Sandrine Miserere

On-chip magneto-immunoassay for Alzheimer's biomarker electrochemical detection by using quantum dots as labels

Electrochemical detection of cadmium-selenide/zinc-sulfide (CdSe@ZnS) quantum dots (QDs) as labeling carriers in an assay for apolipoprotein E (ApoE) detection has been evaluated. The immunocomplex was performed by using tosylactivated magnetic beads as preconcentration platform into a flexible hybrid polydimethylsiloxane (PDMS)-polycarbonate (PC) microfluidic chip with integrated screen printed electrodes (SPE). All the immunoassay was performed in chip and in flow mode. The sensitive electrochemical detection was obtained by square wave anodic stripping voltammetry. ApoE was evaluated for its potential as biomarker for Alzheimers disease detection, achieving a limit of detection (LOD) of ~12.5 ng mL(-1) with a linear range from 10 to 200 ng mL(-1) and high accuracy for diluted human plasma.

Simple on-plastic/paper inkjet-printed solid-state Ag/AgCl pseudoreference electrode.

A miniaturized, disposable, and low cost Ag/AgCl pseudoreference electrode based on inkjet printing has been developed. Silver ink was printed and chlorinated with bleach solution. The reference electrodes obtained in this work showed good reproducibility and stability during at least 30 min continuous measurement and even after 30 days storage without special care. Moreover, the strategy used in this work can be useful for large scale production of a solid-state Ag/AgCl pseudoreference electrode with different designs and sizes, facilitating the coupling with different electrical/electrochemical microsensors and biosensors.

Evaluation of microchip material and surface treatment options for IEF of allergenic milk proteins on microchips

The use of glass and PDMS microchips has been investigated to perform rapid and efficient separation of allergenic whey proteins by IEF. To decrease EOF and to limit protein adsorption, two coating procedures have been compared. The first one consists in immobilizing hydroxypropyl cellulose (HPC) and the second one poly(dimethylacrylamide‐co‐allyl glycidyl ether) (PDMA‐AGE). EOF limitation has been evaluated using frontal electrophoresis of a fluorescent marker of known effective mobility. EOF velocity was decreased by a factor about 100 and 30, respectively. pH gradient formation has been evaluated for each microchip using fluorescent pI markers. It was demonstrated that as expected a coating was essential to avoid pH gradient drift. Both coatings were efficient on glass microchips, but only PDMA‐AGE allowed satisfying focusing of pI markers on PDMS microchips. Fluorescent covalent and noncovalent labelings of milk proteins have been compared by IEF on slab‐gels. IEF separation of three major allergenic whey proteins [β‐lactoglobulin A (pI 5.25) and B (pI 5.35) and α‐lactalbumin (pI 4.2–4.5)] was performed in both microchips. Milk proteins were separated with better resolution and shorter analysis time than by classical CIEF. Finally, better resolutions for milk allergens separation were obtained on glass microchips.

Nanostructured CaCO3-poly(ethyleneimine) microparticles for phenol sensing in fluidic microsystem

A new and simple strategy based on nanostructured CaCO3‐poly(ethyleneimine) (PEI) microparticles (MPs) for phenol sensing using PDMS/glass fluidic microchip is developed. This fluidic microsystem including integrated screen‐printed electrodes modified with CaCO3‐PEI MPs and tyrosinase (Tyr) through cross‐linking with glutaraldehyde, represents a low‐cost platform for phenol detection. The designed fluidic microsystem improves the sensitivity of the biosensor allowing the detection of very low concentrations of phenol (up to 10 nM). This device shows high repeatability and low detection limit, is easy to be fabricated, inexpensive, disposable, and amenable to mass production.

Enhanced detection of quantum dots labeled protein by simultaneous bismuth electrodeposition into microfluidic channel.

In this study, we propose an electrochemical immunoassay into a disposable microfluidic platform, using quantum dots (QDs) as labels and their enhanced detection using bismuth as an alternative to mercury electrodes. CdSe@ZnS QDs were used to tag human IgG as a model protein and detected through highly sensitive stripping voltammetry of the dissolved metallic component (cadmium in our case). The modification of the screen printed carbon electrodes (SPCEs) was done by a simple electrodeposition of bismuth that was previously mixed with the sample containing QDs. A magneto‐immunosandwich assay was performed using a micromixer. A magnet placed at its outlet in order to capture the magnetic beads used as solid support for the immunoassay. SPCEs were integrated at the end of the channel as detector. Different parameters such as bismuth concentration, flow rate, and incubation times, were optimized. The LOD for HIgG in presence of bismuth was 3.5 ng/mL with a RSD of 13.2%. This LOD was about 3.3‐fold lower than the one obtained without bismuth. Furthermore, the sensitivity of the system was increased 100‐fold respect to experiments carried out with classical screen‐printed electrodes, both in presence of bismuth.

An integrated phenol 'sensoremoval' microfluidic nanostructured platform.

Phenol is a widely used chemical that for several reasons may be released into the environment and, consequently, its detection and subsequent destruction into the ground and surface waters are of special importance. Herein, a simple lab-on-a-chip (LOC) device based on biocompatible and biodegradable CaCO3- poly(ethyleneimine) (PEI) nanostructured microparticles (MPs) to detect and remove phenolic wastes is proposed. The detection of phenol using a hybrid polydimethylsiloxane (PDMS)/glass chronoimpedimetric microchip and its removal in the same LOC system through the use of an extra CaCO3-PEI MPs microcolumn is achieved. For the first time, the chronoimpedance technique is applied in a LOC system for phenol sensing in a range of 0.01-10 µM achieving the limit of detection (LOD) of 4.64 nM. Moreover, this device shows a high repeatability with a relative standard deviation of 3% which is almost 4 times lower than that for the chronoamperometry technique. This LOC system represents an integrated platform for phenol sensing and removal (sensoremoval) that can be easily fabricated and is of a low cost, disposable and amenable to mass production.