Stimuli-responsive polymer coatings based on (poly-L-Lysine)-g-poly(N-isopropylacrylamide) to control specific cell adhesion

Abstract : Polymer coatings based on the physorption of comb-like polymers, (Poly-L-Lysine)-g-poly(NIsopropylacrylamide)derivatives (PLL-g-PNIPAM), have been developed to reversibly modulate specific cell adhesion on demand.This technique of coating relies on the spontaneous adsorption of PLL on typical anionic substrates used in biology: a simple bath application of substrates in solution of PLLg-PNIPAM affords a stable polymer adlayer with dense and thermoresponsive poly(NIsopropylacrylamide) brushes. Adsorption of comb-like polymers with different strands enables to easily modulate properties of the coatings. We focused on thermoresponsive poly(N-Isopropylacrylamide-co-ligand) brusheswhere ligand is Biotin or a peptide of adhesion.A versatile synthesis of PLL-g-PNIPAM is presented. This synthesis is based on RAFT polymerization of N-acryloxysuccinimide and post-modifications of both the backbone and the polymer ends. Detection of the transition soluble/insoluble in solution and AFM/QCM-d studies of PNIPAM adlayers demonstrate that the critical temperature in adlayers are close to the one in solution. Stability in terms of composition and thickness has been checked after temperature cycles. The study of the adsorption of Avidin-coated particles suggests that these adlayers can expose/mask Biotin, and so regulate specific interaction by simple change in temperature. To optimize the thermal contrast of ligand accessibility, this study includes measurements on mixed adlayers with functionalized/unfunctionalized brushes. Finally, specific adhesion of HeLa cells can be thermally modulated on adlayers presenting repellent brushes and with controlled densities of adhesive peptides (RGD).A local control has been considered on such coatings by using light stimulus. In this context, azobenzene-containing Poly(NIsopropylacrylamide) were synthesized but they shown only a weak light-response.
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Fabrice Dalier. Stimuli-responsive polymer coatings based on (poly-L-Lysine)-g-poly(N-isopropylacrylamide) to control specific cell adhesion. Polymers. PSL Research University, 2016. English. ⟨NNT : 2016PSLEE019⟩. ⟨tel-01474357⟩

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