The role of peptides in the design of electrochemical biosensors for clinical diagnostics

Peptides represent a promising class of biorecognition elements that can be coupled to electrochemical transducers. The benefits lie mainly in their stability and selectivity toward a target analyte. Furthermore, they can be synthesized rather easily and modified with specific functional groups, thus making them suitable for the development of novel architectures for biosensing platforms, as well as alternative labelling tools. Peptides have also been proposed as antibiofouling agents. Indeed, biofouling caused by the accumulation of biomolecules on electrode surfaces is one of the major issues and challenges to be addressed in the practical application of electrochemical biosensors. In this review, we summarise trends from the last three years in the design and development of electrochemical biosensors using synthetic peptides. The different roles of peptides in the design of electrochemical biosensors are described. The main procedures of selection and synthesis are discussed. Selected applications in clinical diagnostics are also described

The role of peptides in the design of electrochemical biosensors for clinical diagnostics

Peptides represent a promising class of biorecognition elements that can be coupled to electrochemical transducers. The benefits lie mainly in their stability and selectivity toward a target analyte. Furthermore, they can be synthesized rather easily and modified with specific functional groups, thus making them suitable for the development of novel architectures for biosensing platforms, as well as alternative labelling tools. Peptides have also been proposed as antibiofouling agents. Indeed, biofouling caused by the accumulation of biomolecules on electrode surfaces is one of the major issues and challenges to be addressed in the practical application of electrochemical biosensors. In this review, we summarise trends from the last three years in the design and development of electrochemical biosensors using synthetic peptides. The different roles of peptides in the design of electrochemical biosensors are described. The main procedures of selection and synthesis are discussed. Selected applications in clinical diagnostics are also described

Au Nanoparticles Decorated Graphene-Based Hybrid Nanocomposite for As(III) Electroanalytical Detection

Electrochemical sensors integrating hybrid nanostructured platforms are a promising alternative to conventional detection techniques for addressing highly relevant challenges of heavy metal determination in the environment. Hybrid nanocomposites based on graphene derivatives and inorganic nanoparticles (NPs) are ideal candidates as active materials for detecting heavy metals, as they merge the relevant physico-chemical properties of both the components, finally leading to a rapid and sensitive current response. In this work, a hybrid nanocomposite formed of reduced graphene oxide (RGO) sheets, surface functionalized by π-π interactions with 1-pyrene carboxylic acid (PCA), and decorated in situ by Au NPs, was synthesized by using a colloidal route. The hybrid nanocomposite was characterized by cyclic voltammetry and electrochemical impedance spectroscopy with respect to the corresponding single components, both bare and deposited as a layer-by-layer junction onto the electrode. The results demonstrated the high electrochemical activity of the hybrid nanocomposite with respect to the single components, highlighting the crucial role of the nanostructured surface morphology of the electrode and the PCA coupling agent at the NPs-RGO interphase in enhancing the nanocomposite electroactivity. Finally, the Au NP-decorated PCA-RGO sheets were tested by anodic stripping voltammetry of As(III) ion—a particularly relevant analyte among heavy metal ions—in order to assess the sensing ability of the nanocomposite material with respect to its single components. The nanocomposite has been found to present a sensitivity higher than that characterizing the bare components, with LODs complying with the directives established by the U.S. EPA and in line with those reported for state-of-the-art electrochemical sensors based on other Au-graphene nanocomposites

Amperometric separation-free immunosensor for real-time environmental monitoring

Immunoanalytical techniques have found widespread use due to the characteristics of specificity and wide applicability for many analytes, from large polymer antigens, to simple haptens, and even single atoms. Electrochemical sensors offer benefits of technical simplicity, speed and convenience via direct transduction to electronic equipment. Together, these two systems offer the possibility of a convenient, ubiquitous assay technique with high selectivity. However, they are still not widely used, mainly due to the complexity of the associated immunoassay methodologies. A separation-free immunoanalytical technique is described here, which has allowed for the analysis of atrazine in real time and in both quasi-equilibrium and stirred batch configurations. It illustrated that determinations as low as 0.13 muM (28 ppb) could be made using equilibrium incubation with an analytical range of 0.1-10 muM. Measurements could be made between 1 and 10 mM within several minutes using a real-time, stirred batch method. This system offers the potential for fast, simple, cost-effective biosensors for the analysis of many substances of environmental, biomedical and pharmaceutical concern. (C) 2001 Elsevier Science B.V. All rights reserved

Self-powered microneedle-based biosensors for pain-free high-accuracy measurement of glycaemia in interstitial fluid

In this work a novel self-powered microneedle-based transdermal biosensor for pain-free high-accuracy real-time measurement of glycaemia in interstitial fluid (ISF) is reported. The proposed transdermal biosensor makes use of an array of silicon-dioxide hollow microneedles that are about one order of magnitude both smaller (borehole down to 4 µm) and more densely-packed (up to 1×106 needles/cm2) than state-of-the-art microneedles used for biosensing so far. This allows self-powered (i.e. pump-free) uptake of ISF to be carried out with high efficacy and reliability in a few seconds (uptake rate up to 1 µl/s) by exploiting capillarity in the microneedles. By coupling the microneedles operating under capillary-action with an enzymatic glucose biosensor integrated on the back-side of the needle-chip, glucose measurements are performed with high accuracy (±20% of the actual glucose level for 96% of measures) and reproducibility (coefficient of variation 8.56%) in real-time (30 s) over the range 0–630 mg/dl, thus significantly improving microneedle-based biosensor performance with respect to the state-of-the-art

Enhanced performances of RGO-AuNPs hybrids towards electroanalytical applications

In recent years, lot of attention has been devoted to understanding the properties of hybrid nanocomposites, \u201cbrave new materials\u201d made of two or more organic and inorganic components. These systems show enhanced or novel physico-chemical properties with respect to the single components, resulting not only from the sum of the precursors\u2019 ones, but also from interactions occurring at their interface, the so-called \u201cheterojunction\u201d. However, a remaining challenge is to understand in depth the phenomena here originating. In the present work, to start fulfilling this gap, a deep electrochemical study of hybrids made of Reduced Graphene Oxide (RGO) and Au nanoparticles (NPs) is performed, analysing carefully the role played by each single component of the material on the electrochemical properties. In more details, RGO platforms are surface functionalized with 1-aminopyrene or 1-pyrene carboxylic acid that act as heteronucleation and growing sites of the amine- or thiol-coated Au NPs of different dimensions (from 3 to 20 nm). At first, Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) measurements are carried out in order to characterize the different hybrids. Then, the materials are applied as electroanalytical sensors for both organic and inorganic molecules (dopamine and As, respectively) with very promising results, comparable or even better than analogous systems reported in literature. Moreover, preliminary tests on H2O2 detection open the venue to the application of these materials in biosensor applications. The properties of the hybrid nanocomposite, enhanced with respect to those of the single components, are ascribed to charge transfer occurring at the heterojunction from the Au NPs to the RGO, assisted and channelled by the pyrene linker

Electrochemical Characterization and Electroanalytical Aplications of RGO_AuNPs Hybrids

A novel synthetic route for the synthesis of gold nanoparticles (AuNPs) modified graphene electrodes has been developed: Reduced Graphene Oxide (RGO) sheets are functionalized with pyrene linkers acting as growing sites for gold nanoparticles (AuNPs) of different dimensions (approximatively 5, 10 and 20 nm). The Au surface is functionalized with oleylamine or 3,4-dimethylbenzenethiol as capping agents. The hybrid material is deposited onto Carbon Screen Printed Electrodes (C-SPEs) for a deep physico-chemical and electrochemical characterization, using Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) measurements. The role played by every single hybrid counterpart has been investigated, showing a synergistic effect, which is responsible of the enhancement of the system properties. The charge transfer from gold nanoparticles to graphene, assisted and stimulated by the pyrene linker, seems to be the key point to understand the peculiarities of this innovative material. The as prepared RGO-AuNPs hybrids have been used in the electroanalytical detection of both inorganic and organic species (arsenic, H2O2, dopamine), showing promising results in terms of sensitivities and detection limits. In particular, regarding the detection of the neurotransmitter dopamine by means of Differential Pulse Voltammetry in Phosphate Buffer Solution, a LOD of (3.3 \ub1 0.2) ppb has been reached, comparable with other electroanalytical results in the literature and in accordance with the benchmark for this molecule [1]. For arsenic detection, the hybrid devices show increased performances in comparison with bare gold or gold NPs, also allowing speciation between arsenic (III) and (V), appropriately adjusting the experimental conditions. In the case of H2O2, the hybrid devices display high electrocatalytic activity and fast electron-transfer kinetics, representing an ideal platform for developing oxidoreductase-based electrochemical biosensors as well as for detecting H2O2 in real samples. [1] J.A. Ribeiro, P.M.V. Fernandes, C.M. Pereira, F. Silva, Talanta 160 (2016) 653-679

TiO2 Nanocrystals Decorated CVD Graphene for Electroanalytical Sensing

In this work, the manufacturing and characterization of an optically transparent and UV-light photoactive anode, formed of monolayer graphene grown by chemical vapor deposition (CVD) and decorated with a close packed multilayered nanostructured layout of colloidal TiO2 nanocrystals (NCs), are reported. The hybrid material has been prepared by a facile solution-based procedure, which relays on soaking the CVD graphene in a solution of 1-pyrene butyric acid (PBA) surface coated TiO2 NCs, achieved upon implementation of a capping exchange process for displacing the pristine organic ligand deriving from the colloidal synthesis. Pyrene undergoes \u3c0-\u3c0 stacking interactions, anchoring the NCs to the platform with retention of the NC geometry and composition. The NCs immobilize onto the graphene platform with preservation of its aromatic structure and the resulting hybrid has been found optically transparent in the visible spectral range. (Photo)electrochemical investigation shows that the composite material has a promising sensitivity for selectively detecting dopamine and norepinephrine and, concomitantly, exhibits a (photo)electric activity higher than that of bare graphene. Thus, the achieved hybrid material results interesting for the manufacturing of photo-active components to integrate in photo-renewable sensor elements along with photodetectors and solar cells

Functional Hybrids of Multilayer CVD Graphene and Colloidal Anatase Nanocrystals

UV-light photoactive hybrids based on CVD graphene (from 1 to 5 layers) decorated with TiO2 nanocrystals (NC) surface functionalized with 1-pyrene butyric acid (PBA), were prepared by a simple solution-based procedure. PBA functionalization was obtained by a capping exchange procedure onto pre-synthesized organic-capped NCs [1]. An in-depth physico-chemical characterization demonstrated the successful immobilization of the colloidal NCs on the graphene multilayers, which preserves or even enhances the graphene intrinsic structural properties: the electrical conductivity is higher than that measured for bare graphene, due to a p-doping effect, related to a hole transfer from the nano-objects to graphene, mediated by the short aromatic ligand acting as a charge channel. The hybrids properties are strongly dependent on the number of layers of CVD graphene. The use of two redox probes [inner-sphere, surface sensitive (K4Fe(CN)6) and outer-sphere, surface insensitive (Ru(NH3)6Cl3)], in a CV and EIS study, allowed to understand these features, showing a strong difference between the mono-, the bi- and the other multi-layers, in terms of different diffusional mechanism and redox active sites [2]. Moreover, the stacked layers of the pyrene-coated TiO2 NCs are found to increase the electroactivity, the capacitive behavior, as well as the photo-electrical response of graphene, concomitantly maintaining its high charge mobility. The photoelectrical conversion of the hybrid is enhanced of 50% with respect to the bare graphene, with a long recombination lifetime of the photogenerated electron-hole pairs. For all the above reasons, the photoactive composite has a great potential as an optically transparent component for manufacturing photoanodes to be integrated in solar cells or photodetectors and in FETs or (photo)electrochemical sensors, also exploiting the possibility of photorenovating the sensor surface [3]. [1] C. Ingrosso et al., ACS Appl. Mater. & Interfaces 7 (2015) 4151-4159. [2] D.A. Brownson, D.K. Kampouris, C.E. Banks, Chem. Soc. Rev. 41 (2012) 6944-6976. [3] V. Pifferi et al., Anal. Bioanal. Chem. 408(26) (2016), 7339-7349