9 research outputs found

    Простір публічних комунікацій сучасних релігійних організацій

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    Porous aluminum oxide (PAO) is a nanoporous material used for various (bio)­technological applications, and tailoring its surface properties via covalent modification is a way to expand and refine its application. Specific and complex chemical modification of the PAO surface requires a stepwise approach in which a secondary reaction on a stable initial modification is necessary to achieve the desired terminal molecular architecture and reactivity. We here show that the straightforward initial modification of the bare PAO surface with bromo-terminated phosphonic acid allows for the subsequent preparation of PAO with a wide scope of terminal reactive groups, making it suitable for (bio)­functionalization. Starting from the initial bromo-terminated PAO, we prepared PAO surfaces presenting various terminal functional groups, such as azide, alkyne, alkene, thiol, isothiocyanate, and <i>N</i>-hydroxysuccinimide (NHS). We also show that this wide scope of easily accessible tailored reactive PAO surfaces can be used for subsequent modification with (bio)­molecules, including carbohydrate derivatives and fluorescently labeled proteins

    Does it stick? : Macromolecular building blocks for antifouling coatings

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    The undesired deposition of material onto a surface, also known as fouling, is a recurring challenge for many applications. The work described in this Thesis combines the fields of organic chemistry and surface chemistry for the development of antifouling coatings: from the synthesis of the macromolecular building blocks to their application on surfaces as coatings and testing of antifouling properties.Chapter 1 of this thesis provides an introduction to the concepts of fouling and antifouling. The most applied antifouling coating are discussed alongside the most promising, state-of-the-art polymer materials that make up these coatings. Furthermore, macromolecules such as polymers and dendrimers that make for interesting candidates to serve as new building blocks for antifouling coatings are discussed. Especially dendrimers represent interesting candidates due to the high level of control over their architecture and the possibility for multivalent interactions. Zwitterionic dendrimers (ZID) are modified with an equal number of oppositely charged groups have found use in many biomedical applications. However, the design of and control over the synthesis of these dendrimers remains challenging, in particular with respect to achieving full charge-neutral modification of the dendrimer. In Chapter 2 the design, synthesis and characterization of fully zwitterionic, charge-neutral carboxybetaine and sulfobetaine zwitterionic dendrimers is described. Additionally, also the synthesis and characterization of ZIDs that contain a variable number of alkyne and azide groups are presented. Proof-of-principle coupling of an azide-biotin conjugate by click chemistry showed that these ZIDs indeed can be further modified. Especially the functionalized dendrimers are potential candidates for antifouling applications but also for biomedical applications such as drug delivery, since they allow straightforward anchoring or (bio)functionalization via click chemistry.&nbsp;To form an antifouling coating, the developed ZID needs to be coupled to a surface. Chapter 3 reports different strategies to enable covalent immobilization of ZIDs on a surface. The first explored method was amide bond-mediated binding of the ZID’s carboxylates to amine-terminated surfaces. Next to this, two types of click reactions, copper-catalyzed azide-alkyne cycloadditions (CuAAC) and thiol-yne chemistry, between pre-installed functional groups on the ZIDs and the surfaces were tested. These strategies all resulted in monolayers of ZID, although the two click chemistry-based routes yielded slightly higher levels of immobilized ZID, i.e., thicker and more hydrophilic layers. To further increase the immobilization load of the ZID, a grafting-through approach was tested that led to multilayers of ZID by reacting&nbsp; methacrylate-functionalized ZIDs onto a pre-coated surface. The multilayers showed increasing thickness and hydrophilicity with each newly formed layer, and displayed antifouling properties that were slightly better than the oligoethylene oxide monolayers which were used as a reference. &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;For these immobilization strategies, an undesirable surface pre-functionalization step was needed. To circumvent this, the macromolecules themself were designed to have an intrinsic affinity towards the surface. In the research described in Chapter 4, poly(l-lysine) (PLL) was used as a coupling agent. Two different routes were developed to synthesize polymer-dendrimer hybrids by the interconnection of PLL and ZID. The first route led to network-like structures in which PLL and ZIDs were crosslinked by multiple amide bonds. The second route led to a more defined, linear PLL-ZID macromolecule, which was formed via click coupling of multiple ZIDs to a single PLL backbone. These two different types of PLL-ZID systems were self-assembled onto silicon oxide surfaces from aqueous solutions to form thin, hydrophilic coatings. Especially the linear variant yielded good antifouling properties towards single-protein solutions and diluted human serum, as shown in detail by quartz crystal microbalance (QCM) measurements. The formed coatings could be further bio-functionalized using the remaining carboxylate moieties. An on-surface biofunctionalization step by biotin demonstrated the possibility to use the PLL-ZID hybrids coatings for selective detection of target analytes (streptavidin), while the underlying coating maintained its antifouling properties.Chapter 5 presents possibilities to create poly(N-(2-hydroxypropyl)methacrylamide) (HPMA) polymer brush-based coatings without having to perform sensitive polymerization reactions on-surface. HPMA polymers were grafted form a PLL backbone to create a so-called “bottlebrush” polymer, which could self-assemble onto a surface in a similar fashion like the PLL-ZID copolymers reported in Chapter 4. Three routes towards such PLL-HPMA-coated surfaces were developed ranging from “classic” grafting-from to entirely grafting-to in order to compare differences in outcome and overall antifouling performance of the coatings. Additionally, a grafting-to bottlebrush was synthesized that contained 5% carboxybetaine in its side chains, which offered the possibility for further functionalization after an ester activation step. Eventually, all surface modification routes yielded coatings that showed single-protein antifouling properties.Finally, in Chapter 6 the differently developed building blocks and coatings are discussed in terms of synthesis, antifouling properties and ease of application. The findings of this research are placed in a broader context and recommendations for further research are given.&nbsp

    Zwitterionic dendrimer – Polymer hybrid copolymers for self-assembling antifouling coatings

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    In this work, we show two different routes to synthesize polymer-dendrimer hybrids by the coupling of poly(L-lysine) and zwitterionic dendrimers (ZIDs). Poly(L-lysine) (PLL) is used because of its advantageous self-assembly properties onto silicon oxide by charged-based interactions between the lysine groups and the negatively charged surface, whilst the coupled ZIDs provide antifouling properties. The first route yields network-like structures in which PLL and ZIDs are crosslinked by multiple amide bonds. By using different ratios of PLL and ZID, we vary the size of the formed networks. A more defined, linear PLL-ZID macromolecule is formed via coupling of multiple ZIDs to PLL in a controlled way by a copper-catalyzed azide/alkyne cycloaddition (CuAAC) “click” reaction. Following synthesis and characterization of the two different types of PLL-ZID macromolecules, they are self-assembled on silicon oxide surfaces from aqueous solutions in a single step, to form thin, hydrophilic coatings. Their potential use as antifouling coatings is tested by fluorescence microscopy and quartz crystal microbalance (QCM) with foulants such a single proteins and diluted human serum. Finally, by performing an on-surface biofunctionalization step by biotin we demonstrate it is possible to use these polymer-dendrimer hybrids for selective detection of target analytes (here: streptavidin), while the underlying coating maintains its antifouling properties. This method presents a new, straightforward approach for the manufacturing of PLL-ZID based coatings that can be pre-synthesized partly or fully and applied as coating in a single self-assembly step. Both steps can take place in aqueous solution and under ambient conditions, and result in stable coatings that not only display antifouling properties but also maintain the possibility of further functionalization

    Design, Synthesis, and Characterization of Fully Zwitterionic, Functionalized Dendrimers

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    Dendrimers are interesting candidates for various applications because of the high level of control over their architecture, the presence of internal cavities, and the possibility for multivalent interactions. More specifically, zwitterionic dendrimers modified with an equal number of oppositely charged groups have found use in in vivo biomedical applications. However, the design and control over the synthesis of these dendrimers remains challenging, in particular with respect to achieving full modification of the dendrimer. In this work, we show the design and subsequent synthesis of dendrimers that are highly charged while having zero net charge, that is zwitterionic dendrimers that are potential candidates for biomedical applications. First, we designed and fully optimized the synthesis of charge-neutral carboxybetaine and sulfobetaine zwitterionic dendrimers. Following their synthesis, the various zwitterionic dendrimers were extensively characterized. In this study, we also report for the first time the use of X-ray photoelectron spectroscopy as an easy-to-use and quantitative tool for the compositional analysis of this type of macromolecules that can complement techniques such as nuclear magnetic resonance and gel permeation chromatography. Finally, we designed and synthesized zwitterionic dendrimers that contain a variable number of alkyne and azide groups that allow straightforward (bio)functionalization via click chemistry.</p

    PLL-Poly(HPMA) Bottlebrush-Based Antifouling Coatings: Three Grafting Routes

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    In this work, we compare three routes to prepare antifouling coatings that consist of poly(l-lysine)-poly(N-(2-hydroxypropyl)methacrylamide) bottlebrushes. The poly(l-lysine) (PLL) backbone is self-assembled onto the surface by charged-based interactions between the lysine groups and the negatively charged silicon oxide surface, whereas the poly(N-(2-hydroxypropyl)methacrylamide) [poly(HPMA)] side chains, grown by reversible addition-fragmentation chain-transfer (RAFT) polymerization, provide antifouling properties to the surface. First, the PLL-poly(HPMA) coatings are synthesized in a bottom-up fashion through a grafting-from approach. In this route, the PLL is self-assembled onto a surface, after which a polymerization agent is immobilized, and finally HPMA is polymerized from the surface. In the second explored route, the PLL is modified in solution by a RAFT agent to create a macroinitiator. After self-assembly of this macroinitiator onto the surface, poly(HPMA) is polymerized from the surface by RAFT. In the third and last route, the whole PLL-poly(HPMA) bottlebrush is initially synthesized in solution. To this end, HPMA is polymerized from the macroinitiator in solution and the PLL-poly(HPMA) bottlebrush is then self-assembled onto the surface in just one step (grafting-to approach). Additionally, in this third route, we also design and synthesize a bottlebrush polymer with a PLL backbone and poly(HPMA) side chains, with the latter containing 5% carboxybetaine (CB) monomers that eventually allow for additional (bio)functionalization in solution or after surface immobilization. These three routes are evaluated in terms of ease of synthesis, scalability, ease of characterization, and a preliminary investigation of their antifouling performance. All three coating procedures result in coatings that show antifouling properties in single-protein antifouling tests. This method thus presents a new, simple, versatile, and highly scalable approach for the manufacturing of PLL-based bottlebrush coatings that can be synthesized partly or completely on the surface or in solution, depending on the desired production process and/or application.</p

    Ambient Surface Analysis of Organic Monolayers using Direct Analysis in Real Time Orbitrap Mass Spectrometry

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    A better characterization of nanometer-thick organic layers (monolayers) as used for engineering surface properties, biosensing, nanomedicine, and smart materials will widen their application. The aim of this study was to develop direct analysis in real time high-resolution mass spectrometry (DART-HRMS) into a new and complementary analytical tool for characterizing organic monolayers. To assess the scope and formulate general interpretation rules, DART-HRMS was used to analyze a diverse set of monolayers having different chemistries (amides, esters, amines, acids, alcohols, alkanes, ethers, thioethers, polymers, sugars) on five different substrates (Si, Si<sub>3</sub>N<sub>4</sub>, glass, Al<sub>2</sub>O<sub>3</sub>, Au). The substrate did not play a major role except in the case of gold, for which breaking of the weak Au–S bond that tethers the monolayer to the surface, was observed. For monolayers with stronger covalent interfacial bonds, fragmentation around terminal groups was found. For ester and amide-terminated monolayers, in situ hydrolysis during DART resulted in the detection of ions characteristic of the terminal groups (alcohol, amine, carboxylic acid). For ether and thioether-terminated layers, scission of C–O or C–S bonds also led to the release of the terminal part of the monolayer in a predictable manner. Only the spectra of alkane monolayers could not be interpreted. DART-HRMS allowed for the analysis of and distinction between monolayers containing biologically relevant mono or disaccharides. Overall, DART-HRMS is a promising surface analysis technique that combines detailed structural information on nanomaterials and ultrathin films with fast analyses under ambient conditions

    Ambient Surface Analysis of Organic Monolayers using Direct Analysis in Real Time Orbitrap Mass Spectrometry

    No full text
    A better characterization of nanometer-thick organic layers (monolayers) as used for engineering surface properties, biosensing, nanomedicine, and smart materials will widen their application. The aim of this study was to develop direct analysis in real time high-resolution mass spectrometry (DART-HRMS) into a new and complementary analytical tool for characterizing organic monolayers. To assess the scope and formulate general interpretation rules, DART-HRMS was used to analyze a diverse set of monolayers having different chemistries (amides, esters, amines, acids, alcohols, alkanes, ethers, thioethers, polymers, sugars) on five different substrates (Si, Si<sub>3</sub>N<sub>4</sub>, glass, Al<sub>2</sub>O<sub>3</sub>, Au). The substrate did not play a major role except in the case of gold, for which breaking of the weak Au–S bond that tethers the monolayer to the surface, was observed. For monolayers with stronger covalent interfacial bonds, fragmentation around terminal groups was found. For ester and amide-terminated monolayers, in situ hydrolysis during DART resulted in the detection of ions characteristic of the terminal groups (alcohol, amine, carboxylic acid). For ether and thioether-terminated layers, scission of C–O or C–S bonds also led to the release of the terminal part of the monolayer in a predictable manner. Only the spectra of alkane monolayers could not be interpreted. DART-HRMS allowed for the analysis of and distinction between monolayers containing biologically relevant mono or disaccharides. Overall, DART-HRMS is a promising surface analysis technique that combines detailed structural information on nanomaterials and ultrathin films with fast analyses under ambient conditions
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