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Abstract Herein, we propose the first three-dimensional origami paper-based device for the detection of several classes of pesticides by combining different enzyme-inhibition biosensors. This device was developed by integrating two different office paper-based screen-printed electrodes and multiple filter paper-based pads to load enzymes and enzymatic substrates. The versatile analysis of different pesticides was carried by folding and unfolding the filter paper-based structure, without any addition of reagents and any sample treatment (i.e. dilution, filtration, pH adjustment). The paper-based platform was employed to detect paraoxon, 2,4-dichlorophenoxyacetic acid, and atrazine by exploiting the capability of these different types of pesticides (i.e. organophosphorus insecticides, phenoxy-acid herbicides, and triazine herbicide) to inhibit butyrylcholinesterase, alkaline phosphatase, and tyrosinase, respectively. The degree of inhibition correlating to the quantity of pesticides was evaluated by chronoamperometrically monitoring the enzymatic activity in the absence and in the presence of pesticides by using a portable potentiostat. To improve the sensitivity, the paper-based electrodes were modified with carbon black alone in the case of platforms for 2,4-dichlorophenoxyacetic acid and atrazine detection, or decorated with Prussian blue nanoparticles for the detection of paraoxon. The paper-based device was applied for the detection of paraoxon, 2,4-dichlorophenoxyacetic acid, and atrazine at ppb level in both standard solutions and river water sample. The accuracy of this origami multiple paper-based electrochemical biosensor was evaluated in river water by recovery studies, obtaining satisfactory values (e.g. for paraoxon 90 ± 1% and 88 ± 2%, for 10 and 20 ppb, respectively). The proposed three-dimensional origami paper device allows for rapid, cost-effective and accurate pesticide detection in surface water as a result of combining filter and office papers, screen-printing, wax-printing and nanomaterial technology. Graphical abstract fx1 Highlights • 3D paper-based origami device for different types of pesticides. • Reagentless measurement of pesticides. • Inhibition-based enzymatic biosensors. • Wax/screen-printing, paper and nanomaterials for a laboratory-free platform. [ABSTRACT FROM AUTHOR]

Enzyme inhibitors like drugs and pollutants are closely correlated to human and environmental health, thus their monitoring is of paramount importance in analytical chemistry. Enzymatic biosensors represent cost-effective, miniaturized and easy to use devices; particularly biosensors based on enzyme inhibition are useful analytical tools for fast screening and monitoring of inhibitors. The present review will highlight the research carried out in the last 9 years (2006–2014) on biosensors based on enzyme inhibition. We underpin the recent advances focused on the investigation in new theoretical approachs and in the evaluation of biosensor performances for reversible and irreversible inhibitors. The use of nanomaterials and microfluidic systems as well as the applications of the various biosensors in real samples is critically reviewed, demonstrating that such biosensors allow the development of useful devices for a fast and reliable alarm system. [ABSTRACT FROM AUTHOR]

A screen-printed electrode (SPE) modified with a carbon black (CB)-Au nanoparticles (AuNPs) composite is assembled and tested. Electrochemical and morphological investigations highlight the physico-chemical properties of the resulting AuNP-CB-SPE amperometric device with respect to SPEs modified with a single component of the nanocomposite. The effective performance of such a modified electrode in activating electrocatalytic processes, consisting both in oxidation and reduction reactions, is demonstrated. In particular, electrochemical tests on analytes such as glucose, hydrogen peroxide, hydroquinone, and ascorbic acid, evidence that the composite possesses electrocatalytic performance well superior with respect to the relevant mono-component modified SPE. As a consequence, a meaningful lowering of the peak potentials and improvement of the sensor sensitivities is observed when using AuNP-CB-SPEs with respect to both CB-SPEs and AuNP-SPEs. In the case of H 2 O 2 reduction, the occurrence of the electrochemical process at less negative potentials is coupled to an improvement of sensor sensitivity of about one order of magnitude. Concurrently, lower limit of detections, ranging from 20 to 99% less, have been obtained for the major part of the analytes studied, i.e. glucose, hydrogen peroxide and hydroquinone. Preliminary results reported here indicate that AuNP-CB-SPE can be proposed as an efficient amperometric sensor to be used in many analytical applications. [ABSTRACT FROM AUTHOR]

Food and diet are closely linked to human health, and new emerging research fields are attempting to guarantee improvements in food quality and safety. Biosensor technology represents a cutting-edge frontier in environmental and biomedical diagnosis and is at the forefront in the agrifood sector. Smart monitoring of nutrients and fast screening of biological and chemical contaminants are some of the key evolving issues challenging the assessment of food quality and safety. Advances in materials science and nanotechnology, electromechanical and microfluidic systems, protein engineering and biomimetics design are boosting sensing technology from bench to market. This review highlights current and future trends in analytical diagnostic tools focused on the food industry and target analytes to support healthier nutrition. [ABSTRACT FROM AUTHOR]

Abstract: Trehalose is a disaccharide important in foods, serving as a glucose source in many and also as an additive in the food preparation. Because of its peculiar physico-chemical properties it plays an important role as preservative in drying and deep-freezing treatments. A new biosensor for trehalose determination has been realized by means of a flow system, based on a reactor in which the trehalase enzyme catalyses its hydrolysis into two α,d-glucose molecules, and a GOD (glucose oxidase) amperometric biosensor is employed for the glucose determination. The optimum operative conditions have been laid out and a particular attention has been paid to the immobilization procedure of the two enzymes. The electrode used is of the SPE (screen-printed electrode) type and has been activated with the Prussian Blue (PB) and then assembled using GOD immobilized with Nafion. The reactor has been prepared with the trehalase enzyme chemically immobilized on an Immunodyne ABC membrane. As demonstration of its utility, the biosensor has been tested on a real sample of Boletus edulis mushroom. [Copyright &y& Elsevier]

Highlights: [•] A novel laccase-modified screen printed electrode (SPE) has been developed. [•] Bionanocomposite sensor is optimized in terms of enzyme loading, pH and applied potential. [•] Linear range, sensitivity and LOD are assessed for BPA determination. [•] The biosensor has been challenged in tomato juice samples. [ABSTRACT FROM AUTHOR]

Abstract: A thionine-modified carbon paste electrode for catechol and Bisphenol A (BPA) detection is presented. Graphite powder was modified by adsorbing thionine as electrochemical mediator. The electrochemical response of the modified carbon paste electrode (CPE) was determined before electrode modification with tyrosinase. Then, tyrosinase was added in order to assemble a biosensor. Once established the best operative conditions, an interelectrode reproducibility around 7% was obtained and the resulting biosensor showed improved sensitivities and (S =139.6±1.1nA/μM for catechol and S =85.4±1.5nA/μM for BPA) in comparison with the biosensor constructed without thionine (S =104.4±0.5nA/μM for catechol and S =51.1±0.6nA/μM for BPA) and low detection limits (0.15μM for both the electrodes and analytes). Also the comparison with the results reported in the literature showed higher sensitivity and lower detection limit for our biosensor. Moreover the functioning of the thionine-tyrosinase CPE was validated following a biodegradation process of water polluted by BPA and comparing the time changes of BPA concentration inferred by the biosensor calibration curve and those determined by means of HPLC measurements. [Copyright &y& Elsevier]

Abstract: Different tyrosinase carbon paste modified electrodes to determine bisphenol A (BPA) concentration in aqueous solutions have been constructed. Variables examined were in the carbon paste composition and in particular: (i) the immobilized enzyme amount; (ii) the carbon type (powder, single or multi-walled nanotubes); (iii) the nature of the pasting oil (mineral oil, hexadecane and dodecane). For each biosensor type the amperometric response was evaluated with reference to the linear range and sensitivity. Constant reference has been made to the amperometric signals obtained, under the same experimental conditions, towards the catechol, a specific phenolic substrate for tyrosinase. The most efficient biosensors were those constructed by using the following composition for the carbon paste: 10% of tyrosinase, 45% of single wall carbon nanotubes (SWCN) and 45% of mineral oil. This biosensor formulation displayed the following electrochemical characteristics: a sensitivity equal to 138μA/mM, LOD of 0.02μM (based on three times the S/N ratio), linear range of 0.1–12μM and response time of 6min. This experimental work represents a first attempt at construction of a new carbon nanotube-tyrosinase based biosensor able to determine the concentration of BPA, one of the most ubiquitous and hazardous endocrine disruptors which can pollute the drinking and surface water, as well as many products of the food chain. [Copyright &y& Elsevier]

A facile “one-step” route to produce a homogenous and highly stable cobalt phthalocyanine (CoPc)-based dispersion by using carbon black (CB) as supporting material is reported. Herein, CB is proposed as effective material to load CoPc in order to obtain a CB/CoPc hybrid nanocomposite dispersion suitable for modifying screen-printed electrodes (SPEs) by an easy and automatable drop casting approach. CoPc resulted anchored to CB by a non-covalent physisorption, confirmed by IR and UV-visible spectroscopies, allowing to preserve the electrochemical performances of CoPc. The resulting CB/CoPc-modified SPE was tested as sensing tool to detect thiocholine, an enzymatic product of butyrylcholinesterase (BChE). The use of CB/CoPc leads to a highly sensitive thiocholine detection by applying a low potential (+0.05 V vs. internal reference) without fouling problem, a typical drawback that affects the thiol electrochemical detection. The favorable characteristics of the sensor were exploited for an easy BChE biosensor fabrication that renders this biosensor well suitable for mass-production. This electrochemical monoenzymatic biosensor was then challenged towards paraoxon, chosen as model organophosphorous pesticide, obtaining a low detection limit (18 nM). The suitability of the biosensor was tested in a waste water sample obtaining satisfactory recovery values, thus demonstrating its capability in such complex matrix. [ABSTRACT FROM AUTHOR]

Abstract: Heavy metals, as cadmium, attract a rising attention in environmental studies due to their increasing release by human activities and acute toxicity. In situ analytical methods are needed to minimize current uncertainties caused by the transport and conservation of samples. Here, we present the completely automatic determination of Cd in natural waters using a newly developed screen printed electrode sensor (SPE), inserted in a homemade purpose-built flow cell coupled to a Multi-Syringe Flow Injection Analysis system (MSFIA). The working electrode of SPEs was constituted by a carbon film modified with Nafion. Cd was plated on an in situ bismuth film and determined using Square Wave Anodic Stripping Voltammetry. Different chemical conditions of deposition and stripping were studied. A sample/acetic buffer mixture was found to be a well suited medium to form the Bi film and perform the analysis. Cd was quantified via calibration by on line standard additions. The limit of detection was found to be 0.79μgL−1, well below the limit stipulated by the European directive (5μgL−1). Good sample throughput (14h−1) and low consumption of reagent and sample (1.3mL) were also obtained in line with previous works in Cd flow analysis. [Copyright &y& Elsevier]

The characterization of an economic and ease-to-use carbon paste acetylcholinesterase (AChE) based biosensor to determine the concentration of pesticides Paraoxon and Dichlorvos is discussed. AChE hydrolyses acetylthiocholine (ATCh) in thiocoline (TC) and acetic acid (AA). When AChE is immobilized into a paste carbon working electrode kept at +410mV vs. Ag/AgCl electrode, the enzyme reaction rate using acetylthiocholine chloride (ATCl) as substrate is monitored as a current intensity. Because Paraoxon and Dichlorvos inhibit the AChE reaction, the decrease of the current intensity, at fixed ATCl concentration, is a measure of their concentration. Linear calibration curves for Paraoxon and Dichlorvos determination have been obtained. The detection limits resulted to be 0.86ppb and 4.2ppb for Paraoxon and Dichlorvos, respectively, while the extension of the linear range was up 23ppb for the former pesticide and up to 33ppb for the latter. Because the inhibited enzyme can be reactivated when immediately treated with an oxime, the biosensor reactivation has been studied when 1,1′-trimethylene bis 4-formylpyridinium bromide dioxime (TMB-4) and pyridine 2-aldoxime methiodide (2-PAM) were used. TMB-4 resulted more effective. The comparison with the behavior of similar AChE based biosensors is also presented. [ABSTRACT FROM AUTHOR]

Abstract: A simple and reliable technique has been developed for the construction of an amperometric acetylcholinesterase biosensor based on screen-printed carbon electrodes. For the first time, one-step modification using single-walled carbon nanotubes and Co phtalocyanine has been proposed to decrease the working potential and to increase the signal of thiocholine oxidation. The biosensor developed made it possible to detect 5–50ppb of paraoxon and 2–50ppb of malaoxon with detection limits of 3 and 2ppb, respectively (incubation 15min). The biosensor showed high reproducibility when measurements of the substrate and inhibitor were performed (R.S.D. about 1% and 2.5%, respectively). The reliability of the inhibition measurements was confirmed by testing spiked samples of sparkling and tape waters. [Copyright &y& Elsevier]