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Point-of-care devices have attracted a huge interest by the scientific community because of the valuable potentiality for rapid diagnosis and precision medicine through cost-effective and easy-to-use devices for on-site measurement by unskilled personnel. Herein, we reported a smartphone-assisted electrochemical device consisted of a screen-printed electrode modified with carbon black nanomaterial and a commercially available smartphone potentiostat i.e. EmStat3 Blue, for sensitive detection of tyrosine. Once optimized the conditions, tyrosine was detected in standard solutions by square wave voltammetry, achieving a linear range comprised between 30 and 500 μM, with a detection limit equal to 4.4 μM. To detect tyrosine in serum, the interference of another amino acid i.e. tryptophan was hindered using a sample treatment with an extraction cartridge. The agreement of results analyzing serum samples with HPLC reference method and with the developed smart sensing system demonstrated the suitability of this smartphone-assisted sensing tool for cost-effective and rapid analyses of tyrosine in serum samples., (Copyright © 2021 Elsevier B.V. All rights reserved.)

An Enzyme Linked ImmunoMagnetic Electrochemical assay (ELIME) was developed for the detection of the hepatitis A virus (HAV). This system is based on the use of new polydopamine-modified magnetic nanobeads as solid support for the immunochemical chain, and an array of 8 screen-printed electrodes as a sensing platform. Enzymatic-by-product is quickly measured by differential pulse voltammetry. For this purpose, all analytical parameters were optimized; in particular, different blocking reagents were evaluated in order to minimize the nonspecific interaction of bioreagents. Using the ELIME assays, a quantitative determination of HAV can be achieved with a detection limit of 1·10 -11 IU mL -1 and a working range between 10 -10 - 5 × 10 -7 IU mL -1 . The cross-reactivity of the commercial monoclonal antibodies against HAV used in ELIME assays was tested for Coxsackie B4, resulting very low. The sensitivity was also investigated and compared with spectrophotometric sandwich ELISA. The average relative standard deviation (RSD) of the ELIME method was less than 5% for the assays performed on the same day, and 7% for the measurements made on different days. The proposed system was applied to the cell culture of HAV, which title was quantified by Real-Time Quantitative Reverse Transcription PCR (RT¬qPCR). To compare the results, a correlation between the units used in ELIME (IU mL -1 ) and those used in RT¬qPCR (genome mL -1 ) was established using a HAV-positive sample, resulting in 1 IU mL -1 -10 -4 gen mL -1 (R 2  = 0.978). The ELIME tool exhibits good stability and high biological selectivity for HAV antigen detection and was successfully applied for the determination of HAV in tap water., (Copyright © 2021 Elsevier B.V. All rights reserved.)

In this work, a wax-patterned chromatographic paper has been utilized as a holistic platform to 1) synthesize Prussian Blue Nanoparticles (sensing species), 2) load the reagents for the assay, 3) concentrate the sample through multistep, and 4) visualize the determination of silver ions. Waters are continuously affected by changes in the composition, thus the utilization of reagent-free analytical tools is of huge interest for smart drinking water monitoring. Herein, we report the characterization and application of a multi-array paper-based platform for the colorimetric determination of silver ions based on the conversion from Prussian Blue to its silver-based analogue, namely Ag 4 [Fe(CN) 6 ]. In particular, the platform highlights the increase of sensitivity due to paper pre-concentration of sample, that can be easily adapted to the analytical necessities. Within the proposed experimental setup, Ag + is visualized down to a detection limit of 0.9 μM, with high repeatability and satisfactory recoveries in the range comprised between 90 and 113%., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Bisphenol A is one the most relevant endocrine disruptors for its toxicity and ubiquity in the environment, being largely employed as raw material for manufacturing processes of a wide number of compounds. Furthermore, bisphenol A is released in the drinking water when plastic-based bottles are incorrectly transported under sunlight, delivering contaminated drinking water. For the health of human beings and the environment, rapid and on site detection of bisphenol A in drinking water is an important issue. Herein, we report a novel and cost-effective printed electrochemical sensor for an enzymatic-free bisphenol A detection. This sensor encompasses the entire electrochemical cell printed on filter paper and the reagents for the measurement loaded in the cellulose fiber network, for delivering a reagent-free analytical tool. The working electrode was printed using ink modified with carbon black, a cost effective nanomaterial for sensitive and sustainable bisphenol A determination. Several parameters including pH, frequency, and amplitude were optimized allowing for a detection limit of 0.03 μM with two linear ranges 0.1-0.9 μM and 1 μM-50 μM, using square wave voltammetry as electrochemical technique. The satisfactory recovery values found in river and drinking water samples demonstrated the suitability of this sensor for screening analyses in water samples. These results revealed the attractiveness of this paper-based device thanks to the synergic combination of paper and carbon black as cost-effective materials., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier B.V.)

Herein we report a multiplated and biopolymeric-based optical bioassay for organophosphate detection based on the use of acetylcholinesterase (AChE) as biocomponent and biopolymeric electrospun fibrous mats as eco-designed supports for AChE immobilisation. The principle of the detection relays on the decrease of enzymatic activity due to the capability of the organophosphorus pesticides to irreversibly inhibit AChE, which is optically detected using Ellman colorimetric method. The proposed bioassay consists in a novel, cost-effective, and multiplex-based 96-well system, in combination with customised biopolymeric membranes modified with AChE, with the aim to deliver a sustainable analytical tool. Indeed, the designed set-up should provide and guarantee several advantages, including: i) the re-use of plastic multi-plate with the only replacement of polymer dishes in the case of inhibition absence; ii) the exploiting of the properties of the immobilised enzyme, i.e. multiple analysis using the same amount of enzyme, reducing the AChE amount for analysis. In detail, three different biopolymers (i.e. polylactic acid (PLA), polycaprolactone (PCL), and poly-hydroxybutyrate-co-hydroxyvalerate (PHBV)) were investigated and morphologically characterised, as supports for enzyme immobilisation, to identify the optimal one. Among them, PHBV was selected as the best support to immobilise AChE by cross-linking method. The analytical features of the bioassay were then assessed by measuring standard solutions of paraoxon in a range of concentrations between 10 and 100 ppb, achieving a linear range up to 60 ppb and a detection limit of 10 ppb. Thus, the suitability of this sustainable bioassay to detect organophosphate at ppb level was demonstrated., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

In this study we reported the development of a paper-based algal biosensor for the optical detection of nanoencapsulated-atrazine, a forefront nanoformulated herbicide with a high effective post-emergence herbicidal activity. In particular, the unicellular green photosynthetic algae Chlamydomonas reinhardtii was immobilised on a paper substrate soaked with an agar thin film and placed in a glass optical measurement cell, obtaining a totally environmental-friendly device. Nanoencapsulated-atrazine was detected by following the variable fluorescence (1-V J ) parameter, which decreased inversely proportional to the herbicide concentrations, in a range between 0.5 and 200 nM, indicating a linear relationship in the measured dose-response curves and a detection limit of 4 pM. Interference studies resulted in a very slight interference in presence of 2 ppm copper and 10 ppb arsenic at safety limits, as well as a slight matrix effect and a satisfactory recovery value of 96 ± 5% for 75 nM nanoencapsulated-atrazine in tap water. Stability studies were also performed obtaining a good storage stability up to 3 weeks. Results demonstrated the suitability of the proposed paper-based optical biosensor as a valid support in smart agriculture for on site, environmental friendly, cost effective and sensitive nanoencapsulated-atrazine analysis., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Chlorine is the most common chemical compound used for treatment of water at ppm levels, although at higher concentration it can generate harmful disinfection by-products. To easily monitor the correct level of free chlorine, cost-effective and miniaturized devices for fast and on-site detection are required. Herein, we report the development of a novel miniaturized and cost-effective screen-printed electrode modified with carbon black nanomaterial for an effective amperometric detection of free chlorine in swimming pool water. The carbon black was used as working electrode modifier for chlorine quantification at low applied potential, overcoming the fouling problem. In addition, the use of stable and cost-effective carbon black dispersion allows for a mass-production of the modified sensor by an automatable drop casting method. This sensor has demonstrated the capability to detect free chlorine in a linear range of 0.05-200 ppm with a detection limit of 0.01 ppm in standard solution as well as in swimming pool water. The achieved results demonstrated for the first time the suitability of the carbon black as electrode nanomodifier for free chlorine detection, and the possibility to produce a miniaturized and cost-effective carbon black-based printed sensor for reliable free chlorine quantification in water samples., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Bioassays based on enzyme inhibition are analytical tools widely employed for inhibitor analysis. Beside the conventional analytical techniques such as chromatography and mass spectrometry, these bioassays are cost-effective, easy to use, and suitable for in situ measurement but they are often characterised by a quite narrow linear range. Herein, we report a novel graphical method based on integrated Michaelis-Menten equation, valid for all types of reversible inhibition, which provides an extended linear range. The suitability of this innovative approach was demonstrated in the case of fluoride quantification using a colorimetric bioassay based on acetylcholinesterase inhibition. The "half time reaction", estimated by the progress curve of cholinesterase inhibition, was plotted versus the fluoride inhibitor concentration, observing an extended linear range up to 5 mM, instead of 0.6 mM using initial rate measurements. The applicability of this new concept was further demonstrated in the case of catalase enzyme inhibited by cyanide. Furthermore, it was demonstrated that fixed substrate conversion at level of 10-50% allows determination of inhibitor concentration in a wide linear range with high precision and in short time of analysis. This novel theoretical and practical approach allows for the extension of the linear range without any further experiments, with several advantages including low reagent consumption, reduced waste generation and time of measurement., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The development of portable and user-friendly sensing platforms is a hot topic in the field of analytical chemistry. Among others, electroanalytical approaches exhibit a high amenability for reaching this purpose, i.e. the commercial strips for diabetes care are an obvious success. However, providing fully-integrated and user-friendly methods is the leitmotiv. In this work we evaluate the use of a disposable pipette tip, opportunely configured, to realize the first example of lab-on-a-tip. The combination of a pipette tip, wire electrodes, and cotton wool filter, highlights the suitability of producing a novel one-shot electroanalytical platform that does not require expertise-required tasks. To demonstrate the feasibility of this novel method, copper (Cu 2+ ) is detected in water samples by means of anodic stripping voltammetry. The quantification is performed directly into the tip that contains a cotton wool filter: the filter has the double function of purifying the matrices from gross impurities and releasing all the pre-loaded reagents necessary for the assay. After optimizing the experimental parameters, the lab-on-a-tip was capable of detecting Cu 2+ linearly up to 300 μg/L with a detection limit of 6.3 μg/L. The effectiveness of the platform was confirmed by testing 50, 100, and 150 ppb Cu-spiked river water sample with recovery value comprised between 92 and 103%., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Nowadays, environmentally friendly synthesis pathways for preserving the environment and minimizing waste are strongly required. Herein, we propose filter paper as a convenient scaffold for chemical reactions. To demonstrate this novel approach, Prussian Blue Nanoparticles (PBNPs) were synthesized on filter paper by utilizing few μL of its precursors without external inputs, i.e. pH, voltage, reducing agents, and without producing waste as well. The functional paper, named "Paper Blue", is successfully applied in the sensing field, exploiting the reduction of hydrogen peroxide at low applied potential. The eco-designed "Paper Blue" was combined with wax- and screen-printing to manufacture a reagentless electrochemical point-of-care device for diabetes self-monitoring, by using glucose oxidase as the biological recognition element. Blood glucose was linearly detected for a wide concentration range up to 25 mM (450 mg/dL), demonstrating its suitability for management of diabetes and glucose-related diseases. The Paper Blue-based biosensor demonstrated a correlation coefficient of 0.987 with commercial glucose strips (Bayer Contour XT). The achieved results demonstrated the effectiveness of this approach, which is also extendible to other (bio)systems to be applied in catalysis, remediation, and diagnostics., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The recent goal of sustainability in analytical chemistry has boosted the development of eco-designed analytical tools to deliver fast and cost-effective analysis with low economic and environmental impact. Due to the recent focus in sustainability, we report the use of low-cost filter paper as a sustainable material to print silver electrodes and to load reagents for a reagent-free electrochemical detection of chloride in biological samples, namely serum and sweat. The electrochemical detection of chloride ions was carried out by exploiting the reaction of the analyte (i.e. chloride) with the silver working electrode. During the oxidation wave in cyclic voltammetry the silver ions are produced, thus they react with chloride ions to form AgCl, while in the reduction wave, the following reaction occurs: AgCl + e - -->Ag + Cl - . These reactions at the electrode surface resulted in anodic/cathodic peaks directly proportional to the chloride ions in solution. Chloride ions were detected with the addition of only 10μL of the sample on the paper-based electrochemical cell, obtaining linearity up to 200mM with a detection limit equal to 1mM and relative standard deviation lower than 10%. The accuracy of the sensor was evaluated in serum and sweat samples, with percentage recoveries between 93 ± 10 and 108 ± 8%. Moreover, the results achieved with the paper-based device were positively compared with those obtained by using the gold standard method (Ion Selective Electrode) adopted in routine clinical analyses., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Cadmium and lead are highly toxic heavy metals which cause a severe worldwide pollution. In addition to the toxic effect produced by the direct exposure, they can be bioconcentrated and accumulated in living organisms, including humans. Herein, a miniaturized and disposable electrochemical sensor was improved for the simultaneous detection of cadmium and lead ions to study the bioremediation of polluted seawater in presence of the filter-feeding marine organism Styela plicata. A screen-printed electrode modified in situ with a bismuth film was selected using the anodic stripping analysis as detection technique. This sensor was coupled with a portable potentiostat and the detection of cadmium and lead ions was carried out by Square Wave Anodic Stripping Voltammetry, allowing the simultaneous detection of both heavy metals at ppb level (LOD=0.3ppb for lead, 1.5ppb for cadmium). This analytical tool was then applied to assess the bioremediation capacity of S. plicata through a bioremediation experiment, in which the organism has been exposed to seawater artificially polluted with 1000ppb of Cd 2+ and Pb 2+ . The matrix effect of both seawater and acid digested biological samples was evaluated. A bioconcentration phenomenon was observed for both heavy metals through the analysis of S. plicata tissues. In details, Pb 2+ resulted to be about 2.5 times more bioconcentrated than Cd 2+ , giving an effective bioremediation level in seawater of 13% and 40% for Cd 2+ and Pb 2+ , respectively. Thus, our results demonstrate the capability of S. plicata to bioremediate Cd 2+ and Pb 2+ polluted seawater as well as the suitability of the electrochemical sensor for contaminated marine environment monitoring and bioremediation evaluation., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Herein, we report the first example of a paper-based screen-printed biosensor for the detection of ethanol in beer samples. Common office paper was adopted to fabricate the analytical device. The properties of this paper-based screen-printed electrode (SPE) were investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy, and they were compared with the well-established polyester-based SPEs as well. Paper demonstrated similar properties when compared with polyester, highlighting suitability towards its utilization in sensor development, with the advantages of low cost and simple disposal by incineration. A nanocomposite formed by Carbon Black (CB) and Prussian Blue nanoparticles (PBNPs), namely CB/PBNPs, was utilized as an electrocatalyst to detect the hydrogen peroxide generated by the enzymatic reaction between alcohol oxidase (AOx) and ethanol. After optimizing the analytical parameters, such as pH, enzyme, concentration, and working potential, the developed biosensor allowed a facile quantification of ethanol up to 10 mM (0.058 % vol ), with a sensitivity of 9.13 μA/mM cm 2 (1574 μA/% vol cm 2 ) and a detection limit equal to 0.52 mM (0.003% vol ). These satisfactory performances rendered the realized paper-based biosensor reliable over the analysis of ethanol contained in four different types of beers, including Pilsner, Weiss, Lager, and alcohol-free. The proposed manufacturing approach offers an affordable and sustainable tool for food quality control and for the realization of different electrochemical sensors and biosensors as well., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Through the years, scientists have developed cutting-edge technologies to make (bio)sensors more convenient for environmental analytical purposes. Technological advancements in the fields of material science, rational design, microfluidics, and sensor printing, have radically shaped biosensor technology, which is even more evident in the continuous development of sensing systems for the monitoring of hazardous chemicals. These efforts will be crucial in solving some of the problems constraining biosensors to reach real environmental applications, such as continuous analyses in field by means of multi-analyte portable devices. This review (with 203 refs.) covers the progress between 2010 and 2015 in the field of technologies enabling biosensor applications in environmental analysis, including i) printing technology, ii) nanomaterial technology, iii) nanomotors, iv) biomimetic design, and (v) microfluidics. Next section describes futuristic cutting-edge technologies that are gaining momentum in recent years, which furnish highly innovative aspects to biosensing devices., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Herein we describe a novel reagentless paper-based electrochemical phosphate sensor, manufactured with a simple and inexpensive approach. By following three easy steps, consisting of wax patterning, paper chemical modification, and electrode screen-printing, the filter paper provides an effective electroanalytical platform to sense phosphate ions in standard solutions and real samples (river water). The electrochemical properties of the paper-based platform were evaluated, firstly, by using ferricyanide as a redox mediator, proving no analyte-entrapment due to the cellulose lattice. Then, the reference colorimetric method for phosphate ions, which is based on the formation of phosphomolybdic complex, was successfully adapted to a reagentless electrochemically paper-based platform. This novel and highly sustainable configuration readily allows for the determination of phosphate ions with high reproducibility and long storage stability, achieving a detection limit of 4 μM over a wide linear range up to 300 μM. This in-house approach would be able to generically develop an affordable in situ and user-friendly sensing device without the addition of any reagent, to be applied for a broad range of analytes., (Copyright © 2016 Elsevier B.V. All rights reserved.)

In this study, we report a novel assay for the combined on site detection of aflatoxin B1 (AFB1) and ochratoxin A (OTA), through a colorimetric biosensing system for AFB1 and a fluorimetric detection for OTA, exploiting the capability of the portable fibre optic spectrometer to perform both analyses. AFB1 was detected using the acetylcholinesterase (AChE) enzyme that is inhibited by this toxin, and the degree of inhibition was quantified by the Ellman's spectrophotometric method, obtaining a detection limit of 10 µg L(-1). OTA quantification was performed by monitoring its intrinsic fluorescence in methanol, reaching a detection limit of 0.1 µg L(-1). In order to successfully apply the analytical tool in the food analysis, immunoaffinity columns were used. Clean-up and quantification of both AFB1 and OTA in millet samples was obtained by HPLC-dedicated AflaOchra-Test HPLC™ (Vicam™) and Afla-OtaCLEAN™ (LC-Tech) immunoaffinity columns, followed by absorption/fluorescence detection. Millet samples which were fortified with both OTA (50 µg kg(-1)) and AFB1 (20 µg kg(-1)), gave recovery values of 100 ± 6% for OTA, and 110 ± 10% for AFB1, using AflaOchra-Test HPLC™. Single OTA clean-up and quantification in wine samples was obtained, using an OchraTest immunoaffinity column (Vicam™), reaching a detection limit of 0.3 µg L(-1) and recovery values between 80% and 120%. These results demonstrated the possibility of employing a single clean-up and a cost-effective, and easy to use analytical system for both AFB1 and OTA detection at µg kg(-1) (ppb) level. Furthermore, in the case of positive samples, they could be analysed further, using standard chromatographic procedures, without any additional clean-up step, since the same extraction procedure of standard method is proposed in our method., (Copyright © 2015 Elsevier B.V. All rights reserved.)

We report a sensor for phosphate detection based on screen-printed electrodes modified with carbon black nanoparticles. The phosphate was measured in amperometric mode via electrochemical reduction of molybdophosphate complex. Carbon black nanoparticles demonstrated the ability to quantify the molybdophosphate complex at a low applied potential. Some analytical parameters such as the working solution (sulfuric acid 0.1M), applied potential (0.125V vs Ag/AgCl), and molybdate concentration (1mM) were optimized. Using these conditions, a linear range of 0.5-100µM was observed with a detection limit of 0.1µM, calculated as three times the standard deviation of the blank divided by the slope of calibration curve. The system was challenged in drinking, river, aquarium, and waste water samples yielding satisfactory recovery values in accordance with a spectrophotometric reference method which demonstrated the suitability of the screen-printed electrode modified with carbon black nanoparticles coupled with the use of molybdate to detect phosphate in water samples., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A simple graphical method for the determination of reversible inhibition type, inhibition constant (Ki) and estimation of fifty percent of inhibition I₅₀ of an enzyme reaction is described. The method consists of plotting experimental data as "degree of inhibition" versus the inhibitor concentration at two or more concentrations of substrate. Diagnosis of inhibition type is based on determination of and the observation of the shift of the inhibition curves. Relationship between I50 and inhibition constant Ki was discussed. A simplified hyperbolae equation of degree of inhibition showing kinetic orders of 1 and zero at low and high concentrations of inhibitors respectively is proposed. The relative error of inhibitor concentration increased drastically when degree of inhibition reached values of 90%. Examples of published inhibition reports as well as an experimental example of amperometric biosensor based on tyrosinase inhibition by benzoic acid were in agreement with the proposed theoretical approach., (© 2013 Published by Elsevier B.V.)

In this paper we propose the construction and application of a portable multi-purpose biosensor array for the simultaneous detection of a wide range of endocrine disruptor chemicals (EDCs), based on the recognition operated by various enzymes and microorganisms. The developed biosensor combines both electrochemical and optical transduction systems, in order to increase the number of chemical species which can be monitored. Considering to the maximum residue level (MRL) of contaminants established by the European Commission, the biosensor system was able to detect most of the chemicals analysed with very high sensitivity. In particular, atrazine and diuron were detected with a limit of detection of 0.5nM, with an RSD% less than 5%; paraoxon and chlorpyrifos were revealed with a detection of 5 μM and 4.5 μM, respectively, with an RSD% less than 6%; catechol and bisphenol A were identified with a limit of detection of 1 μM and 35 μM respectively, with an RSD% less than 5%., (Copyright © 2012 Elsevier B.V. All rights reserved.)

This work reports the optimisation of a new analytical method for lead ion detection in milk; the electrochemical detection scheme is based on the method that was described in Part I. It features the use of a disposable, environmentally friendly bismuth film electrode to replace the traditionally used (toxic) mercury one while here we report an arduous development of sample treatment so that the simple device can be applied as a screening tool in many settings. For this purpose, a milk pre-treatment procedure by means of wet digestion with HCl, HClO(4), and H(2)O(2) combined with an ultrasonic treatment was developed. The detection of lead ions in treated milk was then carried out using a disposable screen-printed electrode modified with Nafion(®) and an "in situ" bismuth film, with the analysis being performed in anodic stripping voltammetry mode. The analytical method developed allows the detection of milk contaminated with lead ions at a concentration of 20 μg Kg(-1) (legal limit) and it can be proposed as a screening method for routine analysis of lead ions in milk with the advantage of employing inexpensive and portable instrumentation. Moreover, dedicated software supported by a portable instrument introduces procedures that are essential to avoid distortion from ambient lead contamination and also makes it possible for an unskilled operator to carry out each step of the analysis., (Copyright © 2012 Elsevier B.V. All rights reserved.)

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 +410 mV 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 0.86 ppb and 4.2 ppb for Paraoxon and Dichlorvos, respectively, while the extension of the linear range was up 23 ppb for the former pesticide and up to 33 ppb 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., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Lead determination was carried out in the frame of the European Union project Biocop (www.biocop.org) using a bismuth-modified screen-printed electrode (Bi-SPE) and the stripping analysis technique. In order to choose a sensitive Bi-SPE for lead detection, an analytical comparative study of electrodes modified by Bi using "in situ", "ex situ" and "bulk" procedures was carried out. On the basis of the results obtained, we confirmed that the "in situ" procedure resulted in better analytical performances with respect to not only "ex situ" but also to "Bi(2)O(3) bulk" modified electrodes, allowing for a linear range of lead ion concentration from 0.5 to 100 μg L(-1) and a detection limit of 0.15 μg L(-1). We demonstrated that, before the Bi film deposition, an oxidative electrochemical pre-treatment of the working electrode could be useful because it eliminates traces of lead in the graphite-ink, as shown with stripping measurements. It also improves the electrochemical performance of the electrodes as demonstrated with Electrochemical Impedance Spectroscopy (EIS) measurements. The influence of different analytical parameters, such as the electrolyte solution composition (acetate buffer, chloridric acid, nitric acid, perchloric acid) and the ionic strength was investigated in order to evaluate how to treat the sample before the analysis. The morphology of prepared "in situ" Bi-SPEs was also characterized by Atomic Force Microscopy (AFM). Finally, the Bi-SPEs were used to determine the concentration of lead ions in tap and commercial water samples obtaining satisfactory values of the recovery percentage (81% and 98%)., (Copyright © 2011 Elsevier B.V. All rights reserved.)

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 5-50 ppb of paraoxon and 2-50 ppb of malaoxon with detection limits of 3 and 2 ppb, respectively (incubation 15 min). 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 © 2011 Elsevier B.V. All rights reserved.)

E-DNA sensors are a reagentless, electrochemical oligonucleotide sensing platform based on a redox-tag modified, electrode-bound probe DNA. Because E-DNA signaling is linked to hybridization-linked changes in the dynamics of this probe, sensor performance is likely dependent on the nature of the self-assembled monolayer coating the electrode. We have investigated this question by characterizing the gain, specificity, response time and shelf-life of E-DNA sensors fabricated using a range of co-adsorbates, including both charged and neutral alkane thiols. We find that, among the thiols tested, the positively charged cysteamine gives rise to the largest and most rapid response to target and leads to significantly improved storage stability. The best mismatch specificity, however, is achieved with mercaptoethanesulfonic and mercaptoundecanol, presumably due to the destabilizing effects of, respectively, the negative charge and steric bulk of these co-adsorbates. These results demonstrate that a careful choice of co-adsorbate chemistry can lead to significant improvements in the performance of this broad class of electrochemical DNA sensors.

A bienzyme electrochemical probe has been assembled and used to monitor the inhibition of the enzyme protein phosphatase-2A (PP2A) by okadaic acid (OA), taking advantage of the particular characteristics of a biochemical pathway in which PP2A is involved. This enzyme has significant activity toward glycogen phosphorylase a (PHOS a), which in turn catalyzes the conversion of glycogen to glucose-1-phosphate (G-1-P). In addition, PP2A is strongly inhibited by OA and its derivatives. Due to this combination of properties, PP2A was employed to develop an assay system involving a preliminary phase of off-line enzymatic incubations (OA/PP2A, PP2A/PHOS a, PHOS a/glycogen+phosphate). This off-line step was followed by the electrochemical detection of H2O2, which is the final product of two sequential enzymatic reactions: G-1-P with alkaline phosphatase (AP) producing glucose, then glucose with glucose oxidase (GOD) producing hydrogen peroxide. These two enzymes were coimmobilized on a nylon net membrane that was placed over an H2O2 platinum probe inserted into a flow injection analysis (FIA) system. During a first phase of the study, all analytical parameters were optimized. During a subsequent phase, the inhibition of PP2A enzyme by OA was evaluated. The calibration of the system shows a working range for detection of OA between 30 and 250 pg ml(-1). The total analysis time is the sum of 50 min for the off-line enzymatic incubations and 4 min for the biosensor response.

In the present paper, a comparative study using Co-phthalocyanine and Prussian Blue-modified screen-printed electrodes, has been performed. Both the electrodes have demonstrated an easiness of preparation together with high sensitivity towards thicoholine (LOD=5 x 10(-7) and 5 x 10(-6) M for Co-phthalocyanine and Prussian Blue, respectively) with high potentialities for pesticide measurement. Prussian Blue-modified screen-printed electrodes were then selected for successive enzyme immobilization due to their higher operative stability demonstrated in previous works. AChE and BChE enzymes were used and inhibition effect of different pesticides was studied with both the enzymes. AChE-based biosensors have demonstrated a higher sensitivity towards aldicarb (50% inhibition with 50 ppb) and carbaryl (50% inhibition with 85 ppb) while BChE biosensors have shown a higher affinity towards paraoxon (50% inhibition with 4 ppb) and chlorpyrifos-methyl oxon (50% inhibition with 1 ppb). Real samples were also tested in order to evaluate the matrix effect and recovery values comprised between 79 and 123% were obtained.

This paper reports the assembly of a disposable immunosensor based on the direct competitive enzyme-linked immunosorbent assay (ELISA), for simple and fast measurement of 17beta-estradiol (17beta-E2) in bovine serum, using screen-printed electrodes (SPEs) and a Palm-Sens portable electrochemical detector. The immunosensor strip was assembled immobilising, by passive adsorption, anti-rabbit IgG onto the surface of the working SPE electrode. After the interaction between anti-rabbit IgG and rabbit anti-17beta-E2 polyclonal antibodies (PAb), the competition was performed using 17beta-estradiol-alkaline phosphatase conjugate (17beta-E2-AP) synthesised in our laboratory. The enzymatic substrate used for signal generation was 1-naphthylphosphate and its conversion to an electroactive product (1-naphthol) was measured using differential pulse voltammetry (DPV). To develop a prototype for field measurements, the entire competitive protocol has been optimised directly in a blank non-extracted bovine serum. According to the new EU criteria established by the Commission Decision 2002/657/EC for qualitative and quantitative screening methods, the detection capability (CCbeta), was determined. The CCbeta value resulted below the action limit (40 pg mL(-1)) fixed for 17beta-E2) Spiked and real samples were analysed using the electrochemical immunostrips obtaining precision values (relative standard deviation, R.S.D.%) ranging from 8.6 to 17.0% and a recovery (R%) from 88.2 to 120.0%. Results obtained on real samples were confirmed by liquid chromatography coupled on-line with tandem mass spectrometry (LC-MS/MS) using an atmospheric pressure chemical ionisation (APCI) source and a heated nebulizer (HN) interface; this is the method currently used to confirm illegal hormone administration for regulatory purposes. The disposable immunosensor appears suitable as a screening tool for field analysis of bovine serum estradiol.

Detection of phosphate using amperometry was investigated. The phosphomolybdate complex, formed by addition of nitric acid, ammonium molybdate and phosphate, was reduced at a carbon paste electrode polarised at +0.3V (versus Ag/AgCl). The major characteristics observed were simplicity of the equipment, a limited consumption of reagents and a low detection limit (0.3mumoll(-1)), with a linear range between 1 and 20mumoll(-1). The interference of silicate was completely eliminated using an appropriate concentration of nitric acid and ammonium molybdate. The amperometric detection of orthophosphate in seawater using the batch injection analysis (BIA) technique was reported. Moreover, a carbon paste microelectrode was constructed. Its use allows the analysis of small volume of samples with little dilution in supporting electrolyte. This method was applied to the determination of orthophosphate in cyanobacterial biofilms collected from Roman catacombs. There was a good statistical correlation between results obtained with the proposed method and the standard spectrophotometric method.

Electropolymerisation of nonconducting polymer, poly-(1,2-diaminobenzene) on the top of Prussian Blue (PB) modified electrode led to significant improvement of resulting hydrogen peroxide transducer selectivity and operational stability. The reported transducer retained 100% of response during 20 h under the continuous flow of 0.1 mM H(2)O(2), and thus improves the stability level in selective peroxide detection by one order of magnitude. The selectivity value of the PB-poly(1,2-DAB) based H(2)O(2) sensor in relation to ascorbate is approximately 600. No signals to acetaminophen and urate were investigated. PB-poly(1,2-diaminobenzene) modified electrode allows the detection of H(2)O(2) in the flow-injection mode down to 10(-7) M with the sensitivity 0.3 A M(-1) cm(-2), which is only two times lower compared to the uncovered PB based transducer.

An enzyme-based flow-injection amperometric analysis system (FIA) for monitoring of uric acid and glucose is described. The oxidase and peroxidase enzymes are physically coimmobilised in a sandwich-type reactor and ferrocene serves as a mediator. The assays are based on the measurement of a reduction current resulting from the enzymatic reactions, at a glassy carbon electrode held at 0.00 mV (vs. Ag/AgCl). The high selectivity (ascorbic acid did not interfere) is coupled to high sensitivity (a detection limit of 30 and 60 nmol/l for uric acid and glucose, respectively; signal/noise = 3) and good stability (the enzymes remained active for more than 6 weeks at 30 degrees C). The usefulness of the assay in clinical chemistry is illustrated by the measurement of human serum uric acid and glucose concentration. The results obtained were in fairly good agreement with those obtained using conventional hospital laboratory methods.

Amperometric enzyme electrode probes have been constructed for the specific determination of L-lysine and used in batch and flow analysis. The enzyme lysine oxidase was immobilized on a preactivated polymer support which was placed on a platinum electrode. Additional blocking membranes conferred high stability, reproducibility and avoided electrochemical and enzyme interferences. Parameters including pH, temperature, storage and operational times were optimized. Lysine was determined in the range 10(-6)-2.10(-3)M with a detection limit of 5 x 10(-7)M. The Michaelis constant was 2 x 10(-3)M. This value was approximately two order of magnitudes higher than that reported in literature for the free enzyme. The response time of the probe was about 2 min in batch and flow analysis and 30 sec in flow injection analysis (FIA). The resulting probes were stable for more than three months with more than 300 analyses performed. The determination of lysine was carried out by both flow-through analysis and FIA. Analysis in feeds was carried out by acid hydrolysis to liberate lysine; then the solution was analyzed by the bioprobe and HPLC procedures. Results by the two methods correlated well.

Microdialysis probes have been tested to evaluate the influence of flow-rate, probe dimensions and temperature when used as sampling systems inserted subcutaneously for in vivo monitoring of glucose. The probe was coupled with a glucose biosensor obtained from a thin layer electrochemical cell generally used as detector for liquid chromatography. Glucose oxidase was immobilized on a nylon net membrane and it was placed over an acetate cellulose membrane into the cell in contact with the platinum anode.