Nanomaterial-based electrochemical sensors for detection of amino acids.

Amino acids are the building blocks of proteins and muscle tissue. They also play a significant role in physiological processes related to energy, recovery, mood, muscle and brain function, fat burning and stimulating growth hormone or insulin secretion. Accurate determination of amino acids in biological fluids is necessary because any changes in their normal ranges in the body warn diseases like kidney disease, liver disease, type 2 diabetes and cancer. To date, many methods such as liquid chromatography, fluorescence mass spectrometry, etc. have been used for the determination of amino acids. Compared with the above techniques, electrochemical systems using modified electrodes offer a rapid, accurate, cheap, real-time analytical path through simple operations with high selectivity and sensitivity. Nanomaterials have found many interests to create smart electrochemical sensors in different application fields e.g. biomedical, environmental, and food analysis because of their exceptional properties. This review summarizes recent advances in the development of nanomaterial-based electrochemical sensors in 2017-2022 for the detection of amino acids in various matrices such as serum, urine, blood and pharmaceuticals.

Achievements of Graphene and Its Derivatives Materials on Electrochemical Drug Assays and Drug-DNA Interactions.

Graphene, emerging as a true two-dimensional (2D) material, has attracted increasing attention due to its unique physical and electrochemical properties such as high surface area, excellent conductivity, high mechanical strength, and ease of functionalization and mass production. The entire scientific community recognizes the significance and potential impact of graphene. Electrochemical detection strategies have advantages such as being simple, fast, and low-cost. The use of graphene as an excellent interface for electrode modification provides a promising way to construct more sensitive and stable electrochemical (bio)sensors. The review presents sensors based on graphene and its derivatives for electrochemical drug assays from pharmaceutical dosage forms and biological samples. Future perspectives in this rapidly developing field are also discussed. In addition, the interaction of several important anticancer drug molecules with deoxyribonucleic acid (DNA) that was immobilized onto graphene-modified electrodes has been detailed in terms of dosage regulation and utility purposes.

Non-enzymatic electrochemical cholesterol sensor based on strong host-guest interactions with a polymer of intrinsic microporosity (PIM) with DFT study.

Advances in materials science have accelerated the development of diagnostic tools with the last decade witnessing the development of enzyme-free sensors, owing to the improved stability, low cost and simple fabrication of component materials. However, the specificity of non-enzymatic sensors for certain analytes still represents a challenging task, for example the determination of cholesterol level in blood is vital due to its medical relevance. In this work, a reagent displacement assay for cholesterol sensing in serum samples was developed. It is based on coating of a glassy carbon electrode with a polymer of intrinsic microporosity (PIM) that forms a host-guest complex with methylene blue (MB). In the presence of cholesterol, the MB electroactive probe was displaced due to the stronger association of cholesterol guest to the PIM host. The decrease in the oxidative current was proportional to the cholesterol concentration achieving a detection limit of approximately 0.1 nM. Moreover, to further assist the experimental studies, comprehensive theoretical calculations are also performed by using density functional theory (DFT) calculations.

An Overview on Electrochemical Sensors Based on Nanomaterials for the Determination of Drugs of Abuse.

Drug abuse is considered a serious source of economic and social problems. The identification of drugs of abuse is in demand in forensic and clinical toxicology. There are various methods for the determination of these materials, including chromatographic and mass spectrometric techniques. However, most of these techniques need high-cost equipment, they are time-consuming, and they suffer from complicated sample preparation protocols. In contrast, electrochemical methods are low cost, mobile, and they do not require complicated sample preparation protocols. The use of nanomaterials in electroanalysis has gained significant attention in order to improve selectivity, enhance sensitivity, and lower the limit of detections. Nanomaterials have significantly gained research-interest due to their low cost (due to low amounts of materials being used) and their uniquely size-dependent properties. The incorporation of nanomaterials into host matrices is important to prepare nanocomposite sensor films. Unique properties of nanomaterials and hybrid materials, such as mechanical strength, electrical conductivity, optical responsiveness, specific catalytic and magnetic properties, in addition to high surface area per mass ratio are attractive. Besides providing novel properties, nanomaterials allow low-cost electrode fabrication based on simple technologies. The combination of nanotechnology with modern electroanalytical techniques allows innovation in electrical sensing devices with features like increased mass transport, high sensor surface area, and controlled electrode surface micro-environment. The aim of this review is to give an outline of electroanalytical determination based on nanomaterials focusing on illicit drugs in matrices, such as urine, blood, or saliva. We summarize developments in field-based sensors for determining drugs of abuse.

A sensitive nanocomposite design via carbon nanotube and silver nanoparticles: Selective probing of Emedastine Difumarate.

In this study, a novel and sensitive nanocomposite of carboxylate-functionalized multiwalled carbon nanotube (COOH-fMWCNT) and silver nanoparticles (AgNPs) was fabricated and used to modify a glassy carbon electrode (GCE) by a simple drop casting method. Modified electrode was then applied for selective determination of emedastine difumarate (EDD). The COOH-fMWCNT/AgNPs nanocomposite was characterized by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and cyclic voltammetry (CV). EDD showed two oxidation peaks at 0.634 and 1.2 V on the GCE surface. CV results of COOH-fMWCNT/AgNPs/GCE displayed superior electrocatalytic performance in terms of anodic peak current of EDD when compared to AgNPs/GCE, MWCNT/GCE, and COOH-fMWCNT/GCE. The experimental conditions such as effect of pH, supporting electrolyte, effect of accumulation time and potential, scan rate were optimized for getting intense current signals of the target analyte. Under optimized conditions, COOH-fMWCNT/AgNPs/GCE showed a linear current response for oxidation of EDD in the range of 1.0 × 10-7-1.0 × 10-4 M, with a limit of detection (LOD) and quantification (LOQ) of 5.25 nM, 15.9 nM, respectively, in 0.1 M phosphate buffer solution at pH 2.0 using differential pulse adsorptive stripping voltammetry technique. The proposed method was successfully applied for determination of EDD in pharmaceutical dosage form. Satisfactory recovery percentages were achieved from eye drop sample with acceptable RSD values (less than 2 %). Furthermore, the reproducibility, stability and repeatability of the modified electrode were studied.

Carbon nanoparticles with tosyl functional group for distinguishing voltammetric peaks of ascorbic acid and uric acid.

In this approach, electro-oxidation of a mixture of uric acid and ascorbic acid at the surface of tosyl surface carbon nanoparticles/glassy carbon electrode has been performed. The electro-oxidation of these compounds at bare electrode is sluggish and there is no suitable peak separation between them. However, using functionalized carbon nanoparticles, two well-defined anodic peaks with a considerable enhancement in the peak current and a remarkable peak potential separation near 452 mV is obtained. The porous interfacial layer of the carbon nanoparticles modified electrode with a high specific surface area increases the conductive area; molecules can penetrate through the conductive porous channels onto the electrode more easily so leading to higher sensitivity and selectivity. The dynamic linear ranges of 1.0 × 10(-5) to 3.0 × 10(-3)M and 1.0 × 10(-7) to 1.0 × 10(-4)M with detection limits 1.0 × 10(-5)M and 2.0 × 10(-8)M (for S/N=3) were obtained for ascorbic acid and uric acid, respectively. Analytical utility of the modified electrode has been examined successfully using human urine samples and vitamin C commercial tablets.