Biomedical subjects

Nabil El Murr

Publications and source records attributed to Nabil El Murr.

6 recordsLinked to original sources

PubMed2006

Layer-by-layer hydroxymethyl ferrocene modified sensor for one-step flow/stop-flow injection amperometric immunoassay of alpha-fetoprotein.

A rapid one-step flow/stop-flow injection amperometric immunoassay for alpha-fetoprotein (AFP) using a novel home-produced electrochemical sensor was proposed. The sensor was prepared using layer-by-layer adsorption of positively charged poly(allylamine) (PAA) and negatively charged hydroxymethyl ferrocene on a screen-printed electrode (SPE). The electrochemistry of the immobilized ferrocene moieties showed a surface-controlled electrode process. Based on an electrochemical enzyme-linked immunoassay with the immobilized ferrocene moieties as an electron transfer mediator between the electrode and the horseradish peroxidase (HRP)-labeled anti-AFP antibody, a calibration curve with two linear ranges from 5 to 20 and 20 to 150 ng ml-1 and a detection limit of 2 ng ml-1 for AFP determination was obtained under the optimized conditions of 0.891 ml min-1 flow rate, 20 microl injection volume and +25 mV applied potential. The sensor showed good repeatability and reproducibility and retained more than 95% of its original signal after 15 days of storage. The proposed method eliminated the need for washing and addition of any substrate or mediator. The complete assay could be handled in less than 25 min with a one-step injection of a 40 microl sample solution. The proposed method would be valuable for the diagnosis and monitoring of carcinoma and its metastasis.

Biosensing Techniques↗

PubMed2006

A disposable electrochemical immunosensor for flow injection immunoassay of carcinoembryonic antigen.

A new simple immunoassay method for carcinoembryonic antigen (CEA) detection using a disposable immunosensor coupled with a flow injection system was developed. The immunosensor was prepared by coating CEA/colloid Au/chitosan membrane at a screen-printed carbon electrode (SPCE). Using a competitive immunoassay format, the immunosensor inserted in the flow system with an injection of sample and horseradish peroxidase (HRP)-labeled CEA antibody was used to trap the labeled antibody at room temperature for 35 min. The current response obtained from the labeled HRP to thionine-H(2)O(2) system decreased proportionally to the CEA concentration in the range of 0.50-25 ng/ml with a correlation coefficient of 0.9981 and a detection limit of 0.22 ng/ml (S/N=3). The immunoassay system could automatically control the incubation, washing and current measurement steps with good stability and acceptable accuracy. Thus, the proposed method proved its potential use in clinical immunoassay of CEA.

Biosensing Techniques↗

PubMed2004

Synergetic effect for NADH oxidation of ferrocene and zeolite in modified carbon paste electrodes. New approach for dehydrogenase based biosensors.

The development of electrochemical biosensors using dehydrogenases associated with the corresponding cofactor is strongly related to the better understanding of NADH oxidation at the electrode surface. The aim is to lower the necessary overvoltage and consequently to escape interferences and electrode fouling. In this paper, we show that carbon paste electrode (CPE) modified with NaY zeolite fulfils this requirements thanks to its hydrophilic surface. Oxidation of NADH at ferrocene (FcH) modified carbon paste electrode exhibits a rather slow electrocatalytic effect. We demonstrated the existence of synergetic effect on the electrocatalytic oxidation of NADH when the CPE is doped with zeolite (NaY) and FcH mediator or with the zeolite exchanged beforehand with the mediator (Y-Ferricinium, YFcH). This cumulative effect permits to reach high sensitivity for NADH detection and offers new way for the development of enzymatic biosensors using dehydrogenases depending on NADH as cofactor.

Biosensing Techniques↗

PubMed2004

Rapid and sensitive automated method for glucose monitoring in wine processing.

A rapid and sensitive automated method for glucose monitoring that might be employed during wine fermentation and processing was developed. A flow injection (FI) system coupled with an automated dilutor and the "redox-versatile" modified electrode were used to directly measure glucose in wine. To avoid interferences during wine analysis, different formulations of enzymatically modified carbon paste electrodes (CPE) were used and evaluated in oxidation and reduction mode. The best selectivity and sensitivity for glucose monitoring in real samples was obtained in cathodic mode at a fixed potential of 0 V versus Ag/AgCl using a CPE modified with glucose oxidase, horseradish peroxidase, and ferrocene as redox mediator. A total linear range of 0.02-50 g/L glucose was covered using this automated system and allowed the measurement of glucose in dry, medium, and sweet white or red wines without any sample pretreatment. The results showed a good correlation with the standard method, and the proposed method is very rapid, simple, and reliable and does not need skilled operators.

Autoanalysis↗

PubMed2003

Viability of Saccharomyces cerevisiae cells exposed to low-amperage electrolysis as assessed by staining procedure and ATP content.

Assessment of yeast viability by plate counts, ATP determination and FUN-1 viability staining was performed to study sublethal injury of Saccharomyces cerevisiae cells submitted to low-amperage electrolysis. Lethal effects of electrolysis were confirmed by all methods, demonstrated by the decrease in viable counts observed during electrolysis. FUN-1 viability staining and ATP determination appeared to demonstrate higher survivors than plate counts. To study possible recovery of certain yeast cells damaged by electrolysis thus rendering them nonculturable, yeast suspensions were stored in phosphate buffer at 4 and 20 degrees C. Increase in viable counts and ATP content of treated yeast cells was observed during storage at 20 degrees C, whereas viable counts of treated and control yeast cells were shown to decrease during storage at 4 degrees C. The increase in the number of viable cells appeared to be the result of repair of damaged cells rather than regrowth of few cells remaining culturable. The lethal efficacy of electrolysis might be overestimated by plate counts. Further experiments must be done to evaluate the lethal efficacy of electrolysis on microorganisms in real conditions encountered in food products.

Adenosine Triphosphate↗

PubMed2003

Sensitive and reproducible quantification of Cu2+ by stripping with a carbon paste electrode modified with humic acid.

The preparation of a humic acid modified carbon paste electrode (HA-MCPE) as well as the behavior of its surface as complexing agent toward Cu2+ cations are described. Electrochemical studies of the reduction of the complexed cations and of the anodic stripping oxidation of the resulting copper are outlined. The anodic stripping current was correlated to the Cu2+ concentrations. A well-defined method for the preparation of reproducible electrodes is described. The effects on the current response obtained by cyclic voltammetry of the humic acid ratio, the pH, the accumulation time, and the speed scan rate were studied. Calibration graphs were linear over the range 3 x 10(-8)-10(-5) mol L(-1) Cu2+ and the relative standard deviation (R.S.D.) was 1.2% (n=5) for [Cu2+] = 1.6 x 10(-5) mol L(-1). 5 min accumulation time for [Cu2+] > 10(-7) mol L(-1) and 10 min for [Cu2+] < 10(-7) mol L(-1) were sufficient to permit sensitive and reproducible measurements. The electrode was successfully used to measure Cu2+ in real samples and the results were compared to those obtained by the standard method with differential pulse anodic stripping voltammetry.

Carbon↗