New electrode architectures based on poly(methylene green) and functionalized carbon nanotubes: Characterization and application to detection of acetaminophen and pyridoxine

Binary and Ternary Deep Eutectic Solvents for Methylene Green Electropolymerization on Multiwalled Carbon Nanotubes: Optimization, Characterization and Application

Choline chloride (ChCl) based binary and ternary deep eutectic solvents (DES) were evaluated for methylene green electropolymerization with oxalic acid (OA) and ethylene glycol (EG) as hydrogen bond donors. Binary DES ChCl : OA in molar ratios 1 : 1 and 2 : 1 and ChCl : EG 1 : 2 and ternary DES (tDES) in different molar ratios and percentages of water were evaluated. The highest polymer growth was in ChCl : OA : EG-tDES with 13% added water, that had a lower viscosity and higher ionic conductivity when associated with HCl as dopant. This enhanced the formation of more cation radicals and, consequently, more polymer formation. The PMG/MWCNT/GCE-tDES sensor was successfully applied to the simultaneous determination of 5-aminosalicylic acid (5-ASA) and acetaminophen (APAP) by differential pulse voltammetry in the concentration range 1 μM-200 μM, with detection limits of 0.37 μM and 0.49 μM for 5-ASA and APAP, respectively. The sensor demonstrated good repeatability, reproducibility and stability, and was successfully applied in pharmaceutical formulations.

Electrochemical DNA-Sensor Based on Macrocyclic Dendrimers with Terminal Amino Groups and Carbon Nanomaterials

The assembling of thiacalix[4]arene-based dendrimers in cone, partial cone, and 1,3-alternate configuration on the surface of a glassy carbon electrode coated with carbon black or multiwalled carbon nanotubes has been characterized using cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. Native and damaged DNA were electrostatically accumulated on the modifier layer. The influence of the charge of the redox indicator and of the macrocycle/DNA ratio was quantified and the roles of the electrostatic interactions and of the diffusional transfer of the redox indicator to the electrode interface indicator access were established. The developed DNA sensors were tested on discrimination of native, thermally denatured, and chemically damaged DNA and on the determination of doxorubicin as the model intercalator. The limit of detection of doxorubicin established for the biosensor based on multi-walled carbon nanotubes was equal to 1.0 pM with recovery from spiked human serum of 105-120%. After further optimization of the assembling directed towards the stabilization of the signal, the developed DNA sensors can find application in the preliminary screening of antitumor drugs and thermal damage of DNA. They can also be applied for testing potential drug/DNA nanocontainers as future delivery systems.

Martin D, Zebda A. Electrochemical Biosensing of Glucose Based on the Enzymatic Reduction of Glucose

In this work, the enzyme aldehyde reductase, also known as aldose reductase, was synthesized and cloned from a human gene. Spectrophotometric measurements show that in presence of the nicotinamide adenine dinucleotide phosphate cofactor (NADPH), the aldehyde reductase catalyzed the reduction of glucose to sorbitol. Electrochemical measurements performed on an electrodeposited poly(methylene green)-modified gold electrode showed that in the presence of the enzyme aldehyde reductase, the electrocatalytic oxidation current of NADPH decreased drastically after the addition of glucose. These results demonstrate that aldehyde reductase is an enzyme that allows the construction of an efficient electrochemical glucose biosensor based on glucose reduction.

Dicyandiamide-assisted HKUST-1 derived Cu/N-doped porous carbon nanoarchitecture for electrochemical detection of acetaminophen

MOFs-derived metal/carbon materials have been considered as promising candidates for the electrochemical detection of micropollutants. However, the aggregation of metal nanoparticles and structure collapse of precursor MOFs during pyrolysis significantly hamper the improvement on detecting performance. Herein, a dicyandiamide-assisted strategy is utilized to synthesize well-dispersed Cu/N-doped porous carbon nanoarchitecture (CuNC) for the electrochemical detection of acetaminophen (AP). The constructed CuNC sensor exhibits excellent electro-analytical performance for monitoring AP with linear range from 0.01 μM to 921.2 μM, and the low detection limit of 2.46 nM (S/N = 3). The improved performance of CuNC sensor is ascribed to the introduction of dicyandiamide, which can prevent HKUST-1 framework breakage and reduce the aggregation tendency of Cu, leading to the evenly distributed small Cu nanoparticles, abundant N species, hierarchical channel structure, and high conductivity carbon framework. These advantages endow predominant repeatability, stability, and selectivity of CuNC sensor. This strategy provided a novel approach to preparing MOFs-derived carbon nanoarchitectures with excellent electroanalysis performance to monitor micropollutants.

Polyphenazine and polytriphenylmethane redox polymer/nanomaterial-based electrochemical sensors and biosensors: a review

In recent years, an increasing number of studies has demonstrated that redox polymers can be used in simple and effective electrochemical sensing platforms due to their fast electron transfer and electrocatalytic ability. To develop more sensitive and selective electrochemical (bio)sensors, the electrocatalytic properties of redox polymers and the electrical, mechanical, and catalytic properties of various nanomaterials are combined. This review aims to summarize and contribute to the development of (bio)sensors based on polyphenazine or polytriphenylmethane redox polymers combined with nanomaterials, including carbon-based nanomaterials, metal/metal oxide, and semiconductor nanoparticles. The synthesis, preparation, and modification of these nanocomposites is presented and the contribution of each material to the performance of (bio)sensor has been be examined. It is explained how the combined use of these redox polymers and nanomaterials as a sensing platform leads to improved analytical performance of the (bio)sensors. Finally, the analytical performance characteristics and practical applications of polyphenazine and polytriphenylmethane redox polymer/nanomaterial-based electrochemical (bio)sensors are compared and discussed.

Hybrid Nanocomposite Platform, Based on Carbon Nanotubes and Poly(Methylene Blue) Redox Polymer Synthesized in Ethaline Deep Eutectic Solvent for Electrochemical Determination of 5-Aminosalicylic Acid

A novel hybrid composite of conductive poly(methylene blue) (PMB) and carbon nanotubes (CNT) was prepared for the detection of 5-aminosalicylic acid (5-ASA). Electrosynthesis of PMB with glassy carbon electrode (GCE) or with carbon nanotube modified GCE was done in ethaline deep eutectic solvent of choline chloride mixed with ethylene glycol and a 10% v/v aqueous solution. Different sensor architectures were evaluated in a broad range of pH values in a Britton-Robinson (BR) buffer using electrochemical techniques, chronoamperometry (CA), and differential pulse voltammetry (DPV), to determine the optimum sensor configuration for 5-ASA sensing. Under optimal conditions, the best analytical performance was obtained with CNT/PMB_DES/GCE in 0.04 M BR buffer pH 7.0 in the range 5-100 µM 5-ASA using the DPV method, with an excellent sensitivity of 9.84 μA cm^-2 μM^-1 (4.9 % RSD, n = 5) and a detection limit (LOD) (3σ/slope) of 7.7 nM, outclassing most similar sensors found in the literature. The sensitivity of the same sensor obtained in CA (1.33 μA cm^-2 μM^-1) under optimal conditions (pH 7.0, E_app = +0.40 V) was lower than that obtained by DPV. Simultaneous detection of 5-ASA and its analogue, acetaminophen (APAP), was successfully realized, showing a catalytic effect towards the electro-oxidation of both analytes, lowering their oxidation overpotential, and enhancing the oxidation peak currents and peak-to-peak separation as compared with the unmodified electrode. The proposed method is simple, sensitive, easy to apply, and economical for routine analysis.

Biosensors in Drug Discovery and Drug Analysis

Background:

The determination of drugs in pharmaceutical formulations and human biologic fluids is important for pharmaceutical and medical sciences. Successful analysis requires low sensitivity, high selectivity and minimum interference effects. Current analytical methods can detect drugs at very low levels but these methods require long sample preparation steps, extraction prior to analysis, highly trained technical staff and high-cost instruments. Biosensors offer several advantages such as short analysis time, high sensitivity, real-time analysis, low-cost instruments, and short pretreatment steps over traditional techniques. Biosensors allow quantification not only of the active component in pharmaceutical formulations, but also the degradation products and metabolites in biological fluids. The present review gives comprehensive information on the application of biosensors for drug discovery and analysis. Moreover, this review focuses on the fabrication of these biosensors.

Methods:

Biosensors can be classified as the utilized bioreceptor and the signal transduction mechanism. The classification based on signal transductions includes electrochemical optical, thermal or acoustic. Electrochemical and optic transducers are mostly utilized transducers used for drug analysis. There are many biological recognition elements, such as enzymes, antibodies, cells that have been used in fabricating of biosensors. Aptamers and antibodies are the most widely used recognition elements for the screening of the drugs. Electrochemical sensors and biosensors have several advantages such as low detection limits, a wide linear response range, good stability and reproducibility. Optical biosensors have several advantages such as direct, real-time and label-free detection of many biological and chemical substances, high specificity, sensitivity, small size and low cost. Modified electrodes enhance sensitivity of the electrodes to develop a new biosensor with desired features. Chemically modified electrodes have gained attention in drug analysis owing to low background current, wide potential window range, simple surface renewal, low detection limit and low cost. Modified electrodes produced by modifying of a solid surface electrode via different materials (carbonaceous materials, metal nanoparticles, polymer, biomolecules) immobilization. Recent advances in nanotechnology offer opportunities to design and construct biosensors. Unique features of nanomaterials provide many advantages in the fabrication of biosensors. Nanomaterials have controllable chemical structures, large surface to volume ratios, functional groups on their surface. To develop proteininorganic hybrid nanomaterials, four preparation methods have been used. These methods are immobilization, conjugation, crosslinking and self-assembly. In the present manuscript, applications of different biosensors, fabricated by using several materials, for drug analysis are reviewed. The biosensing strategies are investigated and discussed in detail.

Results:

Several analytical techniques such as chromatography, spectroscopy, radiometry, immunoassays and electrochemistry have been used for drug analysis and quantification. Methods based on chromatography require timeconsuming procedure, long sample-preparation steps, expensive instruments and trained staff. Compared to chromatographic methods, immunoassays have simple protocols and lower cost. Electrochemical measurements have many advantages over traditional chemical analyses and give information about drug quantity, metabolic fate of drugs, and pharmacological activity. Moreover, the electroanalytical methods are useful to determine drugs sensitively and selectivity. Additionally, these methods decrease analysis cost and require low-cost instruments and simple sample pretreatment steps.

Conclusion:

In recent years, drug analyses are performed using traditional techniques. These techniques have a good detection limit, but they have some limitations such as long analysis time, expensive device and experienced personnel requirement. Increased demand for practical and low-cost analytical techniques biosensor has gained interest for drug determinations in medical sciences. Biosensors are unique and successful devices when compared to traditional techniques. For drug determination, different electrode modification materials and different biorecognition elements are used for biosensor construction. Several biosensor construction strategies have been developed to enhance the biosensor performance. With the considerable progress in electrode surface modification, promotes the selectivity of the biosensor, decreases the production cost and provides miniaturization. In the next years, advances in technology will provide low cost, sensitive, selective biosensors for drug analysis in drug formulations and biological samples.

An ultra-sensitive electrochemical sensor for the detection of acetaminophen in the presence of etilefrine using bimetallic Pd–Ag/reduced graphene oxide nanocomposites

In this study we report a one-step procedure for the fabrication of Pd–Ag bimetallic nanoparticles on the surface of a graphene oxide (rGO) support.

Electrochemical carbon based nanosensors: A promising tool in pharmaceutical and biomedical analysis

Nanotechnology has become very popular in the sensor fields in recent times. It is thought that the utilization of such technologies, as well as the use of nanosized materials, could well have beneficial effects for the performance of sensors. Nano-sized materials have been shown to have a number of novel and interesting physical and chemical properties. Low-dimensional nanometer-sized materials and systems have defined a new research area in condensed-matter physics within past decades. Apart from the aforesaid categories of materials, there exist various materials of different types for fabricating nanosensors. Carbon is called as a unique element, due to its magnificent applications in many areas. Carbon is an astonishing element that can be found many forms including graphite, diamond, fullerenes, and graphene. This review provides an overview of some of the important and recent developments brought about by the application of carbon based nanostructures to nanotechnology for both chemical and biological sensor development and their application in pharmaceutical and biomedical area.

Highly sensitive interference-free electrochemical determination of pyridoxine at graphene modified electrode: Importance in Parkinson and Asthma treatments

To reduce the side effects in the medication of Parkinson and Asthma, pyridoxine (PY) is administered along with l-3,4-dihydroxyphenyl alanine (l-dopa) and theophylline (TP), respectively. However, excessive dosage of PY leads to nervous disorder. Thus, a sensitive and selective electrochemical method was developed for the determination of PY in the presence of major interferences including TP, l-dopa, ascorbic acid (AA) and riboflavin (RB) using electrochemically reduced graphene oxide (ERGO) film modified glassy carbon electrode (GCE) in this paper. The ERGO fabrication process involves the nucleophilic substitution of graphene oxide at basic pH on amine terminal of 1,6-hexadiamine which was pre-assembled on GCE followed by electrochemical reduction. The electrocatalytic activity of the ERGO modified electrode was examined towards the oxidation of PY. It greatly enhanced the oxidation current of PY in contrast to bare and GO modified GCEs due to facile electron transfer besides π-π interaction between ERGO film and PY. Since TP and l-dopa drugs antagonize the drug action of PY, ERGO modified GCE was also used for the simultaneous determination of PY and l-dopa and PY and TP. Further, the selective determination of PY in the presence of other water soluble vitamins such as ascorbic acid and riboflavin was also demonstrated. Using amperometry, detection of 100nM PY was achieved and the detection limit was found to be 5.6×10(-8)M (S/N=3). The practical application of the present method was demonstrated by determining the concentration of PY in human blood serum and commercial drugs.

Electrochemical sensors based on carbon nanomaterials for acetaminophen detection: A review

This study describes the advancements made over the last five years in the development of electrochemical sensors and biosensors for acetaminophen detection. This study reviews the different configurations based on unmodified and chemically modified carbon nanotubes and graphene. The influence of various modifiers on the two types of materials is presented along with their role on the enhancement of the selectivity and sensitivity of (bio)sensors. The review is focused on a comparative description of the applications of carbon-based nanomaterials towards acetaminophen detection and presents the results in a critical manner.