Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “biosensing”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
PubMed1999

Therapeutic Angiogenesis Using Endocardial Approach to Administration: Techniques and Results.

The availability of various angiogenic growth factors and gene therapy vectors, and the demonstration of their angiogenic potential in animal models of chronic myocardial ischemia, has propelled their investigation in clinical trials of therapeutic angiogenesis in patients with ischemic heart disease. Although most preclinical studies have employed methods of prolonged drug delivery and local therapy, the need for repeated administration and invasive access has limited the clinical usefulness of these delivery strategies. Intracoronary and intravenous delivery, with their potential widespread applicability, has fueled their use in most clinical trials of therapeutic angiogenesis; however, the significant systemic recirculation, limited myocardial retention, and potential for serious systemic adverse events are major limitations to their clinical use. Epicardial delivery using surgical access has been used in several clinical studies, but the need for surgical access and general anesthesia may limit the usefulness of this technique. The development of percutaneous endocardial delivery catheters using fluoroscopic guidance or Biosense NOGA (Biosense Laboratories, Haifa, Israel) electromagnetic three- dimensional navigation system has generated significant interest in the use of this delivery strategy in therapeutic myocardial angiogenesis studies. These strategies are being intensively investigated in preclinical studies with clinical studies soon to follow. We describe the limited experience with these drug delivery devices.

Journal Article↗
PubMed2003

[Electromechanical mapping of myocardial ischemia in coronary occlusion in the pig].

The NOGA-Biosense catheter-based mapping technique has been well studied experimentally in infarction model. However, chronic myocardial ischemia with this new device has not been well explored. Thus, the aim of our study was to assess electromechanical changes in a pig aneroid constricor model. To achieved this aim, ten pigs were studied 21 days after the implantation of an aneroid constrictor around the circumflex artery. Coronary reserve assess by intracoronary Doppler flow wire was reduced in the ischemic lateral area (ILA) compared with the nonischemic zone (NIZ) (1.3 +/- 0.1 in the ILA vs. 2.3 +/- 0.2 in the NSZ; p < 0.01). TM echocardiography was used to evaluate myocardial regional contractility under basal condition and after stress induced by rapid atrial pacing. In stress state, the ischemic zone showed an impaired contractility compared with basal state (wall thickening, 32.7 +/- 7.4% vs. 59.7 +/- 8.6%; p < 0.05) whereas the non ischemic zone did not (53.8 +/- 7.6% vs. 60.8 +/- 10.1%; p = ns). Constrast echography showed a decrease in contrast intensity in subendocardium of the ila compared with the niz (46.2 +/- 16.6 vs. 99.2 +/- 35.6; p = 0.03) in pacing. Ventricular mapping quantified unipolar (UV). bipolar (BV) voltage potentials and endocardial local shortening (LLS) in 9 left ventricular regions. In basal state, electrical potentials were preserved in both zones (UV: 9.1 +/- 1.8 mV in the ischemic vs 11.3 +/- 3.6 mV in the non ischemic zone; p = ns; BV: 4.2 +/- 1.1 mV in the ILA vs. 3.9 +/- 1.5 mV; p = ns). In contrast, LLS was significantly lower in the ischemic compared with non ischemic zone (6.4 +/- 5.4% vs. 17.9 +/- 3.0%, p < 0.001). In conclusion, ventricular mapping with the NOGA-Biosense system can identify the ischemic myocardium. In this pig model, the association of a preserved electrical activity and an impaired mechanical activity characterizes the ischemic myocardium. These findings could be interesting in this model in regard of the new developments of the system in particular in the field of angiogenesis.

Animals↗
PubMed1996

-Rate-responsive pacemaker with an unexpected chronotropic response-.

The pacemaker with rate-responsiveness was a great advance in cardiac stimulation, however, the choice of the best biosensor is still object of research. A 35 year-old woman with a responsive pacemaker implanted due to a complete heart block after interventricular septal defect surgical correction was admitted. The pacemaker showed improper cronothropic response with high frequency due to biosensing malfunction. Malfunction related to muscle stimulation in the generator pocket and a high response rate. A palliative procedure was made until the end of pregnancy, by reducing the sensitivity of biosensing.

Adult↗
PubMed2006

Signal amplification by allosteric catalysis.

In this article we unify a series of recent studies on bio- and chemosensors under a single signaling strategy: signal amplification by allosteric catalysis (SAAC). The SAAC strategy mimics biological signal transduction processes, where molecular recognition between an external signal and a protein receptor is allosterically transduced into catalytically amplified chemical information (usually second messengers). Several recent biosensing and chemosensing studies apply this nature-inspired strategy by using engineered allosteric enzymes, ribozymes, or regulatable organic catalysts. The factors pertinent to achieving high sensitivity and specificity in SAAC strategies are analyzed. The authors believe that these early studies from a variety of research groups have opened up a new venue for the development of sensing technologies where molecular recognition and catalysis can be coupled for practical purposes.

Allosteric Regulation↗
PubMed2025

Aggregation-induced Electrochemiluminescence of AgNCs Enhanced with AuNPs@MXene Composites for Ultrasensitive Detection of microRNA.

MXene, a two-dimensional nanomaterial, has metal conductivity, high electronegativity, functionalized with surface groups, which make it widely applicable in catalysis and biosensing. However, studies on the principle of enhanced electrochemiluminescence (ECL) by MXene composites and the improvement of their performance in catalyzing the ECL reaction are still in their infancy. In this study, gold nanoparticles (AuNPs) are obtained by mild reductive reduction and loaded in&#x2005;situ on the Ti3C2Tx MXene surface to form the composites (AuNPs@MXene). In oxygenated PBS test buffer, AuNPs@MXene enhance the ECL emission of silver nanoclusters (AgNCs) with aggregation-induced electrochemiluminescence (AIECL) properties as luminophore. Approximately 7.5-fold enhancement of ECL signals is obtained by using two ECL enhancement strategies: an efficient AIECL emitter and a co-reaction accelerator. The special nucleic acid structure with "Three Way Junction (TWJ)" enables an ultra-sensitive detection of microRNA, providing an efficient and ultra-sensitive method for microRNA detection. The biosensor achieves a wide detection range of microRNA-21 from 100&#x2005;aM to 1&#x2005;nM, with a low detection limit of 31&#x2005;aM, and exhibits excellent stability, selectivity and high reproducibility in real samples.

MicroRNAs↗
PubMed2002

A biosensor for the detection of triazine and phenylurea herbicides designed using Photosystem II coupled to a screen-printed electrode.

A biosensor for the detection of triazine- and phenylurea-type herbicides was constructed using isolated Photosystem II (PS II) complexes as a biosensing element. PSII isolated from the thermophilic cyanobacterium Synechococcus elongatus was immobilized on the surface of a screen-printed sensor composed of a graphite working electrode and Ag/AgCl reference electrode deposited on a polymeric substrate. The biosensor was mounted in a flow microcell with illumination. The principle of the detection was based on the fact that herbicides selectively block PSII electron transport activity in a concentration-dependent manner. Changes of the activity were registered amperometrically as the rate of photoreduction of an artificial electron acceptor. The setup resulted in a reusable herbicide biosensor with a good stability (half-life of 24 h) and limit of detection of approximately 10(-9) M for diuron, atrazine and simazine.

Biosensing Techniques↗
PubMed2006

Superquenching as a detector for microsphere-based flow cytometric assays.

BACKGROUND: Fluorescent conjugated polymers display high fluorescence quantum yields and enhanced sensitivity to quenching (superquenching) by oppositely charged quenchers through energy or electron transfer. Fluorescent polymers and their quenchers are used in bead-based biosensor applications where the polymers are coated on particles. In this work, we investigate a detection method that utilizes superquenching on microspheres, which can be used for flow cytometric assays. METHODS: Microspheres were coated with the fluorescent cationic polyelectrolyte poly(p-phenylene-ethynylene) (PPE), and its superquenching by 9,10-anthraquinone-2,6-disulfonic acid (AQS) was examined by fluorometric methods in presence and in absence of a barrier to superquenching in the form of an anionic lipid bilayer. RESULTS: Flow cytometry detected superquenching of PPE on microspheres (MS-PPE) by AQS where high levels of reduction in fluorescence were observed. Adding different concentrations of AQS to MS-PPE yielded a Stern-Volmer quenching constant of 0.8x10(6) M-1. While forming an anionic lipid bilayer around the MS-PPE acted as a barrier to superquenching by AQS, disrupting the lipid bilayer allowed superquenching to take place. CONCLUSIONS: The sensitivity of flow cytometry in detecting fluorescence of microspheres and the amplified quenching sensitivity of fluorescent conjugated polymers both offer advantages over other fluorometric methods and conventional quenching detection. This study used superquenching of fluorescent polymers as a new tool in flow cytometry, thus combining the advantages offered by both method and detector. In addition, we employed the formation and the disruption of a supported lipid bilayer in mediating superquenching to offer new biosensing applications.

Anthraquinones↗
PubMed2007

Preparation of nano-tentacle polypyrrole with pseudo-molecular template for ATP incorporation.

Polypyrrole was electrochemically synthesized onto a gold electrode in the presence of sodium p-toluenesulfonate (TSNa) as the key dopant. Under the optimal synthesis condition, the surface morphology of PPy/TSNa was tailored and exhibited a nano-tentacle structure. The resulting rough and fuzzy morphology greatly enhanced the apparent surface area as well as the polymer film conductivity. Adenosine triphosphate (ATP) was then incorporated in the structure by subsequent ion exchanging. This procedure could be envisaged as pseudo-molecular templating to eliminate several shortcomings associated with physical templating. Fourier transform infrared (FTIR) and ultraviolet-visible (UV-vis) spectroscopy were conducted to investigate the incorporation of ATP. The pronounced rough surface of PPy/TSNa provided a higher density of active sites for ATP binding. The resulting PPy/ATP film exhibited a high charged capacity and lower impedance compared to the bare gold electrode. ATP remained stable in the PPy film; however, a negative bias to the electrode stimulated the conducting polymer to release ATP. This concept could serve as a mechanism for drug delivery and biosensing applications.

Adenosine Triphosphate↗
PubMedDate not supplied

Advances in membrane receptor screening and analysis.

During the last decade there has been significant progress in the development of analytical techniques for the screening of ligand binding to membranes and membrane receptors. This review focuses on developments using label-free assays that facilitate ligand-membrane-receptor screening without the need for chemical-, biological- or radiological-labelled reagents. These assays include acoustic, optical surface plasmon resonance biosensing, sedimentation (analytical ultracentrifugation), chromatographic assays, isothermal titration calorimetry and differential scanning calorimetry. The merits and applications of cell-based screening systems and of different model membrane systems, including planar supported lipid layers, bead-supported membranes and lipid micro-arrays, are discussed. Recent advances involving more established techniques including intrinsic fluorescence, FRET spectroscopy, scintillation proximity assays and automated patch clamping are presented along with applications to peripheral membrane proteins, ion channels and G protein-coupled receptors. Novel high-throughput assays for determination of drug- and protein-partitioning in membranes are also highlighted. To aid the experimenter, a brief synopsis of the techniques commonly employed to purify and reconstitute membranes and membrane receptors is included.

Animals↗
PubMed2004

Bionanotechnology based on silica nanoparticles.

We have developed uniform core/shell nanoparticles, consisting of a silica layer coating and pigments or magnetite core, using a water-in-oil microemulsion method. The nanoparticles are highly luminescent and photostable with the size ranging from 5 nm to 400 nm. Bioconjugation of these silica nanoparticles adds unique biofunctions with various molecules such as enzymes, antibodies, and DNA molecules. Significant advantages have been shown in using bioconjugated nanoparticles for biosensing and bioimaging, such as cell staining, DNA detection and separation, rapid single bacterium detection, and biotechnological application in DNA protection.

Animals↗
PubMed2005

Nanostructures and molecular force bases of a highly sensitive capacitive immunosensor.

While biosensors have been constructed using various strategies, there is no report describing nanostructures of antibody-immobilized electrode interface in an immunosensor. Here, atomic force microscopy (AFM) and electrochemistry analyses were employed to construct and characterize the nanostructures and electrochemistry of biosensing surface that was created by a sequential self-assembling of bioactive aminobenzenthiol oligomer (o-ABT), glutareldehyde and anti-transferrin (anti-Tf) antibody on the electrode gold surface. Under AFM, a complete coverage of bioactive o-ABT interface could be achieved by anti-Tf antibody at an optimal concentration. The anti-Tf antibody immobilized on electrode surface of the immunosensor exhibited globular-shape topography with some degree of aggregation. Extensive force-curve analysis allowed mapping the functional spots of the anti-Tf immunosensor. Surprisingly, although immunosensing surface was fully covered by anti-Tf antibodies at the optimal concentration, only about 52% of coated anti-Tf antibody molecules (spots) on the electrode surface were able to specifically capture or bind Tf antigen under AFM. Despite limited functional spots, however, the anti-Tf immunosensor was highly specific and sensitive for sensitizing Tf antigen in solution. The anti-Tf molecules on the immunosensor exhibited a greater molecular force bound to holo-Tf (iron-containing form of Tf) than that to apo-Tf (iron-absent form of Tf). Consistently, the anti-Tf immunosensor had a greater electrochemical capacity to sensitize apo-Tf than holo-Tf, supporting the molecular force-based finding by AFM. Thus, the present study elucidated the nanostructures and molecular force bases for the immunosensing capacity of a highly sensitive capacitive immunosensor.

Apoproteins↗
PubMed2005

Nanomaterial-based amplified transduction of biomolecular interactions.

This article reviews progress in the development of nanomaterials for amplified biosensing and discusses different nanomaterial-based bioamplification strategies. Signal amplification has attracted considerable attention for ultrasensitive detection of disease markers and biothreat agents. The emergence of nanotechnology is opening new horizons for highly sensitive bioaffinity and biocatalytic assays and for novel biosensor protocols that employ electronic, optical, or microgravimetric signal transduction. Nucleic acids and antibodies functionalized with metal or semiconductor nanoparticles have been employed as amplifying tags for the detection of DNA and proteins. The coupling of different nanomaterial-based amplification platforms and amplification processes dramatically enhances the intensity of the analytical signal and leads to ultrasensitive bioassays. The successful realization of the new nanoparticle-based signal amplification strategies requires proper attention to nonspecific adsorption issues. The implications of such nanoscale materials on amplified biodetection protocols and on the development of modern biosensors are discussed.

Adsorption↗
PubMed2004

Creation of highly functional thin films using electrochemical nanotechnology.

This overview describes the results of our recent study of the application of electrochemical nanotechnology to the fabrication of magnetic recording materials, interconnects in ultra-large-scale integrated (ULSI) devices, energy storage materials, and on-chip biosensors. It is important to note that electrochemical processes play significant roles in developing and fabrication such sophisticated materials and devices. In the field of magnetic recording, electrodeposition methods for preparing CoNiFe and CoFe soft magnetic thin films with a high saturation magnetic flux density were newly developed, and the significant issues for obtaining those films are highlighted. In the area of ULSI interconnects, we developed a technique using a self-assembled monolayer (SAM) for direct bonding of the interconnect layer to SiO2, and proposed a novel electroless deposition method for fabricating a diffusion barrier layer. In the field of batteries, electrodeposited SnNi alloy was proposed as a future anode material for Li batteries, and electrochemical MEMS processes were shown to be useful for fabricating micro-sized direct methanol fuel cells (DMFCs) as portable batteries for electronics applications. In the area of chemical sensors, we developed a new process for fabricating field effect transistors (FETs) modified with SAMs for on-chip biosensing applications.

Biosensing Techniques↗
PubMed1999

Comparison of the tetrazolium salt assay for succinate dehydrogenase with the cytosensor microphysiometer in the assessment of compound toxicities.

The cytosensor microphysiometer (a biosensing instrument for detecting cellular metabolism) was compared to the established tetrazolium salt assay as a chemosensitivity test. Two coumarin compounds, 7-hydroxycoumarin and esculetin, were examined to determine their effect on the cellular metabolism of A431 cells over a 24-h exposure period. In the tetrazolium salt assay, 7-hydroxycoumarin caused suppression of the succinate dehydrogenase activity at concentrations greater than 10 microg/ml. Esculetin exerted a more serious effect on succinate dehydrogenase, with decreases in activity observed at greater than 1 microg/ml. The observed effect was dose-dependent for both compounds examined. The metabolic activities of cells exposed to 100 microg/ml of drug were 90.37 +/- 2.8 and 71.62 +/- 2.96 (n = 3), of control values, for 7-hydroxycoumarin and esculetin, respectively. Using the cytosensor microphysiometer to assess metabolic activities, a similar pattern of inhibition was observed, with esculetin more detrimental to cellular metabolism than 7-hydroxycoumarin. The effect was dose- and time-dependent for both compounds. 7-Hydroxycoumarin (100 microg/ml) caused the cellular metabolic rate to drop to 44.21 +/- 5.34% (n = 4) of the control metabolic rate, while 100 microg/ml esculetin caused the metabolic rate to fall to 21.5 +/- 4.54% (n = 4) of the control rate. The cytosensor method proved to be superior to the tetrazolium salt assay for a number of reasons, which are discussed in this paper.

Antioxidants↗
PubMed2000

Development and application of surface plasmon resonance-based biosensors for the detection of cell-ligand interactions.

Surface plasmon resonance (SPR)-based biosensors were investigated with a view to providing a portable, inexpensive alternative to existing technologies for "real-time" biomolecular interaction analysis of whole cell-ligand interactions. A fiber optic SPR-based (FOSPR) biosensor, employing wavelength-dependent SPR, was constructed to enable continuous real-time data acquisition. In addition, a commercially available integrated angle-dependent SPR-based refractometer (ISPR) was modified to facilitate biosensing applications. Solid-phase detection of whole red blood cells (RBCs) using affinity-captured blood group specific antibodies was demonstrated using the BIACORE 1000, BIACORE Probe, FOSPR, and ISPR sensors. Nonspecific binding of RBCs to the hydrogel-based biointerface was negligible. However, the background noise level of the FOSPR-based biosensor was approximately 25-fold higher than that of the widely used BIACORE 1000 system while that of the ISPR-based biosensor was over 100-fold higher. Nevertheless, the FOSPR biosensor was suitable for the analysis of macromolecular analytes contained in crude matrices.

Biosensing Techniques↗
PubMed2005

Biocomposites of covalently linked glucose oxidase on carbon nanotubes for glucose biosensor.

The formation of covalently linked composites of multi-walled carbon nanotubes (MWCNT) and glucose oxidase (GOD) with high-function density for use as a biosensing interface is described. The reaction intermediates and the final product were characterized by using FT-IR spectroscopy, and the MWCNT-coated GOD nanocomposites were examined by atomic force microscopy (AFM) and transmission electron microscopy (TEM). Interestingly, it was found that the GOD-MWCNT composites are highly water soluble. Electrochemical characterization of the GOD-MWCNT composites that were modified on a glassy carbon electrode shows that the covalently linked GOD retains its bioactivity and can specifically catalyze the oxidation of glucose. The oxidation current shows a linear dependence on the glucose concentration in the solution in the range of 0.5-40 mM with a detection limit of 30 microM and a detection sensitivity of 11.3 microA/mMcm2. The present method may provide a way to synthesize MWCNT related composites with other biomolecules and for the construction of enzymatic reaction-based biofuel cells and biosensors.

Biosensing Techniques↗
PubMed2006

Optical and electrochemical detection techniques for cell-based microfluidic systems.

The ability to fabricate microfluidic systems with complex structures and with compatible dimensions between the microfluidics and biological cells have attracted significant attention in the development of microchips for analyzing the biophysical and biochemical functions of cells. Just as cell-based microfluidics have become a versatile tool for biosensing, diagnostics, drug screening and biological research, detector modules for cell-based microfluidics have also undergone major development over the past decade. This review focuses on detection methods commonly used in cell-based microfluidic systems, and provides a general survey and an in-depth look at recent developments in optical and electrochemical detection methods for microfluidic applications for biological systems, particularly cell analysis. Selected examples are used to illustrate applications of these detection systems and their advantages and weaknesses.

Biosensing Techniques↗
PubMed2005

Metal-enhanced fluorescence using anisotropic silver nanostructures: critical progress to date.

In this critical and timely review, the effects of anisotropic silver nanostructures on the emission intensity and photostability of a key fluorophore that is frequently used in many biological assays is examined. The silver nanostructures consist of triangular, rod-like, and fractal-like nanoparticles of silver deposited on conventional glass substrates. The close proximity to silver nanostructures results in greater intensity and photostability of the fluorophore than for fluorophores solely deposited on glass substrates. These new anisotropic silver nanostructure-coated surfaces show much more favorable effects than silver island films or silver colloid-coated substrates. Subsequently, the use of metal-enhanced fluorescence (MEF) for biosensing applications is discussed.

Anisotropy↗