtomic force microscopy (AFM) is used to describe the formation process of polymer/DNA complexes. Two main objectives of this research are presented. The first one is to apply AFM as an effective tool to analyse DNA molecules and different polycation/DNA complexes in order to evaluate their degree of condensation (size and shape). The other one is to search for a relationship between the condensation state of DNA and its transfection efficiency. In this study, linear methacrylate based polymers and globular SuperFect polymers are used in order to induce DNA condensation. Ternary complexes, composed of methacrylate based polymers and polyethylene glycol (PEG)-based copolymers, are also investigated. AFM allows us to confirm good condensation conditions and relate them (or not) to transfection efficiencies. These AFM results (obtained after drying in air) are compared with measurements deduced from Dynamic Light Scattering (DLS) experiments performed in water. This comparison allowed us to identify the structural modifications resulting from deposition on the mica surface

Biodegradable and macroporous polylactide implants for cell transplantation : 1. Preparation of macroporous polylactide supports by solid-liquid phase separation

Freeze-drying of polylactide solutions in 1,4-dioxane has been studied as a way to produce microcellular foams. The thermally induced phase separation has been studied in relation to several processing and formulation parameters. The effects of polymer concentration, chain stereoregularity, polymer molecular weight and cooling rate have been investigated in connection with the porous morphology and the physico-mechanical characteristics of the final foams. As a rule, bundles of channels are formed with a diameter of ~100 μ.m. They have a preferential orientation that fits the cooling direction. A porous substructure (~10 μm) is observed in the internal walls of the tubular macropores. Variations in this general porous morphology-and particularly in the porosity, density, solvent residue, mechanical resistance and degree of regularity in the spatial organization of pores-have been observed when polymer concentration in 1,4-dioxane and polylactide stereoregularity are changed. As expected, cooling rate has a strong effect on the foam morphology, which is essentially controlled by the solvent crystallization. Pores are nothing but the fingerprints of 1,4-dioxane crystallites

Increment in molecular weight of poly (dimethylamino-ethylmethacrylate) based polymers cause strong red blood cell aggregation but not hemolytic response.

Polycations are frequently reported to tailor drug delivery systems, there is still a need to better correlate theirmacromolecular features with their biocompatibility, in particular with blood. In this view, we have analysed the RBC aggregation and hemolysis response caused by poly (dimethylamino-ethylmethacrylate) or poly(ethyleneimine) under a free form, i.e. without their preliminary association with polyanionic drug. Our results highlight that the molecular weight of PDMAEMA significantly affects theRBC aggregationwithout inducing any hemolysis

Adsorption of poly(N-isopropylacrylamide) on glass substrata.

The adsorption of poly(N-isopropylacrylamide) (PNIPAAM), a well known thermosensitive polymer, on glass was investigated by X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The polymer was dissolved in water at low (0.02 g/L) and high (2 g/L) concentration and the tested temperatures were below (25 degrees C) and above (50 degrees C) the lower critical solubility temperature (LCST). Whatever the conditions, a smooth layer of adsorbed molecules spread along the surface was observed. The thickness was about twice higher for high concentration compared to low concentration. The cohesion in the adsorbed layer, as revealed by scraping tests performed by AFM, was higher above the LCST than below the LCST. On top of this adsorbed layer, single-chain coils, globules, or aggregates were present, depending on concentration and temperature. The observation of these additional adsorbed entities was poorly reproducible, presumably due to the lack of shear control upon rinsing. These results emphasize the importance of the characterization of surface morphology to interpret amounts of adsorbed polymers

Hemoreactivity of poly (dimethyl-aminoethyl-methacrylate) designed for the production of stealth red blood cells

Nanobiopharmaceutic