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At least 451 records · Page 25Linked to original sources
PubMed2006

Single-beat noninvasive imaging of cardiac electrophysiology of ventricular pre-excitation.

OBJECTIVES: The aim of this study was to determine whether noninvasive imaging of cardiac electrophysiology (NICE) is feasible in patients with Wolff-Parkinson-White (WPW) syndrome in the clinical setting of a catheter laboratory and to test the accuracy of the noninvasively obtained ventricular activation sequences as compared with that of standard invasive electroanatomic mapping. BACKGROUND: NICE of ventricular activation could serve as a useful tool in the treatment of cardiac arrhythmias and might help improve our understanding of arrhythmia mechanisms. METHODS: NICE works by fusing the data from high-resolution electrocardiographic mapping and a model of the patient's cardiac anatomy obtained by magnetic resonance imaging. The ventricular activation sequence was computed with a bidomain theory-based heart model to solve this inverse problem. Noninvasive imaging of cardiac electrophysiology was performed in 7 patients with WPW syndrome undergoing catheter ablation of the accessory pathway. The position error of NICE was defined as the distance between the site of earliest activation computed by NICE and the successful ablation site identified by electroanatomic mapping (CARTO; Biosense Webster, Diamond Bar, California) for normal atrioventricular (AV) conduction as well as for adenosine-induced AV block. RESULTS: The error introduced by geometric coupling of the CARTO data and the NICE model was 5 +/- 3 mm (model discretization 10 mm). All ventricular accessory pathway insertion sites were identified with an accuracy of 18.7 +/- 5.8 mm (baseline) and 18.7 +/- 6.4 mm (adenosine). CONCLUSIONS: The individual cardiac anatomy model obtained for each patient enables accurate noninvasive electrocardiographic imaging of ventricular pre-excitation in patients with WPW syndrome. Noninvasive imaging of cardiac electrophysiology might be used as a complementary noninvasive approach to localize the origin and help identify and understand the underlying mechanisms of cardiac arrhythmias.

Adult↗
PubMed2005

Gold-conductive polymer nanoparticles: a hybrid material with enhanced photonic reactivity to environmental stimuli.

We have designed a simple synthetic procedure to encapsulate colloidal gold nanoparticles by electrostatic adsorption with water-soluble poly(aniline-2-carboxylic acid). The composite nanoparticles are stable in aqueous buffer and retain the respective optical reactivity of the gold colloid to refractive index increases, and of the conductive polymer to pH changes and oxidoreduction. The new composite displays, however, significant enhancements in photonic performance when compared to the individual components, which seem to result from electronic interplay between the two materials in the hybrid structure. The enhanced photonic reactivity of the composite structure offers new opportunities for biosensing application.

Adsorption↗
PubMed2003

Endoventricular porcine autologous myoblast transplantation can be successfully achieved with minor mechanical cell damage.

OBJECTIVE: Transplantation of skeletal myogenic precursor cells (mpc) into the myocardium using a non-surgical procedure. METHODS: Closed-chest mpc transplantation was assessed in pigs using the NOGA-Biosense device allowing both electromechanical mapping of the left ventricle (LV), and guided mpc injections through endocardium. RESULTS: We successively established that: (1) adequate preimplantation handling of mpc can be achieved when mpc are kept in 0.1% serum albumin-containing medium until implantation; (2) mpc are neither retained nor destroyed in the catheter or the needle and their passage does not affect their survival, growth and differentiation; (3) large numbers of autologous mpc can be actually transplanted in the LV myocardium by transendocardial route, as assessed by post-mortem examination of pigs injected with iron-loaded mpc; (4) cell injection into the myocardium does not induce conspicuous cell mortality since more than 80% of mpc recovered from LV tissue are alive 15 min after injection; (5) mpc injections can be guided into circumscribed LV targets such as infarcted areas, as assessed by comparison of map injection sites with location of iron-loaded mpc at post-mortem examination of LV myocardium. CONCLUSION: This new approach may pave the way for a large spectrum of cell therapies targeting myocardial diseases.

Animals↗
PubMed2003

Diffusion of hydrophilic probes in bicontinuous lipidic cubic phase.

The lipidic cubic phase was prepared by mixing monoolein (monooleoyl-rac-glycerol, MO) with water in 64:36% ratio and applied to the solid support-glassy carbon or platinum electrodes. Highly viscous, homogeneous and transparent cubic phase film remained stable and firmly attached to the electrode surface. In order to describe the efficiency of transport of small hydrophilic molecules within the film, we studied the diffusion of selected redox mediators along the network of aqueous channels present in the cubic phase structure. Loading times, diffusion coefficients and concentrations of the mediators in the layer were determined by voltammetry and chronocoulometry using two types of electrodes: a normal size electrode working in the linear diffusion regime and an ultramicroelectrode working under spherical diffusion conditions. In addition to the well-defined order, transparency and viscosity, the fast transport of small redox mediators through the aqueous channels of the cubic phase and along the interfacial water-lipid region is another important property of this matrix. The diffusion of the hydrophilic probes in the cubic phase was found to be more efficient than in the Nafion layers. Efficient transport of small redox mediators within the cubic phase means that not only enzymes and synthetic catalysts can be incorporated into the phase but also their fast communication with electrode surface will be enabled thanks to the simultaneous incorporation of small mobile redox mediators. This property of the cubic liquid crystalline phases based on lipids makes them especially interesting from the point of view of practical applications in biosensing and bioelectrocatalysis.

Diffusion↗
PubMed2000

Determination of tea catechins.

An overview of analytical methods for the measurement of biologically important tea catechins is presented. Liquid chromatography and capillary electrophoresis are the most cited techniques for catechin separation, identification and quantitation. Liquid chromatography with ultraviolet detection is frequently used; however, mass spectrometry, electrochemical, fluorescence and chemiluminescence detection are also utilized in cases where more sensitive or selective detection is needed. Two modes of capillary electrophoresis, capillary zone electrophoresis and micellar electrokinetic capillary chromatography, have been employed for the determination of catechins. Both modes of capillary electrophoresis are based on ultraviolet detection. Additional analytical techniques, such as gas chromatography, thin-layer chromatography, paper chromatography, spectrophotometry, biosensing, chemiluminescence and nuclear magnetic resonance spectroscopy have also been utilized for the determination of catechins and are reviewed herein.

Catechin↗
PubMed2000

In vivo spectrometric calcium flux recordings of intrinsic Caudate-Putamen cells and transplanted IMR-32 neuroblastoma cells using miniature fiber optrodes in anesthetized and awake rats and monkeys.

A method is described to enable the recording of transient intracellular calcium changes in deep brain structures in anesthetized and awake animals using a fluorescent indicator combined with in vivo optical detection methods. Optrodes were fabricated using a bifurcated fiber-optic cable with an attached infusion guide cannula. After intracranial implantation of an optrode, animals were prepared in the following manner, (1) rats (intra-striatal) and monkeys (intra-putamen) were infused with the fluorescent calcium indicator, Oregon Green, to load intrinsic cells; or (2) rats were intra-striatally transplanted with a slurry of dye-loaded IMR-32 neuroblastoma cells via pipette ejection. Excitation light from an argon-ion laser was launched through the optrode and passed into the tissue. The resulting calcium-induced fluorescence signals were captured by the optrode, then detected and processed by externalized photomultiplier- and CCD-based spectrometer electronics. In approximately 25% of all intrinsic cell recordings, the baseline fluorescence intensity was relatively stable over time whereas in the remainder, large amplitude oscillations were observed with a frequency in the range of 0.5-2 Hz. These Ca(2+) transients were inhibited by local infusion of 10 microM omega-conotoxin MVIIC and 1 microM TTX. Extracellular electrophysiological recordings that were made adjacent to the optrode tip revealed that the Ca(2+) oscillations were in phase with the burst firing of striatal neurons. This suggested that the optical signals had a neuronal origin, most likely from medium spiny neurons. Baseline fluorescence intensity increased during infusion of high [K(+)](o), the calcium ionophore, A-23187, or during temporary bilateral carotid artery occlusion. Monkey (Saimiri sciureus) putamen recordings also affirmed the presence of similar calcium-related transients in a non-human primate. In the transplant preparations, the IMR-32 cells displayed a stable, non-oscillating baseline fluorescence. They were similarly responsive to high [K(+)](o) challenge and appeared viable for at least several hours. Similar optical recording approaches might be applied to monitor other fluorescent, chemiluminescent or bioluminescent events from almost any brain structure. Moreover, transplanted transfected cells expressing a single specific receptor or ion-channel protein may effectively serve as biosensing elements for the measurement of extracellular neurochemical signaling.

Action Potentials↗
PubMed2003

Assessing sediment toxicity and arsenite concentration with bacterial and traditional methods.

Three sediment samples LP (pool where logs are stored), LF (brook through landfill area), KN (Kaskesniemi) which is in Lake Pyhäselkä downstream from the mill, were taken from an old sawmill area and one from the unpolluted Lake Höytiäinen. The arsenite concentration was measured by GFAAS and two arsenite biosensing bacterial strains Pseudomonas fluorescens OS8 (pTPT31) and Escherichia coli MC1061 (pTOO31). The toxicity of sediment and pore water samples was determined by using luminescent bacteria (Flash test) and, further, whole sediment toxicity was measured using 10 days growth test and 50 days emergency test with midges (Chironomus riparius). With the flash test a lowered EC50 value was found only in sediment LF (EC50=0.17 v/v%). The Flash test indicated that all sediment samples taken from the sawmill area were highly toxic to bacteria, whereas growth and the emergence of chironomids showed no effects in other samples than LF. The midges tolerate well the contaminated environment. In contrast, bioavailability of arsenite of sediment samples KN and LF was quite high determined using the biosensor-strains in a direct contact assay. The bioavailable fraction of sediment LP was 6-10% out of the total arsenite concentration obtained with GFAAS (0.46-0.77 microg g-1 dw). The results show that the choice of analysis method grossly affects the outcome without any of the method giving an incorrect result. Different methods measure different parameters of a toxic sample and can thus be used to complement each other.

Arsenites↗
PubMed2001

Improvement of the quality of self assembled bilayer lipid membranes by using a negative potential.

Self-assembled lipid bilayer membranes (s-BLMs) on the tip of Teflon-coated silver electrodes were formed according to the T. Tien method. Their formation process and properties were investigated by capacitance and voltage current cycle measurements. The stability of the membranes was improved and defects were eliminated through the application of a negative dc potential during formation. Cyclic current-voltage measurements were applied to probe membrane integrity, by using an electrolyte interacting with the silver electrode. Oxidation and reduction peaks were observed for non defect-free membranes. These peaks were caused by oxidation of the silver electrode tip and their occurrence was a very sensitive means of measuring membrane integrity. The membrane was a barrier for the ion transport from the electrolyte solution to the electrode surface, and thus defect-free membranes inhibited the appearance of the peaks. With the s-BLMs produced by the described method, binding of ions and proteins to the membrane could be measured repetitively and reproducibly through changes in the system capacitance and the shape of the cyclovoltammogram. The presence of divalent ions lead to a specific increase in total system capacitance of membranes from charged lipids. Protein binding was measured as a decrease of the capacitance, in accordance with the thickness increase of the total membrane after binding. The facility of production and the sensitivity of the aforementioned substances could make the s-BLMs, produced by the described method, a valuable system to be developed in the field of biosensing.

Electrochemistry↗
PubMed2003

Electromechanical mapping versus positron emission tomography and single photon emission computed tomography for the detection of myocardial viability in patients with ischemic cardiomyopathy.

OBJECTIVES: We compared catheter-based electromechanical mapping (NOGA system, Biosense-Webster, Haifa, Israel) with positron emission tomography (PET) and single photon emission computed tomography (SPECT) for prediction of reversibly dysfunctional myocardium (RDM) and irreversibly dysfunctional myocardium (IDM) in patients with severe left ventricular dysfunction. Furthermore, we established the optimal discriminatory value of NOGA measurements for distinction between RDM and IDM. BACKGROUND: The NOGA system can detect viable myocardium but has not been used for prediction of post-revascularization contractile function in patients with ischemic cardiomyopathy. METHODS: Twenty patients (19 males, age [mean +/- SD] 60 +/- 16 years, ejection fraction [EF] 29 +/- 6%) underwent viability testing with NOGA and PET or SPECT before revascularization. Left ventricular function was studied at baseline and six months after revascularization. RESULTS: The EF increased to 34 +/- 13% at six months (p < 0.05 vs. baseline). The 58 RDM and 57 IDM regions differed with regard to unipolar voltage amplitude (UVA) (9.2 +/- 3.9 mV vs. 7.6 +/- 4.0 mV, p < 0.05), normalized UVA (106 +/- 54% vs. 75 +/- 39%, p < 0.05), and tracer uptake (76 +/- 17% vs. 60 +/- 20%, p < 0.05). The NOGA local shortening did not distinguish between RDM and IDM (6.4 +/- 5.8% vs. 5.4 +/- 6.6%). By receiver operating characteristic curve analysis, myocardial tracer uptake had better diagnostic performance than UVA (area under curve [AUC] +/- SE: 0.82 +/- 0.04 vs. 0.63 +/- 0.05, p < 0.05) and normalized UVA (AUC +/- SE: 0.70 +/- 0.05, p < 0.05). Optimal threshold was defined as the value yielding sensitivity = specificity for prediction of RDM. Sensitivity and specificity were 59% at a UVA of 8.4 mV, 65% at a normalized UVA of 83%, and 78% at a tracer uptake of 69%. CONCLUSIONS: The NOGA system may discriminate RDM from IDM with optimal discriminatory values for UVA and normalized UVA of 8.4 mV and 83%, respectively. However, the diagnostic performance does not reach the level obtained by PET and SPECT in patients with severe heart failure.

Aged↗
PubMed2000

Sensitivity deviation: instrumental linearity errors that influence concentration analyses and kinetic evaluation of biomolecular interactions.

Many scientific instruments utilise multiple element detectors, e.g. CCD's or photodiode arrays, to monitor the change in a position of an optical pattern. For example. instruments for affinity biosensing based on surface plasmon resonance (SPR) or resonant mirror are equipped with such detectors. An important and desired property of these bioanalytical instruments is that the calculation of the movement or change in shape follows the true change. This is often not the case and it may lead to linearity errors, and to sensitivity errors. The sensitivity is normally defined as the slope of the calibration curve. A new parameter is introduced to account for the linearity errors, the sensitivity deviation, defined as the deviation from the undistorted slope of the calibration curve. The linearity error and the sensitivity deviation are intimately related and the sensitivity deviation may lead to misinterpretation of kinetic data, mass transport limitations and concentration analyses. Because the linearity errors are small (e.g. 10 pg/mm2 of biomolecules on the sensor surface) with regard to the dynamic range (e.g. 30,000 pg/mm2), they can be difficult to discover. However, the linearity errors are often not negligible with regard to a typical response (e.g. 0-100 pg/mm2). and may therefore cause serious problems. A method for detecting linearity errors is outlined. Further on, this paper demonstrates how integral linearity errors of less than 1% can result in a sensitivity deviation of 10%, a value that in our opinion cannot be ignored in biospecific interaction analysis (BIA). It should also be stressed out that this phenomenon also occurs in other instruments using array detectors.

Kinetics↗
PubMed2001

Functional tethered membranes.

Phospholipid bilayer membranes at the interface between a substrate and an aqueous phase, supported by or tethered to the solid surface via a polymer cushion, a peptide-, protein-, or oligosaccharide-coupling layer have reached a stage at which they are important as a novel model membrane system but also offer potential for practical applications (e.g. for biosensing purposes with membrane-integral receptors). We briefly summarize some of the recent progress made in the structural characterization of the build-up of these rather complex interfacial architectures, in the functionalization of the pure lipid matrix by the reconstitution of proteins, and in the lateral patterning of the membranes as a prerequisite for the construction of membrane chips for massive parallel monitoring of binding events.

Lipid Bilayers↗
PubMed2005

Impedance sensing of DNA binding drugs using gold substrates modified with gold nanoparticles.

Interfacial interactions between immobilized DNA probes and DNA-specific sequence binding drugs were investigated using impedance spectroscopy toward the development of a novel biosensing scheme. The impedance measurements are based on the charge-transfer kinetics of the [Fe(CN)6]3-/4- redox couple. Compared to bare gold surfaces, the immobilization of DNA and then the DNA-drug interaction on electrode surfaces altered the capacitance and the interfacial electron resistance and thus diminished the charge-transfer kinetics by reducing the active area of the electrode or by preventing the redox species from approaching the electrode. Electrochemical deposition of gold nanoparticles on a gold electrode surface showed significant improvement in sensitivity. DNA-capped gold nanoparticles on electrodes act as selective sensing interfaces with tunable sensitivity due to higher amounts of DNA probes and the concentric orientation of the DNA self-assembled monolayer. The specificity of the interactions of two classical minor groove binders, mythramycin, a G-C specific-DNA binding anticancer drug, netropsin, an A-T specific-DNA binding drug and an intercalator, nogalamycin on AT-rich DNA-modified substrate and GC-rich DNA-modified substrate are compared. Using gold nanoparticle-deposited substrates, impedance spectroscopy resulted in a 20-40-fold increase in the detection limit. Arrays of deposited gold nanoparticles on gold electrodes offered a convenient tool to subtly control probe immobilization to ensure suitably adsorbed DNA orientation and accessibility of other binding molecules.

DNA↗
PubMed2004

An optical spot test for the detection of dopamine in human urine using stabilized in air lipid films.

The present technique describes a simple, sensitive spot test for the rapid one-shot detection of dopamine in human urine using lipid films with incorporated resorcin[4]arene receptor that are synthesized by a chemical reaction with a methacrylate polymer on a glass fiber filter. The lipid films without the receptor provided fluorescence under a UV lamp. The use of the receptor in these films quenched this fluorescence, and the color became similar to that of the filters without the lipid films. A drop of dopamine or urine containing this stimulant provided a "switching on" of the fluorescence, which allows the rapid detection of this stimulant in human urine at 10(-8) M concentrations. The novelty of the present work is that it opens new routes in the field of biosensing, i.e., development of sensitive, rapid, and simple methods for detecting species based on the fluorescence of the lipid membranes on a polymer film, and provides a spot test technique for the rapid detection of dopamine. The effect of potent interferences including a wide range of compounds usually found in human urine (i.e., ascorbic aid, glucose, leucine, glycine, tartrate, citrate, bicarbonate, and caffeine) was examined using an aqueous buffered solution that contained the potent interference and dopamine at two lower concentration levels (i.e., 3 x 10(-8)-10(-8) M). The effect of proteins and lipids was also investigated at these two lower dopamine concentration levels in aqueous buffered solution. The results showed no interferences from all these constituents at concentrations usually found in human urine samples; for example, albumin up to 3.22 g/L concentration levels did not provide any interference (i.e., no fluorescence). A drop of urine containing this stimulant provided similar results, i.e., a "switching on" of the fluorescence that allows a technique for the rapid detection of this stimulant in human urine at 10(-8) M concentrations. The technique is not based on a calibration graph but is a semiquantitative method for the detection of dopamine in real samples of urine that can be complimentary to HPLC methods. The difference in color between the samples containing dopamine at concentration levels of 10(-8)-10(-7) M can be easily distinguished by naked eye and a digital camera. An increase of dopamine concentration from 10(-8) to 10(-7) M makes the color more blue whereas the color of the filters remains purple in the blank test (i.e., addition of a urine sample without dopamine or dopamine at concentration levels of 10(-9) M to the filters that contain the lipid membranes with incorporated receptor). The reproducibility of the method was checked in approximately 100 samples, and all of them were found to provide similar results. Note that it was also found that the colors remain stable in the samples containing dopamine for periods of more than two months.

Dopamine↗
PubMed2005

On-chip microfluidic transport and mixing using electrowetting and incorporation of sensing functions.

An integrated system was developed that performs microfluidic transport, mixing, and sensing on a single chip. The operation principle for the microfluidic transport was based on electrowetting. A solution to be transported was confined in a space between a row of gold working electrodes and a protruding poly(dimethylsiloxane) (PDMS) structure. When a negative potential was applied to one of the gold working electrodes, it became hydrophilic, and the solution was transported through the flow channel. The solution could be transported in any desired direction in a network of flow channels by switching on necessary electrodes one by one. Furthermore, two solutions transported through two flow channels could be mixed using a mixing electrode based on the same principle. To demonstrate the applicability of a lab-on-a-chip, an air gap ammonia electrode was integrated by taking advantage of the open structure of the flow channel. Gaseous ammonia that was produced after pH adjustment and diffused through an air gap caused a pH change in the electrolyte layer, which was measured with an iridium oxide pH indicator electrode. The 90% response time was less than 1 min for the millimolar order of ammonia. The calibration curve was linear down to 10 microM. The ammonia-sensing system was also applied to construct biosensing systems for urea and creatinine. A linear relationship was observed between the potential and the logarithm of the concentration of the analytes down to 50 microM for both urea and creatinine. The developed microfluidic system can be a basic building block for future systems.

Journal Article↗
PubMed2005

Protein capture in silica nanotube membrane 3-D microwell arrays.

The microarray format has allowed for rapid and sensitive detection of thousands of analyte DNAs in a single sample, and there is considerable interest in extending this technology to protein biosensing. While glass is the most common substrate for microarrays, its binding capacity is limited because the glass surface is flat. One way to overcome this limitation is to develop arrays based on porous materials. Such "3-D" arrays can provide greater sensitivity because both the capture molecules and the analyte species they bind are immobilized throughout the thickness of the porous material. We describe here 3-D protein microarrays based on nanopore alumina membranes that contain silica nanotubes within the pores. These microarrays are prepared via a plasma-etch method using a TEM grid as the etch mask and consist of individual nanotube-containing microwells imbedded in a Ag film that coats the alumina membrane surface. We show that the microwells can be functionalized with antibodies and that these antibodies can capture their antigen proteins, which serve as prototype analytes. The analyte proteins are fluorescently tagged, which allows for fluorescence microscopy-based imaging of the array. The Ag surrounding the microwells shows very low background fluorescence, thus improving the signal-background ratio obtained from these arrays.

Electrochemistry↗
PubMed2005

Kinetic and equilibrium binding analysis of protein-ligand interactions at poly(amidoamine) dendrimer monolayers.

The interaction of streptavidin (SA) with a biotinylated surface has been of great interest in the development of an interfacial layer for protein immobilization based on self-assembled monolayers (SAMs) and polymeric layers. Here, we demonstrate the unique characteristics of protein-ligand interactions on dendrimer monolayers based on kinetic and equilibrium binding analyses. With amine-ended poly(amidoamine) dendrimers from the first (G1) to fourth (G4) generation, the formation of even, compact dendrimer monolayers on gold was confirmed using FT-IR spectroscopy and ellipsometry. For the SA-biotin interaction, quantitative analysis of bound SA using surface plasmon resonance showed that the saturation binding level of SA was fairly higher in all dendrimer layers when compared to other tested systems of 11-mercaptoundecylamine SAMs and a poly(L-lysine) layer. Kinetic studies revealed that the initial binding rate of SA up to the saturation level was 2-fold higher in all dendrimer layers than in the SAMs regardless of the surface density of functionalized biotin. Concurrently, the dendrimer layers led to much higher values of sticking probability, which is defined as the probability that the SA molecule adsorbs upon collision with a biotinylated surface, at a fixed SA coverage, and prolonged the significant levels around the maximum probability with increasing SA coverage. Plots of the saturation coverage of SA versus the SA concentration in solution showed that SA binding onto the biotinylated G1 and G3 layers fit to a Langmuir isotherm model. Taken together, faster binding of SA and highly ordered packing of the molecules seems to be achieved through typical properties of the dendrimer monolayers such as surface distribution of functionalized biotin, surface corrugation, and flexibility of highly branched larger dendrimers, which provides a guideline for the construction and analysis of an interfacial layer in biosensing applications.

Biotin↗
PubMed2006

Nanoscale glassification of gold substrates for surface plasmon resonance analysis of protein toxins with supported lipid membranes.

Surface plasmon resonance (SPR) spectroscopy, a powerful tool for biosensing and protein interaction analysis, is currently confined to gold substrates and the relevant surface chemistries involving dextran and functional thiols. Drawbacks of using self-assembled monolayers (SAMs) for SPR-related surface modification include limited stability, pinhole defects, bioincompatibility, and nonspecific protein adsorption. Here we report the development of stable nanometer-scale glass (silicate) layers on gold substrates for SPR analysis of protein toxins. The nanoscale silicate layers were built up with layer-by-layer deposition of poly(allylamine hydrochloride) and sodium silicate, followed by calcination at high temperature. The resulting silicate films have a thickness ranging from 2 to 15 nm and demonstrate outstanding stability in flow cell conditions. The use of these surfaces as a platform to construct supported bilayer membranes (SBMs) is demonstrated, and improved performance against protein adsorption on SBM-coated surfaces is quantified by SPR measurements. SBMs can be formed reproducibly on the silicate surface via vesicle fusion and quantitatively removed using injection of 5% Triton X-100 solution, generating a fresh surface for each test. Membrane properties such as lateral diffusion of the SBMs on the silicate films are characterized with photobleaching methods. Studies of protein binding with biotin/avidin and ganglioside/cholera toxin systems show detection limits lower than 1 microg/mL (i.e., nanomolar range), and the response reproducibility is better than 7% RSD. The method reported here allows many assay techniques developed for glass surfaces to be transferred to label-free SPR analysis without the need for adaptation of protocols and time-consuming synthetic development of thiol-based materials and opens new avenues for developing novel bioanalytical technologies for protein analysis.

Avidin↗
PubMed2006

High-performance carbon composite electrode based on an ionic liquid as a binder.

Ionic liquid, n-octylpyridinum hexafluorophosphate (OPFP) has been used to fabricate a new carbon composite electrode with very attractive electrochemical behavior. This type of carbon electrode has been constructed using graphite mixed with OPFP as the binder. The electrode has combined advantages of edge plane characteristics of carbon nanotubes and edge plane pyrolytic graphite electrodes together with the low cost of carbon paste electrodes and robustness of metallic electrodes. It provides a remarkable increase in the rate of electron transfer of different organic and inorganic electroactive compounds and offers a marked decrease in the overvoltage for biomolecules such as NADH, dopamine, and ascorbic acid. It also circumvents NADH surface fouling effects as well as furnishing higher current density for a wide range of compounds tested. Depending on the choice of the electrolyte, the electrode can have the ion-exchange property and adsorptive characteristics of clay-modified electrodes. The proposed electrode thus allows sensitive, low-potential, simple, low-cost, and stable electrochemical sensing of biomolecules and other electroactive compounds. Scanning electron microscopy images indicate significant improvement in the microstructure of the proposed electrode compared to carbon paste electrodes. Such abilities promote new opportunities for a wide range of electrochemical and biosensing applications.

Journal Article↗