Voltammetric and amperometric sensors for determination of epinephrine: A short review (2013-2017)

The present review focuses on voltammetric and amperometric methods applied for determination of epinephrine (EP) in last five years (2013-2017). Occurrence, role and biological importance of EP, as well as non-electrochemical methods for its assessment, are firstly reviewed. The electrochemical behavior of EP is then illustrated, followed by a description of the voltammetric and amperometric methods for EP content estimation in various media. Different methods for development of electrochemical sensors are reviewed, starting from unmodified electrodes to different composites incorporating carbon nanotubes, ionic liquids or various mediators. From this perspective, the interaction between functional groups of the sensor material and the analyte molecule is discussed, as it is essential for analytical characteristics obtained. The analytical performances of the voltammetric or amperometric chemical and biochemical sensors (linear range of analytical response, sensitivity, precision, stability, response time, etc.) are highlighted. Numerous applications of EP electrochemical sensors in fields like pharmaceutical or clinical analysis where EP represents a key analyte, are also presented

Applications of Graphene Quantum Dots in Biomedical Sensors

Due to the proliferative cancer rates, cardiovascular diseases, neurodegenerative disorders, autoimmune diseases and a plethora of infections across the globe, it is essential to introduce strategies that can rapidly and specifically detect the ultralow concentrations of relevant biomarkers, pathogens, toxins and pharmaceuticals in biological matrices. Considering these pathophysiologies, various research works have become necessary to fabricate biosensors for their early diagnosis and treatment, using nanomaterials like quantum dots (QDs). These nanomaterials effectively ameliorate the sensor performance with respect to their reproducibility, selectivity as well as sensitivity. In particular, graphene quantum dots (GQDs), which are ideally graphene fragments of nanometer size, constitute discrete features such as acting as attractive fluorophores and excellent electro-catalysts owing to their photo-stability, water-solubility, biocompatibility, non-toxicity and lucrativeness that make them favorable candidates for a wide range of novel biomedical applications. Herein, we reviewed about 300 biomedical studies reported over the last five years which entail the state of art as well as some pioneering ideas with respect to the prominent role of GQDs, especially in the development of optical, electrochemical and photoelectrochemical biosensors. Additionally, we outline the ideal properties of GQDs, their eclectic methods of synthesis, and the general principle behind several biosensing techniques.DFG, 428780268, Biomimetische Rezeptoren auf NanoMIP-Basis zur Virenerkennung und -entfernung mittels integrierter Ansätz

Graphene as a signal amplifier for preparation of ultrasensitive electrochemical biosensors

Early diagnostics of diseases performed with minimal money and time consumption has become achievable due to recent advances in development of biosensors. These devices use biorecognition elements for selective interaction with an analyte and signal readout is obtained via different types of transducers. Operational characteristics of biosensors have been reported to improve substantially, when a diverse range of nanomaterials was employed. This review presents construction of electrochemical biosensors based on graphene, atomically thin 2D carbon crystals, which is currently intensively studied nanomaterial. The most attractive directions of graphene applications in biosensor preparation are discussed here including novel detection and amplification schemes exploiting graphene’s unique electrochemical, physical and chemical properties. The future of graphene-based biosensors is most likely bright, but there is still a lot of work to do to fulfill high expectations.Slovak scientific grant agency VEGA 2/0162/14 and from the Slovak research and development agency APVV 0282-11 is acknowledged. The research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement No. 311532 and this work has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 317420. This work was funded by the National Priorities Research Program (Qatar National Research Fund), NPRP 6-381-1-078

Molecular tools for the rapid and cost-effective detection of small molecules

L'objectiu d’aquesta tesis fou la identificació de nou aptàmers amb alta afinitat cap a molècules petites i la seva aplicació en el desenvolupament de biosensors i assajos bioanalítics amb una alta sensibilitat. Les molècules diana per a la selecció dels aptàmers van ser la tetrodotoxina (una toxina marina) i la nandrolona (un esteroide anabòlic). Les molècules petites son molècules biològicament actives i la monitorització dels seus nivells en diferents tipus de mostres es de gran interès dins del camp de la biomedicina, la monitorització mediambiental, el control i seguretat alimentaria i l’anàlisi forense. El primer objectiu de la tesis va ser la selecció dels aptàmers necessaris per al desenvolupament dels assajos bioanalítics i els biosensors. Els aptàmers són molècules amb capacitat de bioreconeixement que es poden utilitzar com alternativa als anticossos. Estan formats per àcids nucleics sintètics (ARN/ADN) que poden unir-se de forma específica a la seva molècula diana i que s’obtenen a través d’un procés iteratiu in vitro anomenat SELEX per les seves sigles en anglès (systemic evolution of ligands exponential enrichment). En aquesta tesis es van dur a terme dos metodologies SELEX diferents en combinació amb la “Next generation sequencing” per a la selecció i la identificació dels aptàmers. Varis “binding assays” es van emprar per caracteritzar la afinitat dels aptàmers seleccionats i els candidats amb més afinitat es van escollir per al desenvolupament d’assajos de detecció de les molècules diana. Un assaig híbrid aptàmer-anticòs va ser desenvolupat per a la detecció de tetrodotoxina en extractes de peix globus contaminats. El mateix principi es va utilitzar per al desenvolupament de dos plataformes analítiques diferents: un assaig utilitzant micropous i un format de test ràpid conegut com “dipstick”. Per a la Nandrolona, un assaig colorimètric “label-free” utilitzant nanopartícules d’or va ser desenvolupat, on el canvi de color de vermell a blau indica la presencia de l’analit a la mostra.El objetivo de esta tesis fue la identificación de nuevos aptámeros con alta afinidad hacía moléculas pequeñas y su aplicación en el desarrollo de biosensores y ensayos bioanalíticos con una alta sensibilidad. Las moléculas diana para la selección de los aptámeros fueron la tetrodotoxina (una toxina marina) y la nandrolona (un esteroide anabólico). Las moléculas pequeñas son moléculas biológicamente activas y la monitorización de sus niveles en distintos tipos de muestra es de gran interés dentro del campo de la biomedicina, la monitorización medioambiental, en control y seguridad alimentario y el análisis forense. El primer objetivo de la tesis fue la selección de los aptámeros necesarios para el desarrollo de los ensayos bioanalíticos y los biosensores. Los aptámeros son moléculas con capacidad de bioreconocimiento que se pueden usar como alternativa a los anticuerpos. Están formados por ácidos nucleicos sintéticos (ARN/ADN) que pueden unirse de forma específica a su molécula diana y que se obtienen o seleccionan a través de un proceso in vitro iterativo que se conoce por las siglas en inglés SELEX (systematic evolution of ligands by exponencial enrichment). En esta tesis se llevaron a cabo dos metodologías SELEX distintas junto con el next generation secuencing para la selección e identificación de los aptameros. Distintos “ensayos de unión o afinidad” fueron desarrollados para caracterizar la afinidad de los aptámeros seleccionados y los candidatos con más afinidad se escogieron para desarrollar los ensayos de detección de las moléculas objetivo. Un ensayo híbrido aptámero-anticuerpo fué desarrollado para la detección de tetrodotoxina en extractos de pez globo contaminados. El mismo principio se utilizó para el desarrollo de dos plataformas analíticas distintas: un ensayo usando micropocillos y un formato de test rápido conocido como “dipstick”. Para la Nandrolona, un ensayo colorimétrico “label-free” utilizando nanopartículas de oro fue desarrollado, con el cambió de color de rojo a azul indicando la presencia del analito en la muestra.This thesis was focused on the identification of novel aptamers binding to small molecules and their application to the development of highly sensitive bioanalytical assays and biosensors. The target molecules were the marine toxin Tetrodotoxin and the anabolic steroid Nandrolone. Small molecules are biologically active and monitoring their levels in different types of samples is of high interest in the biomedical field, environmental monitoring, food safety and forensic analysis. The first objective was the selection of aptamers required for the development of the assays and biosensors. Aptamers are biorecognition molecules alternative to antibodies. They are artificial synthetic nucleic acids (RNA/DNA) that bind specifically to their target, and they are selected through an in vitro iterative process called Systematic Evolution of Ligands by Exponential enrichment (SELEX). Two different types of selection methodologies were employed for the identification of aptamers in combination with Next Generation Sequencing. Different binding assays were also developed to enable the characterization of the binding properties of the selected aptamer candidates and the chosen aptamers were finally applied in different assays for target detection. A hybrid antibody-aptamer assay was developed for Tetrodotoxin detection in contaminated puffer fish extracts in a microtiter plate format as well as in the portable lateral flow dipstick format. For Nandrolone, a label-free colorimetric assay was developed using gold nanoparticles (AuNPs) with a red-to-blue color change to indicate the presence of nandrolone

Interacción de nanoestructuras de carbono o metálicas con (bio)moléculas y su aplicación al desarrollo de sensores

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química Analitica y Análisis Instrumental . Fecha de lectura: 26-10-201

Bioanalytical applications of polyoxometalates using molecular tools for detection of DNA and SNPs in primer extension

L'objectiu general de la present tesi és el desenvolupament d'una plataforma per la detecció electroquímica de mutacions genètiques emprant un mètode d'alta especificitat basat en l'extensió de seqüències d'ADN, anomenades cebadors, disposades organitzadament sobre una superfície (APEX). Per tant el treball inclou la preparació de molècules que constitueixen marcadors electroquímics i que van ser posteriorment enllaçades de manera covalent a les quatre bases d'ADN i, a més, el desenvolupament d'una plataforma robusta resistent a altes temperatures, que són necessàries durant la incorporació per la via enzimàtica de les bases d'ADN marcades. En la primera part del present treball, es van sintetitzar dues classes de polioxometalats (anomenats Keggin and Dawson POM) i van ser covalentment enllaçats a seqüències d'ADN. A més, al costat d'altres marcadors electroquímics, van ser enllaçats covalentment a bases d'ADN individuals per a la detecció de mutacions genètiques. A la segona part es va desenvolupar un nou mètode per a la funcionalització de superfícies de carbó vitri basat en processos electroquímics consecutius d'hidrogenació i cloració. Aquestes superfícies modificades van ser utilitzades per a la immobilització de molècules tioladas, incloent ADN tiolado. Finalment, les molècules sintetitzades i les superfícies modificades van ser usades per a la detecció electroquímica de mutacions genètiques seguint la metodologia APEX.El objetivo general de la presente tesis es el desarrollo de una plataforma para la detección electroquímica de mutaciones genéticas empleando un método de alta especificidad basado en la extensión de secuencias de ADN, llamadas cebadores, dispuestas organizadamente sobre una superficie (APEX). Por tanto el trabajo incluye la preparación de moléculas que constituyen marcadores electroquímicos y que fueron posteriormente enlazadas de forma covalente a las cuatro bases de ADN y, además, el desarrollo de una plataforma robusta resistente a altas temperaturas, que son necesarias durante la incorporación por la via enzimática de las bases de ADN marcadas. En la primera parte del presente trabajo, se sintetizaron dos clases de polioxometalatos (llamados Keggin and Dawson POM) y fueron covalentemente enlazados a secuencias de ADN. Además, junto a otros marcadores electroquímicos, fueron enlazados covalentemente a bases de ADN individuales para la detección de mutaciones genéticas. En la segunda parte se desarrolló un nuevo método para la funcionalización de superficies de carbón vítreo basado en procesos electroquímicos consecutivos de hidrogenación y cloración. Estas superficies modificadas fueron utilizadas para la inmovilización de moléculas tioladas, incluyendo ADN tiolado. Finalmente, las moléculas sintetizadas y las superficies modificadas fueron usadas para la detección electroquímica de mutaciones genéticas siguiendo la metodología APEX.This PhD work was started with the intention of developing platform for electrochemical detection of mutations using highly specific method called arrayed primer extension. So the work involves the preparation of labels to be linked with the four different DNA bases and the preparation of robust platform which can withstand the high temperature during enzymatic incorporation of the labelled DNA bases. The first part of this work deals of the preparation of compounds called polyoxometalates (Keggin and Dawson types) and their covalent attachment to DNA sequence and also, to DNA single bases along with other organic redox labels for mutation detection. In the second part while trying to achieve a thermally stable surface tethered DNA probes, a new method of surface functionalisation based on electrochemical hydrogenation followed by electrochemical chlorination of glassy carbon was developed. The so prepared surfaces were used for immobilisation of thiolated molecules including thiolated DNA. Finally the synthesised molecules and modified surfaces were used for electrochemical detection of genetic mutation following the APEX protocol

Investigation of Volatile Organic Compounds (VOCs) released as a result of spoilage in whole broccoli, carrots, onions and potatoes with HS-SPME and GC-MS

Vegetable spoilage renders a product undesirable due to changes in sensory characteristics. The aim of this study was to investigate the change in the fingerprint of VOC composition that occur as a result of spoilage in broccoli, carrots, onions and potatoes. SPME and GC-MS techniques were used to identify and determine the relative abundance of VOC associated with both fresh and spoilt vegetables. Although a number of similar compounds were detected in varying quantities in the headspace of fresh and spoilt samples, certain compounds which were detected in the headspace of spoilt vegetables were however absent in fresh samples. Analysis of the headspace of fresh vegetables indicated the presence of a variety of alkanes, alkenes and terpenes. Among VOCs identified in the spoilt samples were dimethyl disulphide and dimethyl sulphide in broccoli; Ethyl propanoate and Butyl acetate in carrots; 1-Propanethioland 2-Hexyl-5-methyl-3(2H)-furanone in onions; and 2, 3-Butanediol in potatoes. The overall results of this study indicate the presence of VOCs that can serve as potential biomarkers for early detection of quality deterioration and in turn enhance operational and quality control decisions in the vegetable industry