Polymeric luminol on pre-treated screen-prited electrodes for the design of performant reagentless (bio)sensors.

International audienceA performant reagentless electrochemiluminescent (ECL) system for H2O2 detection based on electropolymerized luminol is first presented. In this work, polyluminol is formed under near-neutral conditions onto pre-treated screen-printed electrodes (SPEs). Pre-treatment conditions of the working electrode surface have been optimized so as to obtain the best ECL responses to H2O2 that were increased by a factor as high as 400. Galvanostatic polymerization has been tested as a new process to form polyluminol films. Good performances were obtained in terms of responses to H2O2, with quite the same linear range as the ones obtained under potentiostatic and potentiodynamic modes.The association of the polyluminol film with an H2O2-producing oxidase has also been investigated, using choline oxidase as a model enzyme. Silica glasses obtained by the sol–gel process have been employed for biomolecule immobilization. Polymeric luminol has been coupled with choline oxidase-immobilizing gel under bilayer or monolayer configurations. In the first case, enzyme has been immobilized in a silica gel formed on a polyluminol film. In the second case, the enzymatic gel formed on SPE was soaked in a solution containing monomeric luminol units, allowing them to diffuse and penetrate throughout the porous gel. Then, electrodeposition was performed to polymerize the luminophore within the silica matrix. In both cases, choline could be detected down to micromolar concentrations

Electrochemical Aptasensors

International audienceThis review presents electrochemical aptasensors reported in the literature. Their development has been growing as evidenced by the increasing number of scientific publications on this subject since 2004. Aptasensors are presented according to their transduction mode, including the most described amperometric and impedimetric devices as well as FETs and the first very recently reported potentiometric aptasensor. ‘Signal-on’ (positive readout signal) and less sensitive ‘signal-off’ (negative readout signal) aptasensors are reviewed based on target binding-induced conformational change of aptamers or on target binding-induced strand displacement or even on both processes. Aptamer-labeled and aptamer label-free devices are presented separately

A chimiluminescent Langmuir-Blodgett membrane as the sensing layer for the reagentless monitoring of an immobilzed enzyme activity.

International audienceIn the nanotechnology field, the concept of using biomolecules as an elementary structure to develop self-assembled entities has received considerable attention. Particularly, the ability of amphiphilic molecules like lipids to self-organize into bilayers can be exploited to provide biomimetic membrane models. Langmuir–Blodgett (LB) technology, based on the transfer of an interfacial film onto a solid support, offers the possibility to prepare lipid bilayers suitable for biomolecule immobilization and achievement of nanoscale-organized sensing layers, tailored for the design of miniaturized biosensors. With the aim of immobilizing enzymes in a defined orientation at the surface of LB bilayers, an original strategy has been previously developed in our group. This approach combines two techniques based on molecular self-assembly properties: liposome fusion at an air/buffer interface and Langmuir–Blodgett technology. It allows the functional insertion of a non-inhibitory antibody in lipid bilayers, further used to anchor a soluble enzyme at the surface of the lipid membrane. When associated with an electrochemiluminescent (ECL) sensor, this molecular assembly allows the design of a biomimetic sensor able to closely integrate the recognition and transduction events. However, sensor's performance not only depends on bioactive sensing layer properties, but also on the additional introduction of luminol in the reaction medium which delays ECL reaction. This work explores the potentiality of two neosynthesized amphiphilic luminol derivatives to form a lipid bilayer serving as a matrix used for both antibody insertion and ECL detection in order to develop a new sensing layer allowing a reagentless detection. As a model, choline oxidase activity has been detected. After enzyme immobilization at the surface of the luminol derivative LB bilayer by the way of specific recognition of a non-inhibitory antibody, in situ catalytic generation of hydrogen peroxide is able to trigger ECL reaction in the sensing layer interfaced with an optoelectronic device leading to a reagentless detection of choline oxidase activity