Stem‐Loop DNA Probes for the Voltammetric Determination of Legionella pneumophila on Disposable Screen‐Printed Gold Electrodes

A disposable voltammetric sensor for the detection of DNA sequences specific of Legionella pneumophila is presented. The sensor is based on a sandwich‐hybridization format assay, using a stem‐loop DNA structure as capture probe immobilized onto a screen‐printed gold electrode. The signaling‐DNA probe is labeled with biotin, and streptavidin‐alkaline phosphatase is used as reporter molecule. 1‐Naphthol, the enzymatic hydrolysis product of α‐naphthyl phosphate, is voltammetrically detected. The hairpin‐modified screen‐printed gold electrode allows the detection of a 52‐mer DNA sequence at 400 pM level. With a sample volume of 40 μL, this concentration corresponds to ca. 16 fmol of a DNA sequence specific of L. pneumophila. The analytical performance of this platform is compared with that previously obtained for a sensor constructed on a conventional disk gold electrode with the same geometry (Ø=1.6 mm) and design. A lower quantification limit is obtained with the SPE. In addition, the selectivity is improved as the disposable device shows a better discrimination between L. pneumophila and L. longbeachae or L. micdadei under identical nonstringent conditions.