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Biomedical subjects

Mustafa Musameh

Publications and source records attributed to Mustafa Musameh.

11 recordsLinked to original sources
PubMed2006

Acid stability of carbon paste enzyme electrodes.

This note reports on the unusual protection of several enzymes against harsh pH conditions provided by carbon paste electrodes. Both glucose oxidase and polyphenol oxidase carbon paste amperometric biosensors display a remarkable resistance to acid deactivation compared to conventional biosensors prepared by electropolymeric entrapment of enzymes. For example, the carbon paste enzyme electrodes fully retain their activity upon stressing in strongly acidic conditions (pH approximately 2.0-2.5) for prolonged periods, where conventional (polymer-based) biosensors rapidly lose most of their response. Such unusual acid stability of carbon paste enzyme electrodes is attributed to the "pH memory" of enzymes in the hydrophobic paste environment, to the barrier to hydronium ions provided by the pasting liquid and to decreased conformational mobility.

Acids↗
PubMed2004

Capillary electrophoresis microchip with a carbon nanotube-modified electrochemical detector.

Significant improvements in the performance of a capillary electrophoresis (CE) microchip with an electrochemical detector are observed using a carbon nanotube (CNT)-modified working electrode. The CNT-modified electrode allows CE amperometric detection at significantly lower operating potentials and yields substantially enhanced signal-to-noise characteristics. The electrocatalytic detection is coupled to resistance to surface fouling and hence enhanced stability. Such advantages are illustrated in connection with several classes of hydrazine, phenol, purine, and amino acid compounds. Substantial minimization of surface fouling effects has been demonstrated in connection with the monitoring of phenol and tyrosine. Factors affecting the performance of the new CNT detector were assessed and optimized. CNTs from different sources are evaluated, and the effect of an anodic pretreatment is explored. The broad and significant catalytic activity exhibited by CNT-based CE detectors indicates great promise for a wide range of bioanalytical and environmental applications.

Journal Article↗
PubMed2003

Carbon nanotube screen-printed electrochemical sensors.

The fabrication, and evaluation of carbon-nanotube (CNT)-derived screen-printed (SP) electrochemical sensors based on a CNT ink are reported. The fabricated CNT strips combine the attractive advantages of CNT materials and disposable screen-printed electrodes. Such thick-film CNT sensors have a well-defined appearance, are mechanically stable, and exhibit high electrochemical reactivity.

Biosensing Techniques↗
PubMed2003

Carbon nanotube/teflon composite electrochemical sensors and biosensors.

The fabrication and attractive performance of carbon nanotube (CNT)/Teflon composite electrodes, based on the dispersion of CNT within a Teflon binder, are described. The resulting CNT/Teflon material brings new capabilities for electrochemical devices by combining the advantages of CNT and "bulk" composite electrodes. The electrocatalytic properties of CNT are not impaired by their association with the Teflon binder. The marked electrocatalytic activity toward hydrogen peroxide and NADH permits effective low-potential amperometric biosensing of glucose and ethanol, respectively, in connection with the incorporation of glucose oxidase and alcohol dehydrogenase/NAD(+) within the three-dimensional CNT/Teflon matrix. The accelerated electron transfer is coupled with minimization of surface fouling and surface renewability. These advantages of CNT-based composite devices are illustrated from comparison to their graphite/Teflon counterparts. The influence of the CNT loading upon the amperometric and voltammetric data, as well as the electrode resistance, is examined. SEM images offer insights into the nature of the CNT/Teflon surface. The preparation of CNT/Teflon composites overcomes a major obstacle for creating CNT-based biosensing devices and expands the scope of CNT-based electrochemical devices.

Biosensing Techniques↗
PubMed2003

Solubilization of carbon nanotubes by Nafion toward the preparation of amperometric biosensors.

The ability to solubilize single-wall and multiwall carbon nanotubes (CNT) in the presence of the perfluorinated polymer Nafion is described. Such use of Nafion as a solubilizing agent for CNT overcomes a major obstacle for creating CNT-based biosensing devices. Their association with Nafion does not impair the electrocatalytic properties of CNT. The resulting CNT/Nafion modified glassy-carbon electrodes exhibit a strong and stable electrocatalytic response toward hydrogen peroxide. The marked acceleration of the hydrogen peroxide redox process is very attractive for the operation of oxidase-based amperometric biosensors, as illustrated for the highly selective low-potential (-0.05 V vs Ag/AgCl) biosensing of glucose. These findings open the door for using CNT in a wide range of chemical sensors and nanoscale electronic devices.

Biosensing Techniques↗
PubMed2003

Flow injection amperometric detection of OP nerve agents based on an organophosphorus-hydrolase biosensor detector.

A flow-injection system with an organophosphorus-hydrolase (OPH)-biosensor detector has been developed and characterized for the rapid detection of organophosphorus (OP) nerve agents. The enzyme was immobilized onto a thin-film gold detector through a cystamine-glutaraldehyde coupling. Factors influencing the performance were optimized. The resulting flow system offered a fast, sensitive, selective, and stable response. The peak current increased linearly with the concentration of paraoxon and methyl parathion over the 1-10 microM range (sensitivity, 2.29 and 1.04 nA/microM, respectively). The OPH-biosensor flow injection systems offered low detection limits (e.g. 0.1 microM paraoxon), along with a good precision (R.S.D. of 3.6% for 20 successive injections of a 1.0 microM paraoxon solution). The OPH-biosensor flow detector offers great promise for rapid field screening of OP pesticides and nerve agents.

Aryldialkylphosphatase↗
PubMed2003

Carbon-nanotube-modified glassy carbon electrodes for amplified label-free electrochemical detection of DNA hybridization.

The preparation and attractive performance of carbon-nanotube modified glassy-carbon (CNT/GC) electrodes for improved detection of purines, nucleic acids, and DNA hybridization are described. The surface-confined multiwall carbon-nanotube (MWCNT) facilitates the adsorptive accumulation of the guanine nucleobase and greatly enhances its oxidation signal. The advantages of CNT/GC electrodes are illustrated from comparison to the common unmodified glassy carbon, carbon paste and graphite pencil electrodes. The dramatic amplification of the guanine signal has been combined with a label-free electrical detection of DNA hybridization. Factors influencing the enhancement of the guanine signal are assessed and optimized. The performance characteristics of the amplified label-free electrochemical detection of DNA hybridization are reported in connection to measurements of nucleic-acid segments related to the breast-cancer BRCA1 gene.

Animals↗
PubMed2003

Enzyme-dispersed carbon-nanotube electrodes: a needle microsensor for monitoring glucose.

The preparation of an enzyme-dispersed carbon-nanotube (CNT) electrode, based on mixing glucose oxidase (GOx) within CNT, is described. The new binderless biocomposite was packed within a 21-gauge needle and used for amperometric monitoring of glucose. The resulting microsensor offers a low-potential highly selective and sensitive detection of glucose. The high sensitivity and selectivity are coupled to a wide linear range, prolonged lifetime and oxygen independence. About 80% of the GOx activity is retained during a 24 h thermal stress at 90 degrees C, reflecting the enzyme-stabilization action of CNT. The marked electrocatalytic action towards hydrogen peroxide allows highly selective detection of the glucose substrate at -0.1 V (vs. Ag/AgCl) with no interferences from coexisting ascorbic acid, acetaminophen or uric acid. Linearity prevails up to 40 mM glucose (with analytically useful signals observed up to 0.1 M). Factors affecting the performance of the CNT-based glucose biosensor were assessed and optimized. The attractive performance of the new needle electrode offers great promise for continuous monitoring of glucose in connection to the management of diabetes, and for the biosensing of other metabolites.

Electrochemistry↗
PubMed2002

Single-channel microchip for fast screening and detailed identification of nitroaromatic explosives or organophosphate nerve agents.

A single-channel chip-based analytical microsystem that allows rapid flow injection measurements of the total content of organic explosive or nerve agent compounds, as well as detailed micellar chromatographic identification of the individual ones, is described. The protocol involves repetitive rapid flow injection (screening) assays--to provide a timely warning and alarm--and switching to the separation (fingerprint identification) mode only when harmful compounds are detected. While micellar electrokinetic chromatography, in the presence of sodium dodecyl sulfate (SDS), is used for separating the neutral nitroaromatic explosive and nerve agent compounds, an operation without SDS leads to high-speed measurements of the "total" explosives or nerve agent content. Switching between the "flow injection" and "separation" modes is accomplished by rapidly exchanging the SDS-free and SDS-containing buffers in the separation channel. Amperometric detection was used for monitoring the separation. Key factors influencing the sample throughput, resolution, and sensitivity have been assessed and optimized. Assays rates of about 360 and 30/h can thus be realized for the "total" screening and "individual" measurements, respectively. Ultimately, such development will lead to the creation of a field-deployable microanalyzer and will enable transporting the forensic laboratory to the sample source.

Chemical Warfare Agents↗
PubMed2002

Dual enzyme electrochemical coding for detecting DNA hybridization.

Enzyme-based hybridization assays for the simultaneous electrochemical measurements of two DNA targets are described. Two encoding enzymes, alkaline phosphatase and beta-galactosidase, are used to differentiate the signals of two DNA targets in connection to chronopotentiometric measurements of their electroactive phenol and alpha-naphthol products. These products yield well-defined and resolved peaks at +0.31 V (alpha-naphthol) and +0.63 V (phenol) at the graphite working electrode (vs. Ag/AgCl reference). The position and size of these peaks reflect the identity and level of the corresponding target. The dual target detection capability is coupled to the amplification feature of enzyme tags (to yield fmol detection limits) and with an efficient magnetic removal of non-hybridized nucleic acids. Proper attention is given to the choice of the substrates (for attaining well resolved peaks), to the activity of the enzymes (for obtaining similar sensitivities), and to the selection of the enzymes (for minimizing cross interferences). The new bioassay is illustrated for the simultaneous detection of two DNA sequences related to the BCRA1 breast-cancer gene in a single sample in connection to magnetic beads bearing the corresponding oligonucleotide probes. Prospects for electrochemical coding of multiple DNA targets are discussed.

Alkaline Phosphatase↗