Route to smooth silica-based surfaces decorated with novel self-assembled monolayers (SAMs) containing glycidyl-terminated very long hydrocarbon chains.

Novel glycidyl-terminated organosilicon coupling agents possessing a trialkoxysilyl head group and a very long hydrocarbon chain (C22) were synthesized. Their ability to afford densely packed self-assembled monolayers (SAMs) grafted on silica-based surfaces was investigated. Transmission FT-IR spectra showed that the most regular films were obtained by using trichloracetic acid as the catalyst (10 M%). Atomic force microscopy (AFM) and optical ellipsometry were consistent with well ordered monolayers exhibiting a marked decrease of the surface roughness. Epifluorescence microscopy revealed that these SAMs possessed a better surface reactivity than monolayers obtained with the commercially available (3-glycidoxypropyl) trimethoxysilane (GPTS) upon grafting of a fluorescent probe (dansylcadaverin). Moreover, direct attachment of fluorescent antibodies (RAG-TRITC) through covalent binding led to higher mean fluorescence intensities, showing that these new SAMs possess high potential for the immobilization of biological molecules.

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 SiO2 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 degrees 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 1h. This leads to a detection threshold of 10(6) bacteria/ml in a 500 microl chamber.