Screen-printed electrodes for biosensing: a review (2008–2013)

Screen-printing is one of the most promising approaches towards simple, rapid and inexpensive production of biosensors. Disposable biosensors based on screen printed electrodes (SPEs) including microelectrodes and modified electrodes have led to new possibilities in the detection and quantitation of biomolecules, pesticides, antigens, DNA, microorganisms and enzymes. SPE-based sensors are in tune with the growing need for performing rapid and accurate in-situ analyses and for the development of portable devices. This review (with 226 refs.) first gives an introduction into the topic and then is subdivided into sections (a) on DNA sensors (including methods for the detection of hybridization and damage), (b) on aptasensors (for thrombin, OTA, immunoglobulins and cancer biomarkers), (c) on immunosensors (for microorganisms, immunoglobulins, toxins, hormones, lactoferrin and biomarkers), (d) on enzymatic biosensors (for glucose, hydrogen peroxide, various pharmaceuticals, neurotransmitters, amino acids, NADH, enzyme based sensors).

Electrochemical biosensing based on noble metal nanoparticles

The interest in the fabrication of electrochemical biosensors with high sensitivity, selectivity and efficiency is rapidly growing. In recent years, noble metal nanoparticles (NMNPs), with extraordinary conductivity, large surface-to-volume ratio and biocompatibility, have been extensively employed for developing novel electrochemical sensing platforms and improving their performances. Through distinct surface modification strategies (e.g. self-assembly, layer-by-layer, hybridization and sol-gel technology), NMNPs provide well control over the microenvironment of biological molecules retaining their activity, and facilitate the electron transfer between the redox center of biomolecules and electrode surface. Moreover, NMNPs have been involved into biorecognition events (e.g. immunoreactions, DNA hybridization and ligand-receptor interactions) by conjugating with various biomolecules, chemical labels and other nanomaterials, achieving the signal transduction and amplification. The aim of this review is to summarize different strategies for NMNP-based signal amplification, as well as to provide a snapshot of recent advances in the design of electrochemical biosensing platforms, including enzyme/protein sensors focused on their direct electrochemistry on NMNP-modified electrode surface; immunosensors and gene sensors in which NMNPs not only participate into biorecognition, but also act as electroactive tags to enhance the signal output. In addition, NMNP alloy-based multifunctional electrochemical biosensors are briefly introduced in terms of their unique heterostructures and properties.

Electrochemical sensing of hydrogen peroxide using metal nanoparticles: a review

We are reviewing the state of electrochemical sensing of H₂O₂ based on the use of metal nanoparticles. The article is divided into subsections on sensors based on nanoparticles made from Ag, Pt, Pd, Cu, bimetallic nanoparticles and other metals. Some sensors display high sensitivity, fast response, and good stability. The review is subdivided into sections on sensors based on heme proteins and on nonenzymatic sensors. We also discussed the challenges of nanoscaled sensors and their future aspects.

Carbon nanotubes and graphene in analytical sciences

Nanosized carbon materials are offering great opportunities in various areas of nanotechnology. Carbon nanotubes and graphene, due to their unique mechanical, electronic, chemical, optical and electrochemical properties, represent the most interesting building blocks in various applications where analytical chemistry is of special importance. The possibility of conjugating carbon nanomaterials with biomolecules has received particular attention with respect to the design of chemical sensors and biosensors. This review describes the trends in this field as reported in the last 6?years in (bio)analytical chemistry in general, and in biosensing in particular.

Field-deployable whole-cell bioluminescent biosensors: so near and yet so far

The use of smart supports and bioinspired materials to confine living cells and use them for field-deployable biosensors has recently attracted much attention. In particular, bioluminescent whole-cell biosensors designed to respond to different analytes or classes of analyte have been successfully implemented in portable and cost-effective analytical devices. Significant advances in detection technology, biomaterial science, and genetic engineering of cells have recently been reported. Now the challenge is to move from benchtop traditional cell-based assays to portable biosensing devices. Improvement of the analytical performance of these biosensors depends on the availability of optimized bioluminescent reporters, and promising approaches that go beyond reporter gene technology are emerging. To enable handling of cells as ready-to-use reagents, nature-inspired strategies have been used, with the objective of keeping cells in a dormant state until use. Several issues must still be investigated, for example long-term viability of cells, the possibility of performing real-time analysis, and multiplexing capability.

Layered-double-hydroxide-modified electrodes: electroanalytical applications

Two-dimensional inorganic solids, such as layered double hydroxides (LDHs), also defined as anionic clays, have open structures and unique anion-exchange properties which make them very appropriate materials for the immobilization of anions and biomolecules that often bear an overall negative charge. This review aims to describe the important aspects and new developments of electrochemical sensors and biosensors based on LDHs, evidencing the research from our own laboratory and other groups. It is intended to provide an overview of the various types of chemically modified electrodes that have been developed with these 2D layered materials, along with the significant advances made over the last several years. In particular, we report the main methods used for the deposition of LDH films on different substrates, the conductive properties of these materials, the possibility to use them in the development of membranes for potentiometric anion analysis, the early analytical applications of chemically modified electrodes based on the ability of LDHs to preconcentrate redox-active anions and finally the most recent applications exploiting their electrocatalytic properties. Another promising application field of LDHs, when they are employed as host structures for enzymes, is biosensing, which is described considering glucose as an example.

Poly(ethylene oxide)–poly(ethylene imine) block copolymers as templates and catalysts for the in situ formation of monodisperse silica nanospheres

Block copolymers based on poly(ethylene oxide) (PEO) and poly(ethylene imine) (PEI) are efficient catalysts/templates for the formation of uniform silica nanoparticles. Addition of tetraethylorthosilicate to a solution of PEO–PEI or PEI–PEO–PEI block copolymers results in the formation of silica particles with a diameter of ca. 30 nm and narrow size distribution. The particles precipitated with the diblock copolymers can be redispersed in water after isolation as individual nanoparticles. Evidently, block copolymers based on PEO and PEI serve as excellent templates for the biomimetic and “soft” synthesis of silica nanoparticles.

Hybrid and biohybrid layered double hydroxides for electrochemical analysis

Layered double hydroxides (LDH) are lamellar materials that have been extensively used as electrode modifiers. Nanostructured organic–inorganic materials can be designed by intercalation of organic or metallic complexes within the interlayer space of these materials or by the formation of composite materials based on biopolymers (alginate or chitosan) or biomolecules, such as enzymes. These hybrid or biohybrid materials have interesting properties applicable in electroanalytical devices. From an exhaustive review of the literature, the relevance of these hybrid and biohybrid LDH materials as electrode materials for electrochemical detection of species with an environmental or health impact is evaluated. The analytical characteristics (sensitivity and detection limit) of LDH-based amperometric sensors or biosensors are scrutinized.

Enhanced electrochemical evolution of oxygen by using nanoflowers made from a gold and iridium oxide composite

We report on the synthesis of a composite made from iridium oxide and gold that has a flower-like morphology. The ratio of iridium oxide to gold can be controlled by altering the concentrations of the metal precursors or the pH of the solution containing the reductant citrate. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and laser confocal micro-Raman spectroscopy were applied to characterize the structures of the nanoflowers, and a mechanism of their formation was deduced. The nanoflowers display an electrocatalytic activity in an oxygen evolution reaction (OER) that is significantly enhanced compared to bare iridium oxide nanoparticles. The highest turnover frequency for the OER of the new nanoflowers is 10.9?s^?1, which is almost one order of magnitude better than that of the respective nanoparticles. These attractive features are attributed to the high oxidation states of iridium in the nanoflowers which is caused by the transfer of electronic charge from metal oxides to gold, and also to the flower fractal structure which is thought to provide a much more accessible surface than suspensions of the respective nanoparticle.

Conducting polymer composites with graphene for use in chemical sensors and biosensors

This review (with 79 references) summarizes the recent work on the development of chemical sensors and biosensors based on the use of composites made from conducting polymers (CPs) and graphene. Owing to the unique electrical, mechanical, optical, chemical and structural properties of CP and graphene, these kinds of composites have generated increasing interest in senor field. In this review, we first discuss methods for preparation of CP/GE composites by chemical, electrochemical, or physical methods including electrostatic interactions. We then cover aspects of the fabrication of modified electrodes and the performance of respective sensors with electrochemical, electronic or optical signal transduction. We then discuss sensors for the determination of inorganic and organic species, gases and vapors. We also review the state of the art in respective biosensors for hydrogen peroxide and glucose, for oligomers (DNA, RNA, and aptamers), for biogenic amines, NAD^+/NADH, cytochromes and the like, and in immunosensors. Finally, the perspective and current challenges of CP/GE composites for use in (bio)sensors are outlooked.

Colorimetric and bare-eye detection of alkaline earth metal ions based on the aggregation of silver nanoparticles functionalized with thioglycolic acid

We describe a simple and rapid method for colorimetric and bare-eye detection of the alkaline earth metal ions Mg(II), Ca(II), Sr(II) and Ba(II) based on the use of silver nanoparticles (AgNPs) functionalized with thioglycolic acid (TGA). The TGA ligand was self-assembled onto the AgNPs to form a probe that undergoes a color change from yellow to orange or red on exposure to the alkaline earth ions. It is presumed that the color change is a result of the aggregation of the AgNPs caused by the interaction of the bivalent ions with the carboxy groups on the AgNPs. The color change can be used for bare-eye and colorimetric determination of the alkaline earth metal ions, for example to rapidly determine water hardness.

A hydrogen peroxide biosensor based on direct electron transfer from hemoglobin to an electrode modified with Nafion and activated nanocarbon

A biosensor for hydrogen peroxide (HP) was developed by immobilizing hemoglobin on a glassy carbon electrode modified with activated carbon nanoparticles/Nafion. The characteristics of the sensor were studied by UV?Cvis spectroscopy and electrochemical methods. The immobilized Hb retained its native secondary structure, undergoes direct electron transfer (with a heterogeneous rate constant of 3.37?±?0.5?s^?1), and displays excellent bioelectrocatalytic activity to the reduction of HP. Under the optimal conditions, its amperometric response varies linearly with the concentration of HP in the range from 0.9???M to 17???M. The detection limit is 0.4???M (at S/N?=?3). Due to the commercial availability and low cost of activated carbon nanoparticles, it can be considered as a useful supporting material for construction of other third-generation biosensors.

Plasmonic nanoprobes for intracellular sensing and imaging

Recent advances in integrating nanotechnology and optical microscopy offer great potential in intracellular applications with improved molecular information and higher resolution. Continuous efforts in designing nanoparticles with strong and tunable plasmon resonance have led to new developments in biosensing and bioimaging, using surface-enhanced Raman scattering and two-photon photoluminescence. We provide an overview of the nanoprobe design updates, such as controlling the nanoparticle shape for optimal plasmon peak position; optical sensing and imaging strategies for intracellular nanoparticle detection; and addressing practical challenges in cellular applications of nanoprobes, including the use of targeting agents and control of nanoparticle aggregation.

Highly sensitive and selective voltammetric detection of mercury(II) using an ITO electrode modified with 5-methyl-2-thiouracil, graphene oxide and gold nanoparticles

We have developed an electrochemical sensor for highly selective and sensitive determination of Hg(II). It is based on the specific binding of 5-methyl-2-thiouracil (MTU) and Hg(II) to the surface of an indium tin oxide (ITO) electrode modified with a composite made from graphene oxide (GO) and gold nanoparticles (AuNPs). This leads to a largely enhanced differential pulse voltammetric response for Hg(II). Following optimization of the method, a good linear relationship (R?=?0.9920) is found between peak current and the concentration of Hg(II) in the 5.0–110.0 nM range. The limit of detection (LOD) is 0.78 nM at a signal-to-noise ratio of 3. A study on the interference by several metal ions revealed no interferences. The feasibility of this method was demonstrated by the analyses of real water samples. The LODs are 6.9, 1.0 and 1.9 nM for tap water, bottled water and lake water samples, respectively, and recoveries for the water samples spiked with 8.0, 50.0 and 100.0 nM were 83.9–96.8 %, with relative standard deviations ranging from 3.3 % to 5.2 %.

Centri-voltammetry and biocentri-voltammetry: a review

Centri-voltammetry and biocentri-voltammetry are techniques that combine centrifugation with voltammetry. This review covers (a) definitions; (b) experimental (cell) configurations; (c) effects of centrifugation parameters; and (d) applications of the method to the determination of heavy metals and biological molecules. Specific examples include applications to the determination of xanthine, acetylcholine esterase activity, and of acetyl choline.

Direct electron transfer and biocatalytic activity of iron storage protein molecules immobilized on electrodeposited cobalt oxide nanoparticles

Ferritin was immobilized on a glassy carbon electrode with electrodeposited cobalt oxide nanoparticles, and its direct electron transfer behavior was studied. It exhibits a pair of redox peaks due to direct electron transfer between ferritin and the nanoparticles. Electrochemical parameters including the formal potential (E^0??), the charge transfer coefficient (??), and the apparent heterogeneous electron transfer rate constant (k_s) were determined. The sensor displays excellent biocatalytic activity in terms of reduction of hydrogen peroxide, and this was applied to electrochemical sensing of hydrogen peroxide.

Electrochemical sensors based on graphene materials

Single?Clayered graphene, emerging as a true two?Cdimensional nanomaterial, has tremendous potential for electrochemical catalysis and biosensing as a novel electrode material. Considering the excellent properties of graphene, such as large surface?Cto?Cvolume ratio, high conductivity and electron mobility at room temperature, low energy dynamics of electrons with atomic thickness, robust mechanical and flexibility, we give a general view of recent advances in electrochemical sensors based on graphene. We are highlighting here important applications of graphene and graphene nanocomposites, and the assay strategies in electrochemical sensors for DNA, proteins, neurotransmitters, phytohormones, pollutants, metal ions, gases, hydrogen peroxide, and in medical, enzymatic and immunosensors.

Sensitive detection of tuberculosis using nanoparticle-enhanced surface plasmon resonance

We show that the antigen CFP-10 (found in tissue fluids of tuberculosis patients) can be used as a marker protein in a surface-plasmon resonance (SPR) based method for early and simplified diagnosis of tuberculosis. A sandwich SPR immunosensor was constructed by immobilizing the CFP-10 antibody on a self-assembled monolayer on a gold surface, this followed by blocking it with bovine serum albumin. Following exposure of the sensor surface to a sample containing CFP-10, secondary antibody immobilized on nickel oxide nanoparticles are injected which causes a large SPR signal change. The method has a dynamic range from 0.1 to around 150 ng per mL of CFP-10, and a detection limit as low as 0.1 ng per mL. This is assumed to be due to the high amplification power of the NiO nanoparticles.

A colorimetric method for the determination of lead(II) ions using gold nanoparticles and a guanine-rich oligonucleotide

We have developed a colorimetric method for the determination of Pb(II) ions. It is based on the use of gold nanoparticles and a guanine-rich synthetic oligonucleotide. On addition of Pb(II), the color of the solution turns from red to blue. The ratio of the UV-vis absorption at 630?nm and 525?nm is proportional to the concentration of Pb(II) ions in the range from 10 to 100?nM, and the detection limit is 20?nM. Other metal ions do not interfere if present in up to a 10-fold molar excess. The method was successfully applied to the detection of Pb(II) in lake water and urine. The recovery in case of spiked samples is 92%. The results show that this method is sensitive, simple and fast.

Glucose biosensor based on a platinum electrode modified with rhodium nanoparticles and with glucose oxidase immobilized on gold nanoparticles

We have developed an enzymatic glucose biosensor that is based on a flat platinum electrode which was covered with electrophoretically deposited rhodium (Rh) nanoparticles and then sintered to form a large surface area. The biosensor was obtained by depositing glucose oxidase (GOx), Nafion, and gold nanoparticles (AuNPs) on the Rh electrode. The electrical potential and the fractions of Nafion and GOx were optimized. The resulting biosensor has a very high sensitivity (68.1 μA mM^?1 cm^?2) and good linearity in the range from 0.05 to 15 mM (r?=?0.989). The limit of detection is as low as 0.03 mM (at an SNR of 3). The glucose biosensor also is quite selective and is not interfered by electroactive substances including ascorbic acid, uric acid and acetaminophen. The lifespan is up to 90 days. It was applied to the determination of glucose in blood serum, and the results compare very well with those obtained with a clinical analyzer.