Gabriele Favero

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.

Nanostructured enzymatic biosensor based on fullerene and gold nanoparticles: Preparation, characterization and analytical applications

In this work a novel electrochemical biosensing platform based on the coupling of two different nanostructured materials (gold nanoparticles and fullerenols) displaying interesting electrochemical features, has been developed and characterized. Gold nanoparticles (AuNPs) exhibit attractive electrocatalytic behavior stimulating in the last years, several sensing applications; on the other hand, fullerene and its derivatives are a very promising family of electroactive compounds although they have not yet been fully employed in biosensing. The methodology proposed in this work was finalized to the setup of a laccase biosensor based on a multilayer material consisting in AuNPs, fullerenols and Trametes versicolor Laccase (TvL) assembled layer by layer onto a gold (Au) electrode surface. The influence of different modification step procedures on the electroanalytical performance of biosensors has been evaluated. Cyclic voltammetry, chronoamperometry, surface plasmon resonance (SPR) and scanning tunneling microscopy (STM) were used to characterize the modification of surface and to investigate the bioelectrocatalytic biosensor response. This biosensor showed fast amperometric response to gallic acid, which is usually considered a standard for polyphenols analysis of wines, with a linear range 0.03-0.30 mmol L(-1) (r(2)=0.9998), with a LOD of 0.006 mmol L(-1) or expressed as polyphenol index 5.0-50 mg L(-1) and LOD 1.1 mg L(-1). A tentative application of the developed nanostructured enzyme-based biosensor was performed evaluating the detection of polyphenols either in buffer solution or in real wine samples.

New biosensor for superoxide radical used to evidence molecules of biomedical and pharmaceutical interest having radical scavenging properties

A superoxide dismutase biosensor was used to determine the antioxidant properties of scavenger molecules and the antiradical activity of healthy and diseased human kidney tissues; this biosensor is based on the use of the enzyme superoxide dismutase (SOD), which is physically entrapped in a kappa-carrageenan gel membrane, and of a transducer consisting of an amperometric hydrogen peroxide electrode. Several compounds with scavenging properties were tested, including some commercial drugs.

Kinetic and biochemical properties of high and low redox potential laccases from fungal and plant origin

The electrochemical studies of laccase-mediator systems are aimed at understanding the mechanism of their redox transformation and their efficiency in both homogeneous and heterogeneous reactions; this topic has paramount application spanning from bleaching of paper pulp and the enzymatic degradation of lignin to the biosensors and biofuel cell development. In this paper four different laccases from Trametes hirsuta (ThL), Trametes versicolor (TvL), Melanocarpus albomyces (r-MaL) and Rhus vernicifera (RvL) were characterized from both biochemical and electrochemical points of view. Two of them (TvL and ThL) are high redox potential and two (RvL and r-MaL) are low redox potential laccases. The outline of this work is focused on the determination of catalytic and bioelectrochemical properties of these four enzymes in homogenous solution as well as immobilized onto electrode surface in the presence of a set of different redox mediators. The results measured in the homogenous reaction system correlated well with those measured with the immobilized enzymes. In addition, they are in good agreement with those reported with reference techniques, suggesting that the electrochemical methods employed in this work can be applied well in place of the traditional techniques commonly used for the kinetic characterization of laccases. These results are also discussed in terms of the known amino acid sequences and three-dimensional (3D) structures of the laccases.

The effect of organic solvent properties on the response of a tyrosinase enzyme sensor

The use of an enzyme tyrosinase sensor capable of being employed in non aqueous media represents a good opportunity to investigate the effects of the organic solvent on enzyme activity. Six different solvents are considered (n-heptane, n-hexane, n-pentane, toluene, chloroform, acetonitrile) and two properties of these solvents are studied in particular, i.e. hydrophobicity (as log P) and dielectric constant, taking into account their influence on sensor response. Results are generally in agreement with those found by other authors, who determined the behaviour of the enzyme activity as a function of organic solvents using different methods.

Membrane supported bilayer lipid membranes array: preparation, stability and ion-channel insertion

Abstract In the present paper we describe the preparation and characterization of reconstituted bilayer lipid membranes (BLM) supported on a polycarbonate membrane. BLMs self-assemble on the holes of the membrane, which was previously covered with Au and an octadecanethiol (ODT) self-assembled monolayer (SAM). The obtained mixed hybrid bilayer lipid membranes (MHBLM) array allows recording of relatively intense signals. The steps leading to formation of the system have been investigated, its stability determined and reproducibility evaluated. The insertion of an ion channel (Gramicidin D) and a K + carrier (Valinomycine) was also evaluated.

Superoxide dismutase biosensors for superoxide radical analysis

ABSTRACT Some basic work has been performed on the development and optimisation of superoxide dismutase (SOD) biosensors for superoxide radical analysis. Initially we studied the possibility of obtaining a SOD biosensor using the Clark electrode as indicating sensor. However, the best results were obtained using as indicator a classical amperometric electrode for H2O2. In both cases the superoxide radical was generated in situ using the xanthine/xanthine oxidase (XOD) enzyme system, while the SOD was immobilised in kappa-carrageenan gel. The first application was realised by studying the effects in vitro on the superoxide radical of some molecules commonly accepted as radical scavengers.

Organophosphorus pesticide (Paraoxon) analysis using solid state sensors

A comparison of two new solid-state biosensors for organophosphorus pesticide analysis is presented, both of which employ the inhibiting action of these toxic compounds versus the enzyme butyrylcholinesterase. The indicating sensor used was a graphite electrode, or a FET, coated with an ion-selective polymeric membrane sensitive to pH containing tridodecylamine as exchanger. The former was coupled to the enzyme butyrylcholinesterase immobilised on a functionalized nylon net, while the latter employed the same enzyme coated on the polymeric membrane by means of polyazetidine prepolymer. The responses of the two biosensors to the substrate, i.e. butyrylcholine (BuCh), and to the inhibitor, i.e. Paraoxon, one of the most common organophosphorus pesticides, were tested.

Electron‐Transfer Kinetics of Microperoxidase‐11 Covalently Immobilised onto the Surface of Multi‐Walled Carbon Nanotubes by Reactive Landing of Mass‐Selected Ions

Controlled deposition of biological molecules on nanostructured materials is a basic step towards the realisation of biochip components. In this study we report the investigation of the first covalent immobilisation of mass-selected redox protein on a carboxyl-functionalised multi-walled carbon nanotube (MWCNT) electrode surface by means of ion soft landing. The immobilised protein maintains its biochemical properties, displaying an excellent electrochemical behaviour on the electrode surface. The deposition of mass-selected ions is influenced by several factors, including the charge state and the collision energy of the projectile ions. To elucidate the mechanism involved in the protein reactive landing onto the MWCNT surface, the data obtained from cyclic voltammetry experiments were modelled according to the Marcus theory. The proposed method opens up the way to the development of a new generation of biocomponents with potential use in biosensors, diagnostics, biofuel cells and bioactive films.

A modified amperometric electrode for the determination of free radicals

Abstract In this paper we describe a new electrochemical system able to detect superoxide radicals produced by an enzymatic reaction: the system is based on the reduction of cytochrome c due to the superoxide radical produced in the oxidation reaction of xanthine catalysed by the xanthine oxidase; then the reduced form of the cytochrome is electrochemically detected. Measurements are carried out using first cyclic voltammetry, and then a true carbon paste electrode having cytochrome c as mediator and Fe(III)–protoporphyrin as promoter for continuous superoxide radical determination working at constant applied potential is also proposed.