Square Wave Voltammetry Research Articles

Square-wave voltammetric evaluation of electrochemical constants: Comparative study with other techniques

Square-wave voltammetry was employed for evaluation of electrochemical rate constants for soluble hexacyanoferrate ions as well as for iron hexacyanoferrate (Prussian blue) and nickel hexacyanoferrate immobilized on carbon electrodes. Modelling of square-wave response of immobilized species with assumption of Nernstian behavior, the dimensionless net current peak splitting occurs. The peak value decreases with the rise of square-wave amplitude Esw and splits around the common value of 50 mV. For a quasireversible behavior, the dimensionless net peak current has an extremum depending on both frequency and Esw. At 40 mV, the frequency in the extremum almost coincides with the surface electrochemical rate constant ksur. For practical confirmation, the Prussian blue film was studied at different frequencies (Esw = 50 mV). At lower values, the reaction is relatively fast and net peak current splitting occurs. At higher values, the net response reaches its maximum allowing to evaluate the surface electrochemical rate constant. A comparative investigations of electrode kinetics (for both surface and heterogeneous electrochemical constant) by different electrochemical methods proved the advantages of square-wave pulse technique. In contrast to cyclic voltammetry and electrochemical impedance spectroscopy, the square-wave voltammetry has lower variation of estimated parameters, relatively simple calculations, uncomplicated simulation of different mechanisms.

Rapid and efficient extraction of cerium by forming Al-Ce alloys in LiCl-KCl molten salts

The extraction of lanthanides in spent fuel reprocessing plays a key role in the development of nuclear energy. In this work, the extraction of the typical fissionable cerium elements has been studied by electrolytic co-reduction of Al(III) and Ce(III) in LiCl-KCl-CeCl3 molten salts assisted by KAlCl4. The electrochemical behavior of the reduction of Al(III) and Ce(III) on a molybdenum electrode was studied by cyclic voltammetry (CV), square wave voltammetry (SWV), and open circuit chronopotentiometry (OCP), and specific peaks of five Al-Ce intermetallic compounds were detected. After 2.7 h of galvanostatic electrolysis at a current density of 0.064 A cm-2, the extraction efficiency and current efficiency of Ce(III) reached 99.9 % and 91.3 % respectively. Potentiostatic electrolysis is slightly more efficient, with 99.9 % Ce(III) extraction in 3.5 h at a current efficiency of 97.8 %. The products of electrolysis are rod-shaped alloys (Al11Ce3, Al3Ce, Al2Ce), and the molten salts purified by electrolytic separation are free of impurity signals and can be reused for electrolytic refining.

Decentralized touch-based micronutrition sensor towards personalized nutrition: Parallel detection of sweat ascorbic acid and zinc ions

The zinc (Zn) and ascorbic acid (AA) micronutrient duo has received a considerable attention in individual’s nutrition plans, particularly after the recent pandemic, owing to its distinct beneficial impact on boosting the immune system. Accordingly, there are growing needs for frequent and decentralized measurements of the trace element and micronutrient levels towards well-balanced personalized nutrition. Leveraging natural sweat sampling from the fingertip, we describe here a disposable electrochemical sensor array, consisting of neighboring Zn ion (Zn(II)), and AA electrodes, towards parallel touch-based on-site monitoring of dynamically-changing sweat Zn(II), and AA levels, following the intake of the corresponding nutrition supplements.. A highly permeable poly (vinyl alcohol) (PVA) hydrogel, placed on the dual-electrode sensor array, served for transferring the sweat from the fingertip onto the electrode surface. Zn(II) measurements were performed on a bismuth/Nafion modified screen printed electrode (SPE) with square-wave anodic stripping voltammetry (SWASV), while the AA detection relied on recording of the open circuit potential (OCP) change, on the tetrathiafulvalene-7,7,8,8-tetracyanoquinodimethane (TTF-TCNQ) immobilized SPE. Rapid decentralized measurements of sweat Zn(II) and AA temporal profiles were carried out on the fingertip sweat of healthy subjects after consuming pill supplements in connection to the disposable strip along with hand-held electrochemical analyzer. The utility of the touch-based disposable Zn(II)/AA multisensory platform for parallel measurements of this pair of micronutrients was demonstrated towards personalized nutrition by providing real-time monitoring of the dose-response relationship. Our findings indicate that the new sweat nutrition sensing device holds considerable promise for guiding dietary interventions and enhancing personalized nutrition.

Studies on the Aptasensor Miniaturization for Electrochemical Detection of Lead Ions.

Lead poses severe effects on living organisms, and since Pb2+ ions tend to accumulate in different organs, it is crucial to monitor Pb2+ concentration in samples such as water and soil. One of the approaches is the utilization of biosensors combined with aptamer-based layers for the electrochemical detection of lead ions. Herein, we present the studies of applying miniaturized screen-printed transducers as solid surfaces to fabricate aptamer layers. As the research is the direct continuation of our previous studies regarding the use of gold disk electrodes, the working parameters of elaborated aptasensors were defined, including the range of linear response (10-100 nM), selectivity as well as stability, regeneration, and feasibility of application for the analysis of real samples. This was achieved using voltammetric techniques including cyclic and square-wave voltammetry in the presence of methylene blue redox indicator.

Electrochemical biosensor for the evaluation of monoclonal antibodies targeting the N protein of SARS-CoV-2 virus

The emergence of COVID-19 caused by the coronavirus SARS-CoV-2 has prompted a global pandemic that requires continuous research and monitoring. This study presents a design of an electrochemical biosensing platform suitable for the evaluation of monoclonal antibodies targeting the SARS-CoV-2 nucleocapsid (N) protein. Screen-printed carbon electrodes (SPCE) modified with gold nanostructures (AuNS) were applied to design a versatile and sensitive sensing platform. Electrochemical techniques, including electrochemical impedance spectroscopy (EIS) and square wave voltammetry (SWV), were used to investigate the interactions between immobilised recombinant N (rN) protein and several monoclonal antibodies (mAbs). The electrochemical characterisation of SPCE/AuNS/rN demonstrated a successful immobilisation of rN, enhancing the electron transfer kinetics. Affinity interactions between immobilised rN and four mAbs (mAb-4B3, mAb-4G6, mAb-12B2, and mAb-1G5) were explored. Although mAb-4B3 showed some non-linearity, the other monoclonal antibodies exhibited specific and well-defined interactions followed by the formation of an immune complex. The biosensing platform demonstrated high sensitivity in the linear range (LR) from 0.2 nM to 1 nM with limits of detection (LOD) ranging from 0.012 nM to 0.016 nM for mAb-4G6, mAb-12B2, and mAb-1G5 and limits of quantification (LOQ) values ranging from 0.035 nM to 0.139 nM, as determined by both EIS and SWV methods. These results highlight the system's potential for precise and selective detection of monoclonal antibodies specific to the rN. This electrochemical biosensing platform provides a promising route for the sensitive and accurate detection of monoclonal antibodies specific to the rN protein.

Electrochemical detection of the neurotransmitter glutamate and the effect of the psychotropic drug riluzole on its oxidation response.

Glutamate is the main excitatory neurotransmitter in the brain and plays a leading role in degenerative diseases, such as motor neuron diseases. Riluzole is a glutamate regulator and a therapeutic drug for motor neuron diseases. In this work, the interaction between glutamate and riluzole was studied using cyclic voltammetry and square-wave voltammetry at a glassy carbon electrode (GCE). It was shown that glutamate underwent a two-electron transfer reaction on the GCE surface, and the electrochemical detection limits of glutamate and riluzole were 483μmol/L and 11.47μmol/L, respectively. The results confirm that riluzole can promote the redox reaction of glutamate. This work highlights the significance of electrochemical technology in the sensing detection of the interaction between glutamate and related psychotropic drugs.

Electrochemical determination of riboflavin in pharmaceuticals using unmodified screen printed carbon electrodes.

In this study, we have devised an efficient and rapid approach to detect riboflavin (also known as Vitamin B2 or VB2) utilizing an unaltered screen-printed carbon electrode (SPCE). The unmodified screen-printed electrodes are created within the laboratory, where carbon ink is applied to a ceramic substrate. All experiments pertaining to the investigation of electrochemical behavior and the fine-tuning of crucial experimental parameters were conducted through cyclic voltammetry (CV). For quantitative assessments, square wave voltammetry (SWV) was employed. The findings indicate that unaltered SPCEs exhibit robust current signals during the riboflavin redox reaction. Riboflavin displays a distinct oxidation peak at -0.136V (vs. Ag/AgCl, 3.0M KCl) in a Britton-Robinson buffer solution (BRBS) at pH 2, which was employed for quantification. The electrode demonstrates a broad linear range from 0.05 to 10µM, boasting a detection limit of 0.03µM. Repeatability stands at 1.45%, while reproducibility is 6.61%. Testing the influence of common interfering compounds yielded negligible results. The sensor effectively determines riboflavin content in pharmaceutical formulations without any prior treatment. This method presents an economical, modifier-free sensor with exceptional sensitivity and cost-effectiveness, making it suitable for rapid riboflavin quantification.

Incorporation of Bismuth(III) Oxide Nanoparticles into Carbon Ceramic Composite: Electrode Material with Improved Electroanalytical Performance in 4-Chloro-3-Methylphenol Determination.

In this study, a carbon ceramic electrode (CCE) with improved electroanalytical performance was developed by bulk-modifying it with bismuth(III) oxide nanoparticles (Bi-CCE). Characterization of the Bi-CCE was conducted employing atomic force microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, cyclic voltammetry (CV), and electrochemical impedance spectroscopy. Comparative analysis was conducted using an unmodified CCE. The findings proved that the incorporation of Bi2O3 nanoparticles into the CCE significantly altered the morphology and topography of the ceramic composite, and it improved the electrochemical properties of CCE. Notably, the Bi-CCE demonstrated a prolonged operational lifespan of at least three months, and there was a high reproducibility of the electrode preparation procedure. The developed Bi-CCE was effectively employed to explore the electrochemical behavior and quantify the priority environmental pollutant 4-chloro-3-methylphenol (PCMC) using CV and square-wave voltammetry (SWV), respectively. Notably, the developed SWV procedure utilizing Bi-CCE exhibited significantly enhanced sensitivity (0.115 µA L mol-1), an extended linearity (0.5-58.0 µmol L-1), and a lower limit of detection (0.17 µmol L-1) in comparison with the unmodified electrode. Furthermore, the Bi-CCE was utilized effectively for the detection of PCMC in a river water sample intentionally spiked with the compound. The selectivity toward PCMC determination was also successfully assessed.

Electrochemical immunosensors for 2,4-dichlorophenoxyacetic acid based on 3-aminopropyltrimethoxysilane modified electrodes

A novel electrochemical immunosensor prepared by direct coating of small molecular hapten on glassy carbon electrode (GCE) is reported for the detection of 2,4-dichlorophenoxyacetic acid (2,4-D). The glassy carbon electrodes were activated by electrochemical method and then were further treated with 3-aminoprpyltriethoxysilane (APS) to functionalize the GCE surface with amino groups for covalent linkage to small molecular hapten of 2,4-D with carboxyl groups. The electrodes were characterized by X-ray photoelectron spectroscopy (XPS). The principle of this immunoassay is based on an indirect competitive immunoassay. Analytes of 2,4-D and hapten of 2,4-D immobilized on glassy carbon electrode (GCE) compete for 2,4-D antibodies labeled by horseradish peroxidase (HRP-anti-2,4-D). After complete immunoreaction, the GCE attached HRP-anti-2,4-D tracers was transferred to a substrate solution containing hydroquinone (QH2) and hydrogen peroxide for square wave voltammetry (SWV) detection. Determination conditions were optimized. The SWV anodic peak current decreased linearly with the increase of 2,4-D concentration over the range from 0.10 to 15.0 mg/L 2,4-D with a detection limit of 0.01mg/L. The performance of this electrochemical immunoassay was successfully evaluated with river water spiked with 2,4-D, indicating that this convenient, rapid, and sensitive technique offers great prospect for the monitoring of trace 2,4-D in environment.

Novel Determination of the Influence of Idarubicin upon DNA Chain Structure Using an Electrochemical DNA Biosensor by Voltammetry

Two sequences of DNA (single-strand DNA (ssDNA) and double-strand DNA (dsDNA)) modified disposable electrodes were designed to investigate the effect of antitumor agent drug idarubicine (IDA) on the DNA chain structure. The effect of IDA on DNA structure was analyzed by square wave voltammetry (SWV) depending on not only the guanine signal but also IDA oxidation response. The present study included the electrochemical investigation of IDA and the investigation of the biomolecular interaction between IDA and DNA. IDA was detected in buffer and urine using disposable pencil graphite electrodes (PGE) with SWV and cyclic voltammetry (CV)). The detection limit (LOD) of IDA in urine samples was 0.089 µg mL−1 with SWV under optimum conditions. For the biomolecular interaction of IDA and DNA, all electrochemical conditions, such as the concentration of DNA, concentration of IDA, interaction phase (at electrode surface/in solution phase), the interaction pH, and the interaction time were optimized. IDA interacted biomolecularly with DNA at the electrode surface and in solution phase using two methods. There is no previous electrochemical study performed on the interaction of IDA with ssDNA. Hence, the effect of IDA on both ssDNA and dsDNA was presented for the first time.

Ferrocene-Containing Gallic Acid-Derivative Modified Carbon-Nanotube Electrodes for the Fast Simultaneous and Selective Determination of Cytostatics from Aqueous Solutions

In this work, a ferrocene-containing gallic acid-derivative modified carbon-nanotube paste electrode (Gal-Fc-CNT), obtained through simple mechanical mixing, was studied for the fast simultaneous voltammetric determination of doxorubicin (DOX), capecitabine (CPB), and cyclophosphamide (CPP) as cytostatic indices based on their cumulative signals and the selective determination of DOX. The individual and simultaneous electrochemical behavior of DOX, CPB, and CPP, studied through cyclic voltammetry (CV) on the Gal-Fc-CNT paste electrode at various pHs and potential ranges, allowed for the development of a simple simultaneous determination method as a cytostatic index at a pH of 12 using square-wave voltammetry, which allowed for a better performance than reported electrodes for each individual cytostatic. A faster and selective detection of DOX, with a limit of detection of 75 ng·L−1, was achieved using square-wave voltammetry at a pH of 3. The good results obtained for the real tap water assessment indicated the applicability of the Gal-Fc-CNT paste electrode for practical applications (water samples).

Development of a Biosensor to Detect Venom of Malayan Krait (Bungarus candidus).

Malayan krait (Bungarus candidus) envenoming is a cause of significant morbidity and mortality in many Southeast Asian countries. If intubation and specific antivenom administration are delayed, the most significant life-threatening outcome may be the inhibition of neuromuscular transmission and subsequent respiratory failure. It is recommended that krait-envenomed victims without indications of neurotoxicity, e.g., skeletal muscle weakness or ptosis, immediately receive 10 vials of antivenom. However, the administration of excess antivenom may lead to hypersensitivity or serum sickness. Therefore, monitoring venom concentrations in patients could be used as an indicator for snake antivenom treatment. In this study, we aimed to develop a screen-printed gold electrode (SPGE) biosensor to detect B. candidus venom in experimentally envenomed rats. The gold electrodes were coated with monovalent Malayan krait IgG antivenom and used as venom detection biosensors. Electrochemical impedance spectrometry (EIS) and square wave voltammetry (SWV) measurements were performed to detect the electrical characterization between B. candidus venom and monovalent IgG antivenom in the biosensor. The EIS measurements showed increases in charge transfer resistance (Rct) following IgG immobilization and incubation with B. candidus venom solution (0.1-0.4 mg/mL); thus, the antibody was immobilized on the electrode surface and venom was successfully detected. The lowest current signal was detected by SWV measurement in rat plasma collected 30 min following B. candidus experimental envenoming, indicating the highest level of venom concentration in blood circulation (4.3 ± 0.7 µg/mL). The present study demonstrates the ability of the SPGE biosensor to detect B. candidus venom in plasma from experimentally envenomed rats. The technology obtained in this work may be developed as a detection tool for use along with the standard treatment of Malayan krait envenoming.

Determination of indium by adsorptive stripping voltammetry at the bismuth film electrode using combined electrode system facilitating medium exchange

A novel method of determining indium has been described in this article which uses adsorptive stripping voltammetry (AdSV) and 4-(2-pyridylazo)-resorcinol (PAR) as a chelating agent or as the preconcentration agent. The measurements were performed using square-wave voltammetry by using a combined electrode system, which allows for preconcentration and stripping without opening the circuit. Ex situ plated bismuth film electrode (BiFE) was used as the working electrode. A potential-time program was developed for the inversion cycle stages based on the various factors that affect the magnitude of the inversion signal. The calibration curve was linear in a concentration range of 2·10−7 to 4·10−6 М when the pH is 4.8, accumulation potential is −700 mV, and PAR concentration is 1·10−4 M. The detection limit for the 3σ criterion with an accumulation time of 120 s was 3.5·10−9 М. Several interferences caused by Tl(I), Zn(II), Cu(II), Pb(II), Co(II), Ni(II), Mn(II), Fe(III), Cr(III) ions have been studied, and it has been shown that medium exchange procedure can effectively eliminate some interferences. It was demonstrated that the method can be applied to the determination of indium in tap water and in ITO glass sample.

Development of an inexpensive poly(MO)/CNT@PGE for voltammetric investigation of Methocarbamol in presence of Levofloxacin

This work describes the voltammetric investigation of trace amounts of pain reliever drug methocarbamol (MET) by carbon nanotubes decorated methyl orange polymerized pencil graphite electrode (poly(MO)/CNT@PGE). The proposed modified electrode was prepared by electropolymerization of methyl orange (MO) over the carbon nanotubes (CNTs) decorated on PGE. The geomorphologies of the equipped sensors were accomplished by scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX) and electrochemical impedance spectroscopy (EIS) study. The electrochemical behaviour of MET in presence of levofloxacin (LVF) has been studied by applying different voltammetric techniques in 0.1 M PBS of pH 4.0. The proposed poly(MO)/CNT@PGE shows enhanced peak current with a small negative shift in peak potential for MET over the bare and modified electrodes due to the electrocatalytic features of the modifiers. The different parameters such as effect of polymer layers, pH, scan rate, concentrations, simultaneous and selectivity study for MET were studied by cyclic voltammetry (CV), linear sweep voltammetry (LSV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). The computed limit of detection (LOD) for MET at different concentrations (10.0–110.0 µM for DPV and 1.0–12.0 µM for SWV) was found to be 5.24 µM and 0.69 µM, respectively. The adapted electrode exhibits special characteristic features such as stability, repeatability, reproducibility, fast electron transfer behaviour and charge transfer resistance (Rct). Based on the results obtained, number of electrons (n), number of protons (m), heterogeneous rate constant (ko) and surface concentration (Γ0) of MET have been calculated by using relative formulae. The selectivity and applicability of the modified electrode were premeditated by real sample investigation of MET present in pharmaceutical tablets with good recovery results to confirm the analytical pertinence of the proposed sensor.

Bielectrode Strategy for Determination of CYP2E1 Catalytic Activity: Electrodes with Bactosomes and Voltammetric Determination of 6-Hydroxychlorzoxazone.

We describe a bielectrode system for evaluation of the electrocatalytic activity of cytochrome P450 2E1 (CYP2E1) towards chlorzoxazone. One electrode of the system was employed to immobilize Bactosomes with human CYP2E1, cytochrome P450 reductase (CPR), and cytochrome b5 (cyt b5). The second electrode was used to quantify CYP2E1-produced 6-hydroxychlorzoxazone by its direct electrochemical oxidation, registered using square-wave voltammetry. Using this system, we determined the steady-state kinetic parameters of chlorzoxazone hydroxylation by CYP2E1 of Bactosomes immobilized on the electrode: the maximal reaction rate (Vmax) was 1.64 ± 0.08 min-1, and the Michaelis constant (KM) was 78 ± 9 μM. We studied the electrochemical characteristics of immobilized Bactosomes and have revealed that electron transfer from the electrode occurs both to the flavin prosthetic groups of CPR and the heme iron ions of CYP2E1 and cyt b5. Additionally, it has been demonstrated that CPR has the capacity to activate CYP2E1 electrocatalytic activity towards chlorzoxazone, likely through intermolecular electron transfer from the electrochemically reduced form of CPR to the CYP2E1 heme iron ion.

A novel electrochemical strategy using a newly developed carbon-based sensor for the detection of antihypertensive drug: Hydralazine hydrochloride

Hydralazine hydrochloride (HZH) is a popular nonsteroidal anti-inflammatory vasodilator. HZH was explored using Zirconium-doped ZnO nanoparticles drop-casted on a β-cyclodextrin (β-CDX) modified carbon paste electrode (Zr:ZnO/β-CDX@CPE). X-ray diffraction (XRD) and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX) were used to characterize the sample. Electrochemical impedance spectroscopy (EIS) assessed material performance. HZH was tested under different phosphate buffer conditions using Cyclic voltammetry (CV) and square wave voltammetry (SWV). Results were best at pH 7.0 in the potential range of −0.4 V to 0.7 V. The diffusion electrode technique was utilized to study the effects of different factors on the electrochemical characteristics. Quantitative evaluation of HZH was performed using SWV in the concentration range of 0.8–20 μM, showing linearity. The limit of detection (LOD) and limit of quantification (LOQ) were determined as 4.8 × 10−9 M and 16.2 × 10−9 M, respectively. This innovative technique was successfully applied to measure HZH in biological and water samples.

Development of environmentally friendly voltammetric methods for the individual and simultaneous determination of antihypertensives: Validation and application

In this study, voltammetric methods were developed and validated for the individual determination of lisinopril (LSNP) and its association with hydrochlorothiazide (HCTZ) employing a cathodically pretreated boron-doped diamond (CP-BDD) electrode. The studies of the experimental and instrumental parameters that affect the performance of both methods were carefully carried out by optimizing each parameter. The methods were validated by evaluating the figures of merits recommended by the validation guidelines. The method for the individual determination of LSNP presented a linear working range between 9.99 and 196.01 nmol L−1, with a limit of detection of 3.05 nmol L−1 by differential pulse voltammetry in BR buffer solution (pH 2.0). Simultaneous analytical curves over the concentration ranges of 0.40–3.99 and 0.050–1.045 μmol L−1 for HCTZ and LSNP, respectively, were obtained by square-wave voltammetry in Britton-Robinson buffer solution (pH 3.0). The limit of detection values calculated were 0.052 μmol L−1 and 0.020 μmol L−1, respectively for HCTZ and LSNP. The sensitivity observed for individual analytical curves of HCTZ and LSNP was statistically equal to that obtained for the simultaneous analytical curves at the 95 % confidence level. The developed methods were applied to determine these drugs in environmental, biological, and pharmaceutical samples, with satisfactory results. The method's greenness was assessed demonstrating that both validated methods constitute a greener alternative to conventional analytical methods reported in the literature.

An Electrochemical Aptasensor for the Detection of Freshwater Cyanobacteria.

Aphanizomenon is a genus of cyanobacteria that is filamentous and nitrogen-fixing and inhabits aquatic environments. This genus is known as one of the major producers of cyanotoxins that can affect water quality after the bloom period. In this study, an electrochemical aptasensor is demonstrated using a specific aptamer to detect Aphanizomenon sp. ULC602 for the rapid and sensitive detection of this bacterium. The principal operation of the generated aptasensor is based on the conformational change in the aptamer attached to the electrode surface in the presence of the target bacterium, resulting in a decrease in the current peak, which is measured by square-wave voltammetry (SWV). This aptasensor has a limit of detection (LOD) of OD750~0.3, with an extension to OD750~1.2 and a sensitivity of 456.8 μA·OD750-1·cm-2 without interference from other cyanobacteria. This is the first aptasensor studied that provides rapid detection to monitor the spread of this bacterium quickly in a targeted manner.

Fabrication and characterization of a novel strontium oxide-polythiophene core–shell nanocomposite for in-vitro electrochemical detection of antiplatelet cilostazol drug in formulation and human plasma

The green synthesis of metal or metal oxide nanoparticles utilizing plants is a novel promising approach in bio-nanotechnology. The strontium oxide nanoparticles (SrO NPs) were synthesized for the first time utilizing a plant extract of Green cardamom (Elettaria cardamomum) as a reducing and stabilizing agent. The strontium oxide polythiophene (SrO@PTh) nanocomposite was then prepared by in-situ oxidative polymerization of thiophene on the surface of SrO NPs using anhydrous FeCl3 as an oxidant. FTIR spectrum indicates the coordination of SrO NPs with the binding sites along PTh backbone. TEM analysis resulted in an average particles size of (25 – 50 nm) for SrO NPs and core–shell nanostructure of its composite (SrO@PTh CS) with shell thickness of (20–90 nm). The XRD analysis indicates a crystalline cubic structure of SrO NPs with particles size of ≈ 45 nm in average and interplanar space of (0.24 ∼ 0.36 nm). The crystallinity was relatively diminished to some extent for SrO@PTh CS which exhibits a particle size of about 85 nm and interplanar space of (0.13 ∼ 0.23 nm). A smart and novel electrochemical graphite paste sensor (GPS), based on SrO@PTh CS nanocomposite, has been fabricated for the ultrasensitive in-vitro detection of antiplatelet drug cilostazol. SrO@PTh CS nanocomposite-based square-wave voltammetry biosensor exhibited the lowest limits of detection of 1.99 × 10−10 and 9.83 × 10−10 M for cilostazol drug determination in bulk and human plasma samples, respectively compared to all the reported methods. It exhibited also good reproducibility, repeatability, long-term stability and was free from biological interference effects.

Electrochemical Investigations of Protein Denaturating Agents Dithiobutylamine and Dithiothreitol and of the Antineoplastic Alemtuzumab at Glassy Carbon Electrode

A study to establish redox and thermodynamic properties of the protein denaturing agents dithiobutylamine (DTBA) and dithiothreitol (DTT) and of the monoclonal antibody alemtuzumab (ATZ), in aqueous electrolytes, with different pH values, under different experimental conditions, was carried out on a glassy carbon electrode (GCE), using cyclic voltammetry (CV), differential pulse voltammetry (DPV) and square wave voltammetry (SWV). The voltammetric study demonstrated that DTBA, as well as DTT, were both susceptible to direct electro-oxidation on the electrode surface. The study established that the oxidation of DTBA and DTT took place in three subsequent steps, the first two occurring in the thiol groups forming a cyclic intermediate. The oxidation mechanisms of DTBA and DTT were postulated and proposed. The results using DPV and SWV clearly demonstrated the spontaneous adsorption of ATZ on the hydrophobic GCE surface and that it undergoes electro-oxidation in amino acid residues of tyrosine and tryptophan, exposed superficially on the three-dimensional structure of the protein and on the electrode. An oxidation mechanism of ATZ was also proposed.