Authors: B Serra M Gamella A J Reviejo J M Pingarrón
Publish Date: 2008/06/04
Volume: 391, Issue: 5, Pages: 1853-1860
Abstract
The use of lectins for microorganism biosensors fabrication is proposed Lectins are immobilised onto a goldplated quartz crystal for direct piezoelectric labelfree transduction of the bacteria–lectin binding event using an electrochemical quartz crystal microbalance EQCM Concanavalin A Con A and Escherichia coli were used for the evaluation of the lectin immobilisation method and the biosensor performance Adsorption on nonpolarised and polarised −0200 V goldcoated quartz crystals and immobilisation through avidin–biotin binding were checked for Con A surface attachment Lectin–bacteria binding was evaluated in all cases With a crystal modified with Con A via avidin–biotin immobilisation we obtained a linear calibration plot between 50 × 106 and 20 × 107 cfu mL−1 by measuring frequency changes with E coli concentration 1 h after bacteria addition A remarkable increase in sensitivity was achieved when the analytical solution contained free biotinylated Con A as a consequence of multiple lectin adhesion to Escherichia coli cell wall which produced an accumulation of Con A–E coli conjugates in the form of multilayers at the electrode surface A detection limit of approximately 10 × 104 cfu mL−1 was achieved Moreover nonspecific adsorptions were minimised Using Con A and lectin from Arachis hypogaea different response profiles were achieved for Escherichia coli Staphylococcus aureus and Mycobacterium phlei thus demonstrating the feasibility of bacteria discrimination An approach involving filtering of free and lectinbound bacteria and introduction of a filter in the measuring cell allowed a significant frequency change to be obtained for an E coli concentration of 10 × 103 cfu mL−1 in order to further increase the sensitivity and discriminate between viable and nonviable cells an approach using electrochemical measurements of bacterial catalase activity was also checked
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