Design and 3D printing of an electrochemical sensor for Listeria monocytogenes detection based on loop mediated isothermal amplification

The aim of this work is the design and 3D printing of a new electrochemical sensor for the detection of Listeria monocytogenes based on loop mediated isothermal amplification (LAMP). The food related diseases involve a serious health issue all over the world. Listeria monocytogenes is one of the major problems of contaminated food, this pathogen causes a disease called listeriosis with a high rate of hospitalization and mortality. Having a fast, sensitive and specific detection method for food quality control is a must in the food industry to avoid the presence of this pathogen in the food chain (raw materials, facilities and products). A point-of-care biosensor based in LAMP and electrochemical detection is one of the best options to detect the bacteria on site and in a very short period of time. With the numerical analysis of different geometries and flow rates during sample injection in order to avoid bubbles, an optimized design of the microfluidic biosensor chamber was selected for 3D-printing and experimental analysis. For the electrochemical detection, a novel custom gold concentric-3-electrode consisting in a working electrode, reference electrode and a counter electrode was designed and placed in the bottom of the chamber. The LAMP reaction was optimized specifically for a primers set with a limit of detection of 1.25 pg of genomic DNA per reaction and 100% specific for detecting all 12 Listeria monocytogenes serotypes and no other Listeria species or food-related bacteria. The methylene blue redox-active molecule was tested as the electrochemical transducer and shown to be compatible with the LAMP reaction and very clearly distinguished negative from positive food samples when the reaction is measured at the end-point inside the biosensor

Physicochemical characterization of hydrophobic type III and type V deep eutectic solvents based on carboxylic acids

In the present work, novel type III and type V deep eutectic solvents (DESs) were prepared by mixing choline chloride (ChCl), tetrabutylammonium chloride (TBAC) or thymol as HBA, and different alkyl chain length carboxylic acids as HBD (acetic, oxalic, palmitic, stearic, oleic and linoleic acid) at various molar ratios. The hydrophobic DESs were characterized by infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (1H NMR), concluding the formation of intermolecular interactions, as hydrogen bonds between the precursors. Thermogravimetric analysis (TGA) was used to obtain the thermal decomposition profiles of the prepared DESs, proving interactions between the precursors and decomposition temperatures with values, which are found in the ranges of the precursor constituents and higher than 170 °C. Other physicochemical properties, such as density, thermal expansion coefficient, dynamic viscosity, refractive index, surface tension, and thermal and ionic conductivities have been determined. Furthermore, the ability of these DESs as UV filter extractants from aqueous samples using a dispersive liquid–liquid microextraction (DLLME) previous to liquid chromatographic analysis was demonstrated. Therefore, these type III and type V DESs could be applied to the extraction of pollutants from environmental water samples

Design and 3D printing of an electrochemical sensor for Listeria monocytogenes detection based on loop mediated isothermal amplification

The aim of this work is the design and 3D printing of a new electrochemical sensor for the detection of Listeria monocytogenes based on loop mediated isothermal amplification (LAMP). The food related diseases involve a serious health issue all over the world. Listeria monocytogenes is one of the major problems of contaminated food, this pathogen causes a disease called listeriosis with a high rate of hospitalization and mortality. Having a fast, sensitive and specific detection method for food quality control is a must in the food industry to avoid the presence of this pathogen in the food chain (raw materials, facilities and products). A point-of-care biosensor based in LAMP and electrochemical detection is one of the best options to detect the bacteria on site and in a very short period of time. With the numerical analysis of different geometries and flow rates during sample injection in order to avoid bubbles, an optimized design of the microfluidic biosensor chamber was selected for 3D-printing and experimental analysis. For the electrochemical detection, a novel custom gold concentric-3-electrode consisting in a working electrode, reference electrode and a counter electrode was designed and placed in the bottom of the chamber. The LAMP reaction was optimized specifically for a primers set with a limit of detection of 1.25 pg of genomic DNA per reaction and 100% specific for detecting all 12 Listeria monocytogenes serotypes and no other Listeria species or food-related bacteria. The methylene blue redox-active molecule was tested as the electrochemical transducer and shown to be compatible with the LAMP reaction and very clearly distinguished negative from positive food samples when the reaction is measured at the end-point inside the biosensor.Garbiñe Olabarria as supported by Ekonomiaren Garapen eta Lehiakortasun Saila, Eusko Jaurlaritza [KK-2021/00082]. M. Mounir Bou-Ali was supported by Eusko Jaurlaritza [Research Group Program, IT1505-22]