Electrochemical sensors using screen-printed carbon electrode assemblies modified with the β-cyclodextrin or carboxymethylated β-cyclodextrin polymer films for determination of tricyclic antidepressive drugs

A novel electrochemical sensor based on ꞵ-cyclodextrin/bismuth oxybromide/multi-walled carbon nanotubes modified electrode with in situ addition of tetrabutylammonium bromide for the simultaneous detection and degradation of tebuconazole

A novel electrochemical sensor-based glassy carbon electrode (GCE) was fabricated and applied to simultaneous detection and degradation of tebuconazole (TBZ) for the first time. The GCE was consecutively modified by multi-walled carbon nanotubes (MWCNTs), bismuth oxybromide (BiOBr), ꞵ-cyclodextrin (ꞵ-CD), and in situ addition of tetrabutylammonium bromide (TBABr). The detection was based on the decreasing of Bi signal at its anodic potential (Epa) of 0.05 V. Under the optimum conditions, the modified electrode exhibited a linear response to TBZ in the concentration range 1-100 μg L-1 with a detection limit of 0.9 μg L-1. TBZ was firstly adsorbed on the surface of the modified electrode through host-guest molecule interactions of the ꞵ-CD. The adsorption was further enhanced by the large surface area of BiOBr and MWCNTs. The adsorbed TBZ on the electrode surface hindered the electron transfer of Bi, thus decreasing the oxidation of Bi. In addition, the in situ addition of tetrabutylammonium bromide (TBABr) enriched TBZ via electrostatic interactions, increasing its detection sensitivity. The fabricated electrochemical sensor was applied to determine TBZ in water and soil samples from rice fields with recoveries of 80.5-100.5% and 87.6-112%, respectively. Furthermore, the degradation of TBZ on the modified electrode was studied under a solar light simulator. The degradation percentage (100%) of TBZ (50 µg L-1) was achieved in 5 min owing to the excellent photocatalytic properties of BiOBr.

Supramolecular Electrochemical Sensor for Dopamine Detection Based on Self-Assembled Mixed Surfactants on Gold Nanoparticles Deposited Graphene Oxide

A new supramolecular electrochemical sensor for highly sensitive detection of dopamine (DA) was fabricated based on supramolecular assemblies of mixed two surfactants, tetra-butylammonium bromide (TBABr) and sodium dodecyl sulphate (SDS), on the electrodeposition of gold nanoparticles on graphene oxide modified on glassy carbon electrode (AuNPs/GO/GCE). Self-assembled mixed surfactants (TBABr/SDS) were added into the solution to increase the sensitivity for the detection of DA. All electrodes were characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The supramolecular electrochemical sensor (TBABr/SDS⋅⋅⋅AuNPs/GO/GCE) showed excellent electrocatalytic activity toward the oxidation of DA. Under the optimum conditions, the concentration of DA was obtained in the range from 0.02 µM to 1.00 µM, with a detection limit of 0.01 µM (3s/b). The results displayed that TBABr/SDS⋅⋅⋅AuNPs/GO/GCE exhibited excellent performance, good sensitivity, and reproducibility. In addition, the proposed supramolecular electrochemical sensor was successfully applied to determine DA in human serum samples with satisfactory recoveries (97.26% to 104.21%).

Early-stage cervical cancer diagnosis based on an ultra-sensitive electrochemical DNA nanobiosensor for HPV-18 detection in real samples

BACKGROUND

In several years ago, infection with human papillomaviruses (HPVs), have been prevalent in the worlds especially HPV type 18, can lead to cervical cancer. Therefore, rapid, accurate, and early diagnosis of HPV for successful treatment is essential. The present study describes the development of a selective and sensitive electrochemical biosensor base on DNA, for early detection of HPV-18. For this purpose, a nanocomposite of reduced graphene oxide (rGO) and multiwalled carbon nanotubes (MWCNTs) were electrodeposited on a screen-printed carbon electrode (SPCE). Then, Au nanoparticles (AuNPs) were dropped on a modified SPCE. Subsequently, single strand DNA (ssDNA) probe was immobilized on the modified electrode. The link attached between AuNPs and probe ssDNA provided by L-cysteine via functionalizing AuNPs (Cys-AuNPs). The differential pulse voltammetry (DPV) assay was also used to electrochemical measurement. The measurement was based on the oxidation signals of anthraquninone-2-sulfonic acid monohydrate sodium salt (AQMS) before and after hybridization between the probe and target DNA.

RESULTS

The calibration curve showed a linear range between 0.01 fM to 0.01 nM with a limit of detection 0.05 fM. The results showed that the optimum concentration for DNA probe was 5 µM. The good performance of the proposed biosensor was achieved through hybridization of DNA probe-modified SPCE with extracted DNA from clinical samples.

CONCLUSIONS

According to the investigated results, this biosensor can be introduced as a proprietary, accurate, sensitive, and rapid diagnostic method of HPV 18 in the polymerase chain reaction (PCR) of real samples.

Electroanalysis of Tricyclic Psychotropic Drugs using Modified Electrodes

Background:

Tricyclic psychotropic drugs are defined as a tricyclic rings of the dibenzazepine group with the presence of sulfur and nitrogen atoms. They have been prescribed for antidepressive therapy over the years. Due to their medical importance, many analytical methods have been developed for their monitoring. However, benefits of electrochemical techniques such as costeffectiveness, fast, easy operation and non-destructiveness make them appropriate analytical methods for drug assays. Electrochemical determinations of pharmaceuticals require suitable working electrodes. During years, many electrodes are modified by a variety of modifiers and several sensors were developed based on them. In this regard, nanomaterials, due to their remarkable properties, are one of the most important choices.

Objective:

Here, the application of electroanalytical methods in the determination of electroactive tricyclic psychotropic drugs will be reviewed and the nanomaterials which are used for improvements of the working electrodes will be considered.

Electrochemical Analysis of Antipsychotics

Introduction:

Schizophrenia is seizures accompanied by severe psychotic symptoms, and a steady state of continuation in the form of periods of stagnation. Antipsychotics are now the basis of treatment for schizophrenia and there is no other molecule that is antipsychotic priority in treatment. Antipsychotics can be classified into two groups; dopamine receptor antagonists such as promazine, fluphenazine etc. and serotonin-dopamine antagonists including risperidone, olanzapine, ziprasidone, aripiprazole etc.

Materials and Methods:

Electrochemical methods have been used for the determination of antipsychotic agent just as used in the determination of many drug agents. Nearly all of the antipsychotics are electroactive and can be analyzed by electrochemical methods. Electroanalytical methods offer generally high sensitivity, are compatible with modern techniques, have low cost, low requirements, and compact design. Among the most commonly used types, there are cyclic voltammetry, differential pulse voltammetry, square wave voltammetry and linear sweep voltammetry.

Conclusion:

The aim of this review is to evaluate the main line and the advantages and uses of electroanalytical methods that employed for the determination of antipsychotic medication agents used in schizophrenia. Moreover, applications of the methods to pharmaceutical analysis of Antipsychotics upto- date is also summarized in a table.

An electrochemical molecular recognition-based aptasensor for multiple protein detection

This article reports a simple electrochemical approach for the detection of multiple proteins (thrombin and lysozyme) using Dabcyl-labeled aptamer modified metal nanoparticles (DLAPs). DLAPs were immobilized on β-cyclodextrins (β-CDs) modified electrode by means of host-guest self-assembly. During the time of detection, the aptamers' structure will change due to the specific binding with corresponding proteins that forced DLAPs far away from the electrode that had been modified by β-CDs. Thus, the capture of target proteins onto DLAPs was translated via the electrochemical current signal offered by metal nanoparticles. Linearity of the aptasensor for quantitative measurements was demonstrated. Determinations of proteins in human real serum samples were also performed to demonstrate detection in real clinical samples.

An application of UV-derivative spectrophotometry and bivariate calibration algorithm for study of photostability of levomepromazine hydrochloride

Derivative spectrophotometry and bivariate calibration algorithm were used for study of run of photooxidation of levomepromazine hydrochloride (LV). The actual concentrations of LV and its main degradation product levomepromazine sulphoxide (LV-SO) were calculated using data provided by applied methods. The direct reading of absorbance values at 302 nm and 334 nm were employed for quantification of LV and LV-SO, respectively, in the case of bivariate method. The derivative spectrophotometric method is based on transformation of zero-order spectra into first derivative. The values of first derivative at 334 nm were used for quantification of LV while at 278 nm for assay of LV-SO. The obtained quantitative data were applied for investigation of kinetics of photodegradation of LV.

Association interaction and voltammetric determination of 1-aminopyrene and 1-hydroxypyrene at cyclodextrin and DNA based electrochemical sensors

The aim of this work was voltammetric determination of 1-aminopyrene and 1-hydroxypyrene using carbon paste electrodes modified with cyclodextrin derivatives and double stranded deoxyribonucleic acid (dsDNA). The detection schemes based on a preconcentration and differential pulse voltammetric (DPV) determination at beta-cyclodextrin and gamma-cyclodextrin modified carbon paste electrode (beta-CD/CPE, gamma-CD/CPE), neutral beta-cyclodextrin polymer and carboxymethyl-beta-cyclodextrin polymer modified screen-printed electrode (beta-CDP/SPE, beta-CDPA/SPE) and dsDNA modified screen-printed electrode (DNA/SPE) are proposed for the trace determination of studied analytes within the concentration range from 2 x 10(-8) to 4 x 10(-7) mol dm(-3) and from 2 x 10(-7) to 4 x 10(-6) mol dm(-3) with the limits of quantification down to 10(-8) mol dm(-3). Depending on pH, 1-aminopyrene interacts with both surface attached CD and DNA by electrostatic bonds and supramolecular complexation while 1-hydroxypyrene associates with the CD hosts via complexation. The 1-aminopyrene interaction with dsDNA was confirmed by fluorimetric measurements in the solution phase using a competing DNA-TO-PRO-3 dye complex. In addition, the effect of temperature on this association was investigated using an electrically heated DNA-modified carbon paste electrode (DNA/CPE).

Trimipramine determination in pharmaceutical preparations with an automated multicommutated reversed-flow system

In this work an automated multicommutated flow methodology was implemented for the spectrophotometric determination of trimipramine in pharmaceutical preparations by oxidation with ammonium monovanadate in acidic medium. The developed procedure exploits a new approach for sample/reagent intermixing by combining binary sampling with flow-reversal. Rather than inserting the sample as a single continuous volume the intercalation of multiple small sample and reagent aliquots, under a time-based control, created multiple reaction interfaces that promoted reaction zone homogenisation even in limited dispersion conditions. Additionally, the reaction interfaces were reversed, increasing mutual zone penetration, which contributed to a faster reaction development while assuring a low dispersion pattern. A linear range of determination was verified for trimipramine concentrations between 1.0 and 18.0 microg ml(-1) with a relative standard deviation (n=10) lower than 1.69% and a sample throughput of about 26 samples per hour. The results were in agreement with those obtained by the reference procedure with relative deviations lower then 2.37%.