Abstract:

: Bacterial contamination in food is real and presents a valid danger to human health. Therefore, we focused on the detection of Escherichia coli and Listeria innocua with optical and acoustic methods. In both methods, we used specific DNA aptamers as receptors. For the optical method, we modified gold nanoparticles (AuNPs) with aptamers and analyzed the interaction of AuNPs with bacteria by measurement of the changes in the absorbance spectrum. We also applied white light reflectometry to measure changes in thickness on a silicon chip modified with aminylated aptamer through silica chemistry. We also used quartz crystal microbalance (QCM) in multiharmonic mode. In this case, the thiolated aptamers were chemisorbed at the gold layer of the quartz crystal and the changes in resonant frequency were measured following the addition of bacteria. The limit of detection (LOD) of the optical method using AuNPs was estimated to be 10 5 CFU/mL of Listeria monocytogenes. For the reflectometric method, we were able to detect E. coli at concentrations around 2 × 10 4 CFU/mL. Using TSM, we analyzed the viscoelastic properties of the aptamer layers when they formed at the surface.

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