Detection of superparamagnetic nanoparticles for immunoassays

International audienceWe develop a completely integrated Lab-on-Chip (LoC) for easy, rapid and cost-effective immunoassays. The pathogen sensing system is composed of a microfluidic channel surrounded by planar microcoils which are responsible for the emission and the detection of magnetic fields. The system allows the detection and quantification of superparamagnetic beads used for immunoassays in a “sandwich” antigen-antibody configuration. We successfully tested this device with different concentrations of nanoparticles and determine the limit of detection of the prototype. These results are promising and are a step toward the creation of a portable pathogen sensing device

Système électromagnétique de détection de nanoparticules magnétiques dans une structure microfluidique pour l'immunodétection

The detection and quantification of a biological agent or entity has become paramount to anticipate a possible health threat (epidemic or pandemic), environmental threat or to combat other contextual threats (bioterrorism, chemical and biological weapons, drugs). Consequently, developing a portable cost effective device that could detect and quantify such threats is the research focus of the joint multidisciplinary project between UPMC (Paris 6) laboratories and RWTH university in Aachen, Germany. In the framework of this project, we have studied the multidisciplinary aspects of an electromagnetic microsystem for immunologic detection based on magnetic nanoparticles (MNP) in a microfluidic lab-on-chip (LoC). Because of their extractability and sortability, magnetic nanoparticles are adapted for examination of biological samples, serving as markers for biochemical reactions. So far, the final detection step is mostly achieved by well-known immunochemical or fluorescence-based techniques which are time consuming and have limited sensitivity. Therefore, magnetic immunoassays detecting the analyte by means of magnetic markers constitute a promising alternative. MNP covered with biocompatible surface coating can be specifically bound to analytes, cells, viruses or bacteria. They can also be used for separation and concentration enhancement. The novel frequency mixing magnetic detection method allows quantifying magnetic nanoparticles with a very large dynamic measurement range. In this thesis, emphasis is put on the miniaturized implementation of this detection scheme. Following the development of analytical and multiphysics simulations tools for optimization of both excitation frequencies and detection planar coils, first multilayered printed circuit board prototypes integrating all three different coils along with an adapted microfluidic chip has been designed and realized. These prototypes have been tested and characterized with respect to their performance for limit of detection (LOD) of MNP, linear response and validation of theoretical concepts. Using the frequency mixing magnetic detection technique, a LOD of 15ng/mL for 20 nm core sized MNP has been achieved with a sample volume of 14 μL corresponding to a drop of blood. Preliminary works for biosensing have also been achieved with a state of the art of surface functionalization and a developed proposed biochemical immobilization procedure and preliminary tests of its validation.La détection et quantification d’agent biologique occupe une place prépondérante dans la prévention et la détection des dangers possibles pour la santé publique (épidémie ou pandémie), l’environnement ainsi que d’autres risques contextuelles (bioterrorisme, armes biologique ou chimiques…etc.). Par conséquent, le développement d’un système portable et à moindre coût permettant de détecter ces dangers constitue l’axe de recherche pluridisciplinaire de la collaboration entre différents laboratoires de l’UPMC (Paris 6) et « RWTH university » à Aachen en Allemagne. Dans ce projet, nous avons étudié les aspects pluridisciplinaires d’un microsystème (LoC) électromagnétique de détection immunologique basé sur l’utilisation de nanoparticules magnétiques (MNP). En raison de leur extractabilité et de leur triabilité, les MNP sont adaptées à l'examen d'échantillons biologiques, servant de marqueurs pour des réactions biochimiques. La plupart des techniques classiques de détection existantes sont basées sur des méthodes colorimétrique, fluorescence ou électrochimique qui souffrent en majorité de problème de temps d’analyse et de sensibilité. A cet égard, Les méthodes d’immuno-détection magnétiques constituent une alternative prometteuse. Cette détection est effectuée à l’aide des MNP qui sont spécifiquement bio-fonctionnalisés en surface afin d’être liée à la cible (virus, anticorps…etc). La nouvelle méthode magnétique de mélange de fréquence permet la détection et la quantification de ces MNP avec une grande dynamique. Dans cette thèse, l’effort est dirigé vers la miniaturisation de ce système. Pour ce faire, nous avons développé un ensemble d’outils analytiques et de simulations multiphysiques afin d’optimiser les dimensions des parties électromagnétique (bobines planaires) et microfluidiques. Par la suite, des prototypes de cette structure de détection à partir de bobines en circuits imprimés et de réservoirs microfluidiques en PDMS sont dimensionnés et réalisés. Les performances de ces prototypes ont été évaluées en termes de limite de détection de MNP, linéarité et plage dynamique. En outre, ces prototypes ont permis de valider les outils de dimensionnement réalisés. Une limite de détection de nanoparticules magnétiques de 15ng/mL a été mesurée avec un volume d'échantillon de 14 μL correspondant à une goutte de sang. Finalement, la validation du système quant à l’immuno-détection est abordée avec un état de l’art et le développement d’une procédure de fonctionnalisation biochimique de surface ainsi que des premiers tests pour sa validation

Electromagnetic Microsystem for the Detection of Magnetic Nanoparticles in a Microfluidic Structure for Immunoassays

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Magnetic Detection Structure for LOC Immunoassays, Multiphysics Simulations and Experimental Results

The aim of this work is to develop a completely integrated Lab-On-Chip (LOC) for easy, rapid and cost-effective immunoassays. The pathogen sensing system is composed of a microfluidic channel surrounded by planar microcoils which are responsible for the emission and the detection of magnetic fields. The system allows the detection and quantification of superparamagnetic beads used for immunoassays in a “sandwich” antigen-antibody configuration. Multiphysics simulations have been achieved and preliminary experimental results have allowed to validate the structure

Magnetic frequency mixing detection of magnetic nanoparticles for immunoquantification in a microfluidic structure

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Magnetic Detection Structure for Lab-on-Chip Applications Based on the Frequency Mixing Technique

A magnetic frequency mixing technique with a set of miniaturized planar coils was investigated for use with a completely integrated Lab-on-Chip (LoC) pathogen sensing system. The system allows the detection and quantification of superparamagnetic beads. Additionally, in terms of magnetic nanoparticle characterization ability, the system can be used for immunoassays using the beads as markers. Analytical calculations and simulations for both excitation and pick-up coils are presented; the goal was to investigate the miniaturization of simple and cost-effective planar spiral coils. Following these calculations, a Printed Circuit Board (PCB) prototype was designed, manufactured, and tested for limit of detection, linear response, and validation of theoretical concepts. Using the magnetic frequency mixing technique, a limit of detection of 15 µg/mL of 20 nm core-sized nanoparticles was achieved without any shielding

Microsystème électromagnétique de détection des nanoparticules magnétiques dans une structure microfluidique pour les analyses immunologiques

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Conduction Mechanisms in Au/0.8 nm–GaN/n–GaAs Schottky Contacts in a Wide Temperature Range

Au/0.8 nm–GaN/n–GaAs Schottky diodes were manufactured and electrically characterized over a wide temperature range. As a result, the reverse current Iinv increments from 1 x 10^-7 A at 80 K to about 1 x 10^-5 A at 420 K. The ideality factor n shows low values, decreasing from 2 at 80 K to 1.01 at 420 K. The barrier height q b grows abnormally from 0.46 eV at 80 K to 0.83 eV at 420 K. The tunnel mechanism TFE effect is responsible for the qfi_b behavior. The series resistance Rs is very low, decreasing from 13.80 W at 80 K to 4.26 W at 420 K. These good results are due to the good quality of the interface treated by the nitridation process. However, the disadvantage of the nitridation treatment is the fact that the GaN thin layer causes an inhomogeneous barrier height.12 página