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International audience; Dendrigraft poly(L-lysine) (DGL) polyelectrolytes, obtained by iterative polycondensation of N-trifluoroacetyl-L-lysine-N-carboxyanhydride, constitute very promising candidates in many biomedical applications. In order to get a better understanding of their structure-property relationships in these applications, their absolute average molecular weights have to be accurately measured. Size-exclusion chromatography coupled to a multi-angle laser-light-scattering detector (SEC-MALLS) is known to be the most appropriate analytical tool. These measurements require the determination of the refractive index increment, dn/dc, of these highly branched polycationic macromolecules in aqueous solution. This optical property has to be measured in the same aqueous conditions as SEC-MALLS eluents. Consequently, data are determined and discussed as a function of different aqueous SEC-MALLS eluents, as well as different counter-ions of the many ammonium groups of DGL (generation 3, DGL-3, used as a model herein). The resulting number-average molecular weights, (M) over bar (n), are found to be very dissimilar when the measured dn/dc values are directly considered. In contrast, very close (M) over bar (n) values are obtained (average (M) over bar (n) = 18 700, standard error of 1110 g mol(-1)) with a low coefficient of variation for such data (ca.6% for six analyses), when the dn/dc are corrected by the exact lysine amount (measured by the total Kjeldahl nitrogen method).

Poly-L-lysine is a biocompatible polymer used for drug or gene delivery, for transport through cellular membranes, and as nanosized magnetic resonance imaging contrast agents. Cu(II)-poly-L-lysine complexes are of particular interest for their role in biocatalysis. In this study, poly-L-lysine dendrigrafts (DGLs) at different generations (G2, G3, and G4) are synthesized and characterized in absence and presence of Cu(II) by means of electron paramagnetic resonance (EPR), UV-Vis, potentiometric titration and circular dichroism (CD). The analysis is performed as a function of the [Cu(II)]/[Lys] (=R) molar ratio, pH and generation by identifying differently flexible complexes in different dendrimer regions. The amine sites in the lateral chains become increasingly involved with the increase of pH. The good agreement and complementarity of the results from the different techniques provide an integrate view of the structural and dynamic properties of Cu(II)-DGL complexes implementing their use as biocatalysts.

International audience; Poly(L-lysine) (PLL) dendrigrafts (DGLs) are arborescent biosynthetic polymers of regular and controlled structures. They have specific properties such as biocompatibility and non-immunogenicity, and their surface density of NH2 functions can be easily modified and therefore appears as a powerful tool for the functionalization of hydrophobic polymers used in the context of tissue engineering. In this study, we evaluated several criteria of human skin fibroblasts when cultured with DGL of generations 2, 3 and 4, with linear PLL polymer as reference. In aqueous phase, DGLs and PLL displayed a similar cytotoxicity towards fibroblasts. Plastic culture plates grafted with DGLs were further characterized as homogeneous surfaces by atomic force microscopy and surface characterization by amino density estimation by colorimetric assay. Proliferation of fibroblasts was increased when cultured onto PLL and DGLs monolayers when compared with crude plates. Cellular adhesion was increased by 20% on DGLs in comparison to PLL. Integrin α5 subunit protein expression level was increased after 48 h of culture on DGLs, in comparison to control or PLL-coated surfaces. The presence of DGLs did not lead to overexpression or activation of matrix metalloproteinases 2 and 9. Finally, fibroblasts adhesion was increased by 40% on poly-(lactic-co-glycolic acid) matrices functionalized with DGLs when compared to PLL. Overall, these features make DGL promising candidates for the surface engineering of biomaterials in tissue engineering.

International audience; Herein, we demonstrate the effectiveness of the water-friendly S-sulphonate group as an alternative to traditional thiol protecting groups for subsequent deprotection-bioconjugation reactions, under conditions that are compatible with the use of biochemical samples.