We report a strategy for the reagentless transduction of DNA hybridization into readily detectable electrochemical signal by means conformational change analogous to optical molecular beacon approach. The involves an electroactive, ferrocene-tagged stem-loop structure that self-assembles onto gold electrode facile gold-thiol chemistry. Hybridization induces large in this surface-confined structure, which turn significantly alters electron-transfer tunneling distance between and redoxable...

Whereas spectroscopic and chromatographic techniques for the detection of small organic molecules have achieved impressive results, these methods are generally slow cumbersome, thus development a general means real-time, electronic such targets remains compelling goal. Here we demonstrate potentially general, label-free method small-molecule by building rapid, reagentless biosensor cocaine. The sensor, based on electrochemical interrogation structure-switching aptamer, specifically detects...

Blue, gold, and DNA: A methylene blue (MB) tagged, thrombin-binding DNA aptamer immobilized on a gold surface undergoes large conformational change upon target binding (see schematic representation; eT: electron transfer). This folding produces large, readily measurable in redox current allows the electrochemical detection of thrombin blood serum.

Spectroscopic studies have identified a number of proteins that appear to retain significant residual structure under even strongly denaturing conditions. Intrinsic viscosity, hydrodynamic radii, and small-angle x-ray scattering studies, in contrast, indicate the dimensions most chemically denatured scale with polypeptide length by means power-law relationship expected for random-coil behavior. Here we further explore this discrepancy expanding range characterized denatured-state radii...

We have demonstrated a novel sensing strategy employing single-stranded probe DNA, unmodified gold nanoparticles, and positively charged, water-soluble conjugated polyelectrolyte to detect broad range of targets including nucleic acid (DNA) sequences, proteins, small molecules, inorganic ions. This nearly “universal” biosensor approach is based on the observation that, while specifically inhibits ability DNA prevent aggregation gold-nanoparticles, no such inhibition observed with...

Thrombin binding stabilizes the alternative G-quadruplex conformation of aptamer, liberating methylene blue (MB)-tagged oligonucleotide to produce a flexible, single-stranded DNA element. This allows MB tag collide with gold electrode surface, producing readily detectable Faradaic current at thrombin concentrations as low ∼3 nM.

Gold nanoparticles quench the fluorescence of cationic polyfluorene with Stern–Volmer constants ( K SV ) approaching 10 11 M — 1 , several orders magnitude larger than any previously reported conjugated polymer–quencher pair and 9–10 small molecule dye–quencher pairs. The dependence on ionic strength, charge conjugation length polymer, dimensions (and thus optical properties) suggests that three factors account for this extraordinary efficiency: i amplification quenching via rapid internal...

A limitation of many traditional approaches to the detection specific oligonucleotide sequences, such as molecular beacons, is that each target strand hybridizes with (and thus activates) only a single copy relevant probe sequence. This 1:1 hybridization ratio limits gain most and their sensitivity. Here we demonstrate nuclease-amplified DNA scheme in which exonuclease III used "recycle" molecules, leading greatly improved sensitivity relative to, for example, beacons without any significant...

Biomolecular recognition is versatile, specific, and high affinity, qualities that have motivated decades of research aimed at adapting biomolecules into a general platform for molecular sensing. Despite significant effort, however, so-called "biosensors" almost entirely failed to achieve their potential as reagentless, real-time analytical devices; the only quantitative, reagentless biosensor commercial success so far home glucose monitor, employed by millions diabetics. The fundamental...

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTElectrochemical Detection of Parts-Per-Billion Lead via an Electrode-Bound DNAzyme AssemblyYi Xiao, Aaron A. Rowe, and Kevin W. PlaxcoView Author Information Department Physics, Materials Department, Institute for Polymers Organic Solids, Chemistry Biochemistry, Program in BioMolecular Science Engineering, University California, Santa Barbara, California 93106. Cite this: J. Am. Chem. Soc. 2007, 129, 2, 262–263Publication Date (Web):December...

We herein demonstrate a sandwich assay based on single aptamer sequences is suitable for the direct detection of small molecule targets in blood serum and other complex matrices. By splitting an into two pieces, we convert affinity reagent two-component system which presence target drives formation comprised halves aptamer. To utility this approach have used anticocaine anti-ATP aptamers to fabricate electrochemical sensors directed against representative molecules coaine ATP. Both are...

Significance The ability to monitor arbitrary molecules directly in living subjects as they undergo their daily routines remains one of the “holy grails” bioanalytical chemistry. Such a technology would, for example, vastly improve our knowledge physiology, pharmacokinetics, and toxicology by allowing high-precision measurement drugs metabolites under realistic physiological conditions. Real-time molecular measurements would also provide an unparalleled window into health status (e.g.,...

The development of a biosensor system capable continuous, real-time measurement small-molecule analytes directly in complex, unprocessed aqueous samples has been significant challenge, and successful implementation achieved for only limited number targets. Toward general solution to this problem, we report here the Microfluidic Electrochemical Aptamer-based Sensor (MECAS) chip wherein integrate target-specific DNA aptamers that fold, thus generate an electrochemical signal, response analyte...

An aptamer-based biosensor continuously measures the concentration of drug molecules in blood living animals and patient samples.

We report an electrochemical, aptamer-based (E-AB) sensor for the detection of platelet-derived growth factor (PDGF) directly in blood serum. The E-AB approach employs alternating current voltammetry to monitor target-induced folding a methylene blue-modified, PDGF-binding aptamer. is sensitive, highly selective, and essentially reagentless: we readily detect BB variant PDGF at 1 nM undiluted, unmodified serum 50 pM (1.25 ng/mL) serum-diluted 2-fold with aqueous buffer. sensitivity...

E-DNA sensors, the electrochemical equivalent of molecular beacons, appear to be a promising means detecting oligonucleotides. sensors are comprised redox-modified (here, methylene blue or ferrocene) DNA stem-loop covalently attached an interrogating electrode. Because signaling arises due binding-induced changes in conformation probe, it is likely sensitive nature packing on electrode surface. Here we detail effects probe density, target length, and other aspects crowding properties,...

Electrochemical, aptamer-based (E-AB) sensors, which are comprised of an electrode modified with surface immobilized, redox-tagged DNA aptamers, have emerged as a promising new biosensor platform. In order to further improve this technology we systematically studied the effects probe (aptamer) packing density, AC frequency used interrogate sensor, and nature self-assembled monolayer (SAM) passivate on performance representative E-AB sensors directed against small molecule cocaine protein...

Single-step DNA detection: A microfluidic electrochemical loop mediated isothermal amplification platform is reported for rapid, sensitive, and quantitative detection of pathogen genomic at the point care (see picture). was electrochemically monitored in real time within a monolithic device, thus enabling as few 16 copies Salmonella through single-step process less than an hour. Detailed facts importance to specialist readers are published "Supporting Information". Such documents...

Although potentiostats are the foundation of modern electrochemical research, they have seen relatively little application in resource poor settings, such as undergraduate laboratory courses and developing world. One reason for low penetration is their cost, even least expensive commercially available sell more than one thousand dollars. An inexpensive workstation could thus prove useful educational labs, increase access to electrochemistry-based analytical techniques food, drug...

The electrochemical aptamer-based (E-AB) sensing platform appears to be a convenient (rapid, single-step, and calibration-free) modular approach measure concentrations of specific molecules (irrespective their chemical reactivity) directly in blood even situ the living body. Given these attributes, may thus provide significant opportunities render therapeutic drug monitoring (the clinical practice which dosing is adjusted response plasma measurements) as frequent measurement sugar has become...

The need to calibrate correct for sensor-to-sensor fabrication variation and sensor drift has proven a significant hurdle in the widespread use of biosensors. To maintain clinically relevant (±20% this application) accuracy, example, commercial continuous glucose monitors require recalibration several times day, decreasing convenience increasing chance user errors. Here, however, we demonstrate "dual-frequency" approach achieving calibration-free operation electrochemical biosensors that...

Electrochemical aptamer-based (EAB) sensors encompass the only biosensor approach yet reported that is simultaneously: (1) independent of chemical or enzymatic reactivity its target, rendering it general; (2) continuous and lag-free; (3) selective enough to deploy in situ living body. Consistent with this, vivo EAB supporting seconds-resolved, real-time measurement multiple drugs metabolites have been reported, suggesting may prove value biomedical research diagnosis, treatment, monitoring...