Electrochemical switching of photoelectrochemical processes at CdS QDs and photosystem I-modified electrodes.

Photoactive inorganic CdS quantum dots (QDs) or the native photosystem I (PSI) is immobilized onto a pyrroloquinoline quinone (PQQ) monolayer linked to Au electrodes to yield hybrid relay/QDs (or photosystem) assemblies. By the electrochemical biasing of the electrode potential, the relay units are retained in their oxidized PQQ or reduced PQQH(2) states. The oxidized or reduced states of the relay units dictate the direction of the photocurrent (anodic or cathodic).

Functionalized CdSe/ZnS QDs for the detection of nitroaromatic or RDX explosives.

Chemically modified CdSe/ZnS quantum dots (QDs) are used as fluorescent probes for the analysis of explosives, and specifically, the detection of trinitrotoluene (TNT) or trinitrotriazine (RDX). The QDs are functionalized with electron-donating ligands that bind nitro-containing explosives, exhibiting electron-acceptor properties, to the QD surface, via supramolecular donor-acceptor interactions leading to the quenching of the luminescence of the QDs.

Integration of photoswitchable proteins, photosynthetic reaction centers and semiconductor/biomolecule hybrids with electrode supports for optobioelectronic applications.

Light-triggered biological processes provide the principles for the development of man-made optobioelectronic systems. This Review addresses three recently developed topics in the area of optobioelectronics, while addressing the potential applications of these systems. The topics discussed include: (i) the reversible photoswitching of the bioelectrocatalytic functions of redox proteins by the modification of proteins with photoisomerizable units or by the integration of proteins with photoisomerizable environments; (ii) the integration of natural photosynthetic reaction centers with electrodes and the construction of photobioelectrochemical cells and photobiofuel cells; and (iii) the synthesis of biomolecule/semiconductor quantum dots hybrid systems and their immobilization on electrodes to yield photobioelectrochemical and photobiofuel cell elements.

Optical aptasensors for the analysis of the vascular endothelial growth factor (VEGF).

The vascular endothelial growth factor, VEGF, is an important biomarker for different diseases and clinical disorders. We present a series of optical aptasensor-based sensing platforms for VEGF that include the following: (i) A FRET-based sensor that involves the VEGF-induced separation of aptamer-functionalized quantum dots blocked by a quencher nucleic acid (detection limit 1 nM). (ii) A FRET-based sensor based on the VEGF-induced assembly of the aptamer subunits functionalized with QDs and a dye acceptor (Cy5), respectively (detection limit 12 nM).

Sensitivity and specificity of urinary ethyl glucuronide and ethyl sulfate in liver disease patients.

Background: It is important to monitor alcohol use in the care of patients with liver disease, but patient self-report can be unreliable. We therefore evaluated the performance of urine ethyl glucuronide (EtG) and ethyl sulfate (EtS) in detecting alcohol use in the days preceding a clinical encounter.

Methods: Subjects (n = 120) were recruited at a university-based hepatology clinic or during hospitalization.

APOBEC3G enhances lymphoma cell radioresistance by promoting cytidine deaminase-dependent DNA repair.

APOBEC3 proteins catalyze deamination of cytidines in single-stranded DNA (ssDNA), providing innate protection against retroviral replication by inducing deleterious dC > dU hypermutation of replication intermediates. APOBEC3G expression is induced in mitogen-activated lymphocytes; however, no physiologic role related to lymphoid cell proliferation has yet to be determined. Moreover, whether APOBEC3G cytidine deaminase activity transcends to processing cellular genomic DNA is unknown.

Zn(2+)-ligation DNAzyme-driven enzymatic and nonenzymatic cascades for the amplified detection of DNA.

A generic fluorescence sensing platform for analyzing DNA by the Zn(2+)-dependent ligation DNAzyme as amplifying biocatalyst is presented. The platform is based on the target DNA induced ligation of two substrate subunits and the subsequent opening of a beacon hairpin probe by the ligated product. The strand displacement of the ligated product by the beacon hairpin is, however, of limited efficiency.

Fluorescence detection of DNA, adenosine-5'-triphosphate (ATP), and telomerase activity by zinc(II)-protoporphyrin IX/G-quadruplex labels.

The zinc(II)-protoporphyrin IX (ZnPPIX) fluorophore binds to G-quadruplexes, and this results in the enhanced fluorescence of the fluorophore. This property enabled the development of DNA sensors, aptasensors, and a sensor following telomerase activity. The DNA sensor is based on the design of a hairpin structure that includes a "caged" inactive G-quadruplex sequence.

Optical molecular sensing with semiconductor quantum dots (QDs).

Semiconductor quantum dots (QDs) exhibit unique optical and photophysical properties. These features are implemented to develop optical molecular sensor systems. The review addresses the methods to functionalize the QDs with chemical capping layers that enable the use of the resulting hybrid structures for sensing, and discusses the photophysical mechanisms being applied in the different sensor systems.

Amplified surface plasmon resonance and electrochemical detection of Pb2+ ions using the Pb2+-dependent DNAzyme and hemin/G-quadruplex as a label.

The hemin/G-quadruplex nanostructure and the Pb(2+)-dependent DNAzyme are implemented to develop sensitive surface plasmon resonance (SPR) and electrochemical sensing platforms for Pb(2+) ions. A complex consisting of the Pb(2+)-dependent DNAzyme sequence and a ribonuclease-containing nucleic acid sequence (corresponding to the substrate of the DNAzyme) linked to a G-rich domain, which is "caged" in the complex structure, is assembled on Au-coated glass surfaces or Au electrodes. In the presence of Pb(2+) ions, the Pb(2+)-dependent DNAzyme cleaves the substrate, leading to the separation of the complex and to the self-assembly of the hemin/G-quadruplex on the Au support.

Integrated photosystem II-based photo-bioelectrochemical cells.

Photosynthesis is a sustainable process that converts light energy into chemical energy. Substantial research efforts are directed towards the application of the photosynthetic reaction centres, photosystems I and II, as active components for the light-induced generation of electrical power or fuel products. Nonetheless, no integrated photo-bioelectrochemical device that produces electrical power, upon irradiation of an aqueous solution that includes two inter-connected electrodes is known.

Enzyme-free amplified detection of DNA by an autonomous ligation DNAzyme machinery.

The Zn(2+)-dependent ligation DNAzyme is implemented as a biocatalyst for the amplified detection of a target DNA by the autonomous replication of a nucleic acid reporter unit that is generated by the catalyzed ligation process. The reporter units enhance the formation of active DNAzyme units, thus leading to the isothermal autocatalytic formation of the reporter elements. The system was further developed and applied for the amplified detection of Tay-Sachs genetic disorder mutant, with a detection limit of 1.

Multiplexed aptasensors and amplified DNA sensors using functionalized graphene oxide: application for logic gate operations.

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.

Following glucose oxidase activity by chemiluminescence and chemiluminescence resonance energy transfer (CRET) processes involving enzyme-DNAzyme conjugates.

A hybrid consisting of glucose oxidase-functionalized with hemin/G-quadruplex units is used for the chemiluminescence detection of glucose. The glucose oxidase-mediated oxidation of glucose yields gluconic acid and H(2)O(2). The latter in the presence of luminol acts as substrate for the hemin/G-quadruplex-catalyzed generation of chemiluminescence.

pH-programmable DNA logic arrays powered by modular DNAzyme libraries.

Nature performs complex information processing circuits, such the programmed transformations of versatile stem cells into targeted functional cells. Man-made molecular circuits are, however, unable to mimic such sophisticated biomachineries. To reach these goals, it is essential to construct programmable modular components that can be triggered by environmental stimuli to perform different logic circuits.

Amplified fluorescence aptamer-based sensors using exonuclease III for the regeneration of the analyte.

Quick and easy detection: The Exo III-stimulated regeneration of the analyte by the digestion of supramolecular aptamer-analyte complexes provides a means to develop amplified optical aptasensors (see figure).

Amplified detection of DNA through the enzyme-free autonomous assembly of hemin/G-quadruplex DNAzyme nanowires.

An enzyme-free amplified detection platform is described using the horseradish peroxidase (HRP)-mimicking DNAzyme as an amplifying label. Two hairpin structures that include three-fourths and one-fourth of the HRP-mimicking DNAzyme in caged, inactive configurations are used as functional elements for the amplified detection of the target DNA. In the presence of the analyte DNA, one of the hairpins is opened, and this triggers the autonomous cross-opening of the two hairpins using the strand displacement principle.

DNA nanotechnology.

The base sequence encoded in nucleic acids yields significant structural and functional properties into the biopolymer. The resulting nucleic acid nanostructures provide the basis for the rapidly developing area of DNA nanotechnology. Advances in this field will be exemplified by discussing the following topics: (i) Hemin/G-quadruplex DNA nanostructures exhibit unique electrocatalytic, chemiluminescence and photophysical properties.

Biomolecule/nanomaterial hybrid systems for nanobiotechnology.

The integration of biomolecules with metallic or semiconductor nanoparticles or carbon nanotubes yields new hybrid nanostructures of unique features that combine the properties of the biomolecules and of the nano-elements. These unique features of the hybrid biomolecule/nanoparticle systems provide the basis for the rapid development of the area of nanobiotechnology. Recent advances in the implementation of hybrid materials consisting of biomolecules and metallic nanoparticles or semiconductor quantum dots will be discussed.