Nucleic Acid-based Detection of Bacterial Pathogens Using Integrated Microfluidic Platform Systems

The advent of nucleic acid-based pathogen detection methods offers increased sensitivity and specificity over traditional microbiological techniques, driving the development of portable, integrated biosensors. The miniaturization and automation of integrated detection systems presents a significant advantage for rapid, portable field-based testing. In this review, we highlight current developments and directions in nucleic acid-based micro total analysis systems for the detection of bacterial pathogens. Recent progress in the miniaturization of microfluidic processing steps for cell capture, DNA extraction and purification, polymerase chain reaction, and product detection are detailed. Discussions include strategies and challenges for implementation of an integrated portable platform

Advanced Materials Based on Nanosized Hydroxyapatite

The development of new materials based on hydroxyapatite has undergone a great evolution in recent decades due to technological advances and development of computational techniques. The focus of this review is the various attempts to improve new hydroxyapatite-based materials. First, we comment on the most used processing routes, highlighting their advantages and disadvantages. We will now focus on other routes, less common due to their specificity and/or recent development. We also include a block dedicated to the impact of computational techniques in the development of these new systems, including: QSAR, DFT, Finite Elements of Machine Learning. In the following part we focus on the most innovative applications of these materials, ranging from medicine to new disciplines such as catalysis, environment, filtration, or energy. The review concludes with an outlook for possible new research directionsThis research was funded by MINISTERIO DE CIENCIA E INNOVACIÓN (PID2019-111327GB-100).S

Quantitative full-colour transmitted light microscopy and dyes for concentration mapping and measurement of diffusion coefficients in microfluidic architectures

International audienceA simple and versatile methodology has been developed for the simultaneous measurement of multiple concentration profiles of colourants in transparent microfluidic systems, using a conventional transmitted light microscope, a digital colour (RGB) camera and numerical image processing combined with multicomponent analysis. Rigorous application of the Beer-Lambert law would require monochromatic probe conditions, but in spite of the broad spectral bandwidths of the three colour channels of the camera, a linear relation between the measured optical density and dye concentration is established under certain conditions. An optimised collection of dye solutions for the quantitative optical microscopic characterisation of microfluidic devices is proposed. Using the methodology for optical concentration measurement we then implement and validate a simplified and robust method for the microfluidic measurement of diffusion coefficients using an H-filter architecture. It consists of measuring the ratio of the concentrations of the two output channels of the H-filter. It enables facile determination of the diffusion coefficient, even for non-fluorescent molecules and nanoparticles, and is compatible with non-optical detection of the analyte

Separation and detection of chemical and biological contaminants in fresh produce by plasmofluidic device

Plasmofluidic platforms are considered powerful approaches for onsite, fast, and reliable detection of chemical and biological contaminants in food products. In this study, two different protocols have been developed to separate and detect pesticides and foodborne pathogens, either individually or simultaneously, in fruits and vegetables. For detection of pesticides, a filter-based optofluidic SERS sensor was developed to detect four pesticides, thiabendazole, thiram, endosulfan, and malathion in strawberries. In this method, gold-silver (core-shell) nanoparticles (Au@AgNPs) were synthesized and used for SERS measurement owing to their multiple pesticides SERS detection ability. On-line filtration, sample-nanoparticles mixing, and SERS detection resulted in a fast and powerful detection and determination method for probing trace amounts of pesticides in strawberries. The results of our research showed that our filter-based optofluidic SERS sensor achieved very low limit of detection (LOD) values of about 55, 44, 88, and 54 [mu] g/Kg for thiabendazole, thiram, endosulfan, and malathion, respectively. For detection of food-borne pathogens, a SERS-based microfluidic immunosensor was designed to detect Escherichia coli O157:H7 individually and the mixture of Escherichia coli O157:H7, Salmonella enteritis, and Salmonella enterica subsp. enterica in lettuce and packed salad. The integration of a primary enrichment step with a hydrodynamic flow-focusing microfluidic device and immune SERS-nanoprobes provided a reliable technique for bacterial detection in complex food samples. For individual E. coli O157:H7 analysis, our developed SERS-based microfluidic immunosensor reached a LOD of 0.5 CFU/mL in lettuce. In the multiplex assay, the LOD for the bacterial mixture was found to be 10 CFU/ml in both lettuce and packed salad. This project demonstrates and proves the potentiality of plasmofluidic SERS devices to separate and simultaneously detect multiple chemical and biological contaminants in fresh produce.Includes bibliographical references

Methods for immobilizing receptors in microfluidic devices: A review

In this review article, we discuss state-of-the-art methods for immobilizing functional receptors in microfluidic devices. Strategies used to immobilize receptors in such devices are essential for the development of specific, sensitive (bio)chemical assays that can be used for a wide range of applications. In the first section, we review the principles and the chemistry of immobilization techniques that are the most commonly used in microfluidics. We afterward describe immobilization methods on static surfaces from microchannel surfaces to electrode surfaces with a particular attention to opportunities offered by hydrogel surfaces. Finally, we discuss immobilization methods on mobile surfaces with an emphasis on both magnetic and non-magnetic microbeads, and finally, we highlight recent developments of new types of mobile supports

Microfluidics for Biosensing

There are 12 papers published with 8 research articles, 3 review articles and 1 perspective. The topics cover: Biomedical microfluidics Lab-on-a-chip Miniaturized systems for chemistry and life science (MicroTAS) Biosensor development and characteristics Imaging and other detection technologies Imaging and signal processing Point-of-care testing microdevices Food and water quality testing and control We hope this collection could promote the development of microfluidics and point-of-care testing (POCT) devices for biosensing

Spectromètre à haute résolution à base de nanoparticules d'or pour la détection de neurotransmetteurs

La compréhension des fonctions du cerveau a toujours fasciné les scientifiques travaillant dans différents domaines de recherche et reste un sujet de recherche très vaste et complexe dont la maîtrise requière non seulement une étude approfondie des neurosciences mais aussi des outils facilitant cette étude. La conception de ces outils, tout comme le reste du matériel nécessaire aux études scientifiques, a connu de grands progrès suite aux avances technologiques des différents domaines d'ingénierie. Cependant, certaines molécules, notamment les neurotransmetteurs, qui sont impliquées dans le bon fonctionnement du cerveau et dont le dysfonctionnement est souvent associé aux pathologies neuropsychologiques restent très difficiles à discerner avec précision parmi d'autres molécules avec des propriétés physicochimiques semblables et surtout à cause de leur trop faible concentration dans les liquides physiologiques. Ce problème est encore plus en plus critique pour des applications in situ qui nécessitent une réponse rapide avec un minimum de matériel. Plusieurs méthodes de séparation et de détection moléculaire utilisées dans les autres domaines de recherche, malgré leur succès dans la détection de la plus part des neurotransmetteurs, ne conviennent pas au développement d'un outil de détection compact et réutilisable. Parmi ces méthodes, les plus représentatives sont basées sur des techniques telles que : 1. l'imagerie tomographique, la chromatographie en phase liquide à haute performance et les méthodes analytiques, qui utilisent la dérivatisation et dont la technologie actuelle ne permet pas la miniaturisation. 2. l'électrochimie, dont la sensibilité et la sélectivité sont limitées et dont surtout l'application se limite aux molécules actives aux réactions redox. 3. La colorimétrie, utilisant principalement des marqueurs non-cyclables. Pour des analyses ex situ qui ne nécessitent pas une réponse immédiate, ces techniques peuvent convenir pour réaliser la détection d'un neurotransmetteur donné. Cependant, pour comprendre le fonctionnement du système nerveux au niveau cellulaire, les recherches en neurosciences et en pathologie neuronale bénéficieraient d'un système autonome permettant de faire des mesures continues in situ. Même si ces méthodes fonctionnent au niveau cellulaire, le défi réside dans le fait elles sont difficilement miniaturisables avec les technologies actuelles. Cette thèse de doctorat comporte deux volets de recherche et ses contributions ont été présentées dans cinq conférences internationales et trois articles de journaux publiés ou soumis. L'objectif du premier volet de recherche est de développer une méthode de détection de neurotransmetteurs basée sur la détection du déplacement bathochrome de la bande plasmon de nanoparticules d'or ultrastables fonctionnalisées avec un aptamère spécifique à la molécule cible. L'objectif du deuxième volet de recherche est de concevoir un système compact basé sur la spectroscopie visible pour la détection du déplacement bathochrome de la bande plasmon des nanoparticules d'or utilisées comme biocapteurs de la molécule cible. Les deux volets ont alors pour objectifs spécifiques de : 1. Échantillonner un volume prédéterminé d'une solution inconnue, la mélanger avec un volume adéquat de nanoparticules d'or fonctionnalisées et détecter de façon autonome la concentration de dopamine dans la solution inconnue 2. Réutiliser les nanoparticules d'or ultrastables fonctionnalisées pour des utilisations futures. À ce jour, mis à part mes travaux de recherche, aucune méthode de détection de neurotransmetteurs ou autre molécule, atome ou ion n'utilise des nanoparticules d'or ou autre nano-objets plasmoniques réutilisables. La contribution majeure de ce projet, réalisé dans le premier volet de recherche, est la mise au point d'une méthode de détection moléculaire basée sur des nanoparticules d'or ultrastables et réutilisables qui ne s'agrègent pas dans conditions non supportables par d'autres types de nanoparticules d'or. Pour concrétiser l'objectif de détection de la dopamine in situ, le système optofluidique a été développé dans le deuxième volet de recherche et, en plus d'avoir une résolution spectrale comparable à un spectrophotomètre commercial, son module fluidique permet un échantillonnage automatique dans un volume 11 × 9 × 6 cm³.Understanding the functions of the brain has always fascinated scientists working in different domains and it remains a very broad and complex subject of research requiring not only a depth study of neuroscience but also adequate tools to facilitate this study. The design of these tools, as well as the rest of the scientific equipment, has known great advances due to technological advances in the various fields of engineering. However, some molecules, such as neurotransmitters, which are involved in the adequate brain functions and whose dysfunction is often associated with neuropsychological pathologies remain very difficult to detect with precision among other molecules with similar physicochemical properties due to their very low concentration in physiological fluids. This problem is even more critical for in situ applications which require a quick response with limited equipment. Despite their success in the detection of most neurotransmitters, most molecular separation and detection methods used in other research fields, are not suitable for the development of compact and reusable detection systems. Among these methods, the most representative are based on techniques such as: 1. Tomographic imaging, high-performance liquid chromatography, and derivatization-based analytical methods that are not suitable for miniaturization with current technology. 2. Electrochemistry whose sensitivity and selectivity are limited and whose application is mainly limited to redox-active molecules. 3. Colorimetry based on non-reusable markers. For ex situ analyzes which do not require an immediate response, at least one of these techniques is suitable for the detection of a given neurotransmitter. However, to understand how the nervous system works at the cellular level, research in neuroscience and neuronal pathology may benefit from an autonomous system able to make continuous measurements in situ. Although these methods actually work at the cellular level, the challenge lies in the fact that they are difficult to miniaturize with current technologies. This project has two parts and its contributions have been presented in five international conferences and three published or submitted journal articles. The aim of the first part of the project was to develop a neurotransmitter detection method based on the measurement of the bathochromic shift of aptamer modified ultrastable gold nanoparticles' plasmon band as a response to the concentration of the target molecule. The aim of the second part is to design a compact system based on visible spectroscopy for the detection of the possible bathochromic shift of the plasmon band of the gold nanoparticles used as a probe for the target molecule. The specific objectives of this project include: 1. Sample a predetermined volume of an unknown solution, mix it with an adequate volume of functionalized gold nanoparticles and automatically detect the dopamine concentration in the unknown solution. 2. Reuse functionalized ultrastable gold nanoparticles for future uses. So far, apart from this project, there is any detection method for neurotransmitters or any other molecule, atom, or ion based on reusable gold nanoparticles or any other reusable plasmonic nano-objects. The major contribution, realized in the first part of this project, is the development of a new molecular detection method based on ultrastable and recyclable gold nanoparticles which do not aggregate under the most difficult conditions for other types of gold nanoparticles. Furthermore, to achieve the objective of detecting dopamine in situ, the optofluidic system developed in the second part of this project, not only has a spectral resolution comparable to the commercial laboratory spectrophotometer but also contain a fluidic module to allow automatic sampling and the whole system have a volume of only 11 × 9 × 6 cm³

BioMEMS

As technological advancements widen the scope of applications for biomicroelectromechanical systems (BioMEMS or biomicrosystems), the field continues to have an impact on many aspects of life science operations and functionalities. Because BioMEMS research and development require the input of experts who use different technical languages and come from varying disciplines and backgrounds, scientists and students can avoid potential difficulties in communication and understanding only if they possess a skill set and understanding that enables them to work at the interface of engineering and biosciences. Keeping this duality in mind throughout, BioMEMS: Science and Engineering Perspectives supports and expedites the multidisciplinary learning involved in the development of biomicrosystems. Divided into nine chapters, it starts with a balanced introduction of biological, engineering, application, and commercialization aspects of the field. With a focus on molecules of biological interest, the book explores the building blocks of cells and viruses, as well as molecules that form the self-assembled monolayers (SAMs), linkers, and hydrogels used for making different surfaces biocompatible through functionalization. The book also discusses: Different materials and platforms used to develop biomicrosystems Various biological entities and pathogens (in ascending order of complexity) The multidisciplinary aspects of engineering bioactive surfaces Engineering perspectives, including methods of manufacturing bioactive surfaces and devices Microfluidics modeling and experimentation Device level implementation of BioMEMS concepts for different applications. Because BioMEMS is an application-driven field, the book also highlights the concepts of lab-on-a-chip (LOC) and micro total analysis system (μTAS), along with their pertinence to the emerging point-of-care (POC) and point-of-need (PON) applications