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Fonctionnalisation de nanopore unique par des polymères : conformation, transport et applications

Abstract : Biological channels are proteins inserted in the cell membrane that keep ion equilibrium and ensure the molecule transport. These protein channels can respond to multiple stimuli like light, pH, ion strength and trans-membrane potential to regulate their permeability and selectivity. To mimic these biological pores, artificial nanopores have been has been developed on solid-state or polymer materials. The advantages of such artificial nanopores are simplicity of fabrication and mechanical, chemical stabilities. However the shortcomings are also clear that they usually have less selectivity and responsiveness to external stimuli. To enhance their properties, the functionalization is required in order to change their properties like permeability, selectivity or give them abilities to detect specific biomolecules.In this thesis, we aimed to functionalize track-etched nanopore with polymer for three applications: stimuli-responsive ion channel, osmotic energy harvesting and biosensing. For stimuli-responsive ion channel, we constructed two channels: one is functionalized by layer-by-layer self-assembly of various polyelectrolytes to respond to pH. The second one can respond to light and pH based on chemical grafting of spiropyran-PEG chains. Light induced isomerization and protonation/deprotonation caused by pH change can change the charge and conformation of functional molecules. Thus these changes can modulate ion perm-selectivity of the channel. For osmotic energy harvesting, we have followed two strategies to improve ion selectivity of membrane to get higher energy output. One used layer-by-layer depositing of polyelectrolytes on pore surface to enhance charge density. The other strategy used a high charged hydrogel synthesized inside the pore. Results showed a high energy generation for both two strategies of 20 pW per pore. The hydrogel functionalization makes it possible to use cylindrical geometry which is adequate for high pore density membrane. For biosensing application, we developed a PLL functionalized nanopore to detect oversulfated chondroitine sulfate (OSCS) contamination in heparin samples based on ionic diode principles. After being treated by heparinase, the heparin concentration in residue can quantitatively reflect the OSCS concentration based on ionic current rectification change. This experiment also confirmed the ability of track-etched nanopore to characterize the kinetics of enzymatic degradations. To go further, we immobilized hyaluronidases in the channel to characterize the enzymatic reactions at single molecule level using resistive pulse technique. The results showed that the duration of complexion between one hyaluronidase and one hyaluronic acid molecule for one reaction is around 1 second.In this thesis, we show the strong ability of polyelectrolytes functionalized track-etched nanopore. These well-designed systems can be easily scaled up and these well-developed principles can be used to design other systems to solve more problems in health and energy.
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Tianji Ma. Fonctionnalisation de nanopore unique par des polymères : conformation, transport et applications. Autre. Université Montpellier, 2019. Français. ⟨NNT : 2019MONTS072⟩. ⟨tel-02491527⟩

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