Synthesis of Glyco-Silicas by Cu(I)-Catalyzed “Click-Chemistry” and their Applications in Affinity Chromatography

Click Chemistry for Biofunctional Polymers: From Observing to Steering Cell Behavior

Click chemistry has become one of the most powerful construction tools in the field of organic chemistry, materials science, and polymer science, as it offers hassle-free platforms for the high-yielding synthesis of novel materials and easy functionalization strategies. The absence of harsh reaction conditions or complicated workup procedures allowed the rapid development of novel biofunctional polymeric materials, such as biopolymers, tailor-made polymer surfaces, stimulus-responsive polymers, etc. In this review, we discuss various types of click reactions─including azide-alkyne cycloadditions, nucleophilic and radical thiol click reactions, a range of cycloadditions (Diels-Alder, tetrazole, nitrile oxide, etc.), sulfur fluoride exchange (SuFEx) click reaction, and oxime-hydrazone click reactions─and their use for the formation and study of biofunctional polymers. Following that, we discuss state-of-the-art biological applications of "click"-biofunctionalized polymers, including both passive applications (e.g., biosensing and bioimaging) and "active" ones that aim to direct changes in biosystems, e.g., for drug delivery, antiviral action, and tissue engineering. In conclusion, we have outlined future directions and existing challenges of click-based polymers for medicinal chemistry and clinical applications.

Host-derived mannose glycans trigger a pathogenic γδ T cell/IL-17a axis in autoimmunity

Autoimmune diseases are life-threatening disorders that cause increasing disability over time. Systemic lupus erythematosus (SLE) and other autoimmune diseases arise when immune stimuli override mechanisms of self-tolerance. Accumulating evidence has demonstrated that protein glycosylation is substantially altered in autoimmune disease development, but the mechanisms by which glycans trigger these autoreactive immune responses are still largely unclear. In this study, we found that presence of microbial-associated mannose structures at the surface of the kidney triggers the recognition of DC-SIGN-expressing γδ T cells, inducing a pathogenic interleukin-17a (IL-17a)-mediated autoimmune response. Mice lacking Mgat5, which have a higher abundance of mannose structures in the kidney, displayed increased γδ T cell infiltration into the kidney that was associated with spontaneous development of lupus in older mice. N-acetylglucosamine supplementation, which promoted biosynthesis of tolerogenic branched N-glycans in the kidney, was found to inhibit γδ T cell infiltration and control disease development. Together, this work reveals a mannose-γδ T cell-IL-17a axis in SLE immunopathogenesis and highlights glycometabolic reprogramming as a therapeutic strategy for autoimmune disease treatment.

Contribution of the "Click Chemistry" Toolbox for the Design, Synthesis, and Resulting Applications of Innovative and Efficient Separative Supports: Time for Assessment

The last two decades have seen the rapid expansion of click chemistry methodology in various domains closely related to organic chemistry. It has notably been widely developed in the area of surface chemistry, mainly because of the high-yielding character of reactions of the "click" type. Especially, this powerful chemical reaction toolbox has been adapted to the preparation of stationary phases from the corresponding chromatographic supports. A plethora of selectors can thus be immobilized on either organic, inorganic, or hybrid stationary phases that can be used in different chromatographic modes. This review first highlights the few different chemical ligation strategies of the "click" type that are up to now mainly devoted to the development of functionalized supports for separation sciences. Then, it gives in a second part an up-to-date survey of the different studies dedicated to the preparation of click chemistry-based chromatographic supports while highlighting the powerful and versatile character of the "click" ligation strategy for the design, synthesis, and developments of more and more complex systems that can find promising applications in the area of analytical sciences, in domains as varied as enantioselective separation, glycomics, proteomics, genomics, metabolomics, etc.

Triazolyl Conjugated (Oligo)Phenothiazines Building Blocks for Hybrid Materials-Synthesis and Electronic Properties

The Cu-catalyzed alkyne-azide 1,3-dipolar cycloaddition variant provides a highly efficient entry to conjugated triazolyl-substituted (oligo)phenothiazine organosilicon derivatives with luminescence and reversible redox characteristics. Furthermore, by in-situ co-condensation synthesis several representative mesoporous MCM-41 type silica hybrid materials with embedded (oligo)phenothiazines are prepared and characterized with respect to their structural and electronic properties. The hybrid materials also can be oxidized to covalently bound embedded radical cations, which are identified by their UV/Vis absorption signature and EPR signals.

Puromycin-Modified Silica Microsphere-Based Nascent Proteomics Method for Rapid and Deep Nascent Proteome Profile

Nascent proteome is crucial in directly revealing how the expression of a gene is regulated on a translation level. In the nascent protein identification, puromycin capture is one of the pivotal methods, but it is still facing the challenge in the deep profiling of nascent proteomes due to the low abundance of most nascent proteins. Here, we describe the synthesis of puromycin-modified silica microspheres (PMSs) as the sorbent of dispersive solid-phase microextraction and the establishment of the PMS-based nascent proteomics (PMSNP) method for efficient capture and analysis of nascent proteins. The modification efficiency of puromycin groups on silica microspheres reached 91.8% through the click reaction. After the optimization and simplification of PMSNP, more than 3500 and 3900 nascent proteins were rapidly identified in HeLa cells and mouse brains within 13.5 h, respectively. The PMSNP method was successfully applied to explore changes in the translation process in a biological stress model, namely, the lipopolysaccharide-stimulated HeLa cells. Biological functional analyses revealed the unique characters of the nascent proteomes and exhibited the superiority of the PMSNP in the identification of low abundance and secreted nascent proteins, thus demonstrating the sensitivity and immediacy of the PMSNP method.

Biological Evaluation and Docking Studies of Synthetic Oleanane-type Triterpenoids

Saponins are potential wide-spectrum antitumor drugs, and copper(I) catalyzed azide-alkyne 1,3-dipolar cycloaddition is a suitable approach to synthesizing saponin-like compounds by regioselective glycosylation of the C2/C3 hydroxyl and C28 carboxylic groups of triterpene aglycones maslinic acid (MA) and oleanolic acid (OA). Biological studies on the T-84 human colon carcinoma cell line support the role of the hydroxyl groups at C2/C3, the influence of the aglycone, and the bulky nature of the substituents in C28. OA bearing a α-d-mannose moiety at C28 (compound 18) focused our interest because the estimated inhibitory concentration 50 was similar to that reported for ginsenoside Rh2 against colon cancer cells and it inhibits the G₁-S phase transition affecting the cell viability and apoptosis. Considering that triterpenoids from natural sources have been identified as inhibitors of nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB) signaling, docking studies were conducted to evaluate whether NF-κB may be a potential target. Results are consistent with the biological study and predict a similar binding mode of MA and compound 18 to the p52 subunit from NF-κB but not for OA. The fact that the binding site is shared by the NF-κB inhibitor 6,6-dimethyl-2-(phenylimino)-6,7-dihydrobenzo[d][1,3]oxathiol-4(5H)-one supports the result and points to NF-κB as a potential target of both MA and compound 18.

A bioinspired heterogeneous catalyst based on the model of the manganese-dependent dioxygenase for selective oxidation using dioxygen

A hybrid bioinspired material with manganese(ii) complexes grafted on the surface of a mesostructured porous silica is investigated.

Heterolayered hybrid dendrimers with optimized sugar head groups for enhancing carbohydrate–protein interactions

Novel heterolayered (“onion peel”) hybrid glycodendrimers containing optimised sugar head groups with galactoside and mannoside units with affinities for two different lectins.

CuAAC: An Efficient Click Chemistry Reaction on Solid Phase

Click chemistry is an approach that uses efficient and reliable reactions, such as Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC), to bind two molecular building blocks. CuAAC has broad applications in medicinal chemistry and other fields of chemistry. This review describes the general features and applications of CuAAC in solid-phase synthesis (CuAAC-SP), highlighting the suitability of this kind of reaction for peptides, nucleotides, small molecules, supramolecular structures, and polymers, among others. This versatile reaction is expected to become pivotal for meeting future challenges in solid-phase chemistry.

Preparation of glyco-silica materials via thiol-ene click chemistry for adsorption and separation

A saccharide bonding method based on thiol-ene chemistry was developed and the resulting glyco-silica materials demonstrated great potential in separation science.

Advances in click chemistry for silica-based material construction

Click chemistry is undoubtedly the most powerful 1,3-dipolar cycloaddition reaction in organic synthesis.

Photophysical studies of newly derivatized mono substituted phthalocyanines grafted onto silica nanoparticles via click chemistry

This work reports on the synthesis, characterization and photophysical studies of newly derived phthalocyanine complexes and the phthalocyanine-silica nanoparticles conjugates. The derived phthalocyanine complexes have one terminal alkyne group. The derived phthalocyanine complexes showed improved photophysical properties (ФF, ФT, ΦΔ and τT) compared to the respective phthalocyanine complexes from which they were derived. The derived phthalocyanine complexes were conjugated to the surface of an azide functionalized silica nanoparticles via copper (1) catalyzed cyclo-addition reaction. All the conjugates showed lower triplet quantum yields ranging from 0.37 to 0.44 compared to the free phthalocyanine complexes. The triplet lifetimes ranged from 352 to 484 μs for the conjugates and from 341 to 366 μs for the free phthalocyanine complexes.

Cyclodextrin-functionalized chromatographic materials tailored for reversible adsorption

Novel dendronized silica substrates were synthesized. First- and second- generation polyaryl ether dendrons were appended to silica surfaces. Using Cu(I) mediated cycloaddition "click" chemistry, β-cyclodextrin was tethered to the dendronized surfaces and to a nondendronized surface for comparison purposes. This synthesis strategy affords a modular, versatile method for surface functionalization in which the density of functional groups can be readily varied by changing the generation of dendron used. The surfaces, which are capable of adsorbing target analytes, have been characterized and studied using X-ray photoelectron spectroscopy (XPS) and vibrational sum frequency spectroscopy (VSFS). Fluorescence spectroscopy was used to study the surfaces' ability to retain coumarin 152 (C152). These studies indicated that the β-cyclodextrin functionalized surfaces not only adsorbed C152 but also retained it through multiple aqueous washes. Furthermore, these observations were quantified and show that substrates functionalized with first-generation dendrons have a more than 6 times greater capacity to adsorb C152 than slides functionalized with monomeric β-cyclodextrin. The first-generation dendrons also have 2 times greater the capacity than the larger generation dendrons. This result is explained by describing a dendron that has an increased number of β-cyclodextrin monomers but, when covalently bound to silica, has a footprint too large to optimize the number of accessible monomers. Overall, both dendronized surfaces demonstrated an increased capacity to adsorb targeted analytes over the slides functionalized with monomeric β-cyclodextrin. The studies reported provide a methodology for characterizing and evaluating the properties of novel, highly functional surfaces.

Design and synthesis of multivalent neoglycoconjugates by click conjugations

A highly stereoselective BF₃∙OEt₂-promoted tandem hydroamination/glycosylation on glycal scaffolds has been developed to form propargyl 3-tosylamino-2,3-dideoxysugars in a one-pot manner. Subsequent construction of multivalent 3-tosylamino-2,3-dideoxyneoglycoconjugates with potential biochemical applications was presented herein involving click conjugations as the key reaction step. The copper-catalyzed regioselective click reaction was tremendously accelerated with assistance of microwave irradiation.

A multivalent inhibitor of the DC-SIGN dependent uptake of HIV-1 and Dengue virus

DC-SIGN is a C-type lectin receptor on antigen presenting cells (dendritic cells) which has an important role in some viral infection, notably by HIV and Dengue virus (DV). Multivalent presentation of carbohydrates on dendrimeric scaffolds has been shown to inhibit DC-SIGN binding to HIV envelope glycoprotein gp120, thus blocking viral entry. This approach has interesting potential applications for infection prophylaxis. In an effort to develop high affinity inhibitors of DC-SIGN mediated viral entry, we have synthesized a group of glycodendrimers of different valency that bear different carbohydrates or glycomimetic DC-SIGN ligands and have studied their DC-SIGN binding activity and antiviral properties both in an HIV and a Dengue infection model. Surface Plasmon Resonance (SPR) competition studies have demonstrated that the materials obtained bind efficiently to DC-SIGN with IC50s in the μm range, which depend on the nature of the ligand and on the valency of the scaffold. In particular, a hexavalent presentation of the DC-SIGN selective antagonist 4 displayed high potency, as well as improved accessibility and chemical stability relative to previously reported dendrimers. At low μm concentration the material was shown to block both DC-SIGN mediated uptake of DV by Raji cells and HIV trans-infection of T cells.

Synthetic approach towards ‘click’ modified chalcone based organotriethoxysilanes; UV-Vis study

The efficient linkage of a conjugate chalcone to n-propyltriethoxysilanes via a 1,2,3-triazole is reported. The synthesis involves a Claisen–Schmidt condensation followed by a copper(i) catalyzed azide–alkyne cycloaddition (CuAAC) reaction.

Virus-like glycodendrinanoparticles displaying quasi-equivalent nested polyvalency upon glycoprotein platforms potently block viral infection

Ligand polyvalency is a powerful modulator of protein–receptor interactions. Host–pathogen infection interactions are often mediated by glycan ligand–protein interactions, yet its interrogation with very high copy number ligands has been limited to heterogenous systems. Here we report that through the use of nested layers of multivalency we are able to assemble the most highly valent glycodendrimeric constructs yet seen (bearing up to 1,620 glycans). These constructs are pure and well-defined single entities that at diameters of up to 32 nm are capable of mimicking pathogens both in size and in their highly glycosylated surfaces. Through this mimicry these glyco-dendri-protein-nano-particles are capable of blocking (at picomolar concentrations) a model of the infection of T-lymphocytes and human dendritic cells by Ebola virus. The high associated polyvalency effects (β>10⁶, β/N ~10²–10³) displayed on an unprecedented surface area by precise clusters suggest a general strategy for modulation of such interactions.

Host–pathogen relationships can be mediated by polyvalent glycan ligand–protein interactions. Here well-defined highly valent glycodendrimeric constructs are synthesized that can mimic pathogens, and can inhibit a model of infection by the Ebola virus.

Click chemistry: a new facile and efficient strategy for the preparation of Fe3O4 nanoparticles covalently functionalized with IDA-Cu and their application in the depletion of abundant protein in blood samples

In this study, we report a novel method to synthesize core-shell structured Fe(3)O(4) nanoparticles (NPs) covalently functionalized with iminodiacetic acid (IDA) via click chemistry between the azide and alkyne groups and charged with Cu(2+). Firstly, the Fe(3)O(4)@SiO(2) NPs were obtained using tetraethoxysilane (TEOS) to form a silica shell on the surface of the Fe(3)O(4) core. The azide group-modified Fe(3)O(4)@SiO(2) NPs were obtained by a sol-gel process using 3-azidopropyltriethoxysilane (AzPTES) as the silane agent. Fe(3)O(4)@SiO(2)-N(3) was directly reacted with N-propargyl iminodiacetic via click chemistry, in the presence of a Cu(I) catalyst, to acquire the IDA-modified Fe(3)O(4) NPs. Finally, through the addition of Cu(2+), the Fe(3)O(4)@SiO(2)-IDA-Cu NP product was obtained. The morphology, structure and composition of the NPs were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The resulting NPs showed a strong magnetic response to an externally applied magnetic field, a high adsorption capacity and excellent specificity towards hemoglobin (Hb). In addition, the Fe(3)O(4)@SiO(2)-IDA-Cu NPs can be used for the selective removal of abundant Hb protein in bovine and human blood samples.

Modular click assembly of degradable capsules using polyrotaxanes

A modular approach for the formation of degradable capsules using polyrotaxanes (PRXs) is described. The PRXs consist of α-cyclodextrin (αCD) and poly(ethylene glycol) (PEG), which are both biologically benign and the main degradation products of the capsules. The PRXs were equipped with three alkyne groups at their ends and could be successfully grafted to azide-functionalized silica particles (2.76 μm diameter) using azide-alkyne click chemistry. The assembled PRXs were then cross-linked using a degradable linker. The cross-linked structure was sufficiently robust to allow the formation of capsules after dissolving the template silica particles. The formation of capsules of ca. 2 μm diameter was verified by optical microscopy, TEM, and AFM imaging. The capsules were loaded with the chemotherapy drug doxorubicin (DOX) by conjugating it to the threaded αCDs via their free OH groups, while maintaining degradability of the capsules. Alkyne moieties at the surface of the cross-linked PRX architecture were available for further functionalization of the capsules, as is demonstrated by clicking on fluorescent PEG moieties. The DOX-loaded capsules were degraded within 90 min at 37 °C upon exposure to a 5 mM solution of glutathione in water.

Tin(IV) porphyrin functionalization of electrochemically active fluoride-doped tin-oxide (FTO) via Huisgen [3+2] click chemistry

A novel tetra-alkyne terminated tin(IV) porphyrin 3 was synthesized in good yields and characterized using NMR spectroscopy, high resolution mass spectrometry and X-ray crystallography, the latter revealing interactions with hexane molecules that stabilize the crystal structure of the tin(IV) porphyrin 3. It was then linked to a conductive fluorine-doped tin oxide (FTO) surfaces using Huisgen [3+2] click chemistry. The attachment of the tin(IV) porphyrin to the FTO surface 6 was characterized by X-ray photoelectron spectroscopy (XPS), indicating the presence of the 1,2,3-triazole unit. Electrochemical measurements of the tin(IV) porphyrin modified FTO surface 7 show that it is still electrochemically active with oxidation (Epa) and reduction peaks (Epc) for the ferricyanide redox couple observed at Epc and Epa of -0.144 and +0.568 V vs. Ag | AgCl respectively, representing a modest shift of ca . +/- 0.1–0.15 V, compared to unmodified FTO.

Discrete complexes immobilized onto click-SBA-15 silica: controllable loadings and the impact of surface coverage on catalysis

Azidopropyl functionalized mesoporous silica SBA-15 were prepared with variable azide loadings of 0.03-0.7 mmol g(-1) (~2-50% of maximal surface coverage) through a direct synthesis, co-condensation approach. These materials are functionalized selectively with ethynylated organic moieties through a copper-catalyzed azide alkyne cycloaddition (CuAAC) or "click" reaction. Specific loading within a material can be regulated by either the azide loading or limiting the alkyne reagent relative to the azide loading. The immobilization of ferrocene, pyrene, tris(pyridylmethyl)amine (TPA), and iron porphyrin (FeTPP) demonstrates the robust nature and reproducibility of this two-step synthetic attachment strategy. Loading-sensitive pyrene fluorescence correlates with a theoretically random surface distribution, rather than a uniform one; site-isolation of tethered moieties ~15 Å in length occurs at loadings less than 0.02 mmol g(-1). The effect of surface loading on reactivity is observed in the oxygenation of SBA-15-[Cu(I)(TPA)]. SBA-15-[Mn(II)(TPA)]-catalyzed epoxidation exhibits a systematic dependence on surface loading. A comparison of homogeneous, site-isolated and site-dense complexes provides insight into catalyst speciation and ligand activity.

Selective protein separation using siliceous materials with a trimethoxysilane-containing glycopolymer

A copolymer with α-D-mannose (Man) and trimethoxysilane (TMS) units was synthesized for immobilization on siliceous matrices such as a sensor cell and membrane. Immobilization of the trimethoxysilane-containing copolymer on the matrices was readily performed by incubation at high heat. The recognition of lectin by poly(Man-r-TMS) was evaluated by measurement with a quartz crystal microbalance (QCM) and adsorption on an affinity membrane, QCM results showed that the mannose-binding protein, concanavalin A, was specifically bound on a poly(Man-r-TMS)-immobilized cell with a higher binding constant than bovine serum albumin. The amount of concanavalin A adsorbed during permeation through a poly(Man-r-TMS)-immobilized membrane was higher than that through an unmodified membrane. Moreover, the concanavalin A adsorbed onto the poly(Man-r-TMS)-immobilized membrane was recoverable by permeation of a mannose derivative at high concentration.

Clusters of ligands on dendrimer surfaces

The development of methodology that is designed to allow a significant increase in the patterning and in the functionalization of the dendrimer is the ultimate goal of the research described here. Glycoside clusters based on TRIS were formed using click chemistry and were attached to PAMAM dendrimers. A series of dendrimers bearing tris-mannoside and an ethoxyethanol group was synthesized, and the binding interactions of these dendrimers with Concanavalin A were evaluated using inhibition ELISAs. The results of the inhibition ELISAs suggest that tris-mannoside clusters can replace individual sugars on the dendrimer without loss of function. Since tris-mannoside clustering allows for a redistribution of the dendrimers' surface functionalities, from this chemistry one can envision patterned dendrimers that incorporate multiple groups to increase the function and utility of the dendrimer.

Inorganic-organic hybrid materials through post-synthesis modification: Impact of the treatment with azides on the mesopore structure

Hybrid, hierarchically organized, monolithic silica gels, comprising periodically arranged mesopores and a cellular macroscopic network, have been prepared through a co-condensation reaction of tetrakis(2-hydroxyethyl)orthosilicate with chloromethyl-trimethoxysilane or 3-(chloropropyl)-triethoxysilane. Subsequent conversion of the chloro groups into azido groups, by nucleophilic substitution with NaN(3) in N,N-dimethylformamide, was conducted upon preservation of the monolithic structure. However, treatment with NaN(3) had a strong influence on the structure in the mesoporous regime, with changes such as an increase of mesopore diameter, pore volume and lattice constants, as well as a concomitant decrease of the pore wall thickness, as confirmed by small angle X-ray scattering, transmission electron microscopy, and nitrogen sorption analysis. Similar effects were observed for unmodified silica gels by simple ageing in azide-containing media, whether a relatively small or a sterically demanding counter ion (Na(+) or (H(3)C)(4)N(+)) was used. The structural modification did not seem to depend greatly on whether an organic aprotic solvent (N,N-dimethylformamide, 1,1,3,3-tetramethylurea, 1,3-dimethyl-2-imidazolidinone) or a protic solvent that can form hydrogen bonds, such as water, was used.

Application of click chemistry on preparation of separation materials for liquid chromatography

With the increasing requirement for analysis and separation of samples related to genomics, proteomics, metabolomics, pharmacology and agrochemistry, diverse stationary phases for liquid chromatography have been prepared by Cu(i)-catalyzed 1, 3-dipolar azide-alkyne cycloaddition reaction (CuAAC). It has been proved that CuAAC is a powerful tool for preparing covalently bonded stationary phases. In this tutorial review, we highlighted the preparation of separation materials by immobilization of functional groups on silica beads, polymer beads and agarose via CuAAC and their applications in liquid chromatography and related purposes, such as separation of polar compounds, enrichment of valuable bio-samples, orthogonal two-dimensional HPLC and chiral separation. Meanwhile, agarose-based separation materials for affinity chromatography are reviewed.

"Click" grafting of high loading of polymers and monosaccharides on surface of ordered mesoporous silica

The azide-alkyne cycloaddition "click" reaction was used to covalently bond high loadings of polymers and monosaccharides to the surface of an ordered mesoporous silica. The functionalization process was followed using thermogravimetry, gas adsorption, small-angle X-ray scattering, and infrared spectroscopy. Large-pore SBA-15 silica with cylindrical mesopores of diameter approximately 15 nm was synthesized using triisopropylbenzene as a micelle expander. The surface of the silica was modified with aminopropyl groups that were converted to propargyl-bearing groups through a reaction with 4-pentynoyl chloride. Thus prepared "clickable" pores were reacted with azide-functionalized poly(methyl methacrylate) (PMMA) and oligo(ethylene glycol) as well as protected and deprotected D-galactose. The new "grafting to" procedure allowed us to introduce uniform polymer films of thickness up to about 2 nm without any appreciable pore blocking, even for the polymer loading as high as 25 wt %. Uniform layers of monosaccharides with loadings up to 20 wt % were also obtained with remarkable grafting efficiency. No change in the periodic structure of the silica support was observed throughout the grafting process. These results demonstrate that the "click" reaction is a powerful approach to ordered mesoporous silicas with accessible pores functionalized with high loadings of various macromolecules and biomolecules.