Molecular Microfluidic Bioanalysis: Recent Progress in Preconcentration, Separation, and Detection

This chapter reviews the state-of-art of microfluidic devices for molecular bioanalysis with a focus on the key functionalities that have to be successfully integrated, such as preconcentration, separation, signal amplification, and detection. The first part focuses on both passive and electrophoretic separation/sorting methods, whereas the second part is devoted to miniaturized biosensors that are integrated in the last stage of the fluidic device

Overview of Materials for Microfluidic Applications

For each material dedicated to microfluidic applications, inherent microfabrication and specific physico‐chemical properties are key concerns and play a dominating role in further microfluidic operability. From the first generation of inorganic glass, silicon and ceramics microfluidic devices materials, to diversely competitive polymers alternatives such as soft and rigid thermoset and thermoplastics materials, to finally various paper, biodegradable and hydrogel materials; this chapter will review their advantages and drawbacks regarding their microfabrication perspectives at both research and industrial scale. The chapter will also address, the evolution of the materials used for fabricating microfluidic chips, and will discuss the application‐oriented pros and cons regarding especially their critical strategies and properties for devices assembly and biocompatibility, as well their potential for downstream biochemical surface modification are presented

Magnetic Hyperthermia on γ-Fe2O3@SiO2 Core-Shell Nanoparticles for mi-RNA 122 Detection

Magnetic hyperthermia on core-shell nanoparticles bears promising achievements, especially in biomedical applications. Here, thanks to magnetic hyperthermia, γ-Fe2O3 cores are able to release a DNA target mimicking the liver specific oncotarget miRNA-122. Our silica coated magnetic nanoparticles not only allow the grafting at their surface of a significant number of oligonucleotides but are also shown to be as efficient, by local heating, as 95 °C global heating when submitted to an alternative magnetic field, while keeping the solution at 28 °C, crucial for biological media and energy efficiency. Moreover, a slight modification of the silica coating process revealed an increased heating power, well adapted for the release of small oligonucleotides such as microRNA

Release and Detection of microRNA by Combining Magnetic Hyperthermia and Electrochemistry Modules on a Microfluidic Chip

The heating of a biologic solution is a crucial part in an amplification process such as the catalytic detection of a biological target. However, in many situations, heating must be limited in microfluidic devices, as high temperatures can cause the denaturation of the chip components. Local heating through magnetic hyperthermia on magnetic nano-objects has opened the doors to numerous improvements, such as for oncology where a reduced heating allows the synergy of chemotherapy and thermotherapy. Here we report on the design and implementation of a lab on chip without global heating of samples. It takes advantage of the extreme efficiency of DNA-modified superparamagnetic core–shell nanoparticles to capture complementary sequences (microRNA-target), uses magnetic hyperthermia to locally release these targets, and detects them through electrochemical techniques using ultra-sensitive channel DNA-modified ultramicroelectrodes. The combination of magnetic hyperthermia and microfluidics coupled with on-chip electrochemistry opens the way to a drastic reduction in the time devoted to the steps of extraction, amplification and nucleic acids detection. The originality comes from the design and microfabrication of the microfluidic chip suitable to its insertion in the millimetric gap of toric inductance with a ferrite core

DNA electrochemical hybridization detection in droplets using gold ultramicroelectrodes in a two-electrode configuration.

International audienceA 23-base DNA probe monolayer was self-assembled on a 25-μm gold microelectrode via thiol adsorption. Long-range electron transfer and the use of the redox methylene blue as DNA intercalator were chosen for the monitoring of the hybridization step. The electrochemical properties of the sensor were screened with the [Fe(III)(CN)6]3-/[Fe(II)(CN)6]4- redox couple in cyclic voltammetry in a two-electrode configuration well adapted in the case of microliter biological samples. A study of the stability of the self-assembled monolayer is included in this work. The femtomolar limit of detection for DNA target quantification was deduced from the current density measured and blank measurements depicting the desorption rate of the thiolated DNA probes

DNA electrochemical hybridization detection in droplets using gold ultramicroelectrodes in a two-electrode configuration.

International audienceA 23-base DNA probe monolayer was self-assembled on a 25-μm gold microelectrode via thiol adsorption. Long-range electron transfer and the use of the redox methylene blue as DNA intercalator were chosen for the monitoring of the hybridization step. The electrochemical properties of the sensor were screened with the [Fe(III)(CN)6]3-/[Fe(II)(CN)6]4- redox couple in cyclic voltammetry in a two-electrode configuration well adapted in the case of microliter biological samples. A study of the stability of the self-assembled monolayer is included in this work. The femtomolar limit of detection for DNA target quantification was deduced from the current density measured and blank measurements depicting the desorption rate of the thiolated DNA probes

Hyperthermie magnétique et détection électrochimique pour le relargage et la détection de microARN sans amplification de type PCR

International audienceLa réaction en chaine par polymérase (PCR), méthode de référence pour la mesure d'acides nucléiques ADN en biologie clinique, est basée sur une amplification chimique du nombre des copies d'une ou plusieurs séquences ADN pour pouvoir les amener à un seuil détectable. Bien que robuste, la méthodologie PCR présente l'inconvénient majeur d'être inadaptée pour la biologie d'urgence car le rendu d'un résultat (préparation, extraction, amplification et quantification) peut atteindre entre 4 et 6 heures. L'autre inconvénient, dans le cas des séquences ARN, est une étape supplémentaire de transcription inverse (RT) (ARN en ADN), étape délicate rallongeant encore le temps du protocole. Enfin, la technologie PCR est très consommatrice en énergie à cause des systèmes de régulation nécessaires pour les cycles de températures jusqu'à 95 °C. Cet article présente la preuve de concept d'un nouveau procédé couplant l'hyperthermie magnétique et la détection électrochimique (HDE) en microfluidique pour le relargage et la détection directe en moins de 3 h, à un seuil de détection de 10-18 M, d'un microARN synthétique et spécifique des lésions du foie (miR 122). L'objectif est d'aboutir à une sorte de biopsie microfluidique liquide rapide (1 h 30) pour le diagnostic d'urgence. Mots-clés Microfluidique, électrochimie, hyperthermie, nanoparticules magnétiques, acides nucléiques, PCR

Electrochemical DNA biosensors based on long- range electron transfer: investigating the efficiency of a fluidic channel microelectrode compared to an ultramicroelectrode in a two- electrode setup.

International audienceHere, we describe the transposition of an ultramicroelectrode (UME) setup into a microfluidic chip configuration for DNA biosensors. The hydrodynamic properties of the fluidic channel microelectrode were screened with an [FeIJIII)IJCN) 6 ] 3− /[Fe(II)(CN) 6 ] 4− redox couple by cyclic voltammetry to provide a basis for further biological processes. A 23-base DNA probe was self-assembled into a monolayer on gold microelectrodes both in classical configuration and integrated in a microfluidic setup. Special interest was focused on the DNA target mimicking the liver-specific micro-ribonucleic acid 122 (miRNA122). Long-range electron transfer was chosen for transducing the hybridization. This direct transduction was indeed significantly enhanced after hybridization due to DNA-duplex π-stacking and the use of redox methylene blue as a DNA intercalator. Quantification of the target was deduced from the resulting electrical signal characterized by cyclic voltammetry. The limit of detection for DNA hybridization was 0.1 fM in stopped flow experiments, where it can reach 1 aM over a 0.5 μL s −1 flow rate, a value 10 4-fold lower than the one measured with a conventional UME dipped into an electrolyte droplet under the same analytical conditions. An explanation was that forced convection drives more biomolecules to the area of detection even if a balance between the speed of collection and the number of biomolecules collected has been found. The latter point is discussed here along with an attempt to explain why the sensor has reached such an unexpected value for the limit of detection

Amorphous carbon nitride microband integrated in a microfluidic device for DNA biosensors applications

International audienceThis study presents the use of new kind of carbon electrode materials as ultramicroelectrodes (UMEs) in the field of electrochemical DNA biosensors which has already been proven to be effective in protocols to DNA sequences hybridization. In contrast to other carbon materials such as diamond like carbon, that are difficult to integrate in microfluidic devices due to their high temperature deposition, amorphous carbon nitride (a-CNx) is easily synthesized at room temperature on various materials using sputtering techniques. Here, we report a-CNx use as microband electrodes in Glass/PDMS microfluidic devices. a-CNx electrodes were activated and then biofuntionalized by covalent grafting of a DNA probe as self-assembled monolayer (SAM) with a view to future development of a detection platform targeting circulating DNA or RNA sequences in microfluidic channels