Inhibition-based first-generation electrochemical biosensors: theoretical aspects and application to 2,4-dichlorophenoxy acetic acid detection

In this work, several theoretical aspects involved in the first-generation inhibition-based electrochemical biosensor measurements have been discussed. In particular, we have developed a theoretical-methodological approach for the characterization of the kinetic interaction between alkaline phosphatase (AlP) and 2,4- dichlorophenoxy acetic acid (2,4-D) as representative inhibitor studied by means of cyclic voltammetry and amperometry. Based on these findings, a biosensor for the fast, simple, and inexpensive determination of 2,4-D has been developed. The enzyme has been immobilized on screen-printed electrodes (SPEs). To optimize the biosensor performances, several carbon-based SPEs, namely graphite (G), graphene (GP), and multiwalled carbon nanotubes (MWCNTs), have been evaluated. AlP was immobilized on the electrode surface by means of polyvinyl alcohol with styryl-pyridinium groups (PVA-SbQ) as cross-linking agent. In the presence of ascorbate 2-phosphate (A2P) as substrate, the herbicide has been determined, thanks to its inhibition activity towards the enzyme catalyzing the oxidation of A2P to ascorbic acid (AA). Under optimum experimental conditions, the best performance in terms of catalytic efficiency has been demonstrated by MWCNTs SPE-based biosensor. The inhibition biosensor shows a linearity range towards 2,4-D within 2.1–110 ppb, a LOD of 1 ppb, and acceptable repeatability and stability. This analysis method was applied to fortified lake water samples with recoveries above 90 %. The low cost of this device and its good analytical performances suggest its application for the screening and monitoring of 2,4-D in real matrices

Comparison between a direct-flow SPR immunosensor for ampicillin and a competitive conventional amperometric device: analytical features and possible applications to real samples

In this research, we developed a direct-flow surface plasmon resonance (SPR) immunosensor for ampicillin to perform direct, simple, and fast measurements of this important antibiotic. In order to better evaluate the performance, it was compared with a conventional amperometric immunosensor, working with a competitive format with the aim of finding out experimental real advantages and disadvantages of two respective methods. Results showed that certain analytical features of the new SPR immunodevice, such as the lower limit of detection (LOD) value and the width of the linear range, are poorer than those of a conventional amperometric immunosensor, which adversely affects the application to samples such as natural waters. On the other hand, the SPR immunosensor was more selective to ampicillin, and measurements were more easily and quickly attained compared to those performed with the conventional competitive immunosensor

Nanoparticles modified screen printed electrode for electrochemical determination of COD

The Chemical Oxygen Demand (COD) is a parameter widely used to determine organic pollutants in water and is defined as the number of oxygen equivalents necessary to oxidize the organic compounds. The standard method for COD measurement (the dichromate titration) suffers from several inherent drawbacks such as the long time of the process and the consumption of toxic chemicals. Hence, interest is growing towards those methods employing electrochemical oxidation of organic compounds, as they allow to dispense with toxic reagents and above all to perform a continuous determination. In this work a new electrochemical method for COD measurement has been developed based on direct oxidation of organic molecules on suitably modified electrodic surfaces. In particular, we have developed various sensors based on modified working electrode surfaces obtained by electrodepositing copper and/or nickel oxide nanoparticles onto several commercial screen printed electrodes. Glucose was used as the standard compound for COD measurements: C6H12O6 + 6O2 → 6CO2 + 6H2O The metallic nanoparticles catalyze the oxidation of the glucose, as well as of different organic pollutants, and make the detection possible at relatively low potential, also in presence of chloride as interferent. The analytical parameters were optimized and the results obtained highlight how the electrodeposition of different metallic nanoparticles onto several screen printed electrode surfaces can influence the selectivity and sensitivity towards the COD detection in real matrices, via electrochemical method. The results were compared with those obtained by the standard method and showed a good agreement. These findings provide an interesting strategy to obtain a simple, cheap, portable and eventually continuous sensor for COD measurement

A flow SPR immunosensor based on a sandwich direct method

In this study, we report the development of an SPR (Surface Plasmon Resonance) immunosensor for the detection of ampicillin, operating under flow conditions. SPR sensors based on both direct (with the immobilization of the antibody) and competitive (with the immobilization of the antigen) methods did not allow the detection of ampicillin. Therefore, a sandwich-based sensor was developed which showed a good linear response towards ampicillin between 10-3 and 10-1 M, a measurement time of ≤20 min and a high selectivity both towardsβ-lactam antibiotics and antibiotics of different classes. © 2016 by the author

Simulation-Based Evolutionary Optimization of Air Traffic Management

In the context of aerospace engineering, the optimization of processes may often require to solve multi-objective optimization problems, including mixed variables, multi-modal and non-differentiable quantities, possibly involving highly-expensive objective function evaluations. In Air Traffic Management (ATM), the optimization of procedures and protocols becomes even more complicated, due to the involve-ment of human controllers, which act as final decision points in the control chain. In this article, we propose the use of computational intelligence techniques, such as Agent-Based Modelling and Simulation (ABMS)and Evolutionary Computing (EC), to design a simulation-based distributed architecture to optimize control plans and procedures in the context of ATM. We rely on Agent-Based fast-time simulations to carry out offline what-if analysis of multiple scenarios, also taking into account human-related decisions, during the strategic or pre-tactical phases. The scenarios are constructed using real-world traffic data traces, while multiple optimization variables governed by an EC algorithm allow to explore the search space to identify the best solutions. Our optimization approach relies on ad-hoc multi-objective performance metrics which allow to assess the goodness of the control of aircraft and air traffic regulations. We present experimental results which prove the viability of our approach, comparing them with real-world data traces, and proving their meaningfulness from an Air Traffic Control perspective

Highly Sensitive Electrodic Materials Based on Pt Nanoflowers Grown on Pt Nanospheres for Biosensor Development

In this work we describe the realization of monometallic nanostructures by two simple electrodeposition steps. The surface of the modified electrode was characterized by scanning electron microscopy that confirms a homogeneous deposition of Pt nanospheres decorated with Pt nanoflowers. The so obtained nanostructured sensor exhibited good amperometric response towards hydrogen peroxide sensing at +0.30 V vs Ag|AgCl|Cl-. Therefore, it is especially useful toward glucose detection with reduced interferences. Glucose oxidase was immobilized onto the nanostructured surface by cross-linking with glutaraldehyde and the biosensor was characterized by chronoamperometric method in phosphate buffer. The biosensor showed a sensitivity of 29 ± 2 μA/(mM cm2). Measurements in cell media reveal that the Pt-Pt hybrid nanostructures are promising for real-time glucose monitoring in real biosample

Il nucleo filosofico della scienza

il volume è inserito nella Collana di Filosofia e pubblica gli Atti del Seminario di Storia e filosofia della scienza dell'Università di Lecce (1987-1990)

Application of a nanostructured enzymatic biosensor based on fullerene and gold nanoparticles to polyphenol detection

Electrochemical biosensors provide an attractive means of analyzing the content of a biological sample due to the direct conversion of a biological event to an electronic signal. The signal transduction and the general performance of electrochemical biosensors are often determined by the surface architectures that connect the sensing element to the biological sample at the nanometer scale. The most common surface modification techniques, the various electrochemical transduction mechanisms, and the choice of the recognition receptor molecules all influence the ultimate sensitivity of the sensor.We show herein a novel electrochemical biosensing platformbased on the coupling of two different nanostructured materials (gold nanoparticles and fullerenols) displaying interesting electrochemical features. The use of these nanomaterials improved the electrochemical performance of the proposed biosensor. An application of the nanostructured enzyme-based biosensor has been developed for evaluating the detection of polyphenols either in buffer solution or in real wine samples

Development of carbon-based nano-composite materials for direct electron transfer based biosensors

Nafion, an ion exchange polymer that is very resistant to chemical attack, even by strong oxidant at high temperatures, has found great increasing use as a film material; however, its use as immobilizing agent in third-generation biosensors is hindered due to the low rate of charge transfer in the pure Nafion film. In this work we showed that the use of functionalized multi-walled carbon nanotubes Nafion/MWCNTs composite film for modification of the carbon-based electrode surfaces would increase the charge transfer rate greatly; the composite has proven to efficiently immobilize two different heme proteins (catalase and cytochrome c) and to enhance the electrochemical performances of several carbon electrode materials (glassy carbon, mesoporous graphite, graphite and graphene) either used as classical electrodes or screen printed ones. The electrochemical signal of both redox proteins becomes more reversible and the electron transfer kinetic constant increases. At the same time the biological activity is maintained indicating that the immobilization procedure allows the proteins to retain a native-like structure