Riccarda Antiochia

Beyond graphene : Electrochemical sensors and biosensors for biomarkers detection

Graphenes success has stimulated great interest and research in the synthesis and characterization of graphene-like 2D materials, single and few-atom-thick layers of van der Waals materials, which show fascinating and technologically useful properties. This review presents an overview of recent electrochemical sensors and biosensors based on graphene and on graphene-like 2D materials for biomarkers detection. Initially, we will outline different electrochemical sensors and biosensors based on chemically derived graphene, including graphene oxide and reduced graphene oxide, properly functionalized for improved performances and we will discuss the various strategies to prepare graphene modified electrodes. Successively, we present electrochemical sensors and biosensors based on graphene-like 2D materials, such as boron nitride (BN), graphite-carbon nitride (g-C3N4), transition metal dichalcogenides (TMDs), transition metal oxides and graphane, outlining how the new modified 2D nanomaterials will improve the electrochemical performances. Finally, we will compare the results obtained with different sensors and biosensors for the detection of important biomarkers such as glucose, hydrogen peroxide and cancer biomarkers and highlight the advantages and disadvantages of the use of graphene and graphene-like 2D materials in different sensing platforms.

Amperometric Mediated Carbon Nanotube Paste Biosensor for Fructose Determination

Abstract A new mediated carbon nanotube paste (CNTP) amperometric biosensor for fructose is described. The biosensor is formed by a CNTP electrode modified with an electropolymerized film of 3,4‐dihydroxybenzaldehyde (3,4‐DHB) and is based on the activity of a commercial available D‐fructose dehydrogenase (FDH) immobilized on an immobilon membrane placed on the top of the electrode surface. Analytical parameters such as enzyme immobilization, pH, temperature, and probe lifetime were studied and optimized. The biosensor response current was directly proportional to D‐fructose concentration from 5 × 10−6 to 2 × 10−3 mol/L with a detection limit of 1 × 10−6 mol/L and a good reproducibility (RSD = 1.8%, n = 5). The biosensor was used for the determination of fructose content in three honey samples and validated with a commercial spectrophotometric enzymatic kit.

Alcohol biosensor based on the immobilization of meldola blue and alcohol dehydrogenase into a carbon nanotube paste electrode

Abstract The preparation and electrochemical characterization of a new carbon nanotube paste (CNTP) amperometric biosensor for ethanol is described. The biosensor is formed by a CNTP electrode modified with the phenoxazine compound Meldola Blue (MB) as mediator. It shows a good electrocatalytic activity towards NADH oxidation at potentials around 0.0 V vs. Ag/AgCl, which represents a strong diminution in the overpotential. The biosensor is based on the activity of a commercially available alcohol dehydrogenase enzyme (ADH) and is realized by co‐immobilizing the enzyme ADH, the coenzyme NAD+, and the mediator into the paste. Analytical parameters such as enzyme, co‐enzyme and mediator immobilization concentration, pH, temperature, and probe lifetime are studied and optimized. The biosensor yields a linear response to 1×10−7 –4×10−6 mol/L ethanol at an operating potential of +50 mV (vs. Ag/AgCl), where interfering reactions do not occur, with a detection limit of 1×10−7 mol/L and a good reproducibility (RSD of 2.8%, n=6). Application of the biosensor to the determination of ethanol in alcoholic beverages was achieved successfully.

Rapid and direct determination of fructose in food: A new osmium-polymer mediated biosensor

This paper describes the development and performance of a new rapid amperometric biosensor for fructose monitoring in food analysis. The biosensor is based on the activity of fructose dehydrogenase (FDH) immobilised into a carbon nanotube paste electrode according to two different procedures. The direct wiring of the FDH in a highly original osmium-polymer hydrogel was found to offer a better enzyme entrapment compared to the immobilisation of the enzyme in an albumin hydrogel. The optimised biosensor required only 5U of FDH and kept the 80% of its initial sensitivity after 4months. During this time, the biosensor showed a detection limit for fructose of 1μM, a large linear range between 0.1 and 5mM, a high sensitivity (1.95μAcm(-2)mM), good reproducibility (RSD=2.1%) and a fast response time (4s). Finally, the biosensor was applied for specific determination of fructose in honey, fruit juices, soft and energy drinks. The results indicated a very good agreement with those obtained with a commercial reference kit. No significant interference was observed with the proposed biosensor.

NMR methodologies in the analysis of blueberries.

An NMR analytical protocol based on complementary high and low field measurements is proposed for blueberry characterization. Untargeted NMR metabolite profiling of blueberries aqueous and organic extracts as well as targeted NMR analysis focused on anthocyanins and other phenols are reported. Bligh‐Dyer and microwave‐assisted extractions were carried out and compared showing a better recovery of lipidic fraction in the case of microwave procedure. Water‐soluble metabolites belonging to different classes such as sugars, amino acids, organic acids, and phenolic compounds, as well as metabolites soluble in organic solvent such as triglycerides, sterols, and fatty acids, were identified. Five anthocyanins (malvidin‐3‐glucoside, malvidin‐3‐galactoside, delphinidin‐3‐glucoside, delphinidin‐3‐galactoside, and petunidin‐3‐glucoside) and 3‐O‐α‐l‐rhamnopyranosyl quercetin were identified in solid phase extract. The water status of fresh and withered blueberries was monitored by portable NMR and fast‐field cycling NMR. 1H depth profiles, T2 transverse relaxation times and dispersion profiles were found to be sensitive to the withering.

Untargeted NMR-Based Methodology in the Study of Fruit Metabolites

In this review, fundamental aspects of the untargeted NMR-based methodology applied to fruit characterization are described. The strategy to perform the structure elucidation of fruit metabolites is discussed with some examples of spectral assignments by 2D experiments. Primary ubiquitous metabolites as well as secondary species-specific metabolites, identified in different fruits using an untargeted 1H-NMR approach, are summarized in a comprehensive way. Crucial aspects regarding the quantitative elaboration of spectral data are also discussed. The usefulness of the NMR-based metabolic profiling was highlighted using some results regarding quality, adulteration, varieties and geographical origin of fruits and fruit-derived products such as juices.

Bubble electrodeposition of gold porous nanocorals for the enzymatic and non-enzymatic detection of glucose.

Au nanocorals are grown on gold screen-printed electrodes (SPEs) by using a novel and simple one-step electrodeposition process. Scanning electron microscopy was used for the morphological characterization. The devices were assembled on a three-electrode SPE system, which is flexible and mass producible. The electroactive surface area, determined by cyclic voltammetry in sulphuric acid, was found to be 0.07±0.01cm(2) and 35.3±2.7cm(2) for bare Au and nanocoral Au, respectively. The nanocoral modified SPEs were used to develop an enzymatic glucose biosensor based on H2O2 detection. Au nanocoral electrodes showed a higher sensitivity of 48.3±0.9μA/(mMcm(2)) at +0.45V vs Ag|AgCl compared to a value of 24.6±1.3μA/(mMcm(2)) at +0.70V vs Ag|AgCl obtained with bare Au electrodes. However, the modified electrodes have indeed proven to be extremely powerful for the direct detection of glucose with a non-enzymatic approach. The results confirmed a clear peak observed by using nanocoral Au electrode even in the presence of chloride ions at physiological concentration. Amperometric study carried out at +0.15V vs Ag|AgCl in the presence of 0.12M NaCl showed a linear range for glucose between 0.1 and 13mM.

A Tri-Enzyme Electrode Probe for the Sequential Determination of Fructose and Glucose in the Same Sample

Abstract A new probe for the determination of fructose and glucose has been assembled using a platinum electrode and three enzymes co-immobilized on its surface: fructose dehydrogenase, glucose dehydrogenase and diaphorase. The mechanism of this probe is very simple: when the probe is immersed in a solution containing fructose and glucose and an electrochemical mediator, the current signal is due to the fructose. Then, by adding NAD(P)+ a current response due to the glucose present in solution is obtained. Analytical parameters such as pH, buffer, temperature, concentration of mediator and ratio of the three enzymes co-immobilized have been optimised. Probe stability and reproducibility have been evaluated. Calibration curves for fructose and glucose have been constructed and all analytical parameters optimized. The linear range for both fructose and glucose was from 5×10−6 to 2×10−4 mol/L and the detection limit was 1×10−7 mol/L. The probe has been used to determine the concentration of fructose and gluc...

AuNPs-functionalized PANABA-MWCNTs nanocomposite-based impedimetric immunosensor for 2,4-dichlorophenoxy acetic acid detection.

In this work, we developed an impedimetric label-free immunosensor for the detection of 2,4-Dichlorophenoxy Acetic Acid (2,4-D) herbicide either in standard solution and spiked real samples. For this purpose, we prepared by electropolymerization a conductive polymer poly-(aniline-co-3-aminobenzoic acid) (PANABA) then we immobilized anti-2,4-D antibody onto a nanocomposite AuNPs-PANABA-MWCNTs employing the carboxylic moieties as anchor sites. The nanocomposite was synthesized by electrochemical polymerization of aniline and 3-aminobenzoic acid, in the presence of a dispersion of gold nanoparticles, onto a multi-walled carbon nanotubes-based screen printed electrode. Aniline-based copolymer, modified with the nanomaterials, allowed to enhance the electrode conductivity thus obtaining a more sensitive antigen detection. The impedimetric measurements were carried out by electrochemical impedance spectroscopy (EIS) in faradic condition by using Fe(CN)63-/4- as redox probe. The developed impedimetric immunosensor displayed a wide linearity range towards 2,4-D (1-100ppb), good repeatability (RSD 6%), stability and a LOD (0.3ppb) lower than herbicide emission limits.

Kinetic and thermodynamic aspects of NAD-related enzyme-linked mediated bioelectrocatalysis

The diaphorase-catalyzed electrochemical oxidation of NADH with the aid of quinones (MAP) or ferrocene derivatives (FMCA) as electron transfer mediators was studied by cyclic voltammetry under variable conditions of concentration polarization of NADH near the electrode surface. The suppression of this polarization was obtained by the redox L-lactate dehydrogenase-catalyzed reaction between L-lactate and NAD+. The addition of pyruvate inhibits the formation of NADH owing to the thermodynamically unfavorable (uphill) electron transfer from L-lactate to NAD+. The role played by the uphill/downhill character of the last step of the catalytic chain was illustrated by regenerating NADH using the redox couple gluconolactone/glucose with glucose dehydrogenase as catalyst. The influence on the catalytic wave of the presence of a downhill or uphill step between diaphorase and NAD+/NADH couple was also rationalized via the digital simulation technique using experimental data reported in the literature.