Document Detail

Immunosensor for the determination of Staphylococcus aureus using a tyrosinase-mercaptopropionic acid modified electrode as an amperometric transducer.
MedLine Citation:
PMID:  18189127     Owner:  NLM     Status:  MEDLINE    
An amperometric immunosensor for the quantification of Staphylococcus aureus based on the coimmobilization of rabbit immunoglobulin G (RbIgG) and tyrosinase on a mercaptopropionic acid self-assembled monolayer modified gold electrode is reported. A competitive mode in which protein-A-bearing S. aureus cells and antiRbIgG labeled with alkaline phosphatase (AP) compete for the binding sites of immobilized RbIgG was used. Monitoring of the affinity reaction was carried out by the amperometric detection at -0.15 V of phenol generated in the enzyme reaction with AP, at the tyrosinase-modified electrode through the electrochemical reduction of the o-quinone formed. Optimization of the working variables, such as the immunosensor composition and incubation times, the applied potential, the working pH and the concentration of phenyl phosphate used as the AP substrate, was carried out. Under the optimized conditions, both the repeatability of the measurements and the reproducibility of the responses obtained with different immunosensors yielded relative standard deviation values for the steady-state current lower than 10%. The immunosensor showed a dynamic range from 4.4x10(5) to 1.8x10(7) S. aureus cells mL(-1), with a detection limit of 1.7x10(5) cells mL(-1). The limit of detection was remarkably improved by subjecting S. aureus cells to wall lysis by heat treatment. The value obtained was 2.3x10(3) cells mL(-1), which is adequate for the monitoring of S. aureus contamination levels in some foodstuffs. As an application, milk samples spiked with bacteria at the 4.8x10(3) cells mL(-1) level were analyzed.
Vanessa Escamilla-Gómez; Susana Campuzano; María Pedrero; José M Pingarrón
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2008-01-15
Journal Detail:
Title:  Analytical and bioanalytical chemistry     Volume:  391     ISSN:  1618-2650     ISO Abbreviation:  Anal Bioanal Chem     Publication Date:  2008 Jun 
Date Detail:
Created Date:  2008-05-16     Completed Date:  2008-08-11     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101134327     Medline TA:  Anal Bioanal Chem     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  837-45     Citation Subset:  IM    
Departamento Química Analítica, Facultad de CC. Químicas, Universidad Complutense de Madrid, 28040, Madrid, Spain.
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MeSH Terms
3-Mercaptopropionic Acid / chemistry*
Biosensing Techniques / instrumentation,  methods*
Enzymes, Immobilized / chemistry*
Hydrogen-Ion Concentration
Immunoassay / instrumentation,  methods*
Milk / microbiology
Monophenol Monooxygenase / chemistry*
Reproducibility of Results
Sensitivity and Specificity
Staphylococcus aureus / chemistry*,  immunology
Time Factors
Reg. No./Substance:
0/Enzymes, Immobilized; 107-96-0/3-Mercaptopropionic Acid; EC Monooxygenase

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