Pyranine-modified amphiphilic polymer conetworks as fluorescent ratiometric pH sensors

The fluorescent dye 8-hydroxypyrene-1,3,6-trisulfonate (pyranine) combines high photostability with ratiometric pH detection in the physiological range, making it a prime candidate for optical sensors in biomedical applications, such as pH-based chronic wound monitoring. However, pyranine's high water solubility and the difficulty of covalent attachment pose severe limitations in terms of leaching from sensor matrices. Herein, pyranine-modified nanophase-separated amphiphilic polymer conetworks (APCNs) are reported as fluorescent ratiometric pH sensors. The thin, freestanding APCN membranes composed of one hydrophilic and one hydrophobic polymer provide an optically transparent, flexible, and stable ideal matrix that enables contact between dye and aqueous environment. An active ester-based conjugation approach results in a highly homogeneous and stable pyranine modification of the APCN's hydrophilic phase. This concept effectively solves the leaching challenge for pyranine without compromising its functionality, which is demonstrated by ratiometric pH detection in the range of pH 5–9

Conception de films sensibles multi-stimuli assemblage couche-par-couche pour le contrôle d'adsorption de protéine

L'adsorption de protéine sur une surface artificielle solide est un phénomène fondamental qui détermine la réponse biologique d'un organisme vivant entrant dans n'importe quel matériel d'implant. Donc, l'adaptation de surfaces pour l'adsorption de protéine contrôlée est au coeur de beaucoup de champs de recherche d'aujourd'hui incluant la science de matériels et la biotechnologie. Dans ce contexte, les matériels sensibles de stimulus qui peuvent changer leurs propriétés comme une réponse à une petite monnaie dans leur environnement physicochimique attirent un grand intérêt comme ils permettent la création de surfaces avec des propriétés commutables pour le contrôle d'adsorption de protéine. Dans cette thèse, nous faisons un rapport sur la conception et l'élaboration de films minces sensibles de stimulus multi et de nanotubes. À cette fin, nous avons employé la couche-par-couche robuste et polyvalente…Protein adsorption on a solid artificial surface is a fundamental phenomenon that determines the biological response of a living organism entering any implant material. Therefore, tailoring surfaces for controlled protein adsorption is at the heart of many of today's research fields including biotechnology and materials science. In this context, stimuli-responsive materials that are able to change their properties as a response to a small change in their physico-chemical environment are attracting a great interest as they allow the creation of surfaces with switchable properties for the control of protein adsorption. In this thesis, we report on the design and elaboration of multi stimuli-responsive thin films and nanotubes. For this purpose, we employed the robust and versatile layer-by-layer (LbL) assembly technique to incorporate block copolymers made of poly(acrylic acid) PAA and poly(N-isopropylacrylamide) PNIPAM with tunable and well-controlled block lengths. The combination of ellipsometry, quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance (SPR) and infrared data reveal the possibility to build up (PAH/PAA-b-PNIPAM)n multilayers. The stimuli-responsive properties of these LbL films were examined by monitoring the adsorption of proteins by means of QCM-D and fluorescence measurements, while varying (i) temperature, (ii) pH, (iii) ionic strength, or (iv) a combination of the above parameters. It appears that all these stimuli strongly influence the amount of adsorbed proteins. In short, these new PNIPAM block copolymer-based LbL coatings are easy to build on substrates of various nature and geometry (including nanoporous membranes)

Design of multi-stimuli responsive films through layer-by-layer assembly for the control of protein adsorption

Protein adsorption on a solid artificial surface is a fundamental phenomenon that determines the biological response of a living organism entering any implant material. Therefore, tailoring surfaces for controlled protein adsorption is at the heart of many of today's research fields including biotechnology and materials science. In this context, stimuli-responsive materials that are able to change their properties as a response to a small change in their physico-chemical environment are attracting a great interest as they allow the creation of surfaces with switchable properties for the control of protein adsorption. In this thesis, we report on the design and elaboration of multi stimuli-responsive thin films and nanotubes. For this purpose, we employed the robust and versatile layer-by-layer (LbL) assembly technique to incorporate block copolymers made of poly(acrylic acid) PAA and poly(N-isopropylacrylamide) PNIPAM with tunable and well-controlled block lengths. The combination of ellipsometry, quartz crystal microbalance with dissipation monitoring (QCM-D), surface plasmon resonance (SPR) and infrared data reveal the possibility to build up (PAH/PAA-b-PNIPAM)n multilayers. The stimuli-responsive properties of these LbL films were examined by monitoring the adsorption of proteins by means of QCM-D and fluorescence measurements, while varying (i) temperature, (ii) pH, (iii) ionic strength, or (iv) a combination of the above parameters. It appears that all these stimuli strongly influence the amount of adsorbed proteins. In short, these new PNIPAM block copolymer-based LbL coatings are easy to build on substrates of various nature and geometry (including nanoporous membranes) and they present highly tunable features. This makes them ideal candidates to be employed for applications requiring the control of protein adsorption, such as protein separation or cell culture.(FSA - Sciences de l'ingénieur) -- UCL, 201

Oscillating Reactions Meet Polymers at Interfaces

Chemo-mechanical phenomena, including oscillations and peristaltic motions, are widespread in nature—just think of heartbeats—thanks to the ability of living organisms to convert directly chemical energy into mechanical work. Their imitation with artificial systems is still an open challenge. Chemical clocks and oscillators (such as the popular Belousov–Zhabotinsky (BZ) reaction) are reaction networks characterized by the emergence of peculiar spatiotemporal dynamics. Their application to polymers at interfaces (grafted chains, layer-by-layer assemblies, and polymer brushes) offers great opportunities for developing novel smart biomimetic materials. Despite the wide field of potential applications, limited research has been carried out so far. Here, we aim to showcase the state-of-the-art of this fascinating field of investigation, highlighting the potential for future developments and providing a personal outlook.ISSN:1996-194

Design of stimuli-responsive film through layer-by-layer assembly for the control of protein adsorption

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Hybrid Adsorbent Materials Obtained by the Combination of Poly(ethylene-alt-maleic anhydride) with Lignin and Lignosulfonate

Abstract: Lignin is one of the most available biomass products, but its potential for the development of functional materials has yet to be unleashed. Here, the modification of lignin and lignosulfonate with poly(ethylene-alt-maleic anhydride) [P(E-alt-MA)], a functional polymer of wide industrial use, is accomplished by means of a simple esterification reaction. As a result, hybrid adsorbent materials for water purification can be obtained, which were thoroughly characterized. The combination of P(E-alt-MA) with lignin increased hydrophilicity of the latter, making it dispersible in aqueous environments, while with lignosulfonate it gave rise to a water-insoluble, thus easily recoverable, product. The adsorption properties of the resulting products have been tested against a model water pollutant (methylene blue), demonstrating remarkable adsorption speed (in the order of minutes), adsorption efficiency and stability over a wide range of pH (2–12). Moreover, after the incorporation of magnetite nanoparticles by in situ synthesis, adsorbent materials able to be magnetically recovered were developed. Graphical Abstract: [Figure not available: see fulltext.]

Dual stimuli-responsive coating designed through layer-by-layer assembly of PAA-b-PNIPAM block copolymers for the control of protein adsorption

In this paper, we describe the successful construction, characteristics and interaction with proteins of stimuli-responsive thin nanostructured films prepared by layer-by-layer (LbL) sequential assembly of PNIPAM-containing polyelectrolytes and PAH. PAA-b-PNIPAM block copolymers were synthesized in order to benefit from (i) the ionizable properties of PAA, to be involved in the LbL assembly, and (ii) the sensitivity of PNIPAM to temperature stimulus. The impact of parameters related to the structure and size of the macromolecules (their molecular weight and the relative degree of polymerization of PAA and PNIPAM), and the interaction with proteins under physico-chemical stimuli, such as pH and temperature, are carefully investigated. The incorporation of PAA-b-PNIPAM into multilayered films is shown to be successful whatever the block copolymer used, resulting in slightly thicker films than the corresponding (PAA/PAH)n film. Importantly, the protein adsorption studies demonstrate that it is possible to alter the adsorption behavior of proteins on (PAA-b-PNIPAM/PAH)n surfaces by varying the temperature and/or the pH of the medium, which seems to be intimately related to two key factors: (i) the ability of PNIPAM units to undergo conformational changes and (ii) the structural changes of the film made of weak polyelectrolytes. The simplicity of construction of these PNIPAM block copolymer-based LbL coatings on a large range of substrates, combined with their highly tunable features, make them ideal candidates to be employed for various biomedical applications requiring the control of protein adsorptio