Nucleic acid subunits consisting of fragments of the horseradish peroxidase (HRP)-mimicking DNAzyme and aptamer domains against ATP or sequences recognizing Hg(2+) ions self-assemble, in the presence of ATP or Hg(2+), into the active hemin-G-quadruplex DNAzyme structure. The DNAzyme-generated chemiluminescence provides the optical readout for the sensing events. In addition, the DNAzyme-stimulated chemiluminescence resonance energy transfer (CRET) to CdSe/ZnS quantum dots (QDs) is implemented to develop aptamer or DNA sensing platforms. The self-assembly of the ATP-aptamer subunits/hemin-G-quadruplex DNAzyme, where one of the aptamer subunits is functionalized with CdSe/ZnS QDs, leads to the CRET signal. Also, the functionalization of QDs with a hairpin nucleic acid that includes the G-quadruplex sequence in a ''caged'' configuration is used to analyze DNA. The opening of the hairpin structure by the target DNA assembles the hemin-G-quadruplex DNAzyme that stimulates the CRET signal. By the application of three different sized QDs functionalized with different hairpins, the multiplexed analysis of three different DNA targets is demonstrated by the generation of three different CRET luminescence signals.

This paper reports a versatile seed-mediated growth method for selectively synthesizing single-crystalline rhombic dodecahedral, octahedral, and cubic gold nanocrystals. In the seed-mediated growth method, cetylpyridinium chloride (CPC) and CPC-capped single-crystalline gold nanocrystals 41.3 nm in size are used as the surfactant and seeds, respectively. The CPC-capped gold seeds can avoid twinning during the growth process, which enables us to study the correlations between the growth conditions and the shapes of the gold nanocrystals. Surface-energy and kinetic considerations are taken into account to understand the formation mechanisms of the single-crystalline gold nanocrystals with varying shapes. CPC surfactants are found to alter the surface energies of gold facets in the order {100} > {110} > {111} under the growth conditions in this study, whereas the growth kinetics leads to the formation of thermodynamically less favored shapes that are not bounded by the most stable facets. The competition between AuCl(4)(-) reduction and the CPC capping process on the {111} and {110} facets of gold nanocrystals plays an important role in the formation of the rhombic dodecahedral (RD) and octahedral gold nanocrystals. Octahedral nanocrystals are formed when the capping of CPC on {111} facets dominates, while RD nanocrystals are formed when the reduction of AuCl(4)(-) on {111} facets dominates. Cubic gold nanocrystals are formed by the introduction of bromide ions in the presence of CPC. The cooperative work of cetylpyridinium and bromide ions can stabilize the gold {100} facet under the growth condition in this study, thereby leading to the formation of cubic gold nanocrystals.

The base sequence of nucleic acid encodes structural and functional properties into the biopolymer. Structural information includes the formation of duplexes, G-quadruplexes, i-motif, and cooperatively stabilized assemblies. Functional information encoded in the base sequence involves the strand-displacement process, the recognition properties by aptamers, and the catalytic functions of DNAzymes. This Review addresses the implementation of the information encoded in nucleic acids to develop DNA switches. A DNA switch is a supramolecular nucleic acid assembly that undergoes cyclic, switchable, transitions between two distinct states in the presence of appropriate triggers and counter triggers, such as pH value, metal ions/ligands, photonic and electrical stimuli. Applications of switchable DNA systems to tailor switchable DNA hydrogels, for the controlled drug-release and for the activation of switchable enzyme cascades, are described, and future perspectives of the systems are addressed.

DNAzymes have been recognized as potent therapeutic agents for gene therapy, while their inefficient intracellular delivery and insufficient cofactor supply precludes their practical biological applications.M etal-organic frameworks (MOFs) have emerged as promising drug carriers without in-depth consideration of their disassembled ingredients.Herein, we report aself-sufficient MOF-based chlorin e6modified DNAzyme (Ce6-DNAzyme) therapeutic nanosystem for combined gene therapyand photodynamic therapy(PDT). The ZIF-8 nanoparticles (NPs) could efficiently deliver the therapeutic DNAzyme without degradation into cancer cells. The pH-responsive ZIF-8 NPs disassemble with the concomitant release of the guest DNAzyme payloads and the host Zn 2+ ions that serve,respectively,asmessenger RNA-targeting agent and required DNAzyme cofactors for activating gene therapy. The auxiliary photosensitizer Ce6 could produce reactive oxygen species (ROS) and provide afluorescence signal for the imaging-guided gene therapy/PDT.

Hybrid systems consisting of nucleic-acid-functionalized silver nanoclusters (AgNCs) and graphene oxide (GO) are used for the development of fluorescent DNA sensors and aptasensors, and for the multiplexed analysis of a series of genes of infectious pathogens. Two types of nucleic-acid-stabilized AgNCs are used: one type includes the red-emitting AgNCs (616 nm) and the second type is near-infrared-emitting AgNCs (775 nm). Whereas the nucleic-acid-stabilized AgNCs do not bind to GO, the conjugation of single-stranded nucleic acid to the DNA-stabilized AgNCs leads to the adsorption of the hybrid nanostructures to GO and to the fluorescence quenching of the AgNCs. By the conjugation of oligonucleotide sequences acting as probes for target genes, or as aptamer sequences, to the nucleic-acid-protected AgNCs, the desorption of the probe/nucleic-acid-stabilized AgNCs from GO through the formation of duplex DNA structures or aptamer-substrate complexes leads to the generation of fluorescence as a readout signal for the sensing events. The hybrid nanostructures are implemented for the analysis of hepatitis B virus gene (HBV), the immunodeficiency virus gene (HIV), and the syphilis (Treponema pallidum) gene. Multiplexed analysis of the genes is demonstrated. The nucleic-acid-AgNCs-modified GO is also applied to detect ATP or thrombin through the release of the respective AgNCs-labeled aptamer-substrate complexes from GO.

Ruthenium(II) tris(2,2'-bipyridyl) ([Ru(bpy) 3 ] 2+ ) has received increasing attention in clinical diagnosis and scientific research because of its high sensitivity, wide dynamic range, stability, simplicity, and versatility as an electrochemiluminescent probe. [1] As the electrochemiluminescence (ECL) results from electrochemical reactions between [Ru(bpy) 3 ] 2+ and co-reactants, extensive research has been focused on exploring effective co-reactants for the sensitive determination of [Ru(bpy) 3 ] 2+ , which has important bioanalytical applications. [2] In 1984, Bard and co-workers first reported the determination of [Ru(bpy) 3 ] 2+ ECL using either oxalate or peroxydisulfate as co-reactants. [3] Later, Leland and Powell suggested tripropylamine (TPA) as a co-reactant, [4] and Blackburn et al. soon developed [Ru(bpy) 3 ] 2+ ECL immunoassays and DNA probe assays using TPA as co-reactant and [Ru(bpy) 3 ] 2+ as the label. [5] [Ru(bpy) 3 ] 2+ /TPA ECL assays have been widely used for over fifteen years now. [2,6] Despite its exclusive popularity, TPA has several important disadvantages. [2] First, TPA is toxic and volatile, but it is used in high concentrations (usually up to 100 mm) to attain good sensitivity. Second, its slow electrochemical oxidation rate limits ECL efficiency. Third, high concentrations of acidic phosphate solutions are needed to prepare concentrated neutral solutions of TPA because TPA is basic. Finally, the ECL intensity of the [Ru(bpy) 3 ] 2+ /TPA system depends strongly on electrode materials. For example, the ECL intensity at Pt electrodes is only about 10 % of that at Au electrodes. Thus, it is desirable to find alternatives to TPA.Several groups have studied the ECL from [Ru(bpy) 3 ] 2+ / amine systems under the condition that the concentrations of [Ru(bpy) 3 ] 2+ are higher than that of amines. [2,7] Generally; tertiary amines are more effective than secondary amines, primary amines, and other kinds of co-reactants. Also, electron-donating groups tend to increase ECL. It seemed impossible to find better co-reactants. Recent studies showed that ECL efficiencies can be improved through increasing the electrochemical oxidation rate of amines when the concentration of [Ru(bpy) 3 ] 2+ is much lower than that of the amines, as in the cases of ECL immunoassays and DNA probe assays. To our knowledge, all methods reported to date use additives to increase the oxidation rate of amines and, thus, ECL efficiencies. [8] Also, there have been only a few reports that attempt to find better co-reactants from easily oxidizable tertiary amines.Herein, we report an investigation of the ECL of a series of tertiary amines with various substituents whilst keeping the concentration of [Ru(bpy) 3 ] 2+ lower than that of the amine. The purpose of the present study is to provide a new way to enhance ECL efficiencies by using easily oxidizable tertiary amines, and develop more efficient and environmentally friendly co-reactants for ECL immunoassays and DNA probe assays. Figure 1 shows the dependence of ECL...

Nearly monodisperse Pd nanocubes with controllable sizes were synthesized through a seed-mediated growth approach. By using Pd nanocubes of 22 nm in size as seeds, the morphology of the as-grown nanostructures was fixed as single-crystalline, which enabled us to rationally tune the size of Pd nanocubes. The formation mechanism of initial 22 nm nanocubes was also discussed. The size-dependent surface plasmon resonance properties of the as-synthesized Pd nanocubes were investigated. Compared with previous methods, the yield, monodispersity, perfection of the shape formation, and the range of size control of these nanocubes are all improved. These Pd nanocubes may have potential interests in surface-enhanced Raman scattering, sensors, catalysis, study of size-dependent properties, and fabrication of high-order structures.

Graphene oxide (GO) is implemented as a functional matrix for developing fluorescent sensors for the amplified multiplexed detection of DNA, aptamer-substrate complexes, and for the integration of predesigned DNA constructs that activate logic gate operations. Fluorophore-labeled DNA strands acting as probes for two different DNA targets are adsorbed onto GO, leading to the quenching of the luminescence of the fluorophores. Desorption of the probes from the GO, through hybridization with the target DNAs, leads to the fluorescence of the respective label. By coupling exonuclease III, Exo III, to the system, the recycling of the target DNAs is demonstrated, and this leads to the amplified detection of the DNA targets (detection limit 5 × 10(-12) M). Similarly, adsorption of fluorophore-functionalized aptamers against thrombin or ATP onto the GO leads to the desorption of the aptamer-substrate complexes from GO and to the triggering of the luminescence corresponding to the respective fluorophore, thus, allowing the multiplexed analysis of the aptamer-substrate complexes. By designing functional fluorophore-labeled DNA constructs and their interaction with GO, in the presence (or absence) of nucleic acids, or two different substrates for aptamers, as inputs, the activation of the "OR" and "AND" logic gates is demonstrated.