Graphene nanoflakes on transparent glass electrode sensor for electrochemical sensing of anti-diabetic drug

Electrochemical Assays for the Determination of Antidiabetic Drugs-A Review

This article presents the current state of knowledge regarding electrochemical methods for determining the active substances within drugs that are used in the treatment of type 1 and type 2 diabetes. Electrochemical methods of analysis, due to their sensitivity and easiness, are a great alternative to other, usually more expensive analytical assays. The determination of active substances mentioned in this review is based on oxidation or reduction processes on the surface of the working electrode. A wide variety of working electrodes, often modified with materials such as nanoparticles or conducting polymers, have been used for the highly sensitive analysis of antidiabetic drugs. The presented assays allow us to determine the compounds of interest in various samples, such as pharmaceutical products or different human bodily fluids.

Fabrication and employment of cobalt-doped yttrium iron garnets for the electrochemical analysis of anti-diabetic, metformin in serum of type 2 diabetes mellitus patients

Metformin (MET) is an anti-diabetic drug employed as the first-line therapy for patients of type II diabetes mellitus (T2DM). Overdosage of drugs leads to severe outcomes, and its monitoring in biofluids is vital. The present study develops cobalt-doped yttrium iron garnets and employs them as an electroactive material immobilized on a glassy carbon electrode (GCE) for the sensitive and selective detection of metformin via electroanalytical techniques. The fabrication procedure via the sol-gel method is facile and gives a good yield of nanoparticles. They are characterized by FTIR, UV, SEM, EDX, and XRD. Pristine yttrium iron garnet particles are also synthesized for comparison, where the electrochemical behaviors of varying electrodes are analyzed via cyclic voltammetry (CV). The activity of metformin at varying concentrations and pH is investigated via differential pulse voltammetry (DPV), and the sensor generates excellent results for metformin detection. Under optimum conditions and at a working potential of 0.85 V (vs. Ag/AgCl/3.0 M KCl), the linear range and limit of detection (LOD) obtained through the calibration curve are estimated as 0-60 μM and 0.04 μM, respectively. The fabricated sensor is selective for metformin and depicts a blind response toward interfering species. The optimized system is applied to directly measure MET in buffers and serum samples of T2DM patients.

A ratiometric fluorescent sensor for detection of metformin based on terbium-1,10-phenanthroline-nitrogen-doped-graphene quantum dots

Metformin (MTF), an effective biguanide and oral antihyperglycemic agent, is utilized to control blood glucose levels in patients with type II diabetes mellitus, and the determination of its concentration in biological fluids is one of the main issues in pharmacology and medicine. In this work, highly luminescent nitrogen-doped graphene quantum dots (N-GQDs) were modified using terbium (Tb³⁺)–1,10-phenanthroline (Phen) nanoparticles (NPs) to develop a dual-emission ratiometric fluorescent sensor for the determination of MTF in biological samples. The synthesized N-GQDs/Tb–Phen NPs were characterized using different techniques to confirm their physicochemical properties. The N-GQDs/Tb–Phen NPs showed two characteristic emission peaks at 450 nm and 630 nm by exciting at 340 nm that belong to N-GQDs and Tb–Phen NPs, respectively. The results indicated that the emission intensity of both N-GQDs and Tb–Phen NPs enhanced upon interaction with MTF in a concentration-dependent manner. Also, a good linear correlation between the enhanced fluorescence intensity of the system and MTF concentration was observed in the range of 1.0 nM–7.0 μM and the limit of detection (LOD) value obtained was 0.76 nM. In addition, the prepared probe was successfully used for the estimation of MTF concentration in spiked human serum samples. In conclusion, the reported dual-emission ratiometric fluorescent sensor can be used as a sensitive and simple fluorimetric method for the detection of MTF in real samples.

Shcematic representation of the MTF detection by an enhancing mechanism.

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.

A rapid, simple and ultrasensitive spectrofluorimetric method for the direct detection of metformin in real samples based on a nanoquenching approach

Metformin (MET), as an oral antidiabetic and antihyperglycemic agent, is widely used to treat type II diabetes mellitus. Because of its increasing consumption, developing a fast, simple, and selective method to determine its concentration in biological samples (serum and urine) and pharmaceutical formulations (tablets) is of great interest. In this study, we used a FRET-based fluorescent nanosensor (Tb-phen-AgNPs system) for sensitive detection of MET in tablet and serum samples. This method is based on the enhancing effect of MET on the emission intensity of the Tb-phen complex, which is quenched by AgNPs via energy transfer process (turn off-on mode). A good linear relationship between the MET concentration and enhanced emission intensity of the Tb-phen-AgNPs system was observed in the range of (0.75-3.7) × 10^-6 M under optimum conditions. Limit of detection and limit of quantitation were calculated to be 0.43 × 10^-6 M and 1.31 × 10^-6 M, respectively. This method was successfully used to determine MET concentrations in pharmaceutical dosage form and in spiked serum sample. The obtained recoveries from pharmaceutical formulation and serum sample were in the range 86.75-98.97% and 85.10-100.96%, respectively. Collectively, our results indicated that the method described here is simple, sensitive, cost effective, and free from interference. Therefore, it can be used as an effective and routine method for the direct and rapid determination of MET levels in biological samples such as serum.

Utilizing a nanocomposite consisting of zinc ferrite, copper oxide, and gold nanoparticles in the fabrication of a metformin electrochemical sensor supported on a glassy carbon electrode

The conception and development of a new electrochemical sensor is reported for the detection of metformin (MET). Zinc ferrite and copper oxide nanostructure (ZnFe₂O₄-CuO) and gold nanoparticles (AuNPs) have been used to prepare a nanocomposite in modifying a glassy carbon electrode (GCE). The unique ZnFe₂O₄-CuO/Au nanocomposite was applied as a sensor for the determination of traces of MET by some electroanalytical techniques. Experimental parameters affecting the results were investigated and optimized. Under the optimum conditions and at a working potential of 0.85 V (vs. Ag/AgCl/3.0 M KCl), the sensor response is linear in the MET range of 1.0 nmol L^-1 to 1.0 μmol L^-1 MET. The limit of detection (LOD) is 0.3 nmol L^-1 (at an S/N ratio of 3) and the sensitivity is 1.13 μA μmol L^-1 cm^-2. The sensor was applied to the determination of MET in real samples where it gave acceptable results. Graphical abstract.

Triple-helix molecular switch-based aptasensors and DNA sensors

Utilization of traditional analytical techniques is limited because they are generally time-consuming and require high consumption of reagents, complicated sample preparation and expensive equipment. Therefore, it is of great interest to achieve sensitive, rapid and simple detection methods. It is believed that nucleic acids assays, especially aptamers, are very important in modern life sciences for target detection and biological analysis. Aptamers and DNA-based sensors have been widely used for the design of various sensors owing to their unique features. In recent years, triple-helix molecular switch (THMS)-based aptasensors and DNA sensors have been broadly utilized for the detection and analysis of different targets. The THMS relies on the formation of DNA triplex via Watson-Crick and Hoogsteen base pairings under optimal conditions. This review focuses on recent progresses in the development and applications of electrochemical, colorimetric, fluorescence and SERS aptasensors and DNA sensors, which are based on THMS. Also, the advantages and drawbacks of these methods are discussed.