1,721,101 research outputs found
Dual switchable CRET-induced luminescence of CdSe/ZnS quantum dots (QDs) by the hemin/G-quadruplex-bridged aggregation and deaggregation of two-sized QDs
No full textThe hemin/G-quadruplex-catalyzed generation of chemiluminescence through the oxidation of luminol by H2O2 stimulates the chemiluminescence resonance energy transfer (CRET) to CdSe/ZnS quantum dots (QDs), resulting in the luminescence of the QDs. By the cyclic K+-ion-induced formation of the hemin/G-quadruplex linked to the QDs, and the separation of the G-quadruplex in the presence of 18-crown-6-ether, the ON-OFF switchable CRET-induced luminescence of the QDs is demonstrated. QDs were modified with nucleic acids consisting of the G-quadruplex subunits sequences and of programmed domains that can be cross-linked through hybridization, using an auxiliary scaffold. In the presence of K+-ions, the QDs aggregate through the cooperative stabilization of K+-ion-stabilized G-quadruplex bridges and duplex domains between the auxiliary scaffold and the nucleic acids associated with the QDs. In the presence of 18-crown-6-ether, the K+-ions are eliminated from the G-quadruplex units, leading to the separation of the aggregated QDs. By the cyclic treatment of the QDs with K+-ions/18-crown-6-ether, the reversible aggregation/deaggregation of the QDs is demonstrated. The incorporation of hemin into the K+-ion-stabilized G-quadruplex leads to the ON-OFF switchable CRET-stimulated luminescence of the QDs. By the mixing of appropriately modified two-sized QDs, emitting at 540 and 610 nm, the dual ON-OFF activation of the luminescence of the QDs is demonstrated
Recent Advances in the Synthesis and Functions of Reconfigurable Interlocked DNA Nanostructures
No full textInterlocked circular DNA nanostructures, e.g., catenanes or rotaxanes, provide functional materials within the area of DNA nanotechnology. Specifically, the triggered reversible reconfiguration of the catenane or rotaxane structures provides a means to yield new DNA switches and to use them as dynamic scaffolds for controlling chemical functions and positioning functional cargoes. The synthesis of two-ring catenanes and their switchable reconfiguration by pH, metal ions, or fuel/anti-fuel stimuli are presented, and the functions of these systems, as pendulum or rotor devices or as switchable catalysts, are described. Also, the synthesis of three-, five-, and seven-ring catenanes is presented, and their switchable reconfiguration using fuel/anti-fuel strands is addressed. Implementation of the dynamically reconfigured catenane structures for the programmed organization of Au nanoparticle (NP) assemblies, which allows the plasmonic control of the fluorescence properties of Au NP/fluorophore loads associated with the scaffold, and for the operation of logic gates is discussed. Interlocked DNA rotaxanes and their different synthetic approaches are presented, and their switchable reconfiguration by means of fuel/anti-fuel strands or photonic stimuli is described. Specifically, the use of the rotaxane as a scaffold to organize Au NP assemblies, and the control of the fluorescence properties with Au NP/fluorophore hybrids loaded on the rotaxane scaffold, are introduced. The future prospectives and challenges in the field of interlocked DNA nanostructures and the possible applications are discussed
Au nanoparticle/DNA rotaxane hybrid nanostructures exhibiting switchable fluorescence properties
No full textThe preparation of a DNA rotaxane consisting of a circular nucleic acid interlocked, through hybridization, on a nucleic acid axle and stoppered by two 10-nm-sized Au nanoparticles (NPs) is described. By the tethering of 5-nm- or 15-nm-sized Au NPs on the ring, the supramolecular structure of the rotaxane is confirmed. Using nucleic acids as "fuels" and "anti-fuels", the cyclic and reversible transition of the rotaxane ring across two states is demonstrated. By the functionalization of the ring with fluorophore-modified nucleic acids in different orientations, the transitions of the rings between the sites are followed by fluorescence quenching or surface-enhanced fluorescence. The experimental results are supported by theoretical modeling. © 2013 American Chemical Society
Chiroplasmonic DNA-based nanostructures
No full textChiroplasmonic properties of nanoparticles, organized using DNA-based nanostructures, have attracted both theoretical and experimental interest. Theory suggests that the circular dichroism spectra accompanying chiroplasmonic nanoparticle assemblies are controlled by the sizes, shapes, geometries and interparticle distances of the nanoparticles. In this Review, we present different methods to assemble chiroplasmonic nanoparticle or nanorod systems using DNA scaffolds, and we discuss the operations of dynamically reconfigurable chiroplasmonic nanostructures. The chiroplasmonic properties of the different systems are characterized by circular dichroism and further supported by high-resolution transmission electron microscopy or cryo-transmission electron microscopy imaging and theoretical modelling. We also outline the applications of chiroplasmonic assemblies, including their use as DNA-sensing platforms and as functional systems for information processing and storage. Finally, future perspectives in applying chiroplasmonic nanoparticles as waveguides for selective information transfer and their use as ensembles for chiroselective synthesis are discussed. Specifically, we highlight the upscaling of the systems to device-like configurations
Metal nanoparticle-functionalized DNA tweezers: From mechanically programmed nanostructures to switchable fluorescence properties
No full textDNA tweezers are modified with two 10-nm sized Au NPs and one 5-nm sized Au NP. Upon treatment of the tweezers with fuel and antifuel nucleic acid strands, the switchable closure and opening of the tweezers proceed, leading to the control of programmed nanostructures of the tethered NPs. The tweezers are further modified with a single 10-nm sized nanoparticle, and a fluorophore unit (Cy3), positioned at different distinct sites of the tweezers. The reversible and cyclic fluorescence quenching or fluorescence enhancement phenomena, upon the dynamic opening/closure of the different tweezers, are demonstrated. © 2013 American Chemical Society
Electrochemically Stimulated pH Changes: A Route To Control Chemical Reactivity
No full textA bis-aniline-cross-linked Au nanoparticle (NP) composite is electrochemically prepared on a rough Pt film supported on a Au electrode The electrochemical oxidation of the bis-aniline units to the quinoid state releases protons to the electrolyte solution, while the reduction of the quinoid bridges results in the uptake of protons from the electrolyte. By the cyclic oxidation of the bridging units (E = 0.25 V vs SCE), and their reduction (E = -0 05 V vs SCE), the pH of the solution could be reversibly switched between the values 5 8 and 7 2, respectively The extent of the pH change is controlled by the number of electropolymerization cycles applied to synthesize the Au NP composite, demonstrating a ca 1 5 pH units change by a matrix synthesized using 100 electropolymerization cycles The pH changes are used to reversibly activate and deactivate a C-quadruplex (i-motif)-bridged Mg(2+)-dependent DNAzyme
Electrified Selective "Sponges" Made of Au Nanoparticles
No full textImprinted Au nanoparticle (NP) composites are assembled on Au surfaces by the electropolymerization of thioaniline-functionalized Au NPs in the presence of the imprint molecules, picric acid (1), N,N'-dimethyl-4,4'-bipyridinium (2), and N,N'-dimethylbipyridinium-4,4'-ethylene dichloride (3). The existence of pi-donor acceptor complexes between the substrates (1-3) and the pi-donor thioaniline units associated with the Au NPs or the pi-donor bis-aniline bridges cross-linking the Au NPs on the electrode surfaces led to the formation of the imprinted sites. Upon elimination of the electron acceptors (1-3) from the Au NP matrices, molecular contours for the selective binding of the respective substrates are generated. The bis-aniline bridges linking the Au NPs in the composite exhibit quasireversible redox properties. At E 0.12 V vs Ag ORE, the bridging units exist in the quinoid, pi-acceptor state. As a result, the potential-induced uptake and release of any of the pi-acceptor substrates 1 3 is accomplished. While at E 0.12 V, the bound substrates are released from the matrices, due to transformation of the bridging units to the quinoid pi-acceptor state, which lacks binding affinity for the substrates. The binding and release of the substrates 1-3 to and from the Au NP composites are followed by surface plasmon resonance (SPR) spectroscopy, and the quantitative assay of the uptake and release is monitored by the extent of fluorescence quenching of the solution-soluble fluorescent labels, meso-tetramethyl pyridinium porphyrin (TMPyP(4+)) or Zn(II)-meso-tetraphenylsulfonatoporphyrin (Zn-TPPS(4-)). The electrostimulated functions of the Au NP "sponges" are controlled by several means: (i) Imprinting of the molecular contours for 1-3 in the Au NP composites generates high-affinity binding sites for the imprinted substrates. This leads to higher contents of the bound substrates at the Au NP sponges, as compared to the nonimprinted Au NP composites, and to an impressive selectivity in the association of the imprinted substrates. (ii) The binding capacity of the Au NP composites is substantially improved by the electrosynthesis of the matrices on a rough Pt black support bound to the base Au electrode
Surface Plasmon Resonance Analysis of Antibiotics Using Imprinted Boronic Acid-Functionalized Au Nanoparticle Composites
No full textAu nanoparticles (NPs) are functionalized with thioaniline electropolymerizable groups and (mercaptophenyl)boronic acid. The antibiotic substrates neomycin (NE), kanamycin (KA), and streptomycin (ST) include vicinal diol functionalities and, thus, bind to the boronic acid ligands. The electropolymerization of the functionalized Au NPs in the presence of NE, KA, or ST onto Au surfaces yields bisaniline-cross-linked Au NP composites that, after removal of the ligated antibiotics, provide molecularly imprinted matrixes which reveal high sensitivities toward the sensing of the imprinted antibiotic analytes (detection limits for analyzing NE, KA, and ST correspond to 2.00 +/- 0.21 pM, 1.00 +/- 0.10 pM, and 200 +/- 30 fM, respectively). The antibiotics are sensed by surface plasmon resonance (SPR) spectroscopy, where the coupling between the localized plasmon of the NPs and the surface plasmon wave associated with the Au surface is implemented to amplify the SPR responses. The imprinted Au NP composites are, then, used to analyze the antibiotics in milk samples
Triplex DNA Nanostructures: From Basic Properties to Applications
No full textTriplex nucleic acids have recently attracted interest as part of the rich toolbox of structures used to develop DNA-based nanostructures and materials. This Review addresses the use of DNA triplexes to assemble sensing platforms and molecular switches. Furthermore, the pH-induced, switchable assembly and dissociation of triplex-DNA-bridged nanostructures are presented. Specifically, the aggregation/deaggregation of nanoparticles, the reversible oligomerization of origami tiles and DNA circles, and the use of triplex DNA structures as functional units for the assembly of pH-responsive systems and materials are described. Examples include semiconductor-loaded DNA-stabilized microcapsules, DNA-functionalized dye-loaded metal-organic frameworks (MOFs), and the pH-induced release of the loads. Furthermore, the design of stimuli-responsive DNA-based hydrogels undergoing reversible pH-induced hydrogel-to-solution transitions using triplex nucleic acids is introduced, and the use of triplex DNA to assemble shape-memory hydrogels is discussed. An outlook for possible future applications of triplex nucleic acids is also provided
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