Discriminating Bacteria With Functionalised Nanoporous Xerogels

Abstract

International audienceA new colorimetric and easy-to-use solid sensor for the detection of indole-producing bacteria is described. The sensor is a nanoporous matrix with tailored pores doped with a reactant, DMACA. The sensor turns rapidly from transparent to green-blue when exposed to metabolic indole coming from bacteria cultures, both in liquid and gas phases. An example of the discrimination between indole-positive (Eschericia coli) and indole-negative bacteria (Hafnia alvei), two important contaminants in food industry is given

Facile and fast detection of bacteria via the detection of exogenous volatile metabolites released by enzymatic hydrolysis

“…The xerogel was first ground and the trapped compound is extracted with methanol; the absorption spectrum of the alcoholic solution corresponds to that of indole in solution. To strengthen this hypothesis, the specific reaction of 4-(dimethyl-amino)-cinnamaldehyde, DMACA, with indole was applied, 7 by adding DMACA to the solution. The distinctive blue-green color observed can be attributed to the azafulvenium chloride salt, formed from the reaction of indole with DMACA, thus confirming our hypothesis.…”

“…1a). It is based on the use of transparent porous matrices, whose functions are threefold: (i) the pore size is tailored to trap the volatile metabolite and the matrix acts as a sponge to concentrate the analyte, 7 (ii) the pore cavities are engineered to chemically change the metabolite and improve the detection and (iii) the transparent matrix allows a quantitative measurement of the metabolites with optical absorption measurements.…”

Microbial volatile compounds in health and disease conditions

“…The detection of volatile compounds has been used for many years as part of bacterial identification systems, for example the imvic (indole, methyl red, Voges-Proskauer, and citrate) system which differentiates coliforms according to their production of indole, acetoin, and mixed acid fermentation products, in addition to their ability to metabolize citrate (MacFaddin 1980). This biochemical approach to the detection of microbial volatiles continues to the present day, for example functionalized nanoporous xerogels are currently being developed for detection of the presence of acetate and indole (Crunaire et al 2011).…”

Optical chemical sensors based on hybrid organic–inorganic sol–gel nanoreactors

“…With a single monolithic and transparent xerogel disk whose diameter and thickness are 3 and 0.5 mm respectively (Fig. 4), Crunaire and Tran-Thi 33 have shown that these volatile organic pollutants can be trapped in the disk exposed to a small gas flow (100 mL min À1 ).…”