Copper hydroxide nanostructure-modified carbon ionic liquid electrode as an efficient voltammetric sensor for detection of metformin: a theoretical and experimental study

Electrochemical determination of metformin via a carbon paste electrode modified with an Ag NPs/Cu2O/CuO-decorated bacterial nanocellulose composite

Metformin (MET) is widely used in the treatment of diabetes either alone or in combination with other drugs, in drug discovery to evaluate the anti-diabetic potential of other drugs, and usually as a comparison compound in pharmacokinetics/pharmacodynamics studies. Measuring the concentration of this substance is very important both pre-clinically in different species and clinically in the medical monitoring of diabetic patients to prevent toxicity and ensure adherence to described drugs. Therefore, it is very important to develop a sensitive and selective method to measure MET. In this work, a new electrochemical biosensor based on a carbon paste electrode, modified with bacterial nanocellulose, copper oxide, and silver nanoparticles (Ag NPs/Cu2O/CuO/BNC/CPE) was used for high-sensitivity MET determination. The morphology and structure of this bio-nanocomposite were characterized by ATR-IR, FE-SEM, EDS, mapping, XRD, and DRS techniques. Compared with the CPE electrode, the Ag NPs/Cu2O/CuO/BNC/CPE modified electrode showed much higher electrocatalytic activities toward the oxidation of MET. The measurements were carried out by the cyclic voltammetry technique. Surface conductance was evaluated using the impedance technique. The results showed an increase in surface conductivity. The detection limit was obtained at 42.3 nM and two linear ranges 0.1-76 and 76-1000.0 μM were observed. The developed sensor had good features such as high sensitivity, reproducibility and repeatability, low detection limit, and fast response time. The obtained results from the real sample (MET tablets) were completely satisfactory.

An electrochemical sensor based on synergistic enhancement effects between nitrogen-doped carbon nanotubes and copper ions for ultrasensitive determination of anti-diabetic metformin

Metformin (MET) is the primary medicine for type II diabetes, which produces carcinogenic byproducts during chlorine disinfection, so the detection of MET in aqueous environment is crucial. In this work, an electrochemical sensor based on nitrogen-doped carbon nanotubes (NCNT) has been constructed for ultrasensitive determination of MET in the presence of Cu(II) ions. The excellent conductivity and rich π-conjugated structure of NCNT facilitate the electron transfer rate of fabricated sensor and benefit the adsorption of cation ions. Cu(II) ions can chelate with MET to form MET-Cu(II) complex, which are easily accumulated on the surface of NCNT through cation-π interaction. Attributing to the synergistic enhancement effects of NCNT and Cu(II) ions, the fabricated sensor exhibits excellent analytical performances with a low detection limit of 9.6 nmol L^-1, high sensitivity of 64.97 A mol^-1 cm^-2 and wide linear range of 0.3-10 μmol L^-1. The sensing system has been successfully applied for rapid (20 s) and selective determination of MET in real water samples with satisfactory recoveries (90.2 %-108.8 %). This study provides a robust strategy for MET detection in aqueous environment and holds great promise for rapid risk assessment and early warning of MET.

Deep Eutectic Solvent-Assisted Synthesis of a Strontium Tungstate Bifunctional Catalyst: Investigation on the Electrocatalytic Determination and Photocatalytic Degradation of Acetaminophen and Metformin Drugs

In this work, we propose a modified solid-state approach for the sustainable preparation of a SrWO₄ bifunctional catalyst using thymol-menthol-based natural deep eutectic green solvents (NADESs). Various spectroscopic and morphological techniques analyzed the as-synthesized SrWO₄ particles. Acetaminophen (ATP) and metformin (MTF) were selected as the model drug compounds. The electrochemical detection and photocatalytic degradation of ATP and MTF upon ultraviolet-visible (UV-vis) light irradiation in the presence of as-prepared SrWO₄ particles as an active catalyst are examined. The present study displayed that the proposed catalyst SrWO₄ has enhanced catalytic activity in achieving the optimum experimental conditions, and linear ranges of ATP = 0.01-25.90 μM and MTF = 0.01-25.90 μM, a lower limit of detection (LOD) value (ATP = 0.0031 μM and MTF = 0.008 μM), and higher sensitivity toward ATP and MTF determination were obtained. Similarly, the rate constant was found to be k = ATP = 0.0082 min^-1 and MTF = 0.0296 min^-1 according to the Langmuir-Hinshelwood model, benefitting from the excellent synergistic impact of the SrWO₄ catalyst toward the photocatalytic degradation of the drug molecule. Hence, this work offers innovative insights into the applicability of the as-prepared SrWO₄ bifunctional catalyst as an excellent functional material for the remediation of emerging pollutants in water bodies with a recovery range of 98.2-99.75%.

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.

A Co-Doped Carbon Dot/Silver Nanoparticle Nanocomposite-Based Fluorescence Sensor for Metformin Hydrochloride Detection

In this study, a fluorescence sensor based on nitrogen and phosphorus co-doped carbon dot/silver nanoparticle (NPCD/AgNP) nanocomposites was developed for metformin hydrochloride (MFH) detection. We first utilized the reducing nature of the NPCDs to prepare AgNPs from Ag⁺ and subsequently prepare NPCD/AgNP nanocomposites. The nanocomposite material was characterized by various methods, including electron microscopic methods (SEM and TEM), spectroscopic methods (UV-Vis, PL, FTIR, and XPS spectroscopy), light scattering (ELS), and XRD. Further, we utilized the enhanced fluorescence of the NPCDs as well as the overlap between the fluorescence emission spectrum of the NPCDs and the absorption spectrum of the AgNPs to use the NPCD/AgNP nanocomposites as an effective inner filter effect (IFE) pair for sensing MFH. The IFE between NPCDs and AgNPs in the nanocomposite material resulted in a significant quenching of the fluorescence intensity of the nanocomposites compared to that of the pure NPCDs. However, the fluorescence was recovered when MFH was introduced into the nanocomposite solution. The fluorescence intensity of the nanocomposites increased linearly as the MFH concentration increased from 2 to 100 µg/L. This detection method showed good sensitivity compared to other methods. It also showed high selectivity and high sensing potential for MFH in human serum and yielded acceptable results.

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.

Study of the Hydrogen Evolution Reaction Using Ionic Liquid/Cobalt Porphyrin Systems as Electro and Photoelectrocatalysts

In this work, the design and manufacture of graphite paste (Gr) electrodes is carried out, including N-octylpyridinium hexafluorophosphate (OPyPF6) ionic liquid (IL) as binder and modification with Co-octaethylporphyrin (Co), in order to study the hydrogen evolution reaction (HER) in the absence and presence of light. The system is characterized by XRD and FESEM-EDX (Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy), confirming the presence of all the components of the system in the electrode surface. The studies carried out in this investigation confirm that a photoelectrocatalytic system towards HER is obtained. The system is stable, efficient and easy to prepare. Through cyclic voltammetry and electrochemical impedance spectroscopy, was determined that these electrodes improve their electrochemical and electrical properties upon the addition of OPyPF6. These effects improve even more when the systems are modified with Co porphyrin. It is also observed that when the systems are irradiated at 395 nm, the redox process is favored in energy terms, as well as in its electrical properties. Through gas chromatography, it was determined that the graphite paste electrode in the presence of ionic liquid and porphyrin (Gr/IL/Co) presents a high turnover number (TON) value (6342 and 6827 in presence of light) in comparison to similar systems reported.

A graphene modified carbon ionic liquid electrode for voltammetric analysis of the sequence of the Staphylococcus aureus nuc gene

The authors describe a voltammetric method for the detection of the nuc ssDNA sequence originating from Staphylococcus aureus by using a carbon ionic liquid electrode modified with electrodeposited three-dimensional graphene (3DGR). Probe ssDNA was electrostatically adsorbed on the modified electrode by a potentiostatic method. The porous structure and large surface area of 3DGR greatly increase the amount of immobilized probe ssDNA on the interface, which is beneficial for the reaction with target ssDNA. By using Methylene Blue (MB) as the electrochemical probe, the reduction peak current of MB (best measured at -0.30 V vs. SCE) can be used for detecting hybridization. The differential pulse voltammetric current of MB increases linearly in the 1.0 × 10^-12 mol L^-1 to 1.0 × 10^-6 mol L^-1 nuc concentration range, and the detection limit is 3.3 × 10^-13 mol L^-1 (at 3σ). The DNA sensor was successfully applied to the determination of the PCR product of the gene in pork. Graphical abstract Response of an electrochemical DNA biosensor based on the use of a carbon ionic liquid electrode modified with three-dimensional graphene. It enables sensitive voltammetric detection of the specific sequence of the Staphylococcus aureus nuc gene.

Investigation on direct electrochemical and electrocatalytic behavior of hemoglobin on palladium-graphene modified electrode

Palladium-graphene (Pd-GR) nanocomposite was acted as modifier for construction of the modified electrode with direct electrochemistry of hemoglobin (Hb) realized. By using Nafion as the immobilization film, Hb was fixed tightly on Pd-GR nanocomposite modified carbon ionic liquid electrode. Electrochemical behaviors of Hb modified electrode were checked by cyclic voltammetry and a pair of redox peaks originated from direct electron transfer of Hb was appeared. The Hb modified electrode had excellent electrocatalytic activity to the reduction of trichloroacetic acid and sodium nitrite in the concentration range from 0.6 to 13.0mmol·L^-1 and from 0.04 to 0.5 mmol·L^-1. Therefore Pd-GR nanocomposite was proven to be a good candidate for the fabrication of third-generation electrochemical biosensor.