TITLE

Immunosensor for the determination of Staphylococcus aureus using a tyrosinase—mercaptopropionic acid modified electrode as an amperometric transducer

AUTHOR(S)
Escamilla-Gómez, Vanessa; Campuzano, Susana; Pedrero, María; Pingarrón, José M.
PUB. DATE
June 2008
SOURCE
Analytical & Bioanalytical Chemistry;Jun2008, Vol. 391 Issue 3, p837
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
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 4.4×105 to 1.8×107 S. aureus cells mL−1, with a detection limit of 1.7×105 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 2.3×103 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 4.8×103 cells mL−1 level were analyzed. [Figure not available: see fulltext.]
ACCESSION #
32021859

 

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