Engineered carbon-nanomaterial-based electrochemical sensors for biomolecules

The study of electrochemical behavior of bioactive molecules has become one of the most rapidly developing scientific fields. Biotechnology and biomedical engineering fields have a vested interest in constructing more precise and accurate voltammetric/amperometric biosensors. One rapidly growing area of biosensor design involves incorporation of carbon-based nanomaterials in working electrodes, such as one-dimensional carbon nanotubes, two-dimensional graphene, and graphene oxide. In this review article, we give a brief overview describing the voltammetric techniques and how these techniques are applied in biosensing, as well as the details surrounding important biosensing concepts of sensitivity and limits of detection. Building on these important concepts, we show how the sensitivity and limit of detection can be tuned by including carbon-based nanomaterials in the fabrication of biosensors. The sensing of biomolecules including glucose, dopamine, proteins, enzymes, uric acid, DNA, RNA, and H2O2 traditionally employs enzymes in detection; however, these enzymes denature easily, and as such, enzymeless methods are highly desired. Here we draw an important distinction between enzymeless and enzyme-containing carbon-nanomaterial-based biosensors. The review ends with an outlook of future concepts that can be employed in biosensor fabrication, as well as limitations of already proposed materials and how such sensing can be enhanced. As such, this review can act as a roadmap to guide researchers toward concepts that can be employed in the design of next generation biosensors, while also highlighting the current advancements in the field.ope

A review of nanocomposite-modified electrochemical sensors for water quality monitoring

Electrochemical sensors play a significant role in detecting chemical ions, molecules, and pathogens in water and other applications. These sensors are sensitive, portable, fast, inexpensive, and suitable for online and in-situ measurements compared to other methods. They can provide the detection for any compound that can undergo certain transformations within a potential window. It enables applications in multiple ion detection, mainly since these sensors are primarily non-specific. In this paper, we provide a survey of electrochemical sensors for the detection of water contaminants, i.e., pesticides, nitrate, nitrite, phosphorus, water hardeners, disinfectant, and other emergent contaminants (phenol, estrogen, gallic acid etc.). We focus on the influence of surface modification of the working electrodes by carbon nanomaterials, metallic nanostructures, imprinted polymers and evaluate the corresponding sensing performance. Especially for pesticides, which are challenging and need special care, we highlight biosensors, such as enzymatic sensors, immunobiosensor, aptasensors, and biomimetic sensors. We discuss the sensors’ overall performance, especially concerning real-sample performance and the capability for actual field application

Screen-printed carbon based biosensors and their applications in agri-food safety

This review focuses on the ways in which screen-printed carbon electrodes have been tailored with different biorecognition elements, including enzymes, antibodies, and aptamers, often with other modifiers, such as mediators and nanoparticles, to produce electrochemical biosensors for a variety of analytes of importance in agri-food safety. Emphasis is placed on the strategies of biosensor fabrication and the performance characteristics of the devices. As well as biosensors for a range of analytes in different agri-food matrices, we have also included reports on novel devices that have potential in agri-food safety but as yet have not been applied in this area

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

Cellulose-Based Biosensing Platforms

Cellulose empowers measurement science and technology with a simple, low-cost, and highly transformative analytical platform. This book helps the reader to understand and build an overview of the state of the art in cellulose-based (bio)sensing, particularly in terms of the design, fabrication, and advantageous analytical performance. In addition, wearable, clinical, and environmental applications of cellulose-based (bio)sensors are reported, where novel (nano)materials, architectures, signal enhancement strategies, as well as real-time connectivity and portability play a critical role

Advanced Electrochemical and Opto-Electrochemical Biosensors for Quantitative Analysis of Disease Markers and Viruses

The recent global events of the SARS-CoV-2 pandemic in 2020 have alerted the world to the urgent need to develop fast, sensitive, simple, and inexpensive analytical tools that are capable of carrying out a large number of quantitative analyses, not only in centralized laboratories and core facilities but also on site and for point-of-care applications. In particular, in the case of immunological tests, the required sensitivity and specificity is often lacking when carrying out large-scale screening using decentralized methods, while a centralized laboratory with qualified personnel is required for providing quantitative and reliable responses. The advantages typical of electrochemical and optical biosensors (low cost and easy transduction) can nowadays be complemented in terms of improved sensitivity by combining electrochemistry (EC) with optical techniques such as electrochemiluminescence (ECL), EC/surface-enhanced Raman spectroscopy (SERS), and EC/surface plasmon resonance (SPR). This Special Issue addresses existing knowledge gaps and aids in exploring new approaches, solutions, and applications for opto-electrochemical biosensors in the quantitative detection of disease markers, such as cancer biomarkers proteins and allergens, and pathogenic agents such as viruses. Included are seven peer-reviewed papers that cover a range of subjects and applications related to the strategies developed for early diagnosis

Amperometric enzyme-based detection of agriculturalpesticides on novel carbon nano-onion composites

Actualment hi ha una gran preocupació sobre l'ús de pesticides en l'agricultura i els seus possibles efectes secundaris. Això fa que el desenvolupament de sistemes de detecció sensibles i robustos sigui un pas important en aquesta direcció. D'altra banda, les nano-cebes de carboni (CNOs) són materials molt atractius i prometedors amb estructures definides i propietats electroquímiques notables que amb prou feines s'han estudiat en biosensors. L'objectiu general d'aquesta tesi és estudiar la interacció de diferents plaguicides amb peroxidasa i tirosinasa amb l'objectiu de desenvolupar biosensors per a la seva detecció basats en elèctrodes modificats amb CNOs. Per aconseguir aquest objectiu general, s'ha estudiat: 1) la inhibició de les activitats de peroxidasa i tirosinasa per tres dels plaguicides més utilitzats (2,4-D, 2,4,5-T i glifosat), 2) l'ús d'CNOs oxidades com a suports per a la immobilització d'enzims i un estudi de l'activitat i estabilitat dels enzims immobilitzades, 3) el desenvolupament de biosensors electroquímics per a detecció dels plaguicides abans esmentats basats en els elèctrodes modificats amb composites contenint enzims i CNOs. Aquesta tesi és, per tant, una contribució a un camp de ràpid creixement relacionat amb el desenvolupament de noves classes de nanomaterials de carboni que té com a objectiu ampliar les seves aplicacions actuals en la construcció de sistemes de detecció nous amb millors prestacions.Actualmente existe una gran preocupación sobre el uso de pesticidas en la agricultura y sus posibles efectos secundarios. Esto hace que el desarrollo de sistemas de detección sensibles y robustos sea un paso importante en esta dirección. Por otro lado, las nano-cebollas de carbono (CNOs) son materiales muy atractivos y prometedores con estructuras definidas y propiedades electroquímicas notables que apenas se han estudiado en biosensores. El objetivo general de esta tesis es estudiar la interacción de diferentes plaguicidas con peroxidasa y tirosinasa con el objetivo de desarrollar biosensores para su detección basados ​​en electrodos modificados con CNOs. Para lograr este objetivo general, se ha estudiado: 1) la inhibición de las actividades de peroxidasa y tirosinasa por tres de los plaguicidas más utilizados (2,4-D, 2,4,5-T y glifosato), 2) el uso de CNOs oxidadas como soportes para la inmovilización de enzimas y un estudio de la actividad y estabilidad de las enzimas inmovilizadas, 3) el desarrollo de biosensores electroquímicos para detección de los plaguicidas antes citados basados ​​en los electrodos modificados con composites conteniendo enzimas y CNOs. Esta tesis es, por lo tanto, una contribución a un campo de rápido crecimiento relacionado con el desarrollo de nuevas clases de nanomateriales de carbono que tiene como objetivo ampliar sus aplicaciones actuales en la construcción de sistemas de detección novedosos con mejores prestaciones.There is currently a strong concern on the use of pesticides in agriculture and their possible side effects. This makes the development of sensitive and robust detection systems an important step in this direction. On the other hand, carbon nano-onions are very attractive and promising materials with defined structures and remarkable electrochemical properties that have been scarcely studied in biosensing. The overall objective of this thesis is to study the interaction of different pesticides with peroxidase and tyrosinase with the aim to develop biosensors for pesticide detection based on CNO-modified electrodes. To achieve this general objective, the following aspects have been focused on: 1) the inhibition of peroxidase and tyrosinase activities by three of the most used pesticides (2,4-D, 2,4,5-T and glyphosate), 2) the use of oxidized CNOs as supports for the immobilization of enzymes and a study of the activity and stability of the immobilized enzymes, 3) the development of electrochemical biosensors for pesticide detection based on the prepared CNO-enzyme modified electrodes. This thesis is thus a contribution to a rapidly growing field related with the development of new classes of carbon nano-onion based nanomaterials that aims at expanding their current applications in the construction of novel detection systems with improved performances

Selection and characterization of DNA aptamers for estradiol and ethynylestradiol for aptasensor development

Small organic contaminants have been widely detected in the surface and ground waters of this nation. A sub-class of these contaminants called endocrine disrupting compounds (EDCs) are known to have adverse effects on aquatic and human health. Among the EDCs, natural hormone 17β-estradiol (E2) and synthetic hormone 17α-ethynylestradiol (EE) possess high estrogenic potency and hence are contaminants of interest. Conventional methods to detect these compounds are expensive, time consuming and need implementation by an expert. By contrast, antibody-based assays are relatively inexpensive and commercially available but suffer from poor selectivity. A promising alternative makes use of DNA aptamers as molecular recognition elements. In order to evaluate the potential of DNA aptamers and aptasensors to detect small organics in natural waters, the following objectives were pursued: (1) critically review DNA aptamers and aptasensors developed for small organic molecules and assess their use for monitoring environmentally relevant organics, (2) select and characterize DNA aptamers that bind to E2 and EE and, (3) study the effect of immobilization on the binding affinity of the selected E2 and EE aptamers. A review of ~80 aptamers and ~200 aptasensors for small organics was conducted to identify factors that affect binding affinity of the aptamer and limits of detection (LODs) of the aptasensor. Based on regression analyses, aptamer binding affinities are found to have a weak relationship with hydrophobicity of the target and length of the aptamer (p-values<0.05). Independent t-tests comparing aptasensor LODs suggest that the electrochemical platform is significantly more sensitive than colorimetric and fluorescence-based platforms. The inherent binding affinity of the aptamer was found to have a significant effect on the LOD of the aptasensor. While some fabricated aptasensors are sufficiently sensitive to detect contaminants at environmentally relevant concentrations, they are often associated with complex fabrication steps, and/or interference from structurally similar analogs. As a result, aptasensor commercialization faces many challenges including reusability, reproducibility and robustness. In vitro selections were conducted with different selection pressures to isolate sensitive and selective DNA aptamers for E2 and EE. An equilibrium-filtration assay was used to determine dissociation constants (Kd) of the aptamer towards its parent target and its analogues. The E2 aptamers, E2Apt1 and E2Apt2 were found to have Kd values of 0.6 µM. They bound to analogue estrone (E1) with a similar affinity but were at least 74-fold more selective over EE. The EE aptamers Kd values are 0.5-1 µM. While one EE aptamer (EEApt1) was 53-fold more selective for EE over E2 and E1, the second EE aptamer (EEApt2) bound to all three EDCs (E1, E2 and EE) with similar affinities. The aptamers maintained their binding affinities in natural waters samples (tap water and lake water). DMS probing of the structure of the DNA aptamer revealed that the binding regions were mostly located in the single-stranded loop regions of the aptamer. Aptasensors typically employ immobilized aptamers though the aptamers are selected and characterized while free or unattached in solution. The Kd values of immobilized selective aptamers were evaluated using magnetic microbeads surface for attachment. E2Apt1 immobilized at either end (5′ or 3′) and E2Apt2 immobilized at the 3′ end retain their binding affinity. The binding affinity is inversely correlated to the average linear distance of the binding pocket from the immobilized end. This result suggests that unwanted interactions between the aptamer and other moieties are more likely when the binding pocket is further away from the surface. Binding curve of E2Apt2 immobilized at the 5′ end indicates potential dimerization at high loadings of aptamer on the beads due to increased proximity between aptamer strands. EEApt1 loses its binding affinity upon immobilization potentially due to disruption in its tertiary structure upon attachment to the surface. Despite no loss in binding affinity upon immobilization, E2Apt1 (5′) shows no significant change in electrochemical current on binding to E2 when incorporated into an electrochemical sensor. This result implies an insufficient conformational change of the aptamer on binding to the target. Overall, this work identifies the first aptamers for EE and selective aptamers for E2, while also highlighting the issues with development of aptamers and their eventual incorporation into aptasensors to detect small organics. Two major concerns are (1) immobilizing aptamers in sensor platforms while selections of aptamers are conducted with free/unattached aptamers, resulting in loss of binding affinity and (2) insufficient conformational change of the aptamer on binding to small molecule targets, resulting in a lack of change in the sensor signal. The findings from this dissertation support additional research directions regarding employing free aptamers in sensors and/or conducting new selections for aptamers using a DNA pool that is attached to a surface

Miniaturized immunosensors and innovative motorbased (bio-)sensing strategies for analytical applications

En esta Tesis Doctoral, se han desarrollado inmunosensores miniaturizados y estrategias innovadoras basadas en motores para el biosensado en aplicaciones analíticas centradas en los campos agroalimentario y clínico. El desarrollo de nuevas tecnologías y metodologías para solucionar problemas analíticos y reales es un aspecto clave y exigente en el campo de la química analítica, tendiendo actualmente a realizar análisis sencillo, fácil manejo, miniaturizado, portátil e in situ. En este sentido, los biosensores conforman herramientas analíticas excelentes debido a la sensibilidad y la selectividad reconocidas, junto con su miniaturización inherente. Por otro lado, las metodologías analíticas basadas en nanotecnología, donde los nanomateriales y motores actúan de forma especial, constituyen instrumentos innovadores, prometedores e interesantes para analizar en diferentes áreas. Estos motores, los cuáles se mueven autónomamente a través de energía obtenida de una reacción química en una de las más conocidas variedades, permiten una estrategia de biosensado, la cual depende del movimiento continuo a través de muestras complejas relacionadas con distintas interacciones biomoleculares, llamadas “al vuelo”. Tal movimiento a lo largo de la muestra ayuda a la interacción con el analito generando un nuevo paradigma en la química analítica. Dentro del campo de la química analítica, el análisis de comida es uno de los más importantes temas. Teniendo en cuenta el riesgo en seguridad alimentaria debido a la presencia de amenazas en la comida y productos derivados, existe una necesidad real de desarrollar métodos nuevos capaces de detectar estos productos perjudiciales, y así, asegurar la seguridad de los consumidores. De este modo, el análisis de micotoxinas, metabolitos secundarios tóxicos producidos por hongos, es especialmente relevante debido a los efectos negativos provocados en la salud humana y animal. En consecuencia, siguiendo el objetivo de conservar la seguridad alimentaria, nuevos procedimientos basados en biosensores y metodologías en motores para mejorar los actuales trabajos y explorar otros modos de actuación han significado la principal inspiración para esta tesis doctoral. De este modo, dos inmunosensores basados en partículas magnéticas (como soporte de la reacción inmunológica), usando anticuerpos como elemento de bioreconocimiento. La metodología inmunoanalítica competitiva, va seguida de una reacción enzimática (dada por la peroxidasa de rábano picante) con un sustrato enzimático (peróxido de hidrógeno) y un mediador electroquímico (hidroquinona). Una vez, desarrollados los inmunosensores, se evaluaron analíticamente, incluído con un material de referencia certificado para las Fumonisinas. Además, se realizó un protocolo de calibrado y análisis simultáneo que simplifica las laboriosas metodologías de calibrado. Por otro lado, los micromotores basados en grafeno permiten su utilización como sensores móviles. Aprovechando sus características, la detección de Fumonisina B1 mediante el apagamiento de la fluorescencia de un fluoróforo unido a un aptámero selectivo para Fumonisina B1. De esta manera, el aptámero, que no reconoce a ninguna Fumonisina B1, se une por interacción π‒π al grafeno, apagando la fluorescencia del fluoróforo. Así, durante la estancia en Estados Unidos, se construyó un motor con una aleación de Cu-Pt, la cuál permite un retraso en la iniciación del movimiento. Este retardo puede controlarse mediante el propio combustible (H2O2) o las condiciones del medio. Por último, otros métodos de propulsión fueron explorados, como la propulsión por autodifusioforesis. Una punta de pipeta cortada y sellada, rellena con una disolución de tensioactivo y enzima, se mueve a lo largo de la muestra debido al cambio de tensión superficial provocado por el tensioactivo. Así, gracias a un mediador electroquímico (hidroquinona), se puede determinar peróxido de hidrógeno de forma óptica y electroquímica en muestras de alto interés agroalimentario y clínico