Screen-printed electrodes: Transitioning the laboratory in-to-the field

This short article overviews the use of screen-printed electrodes (SPEs) in the field of electroanalysis and compares their application against traditional laboratory based analytical techniques. Electroanalysis coupled with SPEs can offer low-cost, precise, sensitive, rapid, quantitative information and laboratory equivalent results. The combined use of SPEs and electroanalysis reduces the need of sample transportation and preparation to a centralised laboratory allowing experimentalists to perform the measurements where they are needed the most. We first introduce the basic concepts and principles of analytical techniques to the reader, with particular attention to electroanalysis, and then discuss the application of SPEs to common analytical targets such as food, environmental, forensics, cancer biomarkers and pathogenic monitoring and sensing

Biosensors

A biosensor is defined as a detecting device that combines a transducer with a biologically sensitive and selective component. When a specific target molecule interacts with the biological component, a signal is produced, at transducer level, proportional to the concentration of the substance. Therefore biosensors can measure compounds present in the environment, chemical processes, food and human body at low cost if compared with traditional analytical techniques. This book covers a wide range of aspects and issues related to biosensor technology, bringing together researchers from 11 different countries. The book consists of 16 chapters written by 53 authors. The first four chapters describe several aspects of nanotechnology applied to biosensors. The subsequent section, including three chapters, is devoted to biosensor applications in the fields of drug discovery, diagnostics and bacteria detection. The principles behind optical biosensors and some of their application are discussed in chapters from 8 to 11. The last five chapters treat of microelectronics, interfacing circuits, signal transmission, biotelemetry and algorithms applied to biosensing

Sviluppo di un nuovo sistema voltammetrico microdialitico per lo studio delle variazioni neurochimiche in coltura

A novel dual channel in vitro apparatus, derived from a previously described design, has been coupled with dopamine (DA) microsensors for the flow-through detection of DA secreted from PC12 cells. The device, including two independent microdialysis capillaries, was loaded with a solution containing PC12 cells while a constant medium perfusion (PBS) was carried out using a dual channel miniaturized peristaltic pump. One capillary was perfused with normal PBS, whereas extracellular Ca2+ was removed from extracellular fluid of the second capillary. After a first period of stabilization and DA baseline recording, KCl 75 mM was added to the perfusion fluid of both capillaries. In this manner, a simultaneous treatment–control experimental design was performed to detect K+-evoked Ca2+-dependent DA secretion. For this purpose, self-referencing DA microsensors were developed, and procedures for making, testing, and calibrating them are described in detail. The electronic circuitry was derived from previously published optimized for dual sensor CPA applications. The microdialysis system was tested and validated in vitro, and DA secretion was confirmed by HPLC–EC. PC12 cell viability was quantified before and after each experiment. The proposed apparatus serves as a reliable model for studying the effects of different drugs on DA secretion through the direct comparison of extracellular DA increase in treatment–control experiments performed on the same initial PC12 cell population

Signal Enhancement Strategies in Classical Electrochemiluminescence Techniques for Modern Biosensing

With the ascent of IT, and since Ashton has invented the term Internet of Things (IoT) in 1999, this future idea of connected machines that can do tasks and perform decision-control cycles without human input has become more and more attractive and is today an established future scenario. Obviously, in an IoT, “sensors for everything” are one crucial corner stone of its existence and Analytical chemistry can and must deliver them. While many challenges towards a functioning IoT remain, we are on the verge of its beginning. This can be also seen with “Analytics 4.0” in research and on the market, tending to more IT-connected, portable, easier-controllable and integrated solutions. The entrance of mobility in the health sector or Point-of-Care (POC) diagnostics trends are alike influencing biosensing. Whether in mobile solutions or lab- and clinical environments, versatile, powerful and easy-to-adapt detection strategies like Electrochemiluminescence (ECL) are an attractive option. The ECL molecules [Ru(bpy)3]2+ and luminol represent the most prominent and most abundantly investigated luminophores for ECL since Bard’s accomplishment to make ECL a well-known technique. Because both are also two of the most efficient ECL emitters that can be well-handled in bioanalysis, and are available on the market, they are still today frequently used in research and also commercial applications. To cope with current benchmarks of sensitive detection, however a combination with a certain signal enhancement strategy is recommended. Several different routes can here be employed and one option is dendrimers. PAMAM dendrimers can function as ECL coreactant in [Ru(bpy)3]2+-ECL via their amino groups and at the same time expose primary amino groups as possible bioconjugation elements. Exploring this multi-functionality of the dendrimers was investigated here. This was done on a model system employing PAMAM dendrimers with [Ru(bpy)3]2+-ECL together with biotin/streptavidin as biorecognition element and analyte, respectively. The dendrimer’s bi-functionality was successfully proven and a joint-role of a biorecognition element and a possible reporter function suggests an optimum application in homogeneous assays. A different toolset for ECL signal enhancement is offered by liposomes. Numerous signaling molecules can be encapsulated inside the inner cavity of these synthetic vesicles, while they provide protection from the environment and connection-functionality to probes via lipids and surface groups on the outside. That application was here explored, together with a newly synthesized luminol derivative obtained by a simple synthesis route from commercial starting materials and exhibiting a four times increased ECL efficiency versus standard luminol. That was necessary as a liposome enhancement was denied for the standard luminol through its poor aqueous solubility. The new m-carboxy luminol considerably improved this feature which allowed its own encapsulation in liposomes. The superior signal generation with this dual system was proven in a model sandwich hybridization assay which yielded a 150-times better detection performance than the equal fluorescence-based assay while being almost zero affected through matrices like serum, soil or river water. As such the good performance of luminol ECL together with liposomes for highly sensitive detection applications was demonstrated. A further necessary element with liposomal amplification, are surfactants to set free the signaling molecules. However, this case depicts only one example of a multitude of applications of surfactants in bioassays and biochemical methods. Hence, surfactants are commonly present solution constituents which also have to be considered in general with ECL because they can influence the ECL signals positively or negatively. This was further investigated for luminol ECL by exploring the effect of 13 different surfactants on the luminol ECL efficiency on four different electrode materials. A deeper understanding of the distinct effects was obtained by looking into ECL emission behavior, electrochemical effects, the surfaces and Chemiluminescence effects. After all, the revelation of a complicated mechanism that involves many contributing factors and as such directs signal quenching or enhancement is an important finding for assay design. In this way, the selection of a suitable surfactant is possible to exploit maximum reachable signal efficiencies. A combination of signal enhancement tools like a better ECL molecule derivative, dendrimers, liposomes or surfactants has proven to boost the ECL performance considerably. A further means of signal enhancement is offered via miniaturization, which also makes the detection method better suited towards common application as liquid handling and easier automation are on hand. This can be used for single ECL assays or combinations of different ECL reagents in one system for multi-detection. Different strategies for the miniaturization of an ECL readout-capable system were investigated, taking requirements for [Ru(bpy)3]2+ and luminol as ECL reporters into account. This includes materials, electrochemical demands and simple design. Here, ITO electrodes – while advantageous for luminol ECL could not convince with their performance in [Ru(bpy)3]2+-ECL. Alternatively, laser scribed graphene electrodes have shown to be promising candidates for a future miniaturized system encompassing both, luminol and [Ru(bpy)3]2+ as ECL systems. Ultimately, the different signal amplifying strategies, investigated in this work that can be applied standalone or combined, offer a great toolset for state-of-the-art ECL detection applications in research and also for possible commercial applications

Fundamentals, Applications, and Future Directions of Bioelectrocatalysis

Bioelectrocatalysis is an interdisciplinary research field combining bio-catalysis and electrocatalysis via the utilization of materials derived from biological systems as catalysts to catalyze the redox reactions occurring at an electrode. Bioelectrocatalysis synergistically couples the merits of both biocatalysis and electrocatalysis. The advantages of biocatalysis include high activity, high selectivity, wide substrate scope, and mild reaction conditions. The advantages of electrocatalysis include the possible utilization of renewable electricity as an electron source and high energy conversion efficiency. These properties are integrated to achieve selective biosensing, efficient energy conversion, and the production of diverse products. This review seeks to systematically and comprehensively detail the fundamentals, analyze the existing problems, summarize the development status and applications, and look toward the future development directions of bioelectrocatalysis. First, the structure, function, and modification of bioelectrocatalysts are discussed. Second, the essentials of bioelectrocatalytic systems, including electron transfer mechanisms, electrode materials, and reaction medium, are described. Third, the application of bioelectrocatalysis in the fields of biosensors, fuel cells, solar cells, catalytic mechanism studies, and bioelectrosyntheses of high-value chemicals are systematically summarized. Finally, future developments and a perspective on bioelectrocatalysis are suggested

Selected Papers from the 1st International Electronic Conference on Biosensors (IECB 2020)

The scope of this Special Issue is to collect some of the contributions to the First International Electronic Conference on Biosensors, which was held to bring together well-known experts currently working in biosensor technologies from around the globe, and to provide an online forum for presenting and discussing new results. The world of biosensors is definitively a versatile and universally applicable one, as demonstrated by the wide range of topics which were addressed at the Conference, such as: bioengineered and biomimetic receptors; microfluidics for biosensing; biosensors for emergency situations; nanotechnologies and nanomaterials for biosensors; intra- and extracellular biosensing; and advanced applications in clinical, environmental, food safety, and cultural heritage fields

Electroanalysis of Small Molecule Therapeutics at Nanostructured Electrode Surfaces

The outbreak of COVID-19 in Wuhan, China in December 2019, resulted in the evolution of a global pandemic which caused thousands of deaths worldwide. As little was known about this new coronavirus, many existing drugs were repurposed with the goal to effectively treat the infection. Two such candidates were dexamethasone (DEX) and N-acetyl-L-cysteine (NAC). Relatively few articles have been published relating to their electrochemical determination, and in this project the use of metal nanoparticles, microparticles and films alongside various carbon nano-onions (CNOs) were explored as chemical modifiers in order to maximize their electrochemical responses. Bare, copper microparticle (CuMPs) and copper film (CuF) modified glassy carbon electrodes were exploited in Chapter 2 to examine the DEX electroreduction response, resulting in sensitivities of 2.00 × 102 μA cm-2 mM-1 and 1.13 × 102 μA cm-2 mM-1 for the CuF and CuMP modified GCEs respectively. Pharmaceutical samples in the form of a cream and a solid-state dose, were analysed with recoveries 77.46 – 87.91 %, with 1.93 – 4.97 % variance. Various types of CNOs were electrochemically characterised of which, oxi-BN-doped-CNOs was selected and combined with gold nanoparticles (AuNPs), resulting in an AuNP/oxi-BN-doped CNO/GCE for NAC quantitation (sensitivity 476 μQ cm-2 mM-1 in acetate buffer). Following design and optimisation, a solid dose form of NAC was quantitatively analysed, resulting in 89 – 105 % ± 6.75 % recovery, thus validating the sensors

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