Electrical Biosensors Research Articles

Citations

Citations

Coupling ion channels to receptors for biomolecule sensing

Nanoscale electrical biosensors are promising tools for diagnostics and high-throughput screening systems. The electrical signal allows label-free assays with a high signal-to-noise ratio and fast real-time measurements. The challenge in developing such biosensors lies in functionally connecting a molecule detector to an electrical switch. Advances in this field have relied on synthetic ion-conducting pores and modified ion channels that are not yet suitable for biomolecule screening. Here we report the design and characterization of a novel bioelectric-sensing platform engineered by coupling an ion channel, which serves as the electrical probe, to G-protein-coupled receptors (GPCRs), a family of receptors that detect molecules outside the cell. These ion-channel-coupled receptors may potentially detect a wide range of ligands recognized by natural or altered GPCRs, which are known to be major pharmaceutical targets. This could form a unique platform for label-free drug screening.

The fabrication of carbon nanostructures using electron beam resist pyrolysis andnanomachining processes for biosensing applications

We present a facile, yet versatile carbon nanofabrication method using electron beamlithography and resist pyrolysis. Various resist nanopatterns were fabricated using anegative electron beam resist, SAL-601, and they were then subjected to heattreatment in an inert atmosphere to obtain carbon nanopatterns. Suspended carbonnanostructures were fabricated by the wet-etching of an underlying sacrificial oxide layer.Free-standing carbon nanostructures, which contain 130 nm wide, 15 nm thick, and4 µm long nanobridges, were fabricated by resist pyrolysis and nanomachining processes.Electron beam exposure dose effects on resist thickness and pattern widening were studied.The thickness of the carbon nanostructures was thinned down by etching with oxygenplasma. An electrical biosensor utilizing carbon nanostructures as a conducting channel wasstudied. Conductance modulations of the carbon device due to streptavidin–biotin bindingand pH variations were observed.

Electrically detected displacement assay (EDDA): a practical approach to nucleic acid testing in clinical or medical diagnosis

This paper introduces the electrically detected displacement assay (EDDA), a electrical biosensor detection principle for applications in medical and clinical diagnosis, and compares the method to currently available microarray technologies in this field. The sensor can be integrated into automated systems of routine diagnosis, but may also be used as a sensor that is directly applied to the polymerase chain reaction (PCR) reaction vessel to detect unlabeled target amplicons within a few minutes. Major aspects of sensor assembly like immobilization procedure, accessibility of the capture probes, and prevention from nonspecific target adsorption, that are a prerequisite for a robust and reliable performance of the sensor, are demonstrated. Additionally, exemplary results from a human papillomavirus assay are presented.

Immobilization of olfactory receptors onto gold electrodes for electrical biosensor

We investigate the immobilization of native nanovesicles containing functional olfactory receptors onto gold electrodes by means of atomic force microscopy in liquid. We show that nanovesicles can be adsorbed without disrupting them presenting sizes once immobilized ranging from 50 nm to 200 nm in diameter. The size of the nanovesicles shows no dependence on the electrode hydrophobicity being constant in a height/width ratio close to 1:3. Nevertheless, electrode hydrophobicity does affect the surface coverage, the surface coverage is five times higher in hydrophilic electrodes than on hydrophobic ones. Surface coverage is also affected by nanovesicles dimensions in suspension, the size homogenization to around 50 nm yields a further five fold increment in surface coverage achieving a coverage of about 50% close to the hard spheres jamming limit (54.7%). A single layer of nanovesicles is always formed with no particle overlap. Present results provide insights into the immobilization on electrodes of olfactory receptors for further olfactory electrical biosensor development.

Label-Free Impedance Biosensors: Opportunities and Challenges.

Impedance biosensors are a class of electrical biosensors that show promise for point-of-care and other applications due to low cost, ease of miniaturization, and label-free operation. Unlabeled DNA and protein targets can be detected by monitoring changes in surface impedance when a target molecule binds to an immobilized probe. The affinity capture step leads to challenges shared by all label-free affinity biosensors; these challenges are discussed along with others unique to impedance readout. Various possible mechanisms for impedance change upon target binding are discussed. We critically summarize accomplishments of past label-free impedance biosensors and identify areas for future research.

Porous silicon based structures for the electrical biosensing of glucose

Porous silicon (PS), which is composed of silicon crystals with typical sizes in the range of a few nanometers, shows high specific surface. Thus, its particular surface morphology makes this material very suitable for its use in the field of sensing. Accordingly, PS-based devices with the structure metal/PS/silicon/metal were developed to be used as electrical biosensors. Current–voltage measurements have shown that these devices typically show rectifying characteristics. In addition, it has been found that the current–voltage characteristics show a strong variation as a function of the presence/absence and concentration of biomolecules onto the surface of PS, both for longitudinal and transversal conduction. The present work describes our findings in the correlation between biomolecule surface concentration and current for a given voltage.

Biosensors

Biosensors

Direct electrical detection of DNA synthesis

Rapid, sequence-specific DNA detection is essential for applications in medical diagnostics and genetic screening. Electrical biosensors that use immobilized nucleic acids are especially promising in these applications because of their potential for miniaturization and automation. Current DNA detection methods based on sequencing by synthesis rely on optical readouts; however, a direct electrical detection method for this technique is not available. We report here an approach for direct electrical detection of enzymatically catalyzed DNA synthesis by induced surface charge perturbation. We discovered that incorporation of a complementary deoxynucleotide (dNTP) into a self-primed single-stranded DNA attached to the surface of a gold electrode evokes an electrode surface charge perturbation. This event can be detected as a transient current by a voltage-clamp amplifier. Based on current understanding of polarizable interfaces, we propose that the electrode detects proton removal from the 3'-hydroxyl group of the DNA molecule during phosphodiester bond formation.

Developing nucleic acid-based electrical detection systems.

Development of nucleic acid-based detection systems is the main focus of many research groups and high technology companies. The enormous work done in this field is particularly due to the broad versatility and variety of these sensing devices. From optical to electrical systems, from label-dependent to label-free approaches, from single to multi-analyte and array formats, this wide range of possibilities makes the research field very diversified and competitive. New challenges and requirements for an ideal detector suitable for nucleic acid analysis include high sensitivity and high specificity protocol that can be completed in a relatively short time offering at the same time low detection limit. Moreover, systems that can be miniaturized and automated present a significant advantage over conventional technology, especially if detection is needed in the field. Electrical system technology for nucleic acid-based detection is an enabling mode for making miniaturized to micro- and nanometer scale bio-monitoring devices via the fusion of modern micro- and nanofabrication technology and molecular biotechnology. The electrical biosensors that rely on the conversion of the Watson-Crick base-pair recognition event into a useful electrical signal are advancing rapidly, and recently are receiving much attention as a valuable tool for microbial pathogen detection. Pathogens may pose a serious threat to humans, animal and plants, thus their detection and analysis is a significant element of public health. Although different conventional methods for detection of pathogenic microorganisms and their toxins exist and are currently being applied, improvements of molecular-based detection methodologies have changed these traditional detection techniques and introduced a new era of rapid, miniaturized and automated electrical chip detection technologies into pathogen identification sector. In this review some developments and current directions in nucleic acid-based electrical detection are discussed.

Porous Silicon Optical and Electrical Biosensors

not Available.

Electrical detection of DNA using gold and magnetic nanoparticles and bio bar-code DNA between nanogap electrodes

This paper presents an electrical detection method on a DNA biochip that employs a novel approach for ultra sensitive detection of DNA using self-assembled gold nanoparticles and bio-bar-code-based amplification (BCA) DNA. The experimental study relies on three-components oligonucleotide-modified gold nanoparticles, single-component oligonucleotide-modified magnetic nanoparticles and subsequent detection of amplified target DNA in the form of bio-bar-code ssDNA (single strand DNA) using a chip-based detection method. In this study, the BCA technique measures the bar-code DNA rather than the target DNA. There withal, the DNA chips with nanogap electrodes are fabricated by electron-beam lithography. The gap distance and an electrode height are 300 and 65 nm, respectively. Here, the surface between the electrodes and multilayer of gold nanoparticles is established by the hybridization among single strand BCA, the second capture DNA (C2DNA) and the second probe DNA (P2DNA). Measurable current through nanogap electrodes can be obtained over multilayer gold nanoparticles. In this way, magnetic nanoparticles and bio-bar-code DNA are used to amplify obtainable current through nanogap electrodes from the extremely low concentration of target DNA. The detective concentration of target DNA with electrical DNA biosensor is as low as 1 fM for the analysis of current-voltage curves.

Nano Monitors for Identification of Vulnerable Cardio-Vascular Plaque

AbstractAs our nation's population ages, there will be a substantial demand for surgical services. The best predictor of postoperative outcome is the presence of perioperative ischemia, which is caused by vulnerable coronary plaque rupture. It is not know what makes plaques rupture, but inflammation has been proposed as a unifying etiology. The physiologic perioperative state is one of intense, acute inflammation and thrombosis. This is characterised by the presence of protien- Human Serum C-Reactive Protein( hsCRP) and Myeloperoxidase(MPO). There is a gap in detection capability between gold standard in proteomics detection –Enzyme Linked Immunosorbent Assay (ELISA) assay methods and electrical biosensors.ELISA based protein biomarker detection in too slow to be applicable in early patient bedside treatment. Electrical biosensors on the other hand may overcome this limitation with their improved sensitivity, specificity and rapid detection. In this application we demonstrate the development of nanomembrane based electrical protein “nano monitor”. This technique overcomes the limitations current “state-of- the- art” methods such as:• Specificity in detection of multiple markers that characterizes the disease pathogenesis from a single marker to multiple markers.• Speed of detection from a turnaround time of 12/24 hours to a few minutes.• Sensitivity of detection from milligram/ml to nanogram/ml.

Nanomaterial-based electrochemical biosensors

The unique properties of nanoscale materials offer excellent prospects for interfacing biological recognition events with electronic signal transduction and for designing a new generation of bioelectronic devices exhibiting novel functions. In this Highlight I address recent research that has led to powerful nanomaterial-based electrical biosensing devices and examine future prospects and challenges. New nanoparticle-based signal amplification and coding strategies for bioaffinity assays are discussed, along with carbon-nanotube molecular wires for achieving efficient electrical communication with redox enzyme and nanowire-based label-free DNA sensors.

Ultrasensitive electrical biosensing of proteins and DNA: carbon-nanotube derived amplification of the recognition and transduction events.

A new strategy for dramatically amplifying enzyme-linked electrical detection of proteins and DNA using carbon nanotubes (CNTs) for carrying numerous enzyme tracers and accumulating the enzymatically liberated product on CNT-modified transducer is described. Such a CNT-derived double-step amplification pathway (of both the recognition and transduction events) allows the detection of DNA and proteins down to 1.3 and 160 zmol, respectively, in 25-50 muL samples and indicates great promise for PCR-free DNA analysis. The new protocol is illustrated for monitoring sandwich hybridization and antibody-antigen interactions in connection with alkaline-phosphatase tracers. The DNA-linking of CNTs and particles holds promise also for assembling hybrid nanostructures relevant to molecular electronic devices.

Engineering DNA-electrode connectivities: manipulation of linker length and structure

The development of electrical or electrochemical DNA-based biosensors requires the attachment of oligonucleotides to electrode surfaces through linkages with appropriate structural and electronic properties. Using a straightforward and versatile synthetic method, we prepared DNA molecules with a series of thiol-terminated linkers containing either ethane, hexane, or xylene spacers connected either to a terminal deoxyribose C5′ or thymine C5. The modified oligonucleotides self-assemble on gold electrodes and form densely-packed monolayers. The kinetics and extent of monolayer formation are sensitive to the rigidity of the tether, with the xylene-based linker slowing adsorption to the gold surface relative to the more flexible hexane-based linker. The monolayer formation is also less efficient for double-stranded versus single-stranded DNA. The redox-active intercalator methylene blue (MB) was used to study charge transport through the series of different DNA films. The heterogeneous electron-transfer kinetics are modulated by the structure of the DNA-electrode connection, with a linker attached directly to the 5-CH 3 of thymine facilitating the most efficient charge transport through the film. These studies constitute the first systematic analysis of the effect of linker structure on DNA-electrode coupling, and provide important information for the development of new electrical DNA biosensors.

Electrical Porous Silicon Microarray for dna Hybridization Detection

ABSTRACTThe sensitivity of Porous Silicon (PSi) to the presence of charged molecules and its large internal surface area represent two important properties that make this material and ideal candidate for electrical biosensor development. We have demonstrated the use of a macroporous silicon electrical sensor for label-free detection of DNA hybridization in real time as well as identification of organic solvents in liquid phase. Binding of DNA inside the PSi matrix induces a change in capacitance and conductance. Having demonstrated the suitability of macroporous silicon layers for real time detection of DNA hybridization on single devices, we have extended our findings to the fabrication of a microarray with individual device electrical addressing capabilities. On a crystalline p-type silicon wafer, process steps such as KOH etching and electrochemical dissolution are employed in selected regions to create a free-standing porous membrane for sensing applications. Individual electrical contacts are made on the front side of the wafer while the infiltration of the probe and target molecules is done from the back avoiding any direct interaction of the molecules with the contact sites. We will report on the design considerations of the electrical porous silicon array and the preliminary results obtained using synthetic DNA as a model molecule.

Electrochemical detection of DNA hybridization based on DNA-templated assembly of silver cluster

The growth of metals on DNA templates has generated considerable interest in connection to the design of metallic nanostructures. Here we exploit the DNA-induced generation of metal clusters for developing an electrical biosensing protocol. The new hybridization assay employs a probe-modified gold surface, and is based on the electrostatic ‘collection’ of silver cations along the DNA duplex, the reductive formation of silver nanoclusters along the DNA backbone, dissolution of the silver aggregate and stripping potentiometric detection of the dissolved silver at a thick-film carbon electrode. The new protocol thus combines the inherent signal amplification of stripping analysis with effective discrimination against nonhybridized DNA.

Microparticle detector for biosensor application

We report on the development of a high-sensitivity electrical biosensor that detects analyte molecules labelled by microparticles. Detection is achieved by measuring electrochemical current changes occurring when bead-labelled analyte molecules get specifically bound to microelectrodes. We present measurements with transducers that bear microelectrode arrays with a large number of microelectrodes connected in parallel as well as single addressable microelectrodes. These measurements reveal the very sensitive detection of even one single microparticle. By using magnetic microbeads a magnetic force can be applied to the beads to remove them from the electrodes. When this force exceeds the specific binding force of the analyte molecule the bound microparticles are removed and a signal is produced. We assume that the transducer could also be used for the determination of specific binding forces.

Porous Silicon Electrical Biosensors

ABSTRACTThe highly sensitive surface of porous silicon (PSi) and the possibility to measure changes in its electrical properties can be used for electrical biosensor applications. The sensing scenario can be extended from the well-characterized organic solvents and pH sensors to detection of biological processes involving the presence of charged molecules. We have investigated the change in electrical properties (capacitance and conductance) of macroporous silicon layers upon exposure to organic solvents and water. Evaluation of our sensor to detect a biological event was done by addressing DNA hybridization. As opposed to the previous work published in this field, in our devices the electrical contact is made on the crystalline silicon (c-Si) substrate. This allows a complete exposure of the surface to the sensing species and reduces the generation of ionic currents through the porous silicon matrix. We will report results of a complete characterization of our device including response speed, selectivity and sensitivity.