Nickel nanoparticle–chitosan-reduced graphene oxide-modified screen-printed electrodes for enzyme-free glucose sensing in portable microfluidic devices

Electrodeposition of reduced graphene oxide with chitosan based on the coordination deposition method

The electrodeposition of graphene has drawn considerable attention due to its appealing applications for sensors, supercapacitors and lithium-ion batteries. However, there are still some limitations in the current electrodeposition methods for graphene. Here, we present a novel electrodeposition method for the direct deposition of reduced graphene oxide (rGO) with chitosan. In this method, a 2-hydroxypropyltrimethylammonium chloride-based chitosan-modified rGO material was prepared. This material disperses homogenously in the chitosan solution, forming a deposition solution with good dispersion stability. Subsequently, the modified rGO material was deposited on an electrode through codeposition with chitosan, based on the coordination deposition method. After electrodeposition, the homogeneous, deposited rGO/chitosan films can be generated on copper or silver electrodes or substrates. The electrodeposition method allows for the convenient and controlled creation of rGO/chitosan nanocomposite coatings and films of different shapes and thickness. It also introduces a new method of creating films, as they can be peeled completely from the electrodes. Moreover, this method allows for a rGO/chitosan film to be deposited directly onto an electrode, which can then be used for electrochemical detection.

Electrochemical nonenzymatic sensing of glucose using advanced nanomaterials

An overview (with 376 refs.) is given here on the current state of methods for electrochemical sensing of glucose based on the use of advanced nanomaterials. An introduction into the field covers aspects of enzyme based sensing versus nonenzymatic sensing using nanomaterials. The next chapter cover the most commonly used nanomaterials for use in such sensors, with sections on uses of noble metals, transition metals, metal oxides, metal hydroxides, and metal sulfides, on bimetallic nanoparticles and alloys, and on other composites. A further section treats electrodes based on the use of carbon nanomaterials (with subsections on carbon nanotubes, on graphene, graphene oxide and carbon dots, and on other carbonaceous nanomaterials. The mechanisms for electro-catalysis are also discussed, and several Tables are given where the performance of sensors is being compared. Finally, the review addresses merits and limitations (such as the frequent need for working in strongly etching alkaline solutions and the need for diluting samples because sensors often have analytical ranges that are far below the glucose levels found in blood). We also address market/technology gaps in comparison to commercially available enzymatic sensors. Graphical Abstract Schematic representation of electrochemical nonenzymatic glucose sensing on the nanomaterials modified electrodes. At an applied potential, the nanomaterial-modified electrodes exhibit excellent electrocatalytic activity for direct oxidation of glucose oxidation.

Miniaturized high-performance liquid chromatography instrumentation

Miniaturized high performance liquid chromatography (HPLC) has attracted increasing attention for its potential in high-throughput analyses and point-of-care applications. In this review we highlight the recent advancements in HPLC system miniaturization. We focus on the major components that constitute these instruments along with their respective advantages and drawbacks as well as present a few representative miniaturized HPLC systems. We discuss briefly some of the applications and also anticipate the future development trends of these instrumental platforms.

Review of Electrochemically Triggered Macromolecular Film Buildup Processes and Their Biomedical Applications

Macromolecular coatings play an important role in many technological areas, ranging from the car industry to biosensors. Among the different coating technologies, electrochemically triggered processes are extremely powerful because they allow in particular spatial confinement of the film buildup up to the micrometer scale on microelectrodes. Here, we review the latest advances in the field of electrochemically triggered macromolecular film buildup processes performed in aqueous solutions. All these processes will be discussed and related to their several applications such as corrosion prevention, biosensors, antimicrobial coatings, drug-release, barrier properties and cell encapsulation. Special emphasis will be put on applications in the rapidly growing field of biosensors. Using polymers or proteins, the electrochemical buildup of the films can result from a local change of macromolecules solubility, self-assembly of polyelectrolytes through electrostatic/ionic interactions or covalent cross-linking between different macromolecules. The assembly process can be in one step or performed step-by-step based on an electrical trigger affecting directly the interacting macromolecules or generating ionic species.

Electrochemical microfluidic chip based on molecular imprinting technique applied for therapeutic drug monitoring

In this work, a novel electrochemical detection platform was established by integrating molecularly imprinting technique with microfluidic chip and applied for trace measurement of three therapeutic drugs. The chip foundation is acrylic panel with designed grooves. In the detection cell of the chip, a Pt wire is used as the counter electrode and reference electrode, and a Au-Ag alloy microwire (NPAMW) with 3D nanoporous surface modified with electro-polymerized molecularly imprinted polymer (MIP) film as the working electrode. Detailed characterization of the chip and the working electrode was performed, and the properties were explored by cyclic voltammetry and electrochemical impedance spectroscopy. Two methods, respectively based on electrochemical catalysis and MIP/gate effect were employed for detecting warfarin sodium by using the prepared chip. The linearity of electrochemical catalysis method was in the range of 5×10^-6-4×10^-4M, which fails to meet clinical testing demand. By contrast, the linearity of gate effect was 2×10^-11-4×10^-9M with remarkably low detection limit of 8×10^-12M (S/N=3), which is able to satisfy clinical assay. Then the system was applied for 24-h monitoring of drug concentration in plasma after administration of warfarin sodium in rabbit, and the corresponding pharmacokinetic parameters were obtained. In addition, the microfluidic chip was successfully adopted to analyze cyclophosphamide and carbamazepine, implying its good versatile ability. It is expected that this novel electrochemical microfluidic chip can act as a promising format for point-of-care testing via monitoring different analytes sensitively and conveniently.

In situ fabrication of Ni nanoparticles on N-doped TiO2 nanowire arrays by nitridation of NiTiO3 for highly sensitive and enzyme-free glucose sensing

A novel strategy for Ni NPs/TiO_xN_y NWAs by nitridation of NiTiO₃ NWAs is designed for highly sensitive and selective non-enzymatic glucose sensing.

Recent advancements, key challenges and solutions in non-enzymatic electrochemical glucose sensors based on graphene platforms

This review elucidates the recent advances in graphene platforms in electrochemical non-enzymatic glucose sensors and provides solutions for existing bottlenecks.

Ultra-fast and highly sensitive enzyme-free glucose biosensing on a nickel–nickel oxide core–shell electrode

Ultra-fast (∼1 s) and highly sensitive (1889.8 μA mM⁻¹ cm⁻²) enzyme-free glucose biosensing on a unique NiNiO core–shell electrode.

Nonenzymatic Glucose Sensor Based on In Situ Reduction of Ni/NiO-Graphene Nanocomposite

Ni/NiO nanoflower modified reduced graphene oxide (rGO) nanocomposite (Ni/NiO-rGO) was introduced to screen printed electrode (SPE) for the construction of a nonenzymatic electrochemical glucose biosensor. The Ni/NiO-rGO nanocomposite was synthesized by an in situ reduction process. Graphene oxide (GO) hybrid Nafion sheets first chemical adsorbed Ni ions and assembled on the SPE. Subsequently, GO and Ni ions were reduced by hydrazine hydrate. The electrochemical properties of such a Ni/NiO-rGO modified SPE were carefully investigated. It showed a high activity for electrocatalytic oxidation of glucose in alkaline medium. The proposed nonenzymatic sensor can be utilized for quantification of glucose with a wide linear range from 29.9 μM to 6.44 mM (R = 0.9937) with a low detection limit of 1.8 μM (S/N = 3) and a high sensitivity of 1997 μA/mM∙cm^-2. It also exhibited good reproducibility as well as high selectivity.

Graphene-based screen-printed electrochemical (bio)sensors and their applications: Efforts and criticisms

K.S. Novoselov in his Nobel lecture (December 8, 2010), described graphene as "more than just a flat crystal" and summarized the best possible impression of graphene with (i) it is the first example of 2D atomic crystals, (ii) it demonstrated unique electronic properties, thanks to charge carriers which mimic massless relativistic particles, and (iii) it has promise for a number of applications. The fascinating and unusual properties of this 2D material were indeed recently investigated and exploited in several disciplines including physics, medicine, and chemistry, indicating the extremely versatile and polyedric aspect of this nanomaterial. The utilization of nanomaterials, printed technology, and microfluidics in electroanalysis has resulted in a period that can be called the "Electroanalysis Renaissance" (Escarpa, 2012) in which graphene is without any doubt a forefront nanomaterial. The rise in affordable fabrication processes, along with the great dispersing attitude in a plenty of matrices, have made graphene powerful in large-scale production of electrochemical platforms. Herein, we overview the employment of graphene to customize and/or fabricate printable based (bio)sensors over the past 5 years, including several modification approaches such as drop casting, screen- and inkjet-printing, different strategies of graphene-based sensing, and applications as well. The objective of this review is to provide a critical perspective related to advantages and disadvantages of using graphene in biosensing tools, based on screen-printed sensors.

Non-enzymatic detection of glucose using poly(azure A)-nickel modified glassy carbon electrode

A simple, sensitive and selective non-enzymatic glucose sensor was constructed in this paper. The poly(azure A)-nickel modified glassy carbon electrode was successfully fabricated by the electropolymerization of azure A and the adsorption of Ni(2+). The Ni modified electrode, which was characterized by scanning electron microscope, cyclic voltammetry, electrochemical impedance spectra and X-ray photoelectron spectroscopy measurements, respectively, displayed well-defined current responses of the Ni(III)/Ni(II) couple and showed a good activity for electrocatalytic oxidation of glucose in alkaline medium. Under the optimized conditions, the developed sensor exhibited a broad linear calibration range of 5 μM-12mM for quantification of glucose and a low detection limit of 0.64μM (3σ). The excellent analytical performance including simple structure, fast response time, good anti-interference ability, satisfying stability and reliable reproducibility were also found from the proposed amperometric sensor. The results were satisfactory for the determination of glucose in human serum samples as comparison to those from a local hospital.

Electrodeposition of nickel nanoflowers on screen-printed electrodes and their application to non-enzymatic determination of sugars

Nickel nanoflowers were electrodeposited on screen-printed carbon electrodes for the non-enzymatic catalytic detection of sugars.

The effect of A-site doping in a strontium palladium perovskite and its applications for non-enzymatic glucose sensing

The catalytic activity of a strontium palladium perovskite, Sr₂PdO₃, toward non-enzymatic glucose sensing is strongly affected by the Sr²⁺ A-site partial substitution by Ca²⁺ ions; Sr_2−xCa_xPdO₃ with x = 0–0.7.

Electrochemical Imprinted Polycrystalline Nickel-Nickel Oxide Half-Nanotube-Modified Boron-Doped Diamond Electrode for the Detection of L-Serine

This paper presents a novel and versatile method for the fabrication of half nanotubes (HNTs) using a flexible template-based nanofabrication method denoted as electrochemical imprinting. With use of this method, polycrystalline nickel and nickel(II) oxide (Ni-NiO) HNTs were synthesized using pulsed electrodeposition to transfer Ni, deposited by radio frequency magnetron sputtering on a porous polytetrafluoroethylene template, onto a boron-doped diamond (BDD) film. The Ni-NiO HNTs exhibited semicircular profiles along their entire lengths, with outer diameters of 50-120 nm and inner diameters of 20-50 nm. The HNT walls were formed of Ni and NiO nanoparticles. A biosensor for the detection of L-serine was fabricated using a BDD electrode modified with Ni-NiO HNTs, and the device demonstrated satisfactory analytical performance with high sensitivity (0.33 μA μM(-1)) and a low limit of detection (0.1 μM). The biosensor also exhibited very good reproducibility and stability, as well as a high anti-interference ability against amino acids such as L-leucine, L-tryptophan, L-cysteine, L-phenylalanine, L-arginine, and L-lysine.

Highly Sensitive Detection and Removal of Lead Ions in Water Using Cysteine-Functionalized Graphene Oxide/Polypyrrole Nanocomposite Film Electrode

We synthesized cysteine-functionalized graphene oxide (sGO) using carbonyldiimidazole as a cross-linker via amide and carbamate linkages. The sGO/polypyrrole (PPy) nanocomposite film was grown on the working electrode surface of a screen-printed electrode (SPE) via controlled one-step electrochemical deposition. The sGO/PPy-SPE was used to detect lead ions (Pb(2+)) in water by first depositing Pb(2+) on the working electrode surface for 10 min at -1.2 V, and then anodic stripping by differential pulse voltammetry (DPV). The DPV signals were linear in the ranges of 1.4-28 ppb (R(2) = 0.994), 28-280 ppb (R(2) = 0.997), and 280-14 000 ppb (R(2) = 0.990) Pb(2+). The measurable detection limit of the sensor is 0.07 ppb (S/N = 3), which is more than 2 orders of magnitude below the 10 ppb threshold for drinking water set by the World Health Organization. The average removal efficiency of Pb(2+) deposited on the electrode was 99.2% (S/N = 3), with relative standard deviation (RSD) of 3.8%. Our results indicate good affinity of sGO/PPy nanocomposite to Pb(2+), which can be used to effectively adsorb and remove Pb(2+) in water samples. Therefore, sGO/PPy nanocomposite we synthesized is useful for highly sensitive on-site and real-time monitoring of heavy metal ions and water treatment.

Recent developments in blood glucose sensors

Diabetes has recently become a leading cause of death worldwide. To date, although there is no means to cure or prevent diabetes, appropriate medication and blood sugar monitoring can enhance treatment efficiency, alleviate the symptoms, and diminish the complications of the condition. This review article deals with current growth areas in the market for blood glucose sensors and possible future alternatives, which are generally considered to be the point sample test and the continuous glucose monitor (CGM). Most glucose sensors are enzyme-based, whereas others are enzyme-free. The former class is sensitive and some products are extensively employed for daily self-sensing and in hospital environments as reliable diagnostic tools. The latter class, particularly the boronic acid fluorescent sensor, is facile and extremely promising. Practicality demands that all types of sensors offer accuracy, specificity, and real-time detection.

A simple and sensitive method for determination of Norfloxacin in pharmaceutical preparations

<p>In this approach, a new voltammetric method for determination of norfloxacin was proposed with high sensitivity and wider detection linear range. The used voltammetric sensor was fabricated simply by coating a layer of graphene oxide (GO) and Nafion composited film on glassy carbon electrode. The advantage of proposed method was sensitive electrochemical response for norfloxacin, which was attributed to the excellent electrical conductivity of GO and the accumulating function of Nafion under optimum experimental conditions, the present method revealed a good linear response for determination of norfloxacin in the range of 1×10^-8mol/L-7×10^-6 mol/L with a detection limit of 5×10^-9 mol/L. The proposed method was successfully applied in the determination of norfloxacin in capsules with satisfactory results.</p>

Glycine-assisted synthesis of NiO hollow cage-like nanostructures for sensitive non-enzymatic glucose sensing

In this work, a highly sensitive non-enzymatic glucose sensor was developed based on NiO hollow cage-like nanostructures (NiO HCs).