Modifying stainless steel surfaces with responsive polymers: effect of PS-PAA and PNIPAAM on cell adhesion and oil removal

The treatment of stainless steel surfaces with responsive polymers was investigated using X-ray photoelectron spectroscopy and scanning electron microscopy. Poly (N-isopropylacrylamide) (PNIPAAM) is a temperature-sensitive polymer which is soluble in water below 32 degrees C (Lower Critical Solubility Temperature (LCST)) but collapses and aggregates above 32 degrees C. This polymer was adsorbed at 50 degrees C from solutions at different concentrations, followed by rinsing and different drying procedures. Thereby, a large variety of surface structures could be obtained, from smooth films to surfaces showing marked relief features due to residues of PNIPAAM aggregates. Two poly(styrene)b-poly(acrylic acid), PS-PAA, with different block lengths, were spin-coated on stainless steel and showed preferential exposure of PS blocks at the outermost surface. PNIPAAM-conditioning was shown to strongly reduce yeast cell adhesion and to facilitate the removal of oil soil due to its high water affinity and chain mobility below the LCST. PS-PAA coatings also reduced yeast cell adhesion; this may partly be due to a reorganization of the surface, leading to exposure of PAA chains in contact with water and thus to electrostatic repulsion of the yeast cells

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

Surface morphology and wetting properties of surfaces coated with an amphiphilic diblock copolymer

X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and dynamic wetting measurements with the Wilhelmy plate method were used to characterize layers of three polystyrene-b-poly(acrylic acid) (PS-PAA) diblock copolymers (differing by their block lengths) created by dip coating or spin coating on glass and gold substrata. The copolymer layers were thick and continuous, whatever the substratum, with a preferred exposure of PS chains at the extreme surface for the copolymers with a small PS block. The surface roughness decreased as the PAA/PS block length ratio increased and was larger for dip-coated than for spin-coated layers. The dip-coated layers obtained with the copolymer with the large PAA block presented self-assembled nanostructures of worm-like type. Dynamic wetting measurements showed that the coated layers were able to reorganize, upon immersion-emersion in solution at different pH, due to the deprotonation and swelling of the PAA chains. This phenomenon was dependent on the block length and on the pH. A water contact angle typical of pure PS was obtained with the large PS block. A hydrophilic surface was obtained for the large PAA block after immersion at pH 11. In intermediate situations (large PAA block in water, large PS block at pH 11), the advancing contact angle was dependent on the time of contact with air subsequent to the preceding immersion. This demonstrates the possibility to modulate hydrophobicity-hydrophilicity switching and pH sensitivity of the coatings by the copolymer composition. (C) 2004 Elsevier B.V. All rights reserved

Targeting Ovarian Carcinoma with TSP-1:CD47 Antagonist TAX2 Activates Anti-Tumor Immunity

International audienceTAX2 peptide is a cyclic peptide that acts as an orthosteric antagonist for thrombospondin-1 (TSP-1) interaction with CD47. TAX2 was first described for its anti-angiogenic activities and showed anti-cancer efficacy in numerous preclinical models. Here, we aimed at providing an extensive molecular characterization of TAX2 mode of action, while evaluating its potential in ovarian cancer therapy. Multidisciplinary approaches were used to qualify a TAX2 drug candidate in terms of stability, solubility and potency. Then, efficacy studies, together with benchmark experiments, were performed in relevant mouse models of ovarian carcinoma. TAX2 peptide appears to be stable and soluble in clinically relevant solvents, while displaying a favorable safety profile. Moreover, clinical data mining allowed for the identification of TSP-1 as a relevant pharmacological target in ovarian cancer. In mice, TAX2 therapy inhibits ovarian tumor growth and metastatic dissemination, while activating anti-cancer adaptive immunity. Interestingly, TAX2 also synergizes when administered in combination with anti-PD-1 immune checkpoint inhibitiors. Altogether, our data expose TAX2 as an optimized candidate with advanced preclinical characterization. Using relevant syngeneic ovarian carcinoma models, we highlighted TAX2’s ability to convert poorly immunogenic tumors into ones displaying effective anti-tumor T-cell immunity

Transmembrane Peptides as a New Strategy to Inhibit Neuraminidase-1 Activation

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