| 1. |
- Zhang, Yan, et al.
(författare)
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Classification of Lipases Using Pattern Recognition through Transformation of Dynamic Hemithioacetal Systems
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A complex dynamic hemithioacetal system was generated for the evaluation of lipase reactivities. In combination with pattern recognition methodology, twelve different lipases were successfully classified into three distinct groups following their reaction selectivities and reactivities. A probe lipase was further categorized using the training matrix with predicted reactivity.
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| 2. |
- Zhang, Yan, et al.
(författare)
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Enzyme classification using complex dynamic hemithioacetal systems
- 2016
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 52:28, s. 5053-5056
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Tidskriftsartikel (refereegranskat)abstract
- A complex dynamic hemithioacetal system was generated for the evaluation of lipase reactivities in organic media. In combination with pattern recognition methodology, twelve different lipases were successfully classified into four distinct groups following their reaction selectivities and reactivities. A probe lipase was further categorized using the training matrix with predicted reactivity.
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| 3. |
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| 4. |
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| 5. |
- Al-Bataineh, Sameer A., et al.
(författare)
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Covalent Immobilization of Antibacterial Furanones via Photochemical Activation of Perfluorophenylazide
- 2009
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 25:13, s. 7432-7437
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Tidskriftsartikel (refereegranskat)abstract
- N-(3-Trimethoxysilylpropyl)-4-azido-2,3,5,6-tetrafluorobenzamide (PFPA-silane) was used as a photoactive crosslinker to immobilize antibacterial furanone molecules on silicon oxide surfaces. This immobilization strategy is useful, especially for substrates and molecules that lack reactive functional groups. To this end, cleaned wafers were initially incubated in solutions of different concentrations of PFPA-silane to form a monolayer presenting azido groups on the surface. The functionalized surfaces were then treated with a furanone solution followed by illumination with UV light and extensive rinsing with ethanol to remove noncovalently adhered molecules, In the presented study, we demonstrate the ability to control the surface density of the immobilized furanone molecules by adjusting the concentration of PFPA-silane solution used for surface functionalization using complementary surface analytical techniques. The fluorine in PFPA-silane and the bromine in furanone molecules were convenient markers for the XPS study. The ellipsometric layer thickness of the immobilized furanone molecules on the surface decreased with decreasing PFPA-silane concentration, which correlated with a decline of water contact angle as a sign of film collapse. The intensity of characteristic azide vibration in the MTR IR spectra was monitored as a function of PFPA-silane concentration, and the peak disappeared completely after furanone application followed by UV irradiation. As a complementary technique to XPS, TOF-SIMS provided valuable information on the chemical and molecular structure of the modified surfaces and spatial distribution of the immobilized furanone molecules. Finally, this report presents a convenient, reproducible, and robust strategy to design antibacterial coating based on furanone compounds for applications in human health care.
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| 6. |
- Chada, Sailaja, et al.
(författare)
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Self-assembled nanostructures from homopolymer induced by UV and solvent exposure
- 2008
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 4:11, s. 2164-2167
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Tidskriftsartikel (refereegranskat)abstract
- A simple method for creating self-assembled nanostructures using a single polymer system is reported. When spin-coated polystyrene thin films were irradiated with UV light and treated with toluene, unique nanostructures were observed, evolving from star-shaped networks to arrays of concentric circles. The nanostructure formation is a result of differential responses of crosslinked and oxidized products to the solvent by a combined effect of phase separation and solvent swelling. The nanostructures were observed for polymers of different molecular weights, films of different thicknesses, and on various substrates.
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| 7. |
- Chaudhary, Shilpi, et al.
(författare)
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Controlled short-linkage assembly of functional nano-objects
- 2014
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Ingår i: Applied Surface Science. - : Elsevier BV. - 1873-5584 .- 0169-4332. ; 300, s. 22-28
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we report a method that allows the deterministic, photo-controlled covalent assembly of nanoparticles directly on surface. As a model system, we study the conjugation of molecularly imprinted polymer (MIP) nanoparticles on a glass surface and confirm that the immobilized nanoparticles maintain their molecular recognition functionality. The glass slide was first modified with perfluorophenylazide and then used to bind MIP nanoparticles under UV irradiation. After each step the surface was analyzed by water contact angle measurement, fluorescence microscopy, scanning electron microscopy, and/or synchrotron-based X-ray photoelectron spectroscopy. The MIP nanoparticles immobilized on the glass surface remained stable and maintained specific binding for the template molecule, propranolol. The method developed in this work allows MIP nanoparticles to be directly coupled to a flat surface, offering a straightforward means to construct robust chemical sensors. Using the reported photo conjugation method, it is possible to generate patterned assembly of nanoparticles using a photomask. Since perfluorophenylazide-based photochemistry works with all kinds of organic material, the method developed in this work is expected to enable immobilization of not only MIPs but also other kinds of organic and inorganic-organic core-shell particles for various applications involving photon or electron transfer. (C) 2014 The Authors. Published by Elsevier B.V. All rights reserved.
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| 8. |
- Chen, Xuan, et al.
(författare)
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Glyconanomaterials : Emerging applications in biomedical research
- 2014
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Ingår i: Nano Reseach. - : Springer Science and Business Media LLC. - 1998-0124 .- 1998-0000. ; 7:10, s. 1381-1403
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Forskningsöversikt (refereegranskat)abstract
- Carbohydrates constitute the most abundant organic matter in nature, serving as structural components and energy sources, and mediating a wide range of cellular activities. The emergence of nanomaterials with distinct optical, magnetic, and electronic properties has witnessed a rapid adoption of these materials for biomedical research and applications. Nanomaterials of various shapes and sizes having large specific surface areas can be used as multivalent scaffolds to present carbohydrate ligands. The resulting glyconanomaterials effectively amplify the glycan-mediated interactions, making it possible to use these materials for sensing, imaging, diagnosis, and therapy. In this review, we summarize the synthetic strategies for the preparation of various glyconanomaterials. Examples are given where these glyconanomaterials have been used in sensing and differentiation of proteins and cells, as well as in imaging glycan-medicated cellular responses.
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| 9. |
- Chen, Y. C., et al.
(författare)
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Evaluation of molecularly imprinted polyurethane as an optical waveguide for PAH sensing
- 2004
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Ingår i: NANOSENSING. - : SPIE. ; , s. 513-520
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Konferensbidrag (refereegranskat)abstract
- We developed a numerical model for the fluorescence output efficiency of a molecularly imprinted polymer (MIP) waveguide sensing system. A polyurethane waveguide imprinted with a polycyclic aromatic hydrocarbon (PAH) molecule was fabricated using micromolding in capillaries. The coupling of light into a 5 mm long MIP segment was verified by comparing the output transmission signals of a deuterium lamp from the MIP waveguide collected by, an optical fiber with the background lamp signals collected by the same optical fiber. It was found that polyurethane MIP was an effective waveguide but absorbed much shorter wavelengths, especially ill the UV region. thereby the transmission of light appeared orange/red in color. The high background absorption of polyurethane in the spectrometric regions of interest was found to be a critical problem for sensor sensitivity. Our numerical model shows that the fluorescence output is only 2 X 10(-6) of the input excitation for 25 mM anthracene for a 5mm polyurethane waveguide. A 10 fold decrease of background absorption will increase the fluorescence output 250 times.
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| 10. |
- Chen, Y. C., et al.
(författare)
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Fluorescence anisotropy studies of molecularly imprinted polymers
- 2006
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Ingår i: Luminescence (Chichester, England Print). - : Wiley. - 1522-7235 .- 1522-7243. ; 21:1, s. 7-14
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Tidskriftsartikel (refereegranskat)abstract
- A molecularly imprinted polymer (MIP) is a biomimetic material that can be used as a biochemical sensing element. We studied the steady-state and time-resolved fluorescence and fluorescence anisotropy of anthracene-imprinted polyurethane. We compared MIPs with imprinted analytes present, MIPs with the imprinted analytes extracted, MIPs with rebound analytes, non-imprinted control polymers (non-MIPs) and non-MIPs bound with analytes to understand MIP’s binding behaviour. MIPs and non-MIPs had similar steady-state fluorescence anisotropy in the range 0.11-0.24. Anthracene rebound in MIPs and non-MIPs had a fluorescence lifetime of tau = 0.64 ns and a rotational correlation time of 0, = 1.2-1.5 ns, both of which were shorter than that of MIPs with imprinted analytes present (tau = 2.03 ns and phi(F) = 2.7 ns). The steady-state anisotropy of polymer solutions increased exponentially with polymerization time and might be used to characterize the polymerization extent in situ.
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| 11. |
- Chen, Y. C., et al.
(författare)
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Fluorescence-based optical sensor design for molecularly imprinted polymers
- 2004
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier BV. - 0925-4005 .- 1873-3077. ; 102:1, s. 107-116
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Tidskriftsartikel (refereegranskat)abstract
- A Monte Carlo model was developed to analyze the sensitivity and the performance of a fluorescence-based molecularly imprinted polymer (MIP) sensor. The MIP sensor consisted of highly cross-linked polyurethane containing anthracene binding sites coated on a transparent substrate. The optical properties of MlPs, the quantum yields of anthracene within MIPs, and the fluorescence of MlPs were measured. The rebinding capacity of the MIPs was about 1 mumol/g or roughly seven times binding rate of non-imprinted polymers. The MIP fluorescence emission at 404 nm was measured for thicknesses ranging from 100 to 2000 mum containing templated anthracene concentrations ranging from 60 to 600 ppm for excitation at 358 nm. The emission agreed with model predictions within 15%. This sensing system could only distinguish anthracene down to 15 ppm due to fluorescence from the polymer matrix. To make a fluorescence-based MIP sensor that is capable of detecting one part per billion analyte concentration with a 200 mum thick MIP film, our model suggests that imprinted polymers would need to have an absorption coefficient less than 0.001 cm(-1), or have a quantum yield 10(5) times lower than that of the analyte at the detection wavelength.
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| 12. |
- Chen, Y. C., et al.
(författare)
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Steady-state fluorescence anisotropy studies of molecularly imprinted polymer sensors
- 2004
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Ingår i: MOLECULARLY IMPRINTED MATERIALS-2003. - : Materials Research Society. - 1558997253 ; , s. 35-39
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Konferensbidrag (refereegranskat)abstract
- Molecularly imprinted polymers (MIPs) are used as recognition elements in biochemical sensors. In a fluorescence-based MIP sensor system, it can be difficult to distinguish the analyte fluorescence from the fluorescence of the polymer itself. We studied steady-state fluorescence anisotropy of anthracene imprinted in a polymer (polyurethane) matrix. Vertically polarized excitation light was incident on MIP films coated on silicon wafers; vertically and horizontally polarized emission was measured. We compared the fluorescence anisotropy of MIPs with imprinted molecules, MIPs with the imprinted molecules extracted, MIPs with rebound molecules, and nonimprinted control polymers. It is shown that differences in fluorescence anisotropy between the polymers and imprinted fluorescent molecules may provide a means to discriminate the fluorescence of analyte from that of the background polymer.
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| 13. |
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| 14. |
- Deng, Lingquan, et al.
(författare)
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Stereocontrolled 1-S-glycosylation and comparative binding studies of photoprobe-thiosaccharide conjugates with their O-linked analogs
- 2013
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Ingår i: Pure and Applied Chemistry. - 0033-4545 .- 1365-3075. ; 85:9, s. 1789-1801
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Tidskriftsartikel (refereegranskat)abstract
- The use of thioglycosides and other glycan derivatives with anomeric sulfur linkages is gaining increasing interest, both in synthesis and in various biological contexts. Herein, we demonstrate the occurrence and circumvention of anomerization during 1-S-glycosylation reactions, and present highly efficient and stereocontrolled syntheses of a series of photoprobe-thiosaccharide conjugates. Mutarotation of glycosyl thiols proved to be the origin of the anomeric mixtures formed, and kinetic effects could be used to circumvent anomerization. The synthesized carbohydrate conjugates were then evaluated by both solution- and solid-phase-based techniques. Both binding results showed that the S-linked glycosides interact with their cognate lectins comparably to the corresponding O-analogs in the present cases, thus demonstrating the reliability of the solid-support platform built upon our photo-initiated carbohydrate immobilization method for probing protein bindings, and showing the potential of combining these two means for studying carbohydrate-protein inter-actions.
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| 15. |
- Deng, Lingquan, et al.
(författare)
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Stereoselective synthesis of light-activatable perfluorophenylazide-conjugated carbohydrates for glycoarray fabrication and evaluation of structural effects on protein binding by SPR imaging
- 2011
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Ingår i: Organic and biomolecular chemistry. - : Royal Society of Chemistry (RSC). - 1477-0520 .- 1477-0539. ; 9:9, s. 3188-3198
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Tidskriftsartikel (refereegranskat)abstract
- A series of light-activatable perfluorophenylazide (PFPA)-conjugated carbohydrate structures have been synthesized and applied to glycoarray fabrication. The glycoconjugates were structurally varied with respect to anomeric attachment, S-, and O-linked carbohydrates, respectively, as well as linker structure and length. Efficient stereoselective synthetic routes were developed, leading to the formation of the PFPA-conjugated structures in good yields over few steps. The use of glycosyl thiols as donors proved especially efficient and provided the final compounds in up to 70% total yield with high anomeric purities. PFPA-based photochemistry was subsequently used to generate carbohydrate arrays on a polymeric surface, and surface plasmon resonance imaging (SPRi) was applied for evaluation of carbohydrate-protein interactions using the plant lectin Concanavalin A (Con A) as a probe. The results indicate better performance and equal efficiency of S-and O-linked structures with intermediate linker length.
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| 16. |
- Graupner, R K, et al.
(författare)
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Theoretical model for photochemical or thermally activated immobilization of macromolecules
- 2004
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 20:20, s. 8675-8680
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Tidskriftsartikel (refereegranskat)abstract
- The covalent immobilization of macromolecules on surfaces and within 3-dimensional networks is quantitatively described using a model based on Poisson statistics. This model determines the immobilized density or layer thickness as a function of molecular weight of the macromolecule or radiant exposure prior to and following the surface deposition of the macromolecule. Measurements of immobilized layer thickness provide first-order rate constants for decomposition of the surface-bound linker molecules and an estimate of the surface-bound linker density. The model predicts the relative density of immunocomplexed antibodies as a function of the irradiation time used to immobilize antigens. By providing the average number of bonds to the immobilized molecule, the model enables studies of the effect of multiple bonds on the activity of biomolecules. Experimental data by the authors and from the literature validate the model.
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| 17. |
- Hao, Nanjing, et al.
(författare)
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Glyconanomaterials for biosensing applications
- 2016
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Ingår i: Biosensors & bioelectronics. - : Elsevier. - 0956-5663 .- 1873-4235. ; 76:15, s. 113-130
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Tidskriftsartikel (refereegranskat)abstract
- Nanomaterials constitute a class of structures that have unique physiochemical properties and are excellent scaffolds for presenting carbohydrates, important biomolecules that mediate a wide variety of important biological events. The fabrication of carbohydrate-presenting nanomaterials, glyconanomaterials, is of high interest and utility, combining the features of nanoscale objects with biomolecular recognition. The structures can also produce strong multivalent effects, where the nanomaterial scaffold greatly enhances the relatively weak affinities of single carbohydrate ligands to the corresponding receptors, and effectively amplifies the carbohydrate-mediated interactions. Glyconanomaterials are thus an appealing platform for biosensing applications. In this review, we discuss the chemistry for conjugation of carbohydrates to nanomaterials, summarize strategies, and tabulate examples of applying glyconanomaterials in in vitro and in vivo sensing applications of proteins, microbes, and cells. The limitations and future perspectives of these emerging glyconanomaterials sensing systems are furthermore discussed.
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| 18. |
- Harnish, B., et al.
(författare)
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UV-cross-linked poly(vinylpyridine) thin films as reversibly responsive surfaces
- 2005
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 17:16, s. 4092-4096
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Tidskriftsartikel (refereegranskat)abstract
- We report that UV-cross-linked poly(4-vinylpyridine) (P4VP) films acted as reversibly responsive coatings that controlled surface wettability and swelling toward external stimuli: solvent and pH. The polymer films were prepared simply by spin-coating a solution of P4VP followed by UV irradiation. These cross-linked films, when treated with chloroform, showed similar to 31% increase in film thickness whereas films extracted with methylene chloride or n-butanol exhibited a slight decrease. The increase in film thickness was due to the protonation of pyridyl groups by hydrogen chloride resulting from the photodegeneration of chloroform. The film expanded to minimize repulsion around the charged centers. This hypothesis was further confirmed by exposing the cross-linked film to hydrogen chloride vapor. The film expanded similar to 37% whereas no thickness increase was observed for films exposed to ammonia or methanol vapors. The extent of swelling was monitored in situ using a quartz crystal microbalance sensor. Large oscillation frequency shifts were detected when the UV-cross-linked P4VP film was exposed to acidic buffer solutions. The changes were rapid, and the effect was reversible.
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| 19. |
- Kamra, Tripta, et al.
(författare)
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Photoconjugation of Molecularly Imprinted Polymer Nanoparticles for Surface-Enhanced Raman Detection of Propranolol
- 2015
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 7:49, s. 27479-27485
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Tidskriftsartikel (refereegranskat)abstract
- We report a simple and versatile method to covalently immobilize molecularly imprinted polymer (MIP) nanoparticles on a Raman active substrate (Klarite) using a disulfide-derivatized perfluorophenylazide (PFPA-disulfide). Gold-coated Klarite was functionalized with PFPA-disulfide via a gold sulfur bond. Upon light radiation, the available azido groups were converted to highly reactive singlet perfluorophenyl nitrene that undergoes a CH insertion reaction and form covalent bonds with the MIP nanoparticles. The resulting surfaces were characterized using scanning electron microscopy and surface enhanced Raman spectroscopy to study the morphology and template affinity of the surfaces, respectively. The Raman measurements clearly show a dose-responsive signal when propranolol binds to the MIP surface. Because the MIP particles were covalently attached to the Raman active substrate, the sensing surface was stable and could be reused after regeneration in acetic acid solution. The MIP-based Raman sensor was used successfully to detect propranolol in urine samples (7.7 X 10(-4) M). Our results show that the high selectivity of MLPs and the fingerprint Raman identification can be integrated into a compact sensing unit using high-efficiency photoconjugation. Thus, the method proposed is reliable, efficient and fast for fabricating label-free chemical sensors.
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| 20. |
- Karalius, Antanas, et al.
(författare)
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Formation and Out-of-Equilibrium, High/Low State Switching of a Nitroaldol Dynamer in Neutral Aqueous Media
- 2020
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Ingår i: Angewandte Chemie International Edition. - : Wiley-VCH Verlag. - 1433-7851 .- 1521-3773. ; 59:9, s. 3434-3438
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Tidskriftsartikel (refereegranskat)abstract
- The nitroaldol reaction is demonstrated as an efficient dynamic covalent reaction in phosphate buffers at neutral pH. Rapid equilibration was recorded with pyridine-based aldehydes, and dynamic oligomerization could be achieved, leading to nitroaldol dynamers of up to 17 repeating units. The dynamers were applied in a coherent stimuli-responsive molecular system in which larger dynamers transiently existed out-of-equilibrium in a neutral aqueous system rich in formaldehyde, controlled by nitromethane.
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| 21. |
- Karalius, Antanas, et al.
(författare)
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Rapidly Exchanging, Double-Dynamic, Catalyst-Free Nitroaldol-Hemiacetal Systems for Metal-Responsive Reversible Polymerization
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A spontaneous, catalyst-free, reversible nitroaldol reaction is reported. The reaction wasused to create dynamic systems and to evaluate their scope and applicability. The thermodynamicand kinetic properties of the reaction were estimated, showing substantial solvent effects andatypical behavior regarding fluctuations and conversion overshoots. This was especially the casewhere the dynamic process was coupled with hemiacetal formation. Multifunctional building blockswere furthermore explored to generate responsive molecular systems, where zinc-coordinationcould be used to downregulate the nitroaldol reaction through the amplification of a dihemiacetalspecies. The systems were also extended to dynamic oligomer formation, where the molecularweight could be predictably upregulated by concentration increase and downregulated throughmetal coordination-induced amplification.
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| 22. |
- Knudsen, Daniel, et al.
(författare)
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Creating Microstructures on Silicon Wafers Using UV-Crosslinked Polystyrene Thin Films
- 2009
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Ingår i: Polymer Engineering and Science. - : Wiley. - 0032-3888 .- 1548-2634. ; 49, s. 945-948
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Tidskriftsartikel (refereegranskat)abstract
- We report that UV-crosslinked polystyrene (PS) thin films can be used as an inexpensive wet chemical etch resist to create microstructures on silicon wafers. When spin-coated PS films were irradiated, the polymer undergoes UV-induced crosslinking. Patterned PS films were successfully used as the protective layer withstanding chemical etching with the buffered HF solution. Removal of the polymer films by sonicating in water generated microstructures in silicon wafers. This simple and environmentally friendly procedure employs inexpensive commodity polymer and eliminates the use of organic solvents and harsh conditions in the subsequent development process. POLYM. ENG. SCI., 49:945-948, 2009. (C) 2009 Society of Plastics Engineers
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| 23. |
- Kong, Na, et al.
(författare)
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Carbohydrate conjugation through microwave-assisted functionalization of single-walled carbon nanotubes using perfluorophenyl azides
- 2015
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Ingår i: Carbohydrate Research. - : Elsevier BV. - 0008-6215 .- 1873-426X. ; 405, s. 33-38
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Tidskriftsartikel (refereegranskat)abstract
- Carbohydrate-functionalized single-walled carbon nanotubes (SWNTs) were synthesized using microwave-assisted reaction of perfluorophenyl azide with the nanotubes. The results showed that microwave radiation provides a rapid and effective means to covalently attach carbohydrates to SWNTs, producing carbohydrate-SWNT conjugates for biorecognition. The carbohydrate-functionalized SWNTs were furthermore shown to interact specifically with cognate carbohydrate-specific proteins (lectins), resulting in predicted recognition patterns. The carbohydrate-presenting SWNTs constitute a new platform for sensitive protein-or cell recognition, which pave the way for glycoconjugated carbon nanomaterials in biorecognition applications.
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| 24. |
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| 25. |
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| 26. |
- Kong, Na, et al.
(författare)
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Carbohydrate Functionalization of Few-Layer Graphene through Microwave-Assisted Reaction of Perfluorophenyl Azide
- 2019
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Ingår i: ACS Applied Bio Materials. - : American Chemical Society. - 2576-6422. ; 2:1, s. 284-291
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Tidskriftsartikel (refereegranskat)abstract
- The excellent physical and chemical properties of graphene make it an attractive nanomaterial and a component in high-performance nanocomposite materials. To prepare graphene-based nanocomposite materials, chemical functionalization is often necessary. Water-soluble ligands such as carbohydrates not only make the functionalized graphene compatible with aqueous media, but also introduce biorecognition, which is important for graphene to be used in biotechnology. In this study, we report the derivatization of few-layer graphene (FLG) with carbohydrates through microwave-assisted reaction of perfluorophenyl azide (PFPA). FLG was first treated with PFPA under microwave radiation. Subsequent conjugation with glycosyl amine gave carbohydrate-presenting FLG. Thermogravimetric analysis showed that microwave radiation gave a higher degree of functionalization compared to conventional heating, with higher weight losses for both PFPA and Man ligands. The carbohydrates (mannose and galactose) retained their bioactivity, as demonstrated by the lectin binding assays. Higher degree of binding toward lectins was obtained for the carbohydrate-functionalized FLG prepared by microwave radiation than the conventional heating.
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| 27. |
- Kong, Na, 1984-
(författare)
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Carbohydrate-Functionalized Nanomaterials : Synthesis, Characterization and Biorecognition Studies
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on the development of carbohydrate coupling chemistry on nanomaterials and their biological activity studies. It is divided into two parts:In part one, two carbohydrate immobilization approaches, based on perfluorophenyl azide (PFPA)-functionalized silica nanoparticles (SNPs), are presented, where the binding affinity of the glyconanoparticles was evaluated through carbohydrate-lectin interaction. In the first approach, PFPAfunctionalized SNPs were treated with propargylated glycosides and functionalized under copper-catalyzed azide-alkyne cycloaddition (CuAAC) conditions to give glyconanoparticles. For the second approach, a metal-free coupling chemistry based on perfluorophenyl azide-aldehyde-amine cycloaddition (AAAC) was developed for carbohydrate immobilization on PFPA-functionalized SNPs using glycosyl amine and phenylacetaldehyde. Subsequently, a quantitative fluorine nuclear magnetic resonance (19F qNMR) technique was developed to determine the carbohydrate density on the glyconanoparticles. The addition of an internal standard allowed the accurate determination of carbohydrate density, which was then used to calculate the apparent dissociation constant (Kd ) of the glyconanoparticles with lectin by a ligand competition assay. The developed approaches proved general and versatile, and the carbohydrate-presenting nanoplatforms showed high binding specificity in lectin binding.In part two, microwave irradiation was used to functionalize carbon nanomaterials with PFPA followed by carbohydrate conjugation. The microwave-assisted method proved efficient for a number of carbon nanomaterials including carbon nanotubes (CNTs), graphene and fullerene. The carbohydrates on the glyconanomaterials retained their binding patterns towards cognate lectins.
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| 28. |
- Kong, Na, et al.
(författare)
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Catalyst-Free Cycloaddition Reaction for the Synthesis of Glyconanoparticles
- 2016
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 8:41, s. 28136-28142
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Tidskriftsartikel (refereegranskat)abstract
- A new conjugation method for the immobilization of carbohydrates on nanomaterials was demonstrated simply by mixing perfluorophenyl azide-functionalized silica nanoparticles (SNPs), an amine-derivatized carbohydrate, and phenylacetaldehyde under ambient conditions without any catalyst. The density of carbohydrates on the glyconanoparticles was determined using the quantitative F-19 NMR (F-19 qNMR) technique; for example, the density of D-mannose (Man) on Man-SNPs was 2.5 +/- 0.2 x 10(-16) nmol/nm(2). The glyconanoparticles retained their binding affinity and selectivity toward cognate lectins. The apparent dissociation constant of the glyconanoparticles was measured by a fluorescence competition assay, where the binding affinity of Man-SNPs was almost 4 orders of magnitude higher than that of Man with concanavalin A. Moreover, even with a ligand density of 2.6 times lower than Man-SNPs synthesized by the copper catalyzed azide-alkyne cycloaddition, the binding affinity of Man-SNPs prepared by the current method was more than 4 times higher.
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| 29. |
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| 30. |
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| 31. |
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| 32. |
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| 33. |
- Kong, Na, et al.
(författare)
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Quantitative Fluorine NMR To Determine Carbohydrate Density on Glyconanomaterials Synthesized from Perfluorophenyl Azide-Functionalized Silica Nanoparticles by Click Reaction
- 2015
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 87:18, s. 9451-9458
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Tidskriftsartikel (refereegranskat)abstract
- A quantitative fluorine NMR (F-19 qNMR) method was developed to determine the carbohydrate density on glyconanomaterials. Mannose (Man)- and galactose (Gal)-conjugated silica nanoparticles (SNPs) were synthesized from perfluorophenyl azide (PFPA)-functionalized SNPs and propargylated Man or Gal by copper-catalyzed azide-alkyne cycloaddition (click reaction). After treating PFPA-SNPs or Man-SNPs with hydrofluoric acid followed by lyophilization, the remaining residues were directly subjected to F-19 NMR analysis. The density of PFPA on PFPA-SNP was determined to be 7.7 +/- 0.2 x 10(-16) nmol/nm(2) and Man on Man-SNP to be 6.4 +/- 0.2 x 10(-16) nmol/nm(2) giving a yield of similar to 83% for the click coupling reaction. The apparent dissociation constant (K-d) of Man-SNPs with fluorescein isothiocyanate(FITC)-concanavalin A (Con A) was determined using a fluorescence competition assay to be 0.289 +/- 0.003 mu M, which represents more than 3 orders of magnitude affinity increase compared to free Man with Con A.
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| 34. |
- Kubo, Takuya, et al.
(författare)
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Polymer-based photocoupling agent for the efficient immobilization of nanomaterials and small molecules
- 2011
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 27:15, s. 9372-9378
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Tidskriftsartikel (refereegranskat)abstract
- A highly efficient photocoupling agent, based on perfluorophenylazide (PFPA)-conjugated polyallylamine (PAAm), was developed for the efficient immobilization of polymers, nanoparticles, graphene, and small molecules. The conjugate, PAAm–PFPA, was synthesized, and the percentage of the photoactive moiety, PFPA, can be controlled by the ratio of the two components in the synthesis. By treating epoxy-functionalized wafers with PAAm–PFPA, photoactive surfaces were generated. Compared with the PFPA surface, these polymer-based photocoupling matrix resulted in significantly enhanced immobilization efficiencies, especially for nanomaterials and small molecules. Thus, polystyrene nanoparticles (PS NPs) and alkyl-functionalized silica nanoparticles (SNPs) were successfully immobilized on the PAAm–PFPA surface, resulting in a high material density. Graphene flakes patterned on the PAAm–PFPA surface showed improved feature resolution in addition to a higher material density compared to that of flakes immobilized on the PFPA surface. Furthermore, 2-O-α-d-mannopyranosyl-d-mannopyranose (Man2) immobilized on the PAAm–PFPA surface exhibited significantly enhanced signals when treated with lectin concanavalin A (Con A).
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| 35. |
- Liu, Li, et al.
(författare)
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A general approach to the covalent immobilization of single polymers
- 2006
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 45:37, s. 6207-6210
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Tidskriftsartikel (refereegranskat)abstract
- Stuck fast: The covalent immobilization of polymeric single molecules is achieved by the photochemically induced C-H/N-H insertion reaction of perfluorophenylazides (see picture). When the concentration of the surface azido groups is decreased, isolated polymeric single molecules are observed. This technique is especially suited for materials that do not possess functional groups and are difficult to be immobilized by other means. (Chemical Equation Presented).
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| 36. |
- Liu, Li-Hong, et al.
(författare)
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A simple and scalable route to wafer-size patterned graphene
- 2010
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 20:24, s. 5041-5046
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Tidskriftsartikel (refereegranskat)abstract
- Producing large-scale graphene films with controllable patterns is an essential component of graphene-based nanodevice fabrication. Current methods of graphene pattern preparation involve either high cost, low throughput patterning processes or sophisticated instruments, hindering their large-scale fabrication and practical applications. We report a simple, effective, and reproducible approach for patterning graphene films with controllable feature sizes and shapes. The patterns were generated using a versatile photocoupling chemistry. Features from micrometres to centimetres were fabricated using a conventional photolithography process. This method is simple, general, and applicable to a wide range of substrates including silicon wafers, glass slides, and metal films.
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| 37. |
- Liu, Li-Hong, et al.
(författare)
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Derivitization of Pristine Graphene with Well-Defined Chemical Functionalities
- 2010
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 10:9, s. 3754-3756
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Tidskriftsartikel (refereegranskat)abstract
- Covalent functionalization of pristine graphene poses considerable challenges due to the lack of reactive functional groups. Herein, we report a simple and general method to covalently functionalize pristine graphene with well-defined chemical functionalities. It is a solution-based process where solvent-exfoliated graphene was treated with perfluorophenylazide (PFPA) by photochemical or thermal activation. Graphene with well-defined functionalities was synthesized, and the resulting materials were soluble in organic solvents or water depending on the nature of the functional group on PFPA.
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| 38. |
- Liu, Li-Hong, et al.
(författare)
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Electrical Properties of Covalently Immobilized Single-Layer Graphene Devices
- 2011
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Ingår i: Journal of Nanoscience and Nanotechnology. - : American Scientific Publishers. - 1533-4880 .- 1533-4899. ; 11:2, s. 1288-1292
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Tidskriftsartikel (refereegranskat)abstract
- Arrays of covalently immobilized and aligned graphene ribbons have been successfully prepared on silicon wafers. The effect of covalent modification on the electrical properties of the single-layer graphene was investigated. The effective electron field mobility of the constructed FETs, measured at 2700 cm(2)V(-1)s(-1), was higher than that for graphene film directly deposited on SiO(2), possibly due to lower phonon scattering from the substrate surface, implying that the field effect mobilities may be enhanced with proper choice of substrates. The contact resistance between Cr electrodes and the single-layer graphene ribbon was determined to be 1.62 k Omega from the TLM structures.
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| 39. |
- Liu, Li-Hong, et al.
(författare)
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Functionalization of pristine graphene with perfluorophenyl azides
- 2011
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 21:10, s. 3273-3276
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we highlight the recent work on the covalent functionalization of pristine graphene with perfluorophenyl azides (PFPAs). Three approaches were developed where PFPAs were employed to derivatize pristine graphene with well-defined functional groups, to fabricate graphene films and ribbons, and to generate patterned graphene structures by photolithography.
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| 40. |
- Liu, Li-Hong, et al.
(författare)
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Perfluorophenyl Azides : New Applications in Surface Functionalization and Nanomaterial Synthesis
- 2010
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Ingår i: Accounts of Chemical Research. - : American Chemical Society (ACS). - 0001-4842 .- 1520-4898. ; 43:11, s. 1434-1443
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Forskningsöversikt (refereegranskat)abstract
- A major challenge in materials science is the ongoing search for coupling agents that are readily synthesized, capable of versatile chemistry, able to easily functionalize materials and surfaces, and efficient in covalently linking organic and inorganic entities. A decade ago, we began a research program investigating perfluorophenylazides (PFPA) as the coupling agents in surface functionalization and nanomaterial synthesis. The p-substituted PFPAs are attractive heterobifunctional coupling agents because of their two distinct and synthetically distinguishable reactive centers: (i) the fluorinated phenylazide, which is capable of forming stable covalent adducts, and (ii) the functional group R, which can be tailored through synthesis. Two approaches have been undertaken for material synthesis and surface functionalization. The first method involves synthesizing PFPA bearing the first molecule or material with a functional linker R and then attaching the resulting PFPA to the second material by activating the azido group. In the second approach, the material surface is first functionalized with PFPA via functional center R, and coupling of the second molecule or material is achieved with the surface azido groups. In this Account, we review the design and protocols of the two approaches, providing examples in which PFPA derivatives were successfully used in material surface functionalization, ligand conjugation, and the synthesis of hybrid nanomaterials. The methods developed have proved to be general and versatile, and they are applicable to a wide range of materials (especially those that lack reactive functional groups or are difficult to derivatize) and to various substrates of polymers, oxides, carbon materials, and metal films. The coupling chemistry can be initiated by light, heat, and electrons. Patterned structures can be generated by selectively activating the areas of interest. Furthermore, the process is easy to perform, and light activation occurs in minutes, greatly facilitating the efficiency of the reaction. PFPAs indeed demonstrate many benefits as versatile surface coupling agents and offer opportunities for further exploration.
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| 41. |
- Liu, Li-Hong, et al.
(författare)
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Photoinitiated Coupling of Unmodified Monosaccharides to Iron Oxide Nanoparticles for Sensing Proteins and Bacteria
- 2009
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Ingår i: Bioconjugate chemistry. - : American Chemical Society (ACS). - 1043-1802 .- 1520-4812. ; 20:7, s. 1349-1355
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Tidskriftsartikel (refereegranskat)abstract
- We report a versatile approach for the immobilization of unmodified monosaccharides onto iron oxide nanoparticles. Covalent coupling of the carbohydrate onto iron oxide nanoparticle surfaces was accomplished by the CH insertion reaction of photochemically activated phosphate-functionalized perfluorophenylazides (PFPAs), and the resulting glyconanoparticles were characterized by IR, TGA, and TEM. The surface-bound D-mannose showed the recognition ability toward Concanavalin A and Escherichia coli strain ORN178 that possesses mannose-specific receptor sites. Owing to the simplicity and versatility of the technique, together with the magnetic property of iron oxide nanoparticles, the methodology developed in this study serves as a general approach for the preparation of magnetic glyconanoparticles to be used in clinical diagnosis, sensing, and decontamination.
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| 42. |
- Liu, Li-Hong, et al.
(författare)
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Simple Method for the Covalent Immobilization of Graphene
- 2009
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 9:9, s. 3375-3378
-
Tidskriftsartikel (refereegranskat)abstract
- We present a simple and efficient method to immobilize graphene on silicon wafers using perfluorophenylazide (PFPA) as the coupling agent. Graphene sheets were covalently attached to PFPA-functionalized wafer surface by a simple heat treatment under ambient conditions. The formation of single and multiple layers of graphene were confirmed by Raman spectroscopy and optical and atomic force microscopy. Evidence of covalent bond formation between graphene and PFPA decorated silicon wafer was given by X-ray photoelectron spectroscopy and sonication treatment.
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| 43. |
- Liu, Li, et al.
(författare)
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Surface and interface control on photochemically initiated immobilization
- 2006
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 128:43, s. 14067-14072
-
Tidskriftsartikel (refereegranskat)abstract
- Surface and interface properties are important in controlling the yield and efficiency of the photochemically initiated immobilization. Using a silane-functionalized perfluorophenyl azide (PFPA-silane) as the photoactive cross-linker, the immobilization of polymers was studied by adjusting the density of the surface azido groups. Dilution of the photolinker resulted in a gradual decrease in the density of surface azido groups as well as the thickness of the immobilized film. When a nonphotoactive silane was added to PFPA-silane, the film thickness decreased more rapidly, suggesting that the additive competed with PFPA-silane and effectively reduced the density of the surface azido groups. The effect of surface topography was studied by adding a nonphotoactive silane with either a shorter (n-propyltrimethoxysilane (PTMS)) or a longer spacer (n-octadecyltrimethoxysilane (ODTMS)). In most cases the long chain ODTMS shielded the surface azido groups, resulting in a more rapid decrease in film thickness as compared to PTMS treated under the same conditions. As the density of the surface azido groups decreased, the immobilized polymer changed from smooth films to patched structures and, eventually, single polymer molecules.
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| 44. |
- Liu, Wei, et al.
(författare)
-
Surface plasmon resonance imaging of limited glycoprotein samples
- 2008
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Ingår i: The Analyst. - : Royal Society of Chemistry (RSC). - 0003-2654 .- 1364-5528. ; 133:9, s. 1268-1273
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Tidskriftsartikel (refereegranskat)abstract
- A surface plasmon resonance imaging method has been developed for high throughput recognition and determination of low level glycoproteins with limited sample volume at least down to 50 nL. Chicken ovalbumin and immunoglobulin G were chosen as model compounds while bovine serum albumin and lysozyme were used as control. Each protein, at a concentration of 0.0080-1.0 mg mL(-1), was printed on one gold sensing film, and the films were simultaneously reacted with a probe solution and viewed using a laboratory-built surface plasmon resonance imaging system. The imaging signals were dependent on the concentration and the type of analyte, with a limit of detection down to at least 0.5 ng. The glycoproteins dotted at either 1.0 mg mL(-1) or 0.010 mg mL(-1) were easily differentiated from the non-glycoproteins by reaction with 200 nM concanavalin A (con A), giving a limit of recognition down also to 0.5 ng glycoprotein. This imaging method was hence considered a new tool for analyzing glycoproteins.
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| 45. |
- Liyanage, Sajani H., et al.
(författare)
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Azide-Masked Fluorescence Turn-On Probe for Imaging Mycobacteria
- 2023
-
Ingår i: JACS Au. - : American Chemical Society (ACS). - 2691-3704. ; 3:4, s. 1017-1028
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Tidskriftsartikel (refereegranskat)abstract
- A fluorescence turn-on probe, an azide-masked and trehalosederivatized carbazole (Tre-Cz), was developed to image mycobacteria. The fluorescence turn-on is achieved by photoactivation of the azide, which generates a fluorescent product through an efficient intramolecular C-H insertion reaction. The probe is highly specific for mycobacteria and could image mycobacteria in the presence of other Gram-positive and Gram-negative bacteria. Both the photoactivation and detection can be accomplished using a handheld UV lamp, giving a limit of detection of 10(3) CFU/mL, which can be visualized by the naked eye. The probe was also able to image mycobacteria spiked in sputum samples, although the detection sensitivity was lower. Studies using heat-killed, stationary-phase, and isoniazid-treated mycobacteria showed that metabolically active bacteria are required for the uptake of Tre-Cz. The uptake decreased in the presence of trehalose in a concentration-dependent manner, indicating that Tre-Cz hijacked the trehalose uptake pathway. Mechanistic studies demonstrated that the trehalose transporter LpqY-SugABC was the primary pathway for the uptake of Tre-Cz. The uptake decreased in the LpqY-SugABC deletion mutants Delta lpqY, Delta sugA, Delta sugB, and Delta sugC and fully recovered in the complemented strain of Delta sugC. For the mycolyl transferase antigen 85 complex (Ag85), however, only a slight reduction of uptake was observed in the Ag85 deletion mutant Delta Ag85C, and no incorporation of Tre-Cz into the outer membrane was observed. The unique intracellular incorporation mechanism of Tre-Cz through the LpqY-SugABC transporter, which differs from other trehalose-based fluorescence probes, unlocks potential opportunities to bring molecular cargoes to mycobacteria for both fundamental studies and theranostic applications.
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| 46. |
- Ndugire, William, et al.
(författare)
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Gold Nanoclusters as Nanoantibiotic Auranofin Analogues
- 2022
-
Ingår i: Advanced Healthcare Materials. - : John Wiley & Sons. - 2192-2640 .- 2192-2659. ; 11:9
-
Tidskriftsartikel (refereegranskat)abstract
- Auranofin, a gold(I)-complex with tetraacetylated thioglucose (Ac(4)GlcSH) and triethylphosphine ligands, is an FDA-approved drug used as an anti-inflammatory aid in the treatment of rheumatoid arthritis. In repurposing auranofin for other diseases, it was found that the drug showed significant activity against Gram-positive but was inactive against Gram-negative bacteria. Herein, the design and synthesis of gold nanoclusters (AuNCs) based on the structural motif of auranofin are reported. Phosphine-capped AuNCs are synthesized and glycosylated, yielding auranofin analogues with mixed triphenylphosphine monosulfonate (TPPMS)/Ac(4)GlcSH ligand shells. These AuNCs are active against both Gram-negative and Gram-positive bacteria, including multidrug-resistant pathogens. Notably, an auranofin analogue, a mixed-ligand 1.6 nm AuNC 4b, is more active than auranofin against Pseudomonas aeruginosa, while exhibiting lower toxicity against human A549 cells. The enhanced antibacterial activity of these AuNCs is characterized by a greater uptake of Au by the bacteria compared to Au-I complexes. Additional factors include increased oxidative stress, moderate inhibition of thioredoxin reductase (TrxR), and DNA damage. Most intriguingly, the uptake of AuNCs are not affected by the bacterial outer membrane (OM) barrier or by binding with the extracellular proteins. This contrasts with Au-I complexes like auranofin that are susceptible to protein binding and hindered by the OM barrier.
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| 47. |
- Ndugire, William, et al.
(författare)
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Turning on the Antimicrobial Activity of Gold Nanoclusters Against Multidrug-Resistant Bacteria
- 2023
-
Ingår i: Angewandte Chemie International Edition. - : John Wiley & Sons. - 1433-7851 .- 1521-3773. ; 62:11
-
Tidskriftsartikel (refereegranskat)abstract
- In this work, we show that the addition of thiourea (TU) initiated broad-spectrum antimicrobial activity of otherwise inactive D-maltose-capped gold nanoclusters (AuNC-Mal). For example, AuNC-Mal/TU was effective against multidrug-resistant Pseudomonas aeruginosa with a minimum inhibitory concentration (MIC) of 1 mu g mL(-1) (2.5 mu M [Au]) while having 30-60 times lower in vitro cytotoxicity against mammalian cells. The reaction of AuNC-Mal and TU generated the antimicrobial species of [Au(TU)(2)](+) and smaller AuNCs. TU increased the accumulation of Au in bacteria and helped maintain the oxidation state as Au-I (vs. Au-III). The modes of action included the inhibition of thioredoxin reductase, interference with the Cu-I regulation and depletion of ATP. Moreover, the antimicrobial activity did not change in the presence of colistin or carbonyl cyanide 3-chlorophenylhydrazone, suggesting that AuNC-Mal/TU was indifferent to the outer membrane barrier and to bacterial efflux pumps.
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| 48. |
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| 49. |
- Norberg, Oscar, et al.
(författare)
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Photo-Click Immobilization of Carbohydrates on Polymeric Surfaces - A Quick Method to Functionalize Surfaces for Biomolecular Recognition Studies
- 2009
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Ingår i: Bioconjugate chemistry. - : American Chemical Society (ACS). - 1043-1802 .- 1520-4812. ; 20:12, s. 2364-2370
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Tidskriftsartikel (refereegranskat)abstract
- Methods to rapidly functionalize specific polymeric surfaces with alkynes, which can subsequently be linked to azide-containing carbohydrates, are presented. The methods comprise two main concepts: azide photoligation and Cu-catalyzed azide-alkyne cycloaddition. 2-Azidoethyl-functionalized CL-D-mannopyranoside was synthesized and covalently attached to alkyne-functionalized polymeric surfaces using the techniques. The protein recognition properties of the carbollydrate-presenting surfaces were evaluated using quartz crystal microbalance biosensor instrumentation.
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| 50. |
- Norberg, Oscar, et al.
(författare)
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Photo-Click Immobilization on Quartz Crystal Microbalance Sensors for Selective Carbohydrate-Protein Interaction Analyses
- 2011
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 83:3, s. 1000-1007
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Tidskriftsartikel (refereegranskat)abstract
- A photoclick method based on azide photoligation and Cu-catalyzed azide-alkyne cycloaddition has been evaluated for the immobilization of carbohydrates to polymeric materials. The biomolecular recognition properties of the materials have been investigated with regard to applicable polymeric substrates and selectivity of protein binding. The method was used to functionalize a range of polymeric surfaces (polystyrene, polyacrylamide, poly(ethylene glycol), poly(2-ethyl-2-oxazoline), and polypropene) with various carbohydrate structures (based on alpha-D-mannose, beta-D-galactose, and N-acetyl-beta-D-glucosamine). The functionalized surfaces were evaluated in real-time studies of protein-carbohydrate interactions using a quartz crystal microbalance flow through system with a series of different carbohydrate-binding proteins (lectins). The method proved to be robust and versatile, resulting in a range of efficient sensors showing high and predictable protein selectivities.
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