A Love wave immunosensor for whole E. coli bacteria detection using an innovative two-step immobilisation approach

The efficiency of a monomolecular film of (3-glycidoxypropyl) trimethoxysilane (GPTS) on a shear horizontal guided (Love) acoustic wave immunosensor to detect whole Escherichia coli ( E. coli) bacteria is demonstrated. Direct anti- E. coli antibodies grafting onto the sensor surface did not lead to a significant bacteria immobilisation, partially attributed to the SiO 2 sensor surface roughness. An innovative method has been set up to get around this difficulty and to detect whole bacteria. It consists in grafting goat anti-mouse antibodies (GAM) onto the sensor surface in a first step and introducing E. coli bacteria mixed with anti- E. coli antibodies onto the sensor in a second step. We describe the characteristics of such a technique like sample preparation time (lower than 30 min) and temperature improvements. A 37 °C experimental temperature led to the fastest bacteria binding kinetic, reducing the total analysis time. This method enables to keep the specificity of the antibody/antigen interaction and provides significant results in less than 1 h. This leads to a detection threshold of 10 6 bacteria/ml in a 500 μl chamber.