Sensitive Voltammetric Determination of Niclosamide at a disposable pencil graphite electrode

Suitably Incorporated Hydrophobic, Redox-Active Drug in Poly Lactic Acid-Graphene Nanoplatelet Composite Generates 3D-Printed Medicinal Patch for Electrostimulatory Therapeutics

Polymer carbon composites have been reported for improved mechanical, thermal and electrical properties to provide reduced side effect by 3D printing personalized biomedical drug delivery devices. But control on homogeneity in loading and release of dopants like carbon allotropes and drugs, respectively, in the bulk and on the surface has always been a challenge. Herein, we are reporting a methodological cascade to achieve a model, customizable, 3D printed, homogeneously layered and electrically stimulatory, PLA-Graphene nanoplatelet (hl-PLGR) based drug delivery device, called 3D-est-MediPatch. The medicinal patch has been prepared by 3D-printing a Nic-hl-PLGR composite obtained by incorporating a redox active model drug, niclosamide (Nic) in hl-PLGR. The composite of Nic-hl-PLGR was characterized in three sequentially complex forms─composite film, hot melt extruded (HME) filament, and 3D printed (3DP) patches to understand the effect of filament extrusion and 3D-printing processes on Nic-hl-PLGR composite and overall drug incorporation efficiency and control. The incorporation of graphene was found to improve the homogeneity of the drug, and the hot melt extrusion improved the dispersion of drug and graphene fillers in the composite. The electroresponsive drug release from the Nic-hl-PLGR composite was found to be controllably accelerated compared to the drug release by diffusion, in simulated buffer condition. The released drug concentration was found to reach within the IC50 range for malignant melanoma cell (A375) and showed in vitro selectively, with reduced effects in noncancerous, fibroblast cells (NIH3T3). Further, the feasibility of application for this system was assessed in generating personalized 3D-est-MediPatch for skin, liver and spleen tissues in ex-vivo scenario. It showed excellent feasibility and efficacy of the 3D-est-MediPatch in controlled and personalized release of drugs during electrostimulation. Thus, a model platform, 3D-est-MediPatch, could be achieved by suitably incorporating a hydrophobic, redox-active drug (niclosamide) in poly lactic acid-graphene nanoplatelet composite for electrostimulatory therapeutics with reduced side effects.

Design and fabrication of electrochemical sensor based on NiO/Ni@C-Fe3O4/CeO2 for the determination of niclosamide

In this study, we aimed to enhance and accelerate the electrochemical properties of a glassy carbon-based voltammetric sensor electrode. This was achieved through the modification of the electrode using a nanocomposite derived from a metal-organic framework, which was embedded onto a substrate consisting of metal oxide nanoparticles. The final product was an electrocatalyst denoted as NiO/Ni@C-Fe3O4/CeO2, tailored for the detection of the drug niclosamide. Several techniques, including FT-IR, XRD, XPS, FE-SEM, TEM, and EDS, were employed to characterize the structure and morphology of this newly formed electroactive catalyst. Subsequently, the efficiency of this electrocatalyst was evaluated using cyclic voltammetry and electrochemical impedance spectroscopy techniques. Differential pulse voltammetry was also utilized to achieve heightened sensitivity and selectivity. A comprehensive exploration of key factors such as the catalyst quantity, optimal instrumental parameters, scan rate influence, and pH effect was undertaken, revealing a well-regulated reaction process. Furthermore, the sensor's analytical performance parameters were determined. This included establishing the linear detection range for the target compound within a specified concentration interval of 2.92 nM to 4.97 μM. The detection limit of 0.91 nM, repeatability of 3.1%, and reproducibility of 4.8% of the sensor were calculated, leading to the observation of favorable stability characteristics. Conclusively, the developed electrochemical sensor was successfully employed for the quantification of niclosamide in urine samples and niclosamide tablets. This application highlighted not only the sensor's high selectivity but also the satisfactory and accurate outcomes obtained from these measurements.

Techniques for analytical estimation of COVID-19 clinical candidate, niclosamide in pharmaceutical and biomedical samples

Niclosamide is a well-known broad-spectrum antiparasitic drug used for human as well as veterinary tapeworm infections. Recently, it attracted attention as an antiviral agent for treating coronavirus disease 2019. It is administered orally in humans to treat tapeworm infections. Furthermore, it is a registered pesticide and molluscicide to control infections in the aquaculture industry. Its chronic environmental exposure has potential toxicities when such contaminated seafood is consumed. Therefore, monitoring its residual concentration in food products (seafood, water, water waste, etc.) and pharmaceuticals (active pharmaceutical ingredients, bulk drugs, and formulations) is imperative. The present review critically investigates the sophisticated techniques employed for analyzing niclosamide, its degradation products, and metabolites in various samples and matrices. The future scope for green analytical methods, green sample extraction and preparation is also deliberated.

Recent Developments in Voltammetric Analysis of Pharmaceuticals Using Disposable Pencil Graphite Electrodes

The even growing production of both well-known and new derivatives with pharmaceutical action involves the need for developing facile and reliable methods for the analysis of these compounds. Among the widely used instrumental techniques, the electrochemical ones are probably the simplest and the most rapid, also having good performance characteristics. However, the key tool in electroanalysis is the working electrode. Due to the inherent electrochemical and economic advantages of the pencil graphite electrode (PGE), the interest in its applicability in the analysis of different analytes has continuously increased in recent years. Thus, this paper aims to review the scientific reports published in the last 10 years on the use of the disposable eco- and user-friendly PGEs in the electroanalysis of compounds of pharmaceutical importance in different matrices. The PGE characteristics and designs (bare or modified with various types of materials), along with their applications and performance parameters (e.g., linear range, limit of detection, and reproducibility), will be discussed, and their advantages and limitations will be critically emphasized.

Electro-analytical sensing of anti-hypotensive agents: application to dosage forms and human urine

A new and valid method was developed for the quantitative voltammetric analysis of midodrine hydrochloride (MID) in pharmaceutical tablets (Midodrine) and biological samples. The method is based on electro-oxidation of MID supported by both disposable pencil electrode (PE) and glassy carbon electrode (GCE). The analysis was carried out using cyclic voltammetry, differential pulse voltammetry (DPV), and square wave voltammetry (SWV) techniques. The proposed analytical method was validated according to ICH guidelines. MID was successively assayed at concentration ranges of 1.15-6.55 and 0.58-3.05 μg mL^-1 at PE. Also, MID was successively assayed at concentration ranges of 1.15-5.28 and 2.86-27.6 μg mL^-1 at GCE for DPV and SWV methods, respectively. The proposed method was successfully used for the analysis of MID in its dosage form and human urine with good recoveries of 99.66 ± 0.33, 99.8 ± 0.45 at PE and 99.8 ± 0.25, 98.7 ± 1.27 at GCE for the DPV and SWV methods, respectively. The suggested method could be applied to the studied drug in the quality control lab as well as in its pharmacokinetic studies.

Amperometric detection of tumor suppressor protein p53 via pencil graphite electrode for fast cancer diagnosis

Cancer occupies the second place in terms of worldwide mortality. Early and fast diagnosis of cancer helps clinicians to expand therapeutic approaches ultimately leading towards early diagnosis of cancer patients. In the present work, we delineated an amperometric immunosensor to diagnose cancer to detect p53, a biomarker for cancer. The immunosensor was fabricated by immobilizing anti-p53 antibodies onto the pencil graphite electrode (PGE). The immobilization of probe was studied by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The immunosensor was optimized for pH, incubation temperature, antibody concentration, incubation time and antigen concentration. The developed immunosensor, showed a linear range between 10 pgmL^-1 to 10 ngmL^-1 with a detection limit (LOD) of 10 pgmL^-1. p53 antigen was analyzed by measuring current under optimal conditions. The occurrence of p53 was determined in sera of prostate, breast, colon and lung cancer patients by the present immunosensor. The lower incubation time i.e., fast response and lower LOD demonstrated an improved p53 immunosensor for early diagnosis of cancer.

Three-dimensional hierarchical porous carbon coupled with chitosan based electrochemical sensor for sensitive determination of niclosamide

Herein, a simple, low-cost, environment-friendly strategy was proposed to prepare the composite of three-dimensional hierarchical porous carbon and chitosan, which was applied to modify the glass carbon electrode to fabricate an electrochemical sensor for the determination of niclosamide. The three-dimensional porous carbon with interconnected conductive network, high surface area, and self-generated oxygen-containing functional groups was prepared by salt-templating method with glucose as carbon source and eutectic mixture of LiBr/KBr as both activating and pore-forming agent. During the subsequent ultrasonic process, chitosan with excellent filming property, strong adsorption ability, and good dispersibility was successfully decorated on the obtained porous carbon to further enhance the determination performance of niclosamide. Benefitting from the multi-functional integration of three-dimensional hierarchical porous carbon and chitosan, the fabricated sensor presented a low limit of detection (6.7 nM) in the linear concentration range from 0.01 to 10 µM. Moreover, the fabricated sensor could show good repeatability, reproducibility, stability, and selectivity. Most important, the decent practicability for the detection of niclosamide was obtained in different food samples with low relative standard deviation and satisfactory recoveries. This work provides a very valuable reference for the sensitive determination of niclosamide in food samples.

Anodic Adsorptive Stripping Voltammetric Determination of Rafoxanide on Glassy Carbon Electrode

AIMS AND OBJECTIVE

The development of easy, accurate, reliable technique which is characterized by low cost, minimal sample pre-treatment, and short analysis time to monitor RFX residues in milk samples before distribution to consumers.

BACKGROUND

Literature survey reveals several analytical methods, including high-performance liquid chromatography (HPLC), ultra-performance liquid chromatography (UPLC) and thin-layer chromatography (TLC)-densitometry. These methods are time consuming, require additional steps like preconcentration or multisolvent extraction, trained technicians, and expensive instruments.

MATERIALS AND METHODS

The electrochemical analysis of RFX was effectively established by the adsorptive stripping method on GCE due to the effective interfacial accumulation of RFX on the electrode surface. The RFX adsorptive accumulation is followed by electrochemical measurement of the accumulated analyte.

RESULTS

The electrochemical oxidation of RFX was studied at glassy carbon electrodes (GCE) in Britton-Robinson buffer (BR) solutions over the pH range from 2.0-12.0 using cyclic and differential pulse voltammetry (DPV). The oxidation of the drug was accomplished in a single irreversible, adsorption-controlled step within the pH range 4.0-9.0. Therefore, the application of GCE for a sensitive and selective quantification of RFX by adsorptive stripping voltammetry was reported. This format was satisfactorily applied for the determination of RFX in bovine milk. Limit of detection (LOD) of 1.25 μg kg-1 of milk and mean recoveries of 97.8 to 107.5% were achieved.

CONCLUSION

The proposed method might be competitive with the HPLC techniques. The detection limit found for RFX on GCE for milk samples, after medium exchange, was well below the MRLs, the maximum concentration of a veterinary drug residue legally permissible in food, are proposed by the European Medicines Agency.

Facile synthesis of Vulcan XC-72 nanoparticles-decorated halloysite nanotubes for the highly sensitive electrochemical determination of niclosamide

We report a scalable and controllable ultrasound-assisted strategy for the preparation of Vulcan XC-72 nanoparticles-decorated halloysite nanotubes (HNTs@VXC-72), which was applied to modify glassy carbon electrode (GCE) for the highly sensitive electrochemical determination of niclosamide (NA). For the HNTs@VXC-72 nanocomposite, VXC-72 nanoparticles with excellent electrical conductivity and good dispersing property contributed to the formation of the interconnected conductive network; HNTs possessed good adsorption performance and promoted the electrochemical redox reaction. The research results showed that the combination of VXC-72 nanoparticles and HNTs produced the effect of synergistic enhancement. The HNTs@VXC-72/GCE sensor could show a relatively low detection limit of 3.28 nM in the great linear NA concentration range of 0.01-1 µM. When used for the NA determination in food samples, the HNTs@VXC-72/GCE sensor exhibited good practical feasibility with low RSD and acceptable recoveries, which provided a promising NA determination approach to ensure food safety.

Ecotoxicological assessment and electrochemical remediation of doxorubicin

Doxorubicin (DOX) is an anthracycline widely used in treatments of several cancers, so it has found in hospital effluents with a significant concentration (above 1 μg L^-1). Electrochemical remediation is an alternative to promote its degradation. The aim of this work was to evaluate the ability of nanostructured graphite electrodes with metallic oxides to degrade DOX by electro-oxidation (EO). Graphite, TiO₂@graphite and AuO-TiO₂@graphite electrodes were used in medium with tap water or 10 mmol L^-1 NaCl. DOX treatments at concentrations of 1.25-5 mg L^-1 were carried out in a voltage source with 1.5-5 V. The cathode used was the platinum electrode. The treatment of DOX 1.25 mg L^-1 with 10 mmol L^-1 NaCl electrolyte using the AuO-TiO₂@graphite electrode at 5 V and 1 mA was the best methodology to promote its degradation. Also, the modified electrode was efficient to DOX degradation after 17 cycles of reuse. An energy expenditure of 1.11 and 0.2 kWh m^-3 were obtained for 3 and 50 mL of treatment, respectively. Fish embryo acute toxicity test with zebrafish (Danio rerio) were performed before and after treatment by EO using NaCl. This treatment caused no effect on embryo-larval development, however it induced significant damage in the DNA of the zebrafish larvae after 96 h of exposure, which emphasizes the importance of a depth ecotoxicological evaluation during the development of EO methodologies.

Voltammetric Evaluation of Diclofenac Tablets Samples through Carbon Black-Based Electrodes

Diclofenac (DIC) is a non-steroidal anti-inflammatory drug of wide use around the world. Electroanalytical methods display a high analytical potential for application in pharmaceutical samples but the drawbacks concerning electrode fouling and reproducibility are of major concern. Henceforth, the aim of this work was to propose the use of alternative low-cost carbon black (CB) and ionic liquid (IL) matrix to modify the surface of pencil graphite electrodes (PGE) in order to quantify DIC in raw materials, intermediates, and final products, as well as in stability assays of tablets. The proposed method using CB+IL/PGE displayed good recovery (99.4%) as well as limits of detection (LOD) of 0.08 µmol L-1 and limits of quantification (LOQ) of 0.28 µmol L^-1. CB+IL/PGE response was five times greater than the unmodified PGE. CB+IL-PGE stands as an interesting alternative for DIC assessment in different pharmaceutical samples.

Pencil Graphite Electrodes: A Versatile Tool in Electroanalysis

Due to their electrochemical and economical characteristics, pencil graphite electrodes (PGEs) gained in recent years a large applicability to the analysis of various types of inorganic and organic compounds from very different matrices. The electrode material of this type of working electrodes is constituted by the well-known and easy commercially available graphite pencil leads. Thus, PGEs are cheap and user-friendly and can be employed as disposable electrodes avoiding the time-consuming step of solid electrodes surface cleaning between measurements. When compared to other working electrodes PGEs present lower background currents, higher sensitivity, good reproducibility, and an adjustable electroactive surface area, permitting the analysis of low concentrations and small sample volumes without any deposition/preconcentration step. Therefore, this paper presents a detailed overview of the PGEs characteristics, designs and applications of bare, and electrochemically pretreated and chemically modified PGEs along with the corresponding performance characteristics like linear range and detection limit. Techniques used for bare or modified PGEs surface characterization are also reviewed.

Development of a disposable and low-cost electrochemical sensor for dopamine detection based on poly(pyrrole-3-carboxylic acid)-modified electrochemically over-oxidized pencil graphite electrode

In this study, preparation of a single-use electrochemical sensor for the selective and sensitive determination of dopamine (DOP) was investigated by electrochemical polymerization of pyrrole-3-carboxylic acid on electrochemically over-oxidized pencil graphite electrode (p(P3CA)/EOPGE). Cyclic voltammetry measurements of Fe(CN)₆^4-/3- indicated that the electrochemically over-oxidized PGE (EOPGE) showed superior electron transfer characteristics according to bare PGE. The ionized carboxyl groups found in the structure of poly(pyrrole-3-carboxylic acid) (p(P3CA)) showed high affinity towards positively charged DOP. The combination of the advantages of EOPGE and p(P3CA) in p(P3CA)/EOPGE led to a synergistic effect on the electrochemical oxidation of DOP. The effects of experimental variables on the voltammetric performance of the p(P3CA)/EOPGE were examined by preparing the electrodes at different conditions. The p(P3CA)/EOPGE showed high selectivity towards DOP by discriminating its oxidation potential from the common interfering substances such as ascorbic and uric acids. The p(P3CA)/EOPGE showed linear responses in the electrochemical oxidation of DOP between the concentration values of 0.025µM and 7.5µM. Detection limit was determined as 0.0025µM according to signal to noise ratio (S/N: 3). Analytical application of p(P3CA)/EOPGE was successfully tested in the determination of DOP in blood serum and pharmaceutical samples.

An ultrasensitive electrochemiluminescent sensor based on a pencil graphite electrode modified with CdS nanorods for detection of chlorogenic acid in honeysuckle

In this paper, a novel and ultrasensitive electrochemiluminescent sensor employing a solvothermal-synthesized CdS nanorod-modified pencil graphite electrode (CdS/PGE) for the determination of chlorogenic acid (CA) is fabricated. In the first step, the PGE surface is modified using CdS nanorods. In the next step, the developed electrode is used to detect CA using a electrochemiluminescent (ECL) technique, in which potassium persulfate (K₂ S₂ O₈ ) served as a co-reactant. The possible ECL mechanism is investigated, and the influences of pH and cyclic voltammetric scanning rate on the signal response are studied. The ECL intensity decreases quantitatively in relation to the concentration of the target molecule. Under optimized conditions, the linear correlation between the quenched ECL intensity and the logarithm of CA concentration is observed in the range from 2 × 10^-9 to 8 × 10^-7  mol L^-1 with a limit of detection of 1 × 10^-9  mol L^-1 . This proposed method is applied to the analysis of CA in honeysuckle flower, giving recoveries of 99-107%. The experimental results demonstrate that this ECL sensor shows good stability and reproducibility.

Electrically stimulated liquid phase microextraction combined with differential pulse voltammetry: a new and efficient design for in situ determination of clozapine from complicated matrices

Electromembrane extraction combined with differential pulse voltammetry for in situ determination of clozapine from complicated matrices.

Photoelectrochemical glucose biosensor based on a dehydrogenase enzyme and NAD+/NADH redox couple using a quantum dot modified pencil graphite electrode

A simple, disposable and economical modified electrode was prepared by electrodeposition of hybrid quantum dots onto a pencil graphite electrode surface and immobilization of glucose dehydrogenase onto the quantum dot modified electrode.

Utility of Activated Glassy Carbon and Pencil Graphite Electrodes for Voltammetric Determination of Nalbuphine Hydrochloride in Pharmaceutical and Biological Fluids

This work compares voltammetric response of nalbuphine hydrochloride (NP·HCl) at both activated glassy carbon and pencil graphite electrodes. The electrochemical oxidation of the drug was studied using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and square wave voltammetry (SWV) techniques. For analytical purpose a well-resolved irreversible diffusion controlled voltammetric peak was established in Britton-Robinson (B-R) buffer solution of pH 6.00 using pencil graphite electrode (PGE). Using activated glassy carbon electrode (GCE) a well-resolved irreversible diffusion controlled voltammetric peak was obtained at pH 7.00 using the same buffer solution. According to the linear relationship between the peak current and NP·HCl concentration, DPV and SWV methods were developed for their quantitative determination in pharmaceutical and human biological fluids. The linear response was obtained in the range from1.6×10-5to1.5×10-4 mol L−1using PGE and from12.5×10-6to13.75×10-5 mol L−1using a GC electrode, respectively. Precision and accuracy of the developed method were checked by recovery studies.

Development of a Novel, Low-Cost, Disposable Wooden Pencil Graphite Electrode for Use in the Determination of Antioxidants and Other Biological Compounds

The development of portable sensors that can be used outside the lab is an active area of research in the electroanalytical field. A major focus of such research is the development of low-cost electrodes for use in these sensors. Current electrodes, such as glassy-carbon electrodes (GCEs), are costly and require time-consuming preparation. Alternatives have been proposed, including mechanical pencil-lead electrodes (MPEs). However, MPEs themselves possess numerous drawbacks, particularly structural fragility. In this paper, we present a novel pencil-graphite electrode (PGE) fabricated from a regular HB#2 pencil. This PGE is a simple, disposable, extremely low-cost alternative to GCEs ($0.30 per PGE, vs. $190 + per GCE), and possesses the structural stability that MPEs lack. PGEs were characterized by square-wave voltammetry of ferricyanide, gallic acid, uric acid, dopamine, and several foodstuffs. In all cases, PGEs demonstrated sensitivities comparable or superior to those of the GCE and MPE (LOD = 5.62 × 10⁻⁴ M PGE, 4.80 × 10⁻⁴ M GCE, 2.93 × 10⁻⁴ M MPE). Signal areas and peak heights were typically four to ten times larger for the PGE relative to the GCE.