NiO/SWCNTs coupled with an ionic liquid composite for amplified carbon paste electrode; A feasible approach for improving sensing ability of adrenalone and folic acid in dosage form

Metal oxide nanomaterials based electrochemical and optical biosensors for biomedical applications: Recent advances and future prospectives

The amalgamation of nanostructures with modern electrochemical and optical techniques gave rise to interesting devices, so-called biosensors. A biosensor is an analytical tool that incorporates various biomolecules with an appropriate physicochemical transducer. Over the past few years, metal oxide nanomaterials (MONMs) have significantly stimulated biosensing research due to their desired functionalities, versatile chemical stability, and low cost along with their unique optical, catalytic, electrical, and adsorption properties that provide an attractive platform for linking the biomolecules, for example, antibodies, nucleic acids, enzymes, and receptor proteins as sensing elements with the transducer for the detection of signals or signal amplifications. The signals to be measured are in direct proportionate to the concentration of the bioanalyte. Because of their simplicity, cost-effectiveness, portability, quick analysis, higher sensitivity, and selectivity against a broad range of biosamples, MONMs-based electrochemical and optical biosensing platforms are exhaustively explored as powerful early-diagnosis tools for point of care applications. Herein, we made a bibliometric analysis of past twenty years (2004-2023) on the application of MONMs as electrochemical and optical biosensing units using Web of Science database and the results of which clearly reveal the increasing number of publications since 2004. Geographical area distribution analysis of these publications shows that China tops the list followed by the United States of America and India. In this review, we first describe the electrochemical and optical properties of MONMs that are crucial for the creation of extremely stable, specific, and sensitive sensors with desirable characteristics. Then, the biomedical applications of MONMs-based bare and hybrid electrochemical and optical biosensing frameworks are highlighted in the light of recent literature. Finally, current limitations and future challenges in the field of biosensing technology are addressed.

In situ electrodeposition of bismuth oxide nanowires @MWNT on the carbon fiber microelectrode for the sensitively electrochemical detection of folic acid

A microminiaturized electrochemical device, BiO@CNW/CFE was fabricated based on the in situ co-electrodeposition of bismuth oxide nanowires (BiNWs) and multi-walled carbon nanotubes (MWNTs) on the surface of carbon fiber electrode (CFE). The nanostructure of BiNWs could bind MWNTs on the surface of CFE during the precipitation of bismuth at the potential of -1.1 V. The vimineous nanostructure of BiO@CNW improved the surface area and electrochemical activity of the microelectrode. With the low background noise, folic acid (FA) can be detected sensitively by BiO@CNW/CFE based on the electrochemical reduction via the method of square wave voltammetry. The linear range of FA in sodium acetate-acetic acid buffer was achieved in the range of 5.00 nM-200 nM, the detection limit was estimated to be 0.63 nM. The recoveries of FA in human serum and artificial cerebral spinal fluid were between 99% and 103%, which indicates BiO@CNW/CFE was a reliable sensor for the detection of FA in biological samples.

Simple turn-off fluorescence sensor for determination of raloxifene using gold nanoparticles stabilized by chitosan hydrogel

It is essential to develop a simple, applicable, and reliable assay to anticancer drug raloxifene (RAF) because of its significant usage and side effect due to entering residue in the environment. Fluorescence sensors developed and widely used because of them high selectivity, fast-response, and highly-sensitivity. The gold nanoparticles using chitosan hydrogel was synthesized and applied as a fluorescence sensor to determine the trace amount of RAF. The characterization methods including DLS, FE-SEM, EDX, XRD, and FT-IR were performed to confirm the synthesized structure. This sensor turned off the fluorescent signals proportional to RAF concentrations at 400 nm. The RAF can be detected in the linear range from 5 × 10^-7 to 5 × 10^-5 M. Limits of detection and quantification were obtained as 34 × 10^-8 and 11 × 10^-7 M as well as the relative standard deviation calculated as 1.63% in RAF measuring. The effective parameters on quenching efficiency were studied by central composite design (CCD) with response surface methodology (RSM). The effective parameters in RAF determination, include analyte concentration, temperature, contact time, and pH, were obtained as 35 μM, 30 °C, 8 min, and pH = 8.5. The sensor was applied to determine the RAF concentrations in biological and environmental samples with satisfactory recoveries between 97.5% and 109%.

(Bio)Sensing Strategies Based on Ionic Liquid-Functionalized Carbon Nanocomposites for Pharmaceuticals: Towards Greener Electrochemical Tools

The interaction of carbon-based nanomaterials and ionic liquids (ILs) has been thoroughly exploited for diverse electroanalytical solutions since the first report in 2003. This combination, either through covalent or non-covalent functionalization, takes advantage of the unique characteristics inherent to each material, resulting in synergistic effects that are conferred to the electrochemical (bio)sensing system. From one side, carbon nanomaterials offer miniaturization capacity with enhanced electron transfer rates at a reduced cost, whereas from the other side, ILs contribute as ecological dispersing media for the nanostructures, improving conductivity and biocompatibility. The present review focuses on the use of this interesting type of nanocomposites for the development of (bio)sensors specifically for pharmaceutical detection, with emphasis on the analytical (bio)sensing features. The literature search displayed the conjugation of more than 20 different ILs and several carbon nanomaterials (MWCNT, SWCNT, graphene, carbon nanofibers, fullerene, and carbon quantum dots, among others) that were applied for a large set (about 60) of pharmaceutical compounds. This great variability causes a straightforward comparison between sensors to be a challenging task. Undoubtedly, electrochemical sensors based on the conjugation of carbon nanomaterials with ILs can potentially be established as sustainable analytical tools and viable alternatives to more traditional methods, especially concerning in situ environmental analysis.

Recent Advantages of Mediator Based Chemically Modified Electrodes; Powerful Approach in Electroanalytical Chemistry

Background:

Modified electrodes have advanced from the initial studies aimed at understanding electron transfer in films to applications in areas such as energy production and analytical chemistry. This review emphasizes the major classes of modified electrodes with mediators that are being explored for improving analytical methodology. Chemically modified electrodes (CMEs) have been widely used to counter the problems of poor sensitivity and selectivity faced in bare electrodes. We have briefly reviewed the organometallic and organic mediators that have been extensively employed to engineer adapted electrode surfaces for the detection of different compounds. Also, the characteristics of the materials that improve the electrocatalytic activity of the modified surfaces are discussed.

Objective:

Improvement and promotion of pragmatic CMEs have generated a diversity of novel and probable strong detection prospects for electroanalysis. While the capability of handling the chemical nature of the electrode/solution interface accurately and creatively increases , it is predictable that different mediators-based CMEs could be developed with electrocatalytic activity and completely new applications be advanced.

Properties and Recent Advantages of N,N’-dialkylimidazolium-ion Liquids Application in Electrochemistry

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N,Nʹ-dialkylimidazolium-ion liquids is one of the important ionic liquids with a wide range of application as conductive electrolyte and in electrochemistry. The modified electrodes create a new view in fabrication of electroanalytical sensors. Many modifiers have beeen suggested for modification of electroanalytical sensor since many years ago. Over these years, ionic liquids and especially room temperature ionic liquids have attracted more attention due to their wide range of electrochemical windows and high electrical conductivity. N,Nʹ-dialkylimidazolium-ion liquids are one of the main important ionic liquids suggested for modification of bare electrodes and especially carbon paste electrodes. Although many review articles have reported onthe use of ionic liquids in electrochemical sensors, no review article has been specifically introduced so far on the review of the advantages of N,Nʹ-dialkylimidazolium ionic liquid. Therefore, in this review paper we focused on the introduction of recent advantages of N,Nʹ-dialkyl imidazolium ionic liquid in electrochemistry.

Electrochemical investigations and theoretical studies of biocompatible niacin-modified carbon paste electrode interface for electrochemical sensing of folic acid

The modified electrode–analyte interaction is critical in establishing the sensing mechanism and in developing an electrochemical sensor. Here, the niacin-modified carbon paste electrode (NC/CPE) was fabricated for electrochemical sensing applications. The two stable structures of the niacin were optimized and confirmed by the absence of negative vibrational frequency, at B3LYP and B3LYP-GD3BJ level and 6–311 g** basis set. The physical and quantum chemical quantities were used to explain the molecular stability and electronic structure-related properties of the niacin. The natural bond orbital (NBO) analysis was performed to disclose the donor–acceptor interactions that were a critical role in explaining the modifier–analyte interaction. The fabricated NC/CPE was used for the determination of folic acid (FA) in physiological pH by cyclic voltammetry (CV) method. The limit of detection (LOD) for FA at NC/CPE was calculated to be 0.09 µM in the linear concentration range of 5.0 µM to 45.0 µM (0.2 M PBS, pH 7.4) by CV technique. The analytical applicability of the NC/CPE was evaluated in real samples, such as fruit juice and pharmaceutical sample, and the obtained results were acceptable. The HOMO and LUMO densities are used to identify the nucleophilic and electrophilic regions of niacin. The use of density functional theory-based quantum chemical simulations to understand the sensory performance of the modifier has laid a new foundation for fabricating electrochemical sensing platforms.

Quantum Chemical Studies and Electrochemical Investigations of Polymerized Brilliant Blue-Modified Carbon Paste Electrode for In Vitro Sensing of Pharmaceutical Samples

To develop an electrochemical sensor for electroactive molecules, the choice and prediction of redox reactive sites of the modifier play a critical role in establishing the sensing mediating mechanism. Therefore, to understand the mediating mechanism of the modifier, we used advanced density functional theory (DFT)-based quantum chemical modeling. A carbon paste electrode (CPE) was modified with electropolymerization of brilliant blue, later employed for the detection of paracetamol (PA) and folic acid (FA). PA is an analgesic, anti-inflammatory and antipyretic prescription commonly used in medical fields, and overdose or prolonged use may harm the liver and kidney. The deficiency of FA associated with neural tube defects (NTDs) and therefore the quantification of FA are very essential to prevent the problems associated with congenital deformities of the spinal column, skull and brain of the fetus in pregnant women. Hence, an electrochemical sensor based on a polymerized brilliant blue-modified carbon paste working electrode (BRB/CPE) was fabricated for the quantification of PA and FA in physiological pH. The real analytical applicability of the proposed sensor was judged by employing it in analysis of a pharmaceutical sample, and good recovery results were obtained. The potential excipients do not have a significant contribution to the electro-oxidation of PA at BRB/CPE, which makes it a promising electrochemical sensing platform. The real analytical applicability of the proposed method is valid for pharmaceutical analysis in the presence of possible excipients. The prediction of redox reactive sites of the modifier by advanced quantum chemical modeling-based DFT may lay a new foundation for researchers to establish the modifier–analyte interaction mechanisms.

Diffusivity and free anion concentration of ionic liquid composite polybenzimidazole membranes

PBI composite membranes containing 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM-NTf₂) at 1, 5, 10, 20 and 50 wt% have been prepared and the conductivity has been analyzed by electrochemical impedance spectroscopy.

Electrochemical Voltammogram Recording for Identifying Varieties of Ornamental Plants

An electrochemical voltammogram recording method for plant variety identification is proposed. Electrochemical voltammograms of Vistula, Andromeda, Danuta, Armandii 'Apple Blossom,' Proteus, Hagley Hybrid, Violet Elizabeth, Kiri Te Kanawa, Regina, and Veronica's Choice were recorded using leaf extracts with two solvents under buffer solutions. The voltametric data recorded under different conditions were derived as scatter plots, 2D density patterns, and hot maps for variety identification. In addition, the voltametric data were further used for genetic relationship studies. The dendrogram deduced from the voltammograms was used as evidence for relationship study. The dendrogram deduced from voltametric data suggested the Andromeda, Danuta, Proteus, Regina, and Hagley Hybrid were closely related, while Violet Elizabeth and Veronica's Choice were closely related. In addition, Vistula and Armandii 'Apple Blossom' could be considered outliers among the varieties.

Development of Electrochemical Oscillation Method for Identification of Prunus persica, Prunus davidiana, and Prunus armeniaca Nuts

In this work, an electrochemical oscillation system has been developed using the Belousov-Zhabotinsky reaction. The effect of the combination of each reagent, reaction temperature, and stirring speed on the induction period, oscillating period, and oscillating life were optimized. The nuts of Prunus persica, Prunus davidiana, and Prunus armeniaca have been widely used for medical purposes. The proposed electrochemical oscillation system was then used for the identification of P. persica, P. davidiana, and P. armeniaca. Three nuts exhibited very different electrochemical oscillation profiles. The dendrogram was divided into three main principal infrageneric clades. Each cluster only contains one species, suggesting that no outlier was observed in this study. Based on the discussed results, we proposed a simple method for herbal medicine identification.