Differential Pulse Voltammetric Research Articles

Solid Bismuth Drop Electrode – A New Tool for Voltammetric Determination of Electrochemically Reducible Organic Compounds

Solid bismuth drop electrode (SBiDE) is a new working electrode commercially available on the Czech market from 2020 by the company Metrohm. The aim of this work was to verify the applicability of the SBiDE in the voltammetric determination of a model organic substance. According to the available information, this is the very first published work on this topic. Metronidazole (an antibiotic used to treat diseases caused by both Gram-positive and Gram-negative anaerobic bacteria) was chosen in this study as a model drug representing electrochemically reducible biologically active compounds. Under optimum conditions (Britton-Robinson buffer of pH 12.0 used as the supporting electrolyte and no electrochemical regeneration of the working electrode surface), a linear calibration dependence of metronidazole was recorded in the concentration range from 1 to 600 μmol L–1, with the limits of detection (LOD) and quantification (LOQ) of 0.41 μmol L–1 and 1.4 μmol L–1, respectively. The newly developed differential pulse voltammetric (DPV) method has also been successfully applied in the determination of metronidazole in various dosage forms.

A voltammetric method coupled with chemometrics for determination of a ternary antiparkinson mixture in its dosage form: greenness assessment

An electroanalytical methodology was developed by direct differential pulse voltammetric (DPV) measurement of Levodopa (LD), Carbidopa (CD) and Entacapone (ENT) mixture using bare glassy carbon electrode (GCE) in Britton Robinson (BR) buffer (pH = 2.0). A multivariate calibration model was then applied to the exported preprocessed voltammetric data using partial least square (PLS) as a chemometric tool. Additionally, the model was cross-validated and the number of latent variables (LVs) were determined to produce a reliable model for simultaneous quantitation of the three drugs either in their synthetic mixtures or in their marketed pharmaceutical formulation with high accuracy and precision. Data preprocessing was used to tackle the problem of lacking bi-linearity which is commonly found in electrochemical data. The proposed chemometric model was able to provide fast and reliable technique for quantitative determination of antiparkinson drugs in their dosage forms. This was successfully achieved by utilizing sixteen mixtures as calibration set and nine mixtures as validation set. The percent recoveries for LD, CD and ENT were found to be 100.05% ± 1.28%, 100.04% ± 0.53% and 99.99% ± 1.25%, respectively. The obtained results of the proposed method were statistically compared to those of a previously reported High Performance Liquid Chromatography (HPLC) methodology. Finally, the presented analytical method strongly supports green analytical chemistry regarding the minimization of potentially dangerous chemicals and solvents, as well as reducing energy utilization and waste generation.

A dual-channel electrochemical biosensor enables concurrent detection of pathogens and antibiotic resistance

Diarrheagenic E. coli infections, commonly treated with β-lactam antibiotics, contribute to antibiotic resistance - a pressing public health concern. Rapid monitoring of pathogen antibiotic resistance is vital to combat antimicrobial spread. Current bacterial diagnosis methods identify pathogens or determine antibiotic resistance separately, necessitating multiple assays. There is an urgent need for tools that simultaneously identify infectious agents and their antibiotic resistance at the point of care (POC). We developed an integrated electrochemical chip-based biosensor for detecting enteropathogenic E. coli (EPEC), a major neonatal diarrheal pathogen, using an antibody against a virulence marker, termed EspB, and the β-lactam resistance marker, β-lactamase. A dual-channel microfabricated chip, bio-functionalized with a specific EspB monoclonal antibody, and nitrocefin, a β -lactamase substrate was utilized. The chip facilitated electrochemical impedance spectroscopy (EIS)-based detection of EspB antigen and EspB-expressing bacteria. For β-lactam resistance profiling, a second channel enabled differential-pulse voltammetric (DPV) measurement of hydrolyzed nitrocefin. EIS-based detection of EspB antigen was calibrated (LOD: 4.3 ng/mL ±1 and LOQ: 13.0 ng/mL ±3) as well as DPV-based detection of the antibiotic resistance marker, β-lactamase (LOD: 3.6 ng/mL ±1.65 and LOQ: 10 ng/mL ±4). The integrated EIS and DPV biosensor was employed for the simultaneous detection of EspB-expressing and β-lactamase-producing bacteria. The combined readout from both channels allowed the distinction between antibiotic-resistant and -sensitive pathogenic bacteria. The integrated electrochemical biosensor successfully achieved simultaneous, rapid detection of double positive EspB- and β-lactamase-expressing bacteria. Such distinction enabled by a portable device within a short assay time and a simplified sample preparation, may be highly valuable in mitigating the spread of AMR. This new diagnostic tool holds promise for the development of POC devices in clinical diagnosis.

Facile synthesis of PEDOT@rGO nanocomposites for novel electrochemical sensor for the determination of 4-chlorophenol in a real water sample

A sensitive electrochemical sensor was developed for the detection of 4-chlorophenol (4-CP) using the nanocomposite based on poly (3,4-ethylenedioxythiophene) and reduced graphene oxide (PEDOT-rGO). The GC electrode modified with the proposed nanocomposite was characterized using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and electrochemical impedance spectroscopy. The Raman analysis confirmed the successful incorporation of PEDOT onto the reduced graphene oxide (rGO) surface. It is also observed in the SEM analysis that PEDOT nanoparticles were spread over the rGO sheet. The lower charge transfer resistance (Rct) values for PEDOT-rGO/GCE compared to PEDOT/GCE in electrochemical impedance spectroscopy confirms the unique conducting properties of rGO and the higher surface area of PEDOT in the proposed composite on the GCE surface. The cyclic voltammetric and differential pulse voltammetric (DPV) results has indicated that the PEDOT-rGO-modified glassy carbon electrode is an excellent electrocatalyst for the detection of 4-CP compared to PEDOT and rGO. This counterpart exhibited a good linear relationship in the range of 5–250 μM, with a detection limit of 12 nM in the DPV technique. This sensor was also employed for the determination of 4-CP in river water samples. The accuracy of the analytical electrochemical sensor for 4-CP was comparatively analyzed using the obtained UV–visible spectral data, indicating a detection limit of 21 nM. Hence, the electrochemical method was successfully employed to obtain a lower detection limit for 4-CP than that for electronic absorption spectral observations. All the observed results were consistent with our expectations and showed that this novel PEDOT-rGO/GCE has good repeatability and stability and without any impactable interference behavior.

Porous Zinc Oxide and Functionalized Multiwalled Carbon Nanotubes Composite as Electrode Material for Enhanced Electrochemical Sensing of an Anticancer Drug, Dasatinib

An anticancer drug, dasatinib (DAS), is used to treat prostate cancer, chronic myelogenous leukaemia, and acute lymphoblastic leukaemia. In the present work, we describe the preparation of zinc oxide (ZnO) nanoparticles (NPs) using Averrhoa bilimbi leaf extract. These ZnO NPs were combined with functionalized multi-walled carbon nanotubes (f-MWCNT) to prepare a ZnO@f-MWCNT nanocomposite for electrochemical sensing of DAS. The prepared electrode materials, ZnO NPs, f-MWCNT, and ZnO@f-MWCNT, were characterised by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), the Fourier-transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM), zeta potential, and the dynamic light scattering (DLS) techniques. DAS exhibited a significant enhancement (18-fold) in the oxidation peak current at ZnO@f-MWCNT, 10-fold at f-MWCNT, and 6-fold at ZnO NPs as compared to that at bare GCE. Under optimised conditions, a linear relationship was noticed among the peak current and concentration of DAS in the range of 0.03–82.65 μM and 0.01–122.45 μM for the differential pulse voltammetric (DPV), and square wave voltammetric (SWV) methods, respectively. Further, the applicability of the proposed sensor was demonstrated by analysing pharmaceutical and biological samples containing DAS. Higher percentage recovery values, and lower relative standard deviation (RSD) values highlighted the accuracy and precision proposed electrochemical methods.

Point-of-care dengue detection: polydopamine-modified electrode for rapid NS1 protein testing for clinical samples.

Early diagnosis of dengue infection by detecting thedengue virus non-structural protein 1 (DENV-NS1) is important to the patients to initiate speedy treatment. Enzyme-linked immunosorbent assay (ELISA)-based NS1 detection and RT-PCR are time-consuming and too complex to be employed in remote areas of dengue-endemic countries. Meanwhile, those of NS1 rapid test by lateral flow assay suffer from low detection limit. Electrochemical-based biosensors using screen-printed gold electrodes (SPGEs) have become a reliable detection method to convey both ELISA's high sensitivity and rapid test portability. In this research, we developed an electrochemical biosensor for DENV-NS1 detection by employing polydopamine (PDA)-modified SPGE. The electrodeposition of PDA on the surface of SPGE serves as a bioconjugation avenue for anti-NS1 antibody through a simple and low-cost immobilization procedure. The biosensor performance was evaluated to detect DENV-NS1 protein in PBS and human serum through a differential pulse voltammetric (DPV) technique. The developed sensing platform displayed a low limit of detection (LOD) of 1.63pgmL-1 and a wide linear range of 10pgmL-1 to 1ngmL-1 (R2 ∼ 0.969). The sensing platform also detected DEV-NS1 from four different serotypes in the clinical samples collected from dengue patients in India and Indonesia, with acceptable sensitivity, specificity, and accuracy values of 90.00%, 80.95%, and 87.65%, respectively. This result showcased the facile and versatile method of PDA coating onto the surface of screen-printed gold electrodes for a miniaturized point-of-care (PoC) detection device.

Challenging electroanalytical method for the determination of mirabegron in biological samples and pharmaceutical formulations

A simple, economic, sensitive, and time-saving differential pulse voltammetric (DPV) procedure using nanostructured zinc oxide modified carbon paste electrode (nano ZnO-CPE) in conjunction with an anionic surfactant sodium dodecyl sulfate (SDS) was developed for ultra- sensitive detection of mirabegron (MIR), the most prescribed pharmaceutical drug in treatment of overactive bladder (OAB). The use of nanostructured zinc oxide CPE modifier increased the electrode active surface area as well as improved the process of electron transfer, also it was found that at optimal conditions MIR electrochemical process was both irreversible and diffusion-regulated. The morphological characterization of the fabricated electrode was performed using field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX). MIR voltammetric behavior was investigated using Nano ZnO-CPE in different content and electrode compositions. Therefore, ultra-sensitive results were attained with a linearity range of (0.55 to 100.20 ng ml−1) and a low limit of detection (LOD) of 0.51 ng ml−1 and limit of quantification (LOQ) of 1.54 ng ml−1 in a 0.04 M Britton-Robinson (BR) buffer at an adjusted pH of 6.0 with scan rate 100 mV s−1. Furthermore, the proposed approach was successful in measuring MIR with acceptable percentage recoveries (99.81–100.11 %) in pharmaceutical dosage form and varying concentration ranges in biological samples (99.74–100.35 %). The proposed method has been validated using ICH criteria and proven to be accurate and repeatable.

Voltammetric behavior of solifenacin succinate on gold, glassy carbon and boron-doped diamond electrodes: Stability testing and determination

The anticholinergic drug, solifenacin, is frequently used for the treatment of the urological tract for urinary incontinence, and urinary frequency. The development of reliable and effective solifenacin electrochemical sensors is of great importance for the pharmaceutical industry and clinical practice. In this work, the electrochemical behavior of solifenacin succinate (SOL) was studied using three different working electrodes: gold (Au), glassy carbon (GCE) and boron-doped diamond electrode (BDDE). The cyclic voltammetric (CV) measurements performed in 0.05 M NaHCO3 indicated that the SOL oxidation process is irreversible and diffusion-controlled at all investigated working electrodes. Afterwards, the testing of SOL electrochemical stability and the possibility of its electrochemical degradation was performed at the Au electrode by the cycling of the potential during 3 h and continuously to 6 h. It was shown that the SOL was electrochemically transformed into another electroactive species and its degradation was excluded. For electroanalytical application, the anodically pretreated BDDE (+2.0 V; 30 s) was selected. Various experimental parameters were optimized, including the pH of the aqueous Britton-Robinson (B-R) buffer as a supporting electrolyte (from pH 2.0 to 11.98) and the most intensive peak of the target analyte was at pH 11.0, so this pH value was chosen as the optimum for further measurements. Based on the correlation of the SOL peak intensity and different concentrations, the developed differential pulse voltammetric (DPV) method was characterized by a linear concentration range from 0.041 to 2.50 µM, with a correlation coefficient of 0.999, and a relative standard deviation of 0.3 %. Taking into account the sensitivity of the developed DPV method towards the electrochemical oxidation of SOL, a very low detection limit of 0.012 µM in the model system was achieved. The BDDE showed adequate selectivity for SOL in the presence of the investigated interferents. The obtained results indicate that the BDDE with an optimized DPV method could be applied for the trace-level electroanalytical determination of SOL in human urine sample with excellent recovery and reproducibility.

Gold particle-modified glassy carbon electrode: an advanced electrochemical sensor for dipyrone monitoring

This study presents the development and optimization of a gold particle-modified glassy carbon electrode (Au/GCE) as an advanced electrochemical sensor for monitoring dipyrone (DIP), a commonly used pharmaceutical compound. The objective of this study was to enhance the sensitivity and accuracy of DIP quantification through efficient experimental planning and the incorporation of gold particles onto the surface of the GCE. The electrodeposition of gold particles onto the GCE significantly improved the response of DIP in a 0.5 mol L−1 H2SO4 solution. By employing a design of experiments (DoE) approach, we optimized the differential pulse voltammetric (DPV) method, resulting in enhanced performance, including the achievement of a remarkably low limit of detection (0.15 µmol L−1). To assess the accuracy of the electroanalytical method, we conducted extensive recovery tests, which yielded recovery values ranging from 98.9% to 104% for DIP concentration in pharmaceutical formulations. These results emphasize the selectivity and robustness of the developed electroanalytical method, positioning it as a reliable tool for monitoring DIP. The comprehensive account of experimental procedures, optimization strategies, and analytical validation presented in this study establish the efficacy and potential applications of the developed sensor in pharmaceutical analysis. Overall, this research contributes valuable insights into the field of electrochemical sensing and offers promising prospects for its application in various pharmaceutical and clinical settings.

Voltammetric Determination of Phenylephrine Hydrochloride at Poly (Diphenylamine Sulfonic Acid) Electrode

The electrochemical behaviour was studied, and the determination method of phenylephrine hydrochloride (PHE) at wide pH range at poly (Diphenylamine Sulfonic Acid, DPSA), using cyclic voltammetric (CV), differential pulse voltammetric (DPV) techniques. Optimum conditions and optimization of parameters for analytical applications were obtained by DPV technique, this technique was selected for the determination. Using optimized DPV technique, the current was linear within a concentration range between 10–100 nM in pH 6.5 phosphate buffer (PBS). Furthermore, poly (DPSA) electrodes were successfully applied to the determination of PHE in spiked urine and pharmaceutical preparations, rapid and low-cost method. The repeatability, accuracy and precision of the developed technique were checked.

A novel and intelligent chemometric-electrochemical-enzymatic biosensing procedure and mimicking a clinical condition environment to trick the red blood cells for counting them under physiological conditions: A new connection among chemometry, electrochemistry and hematology

Here, a novel electrochemical biosensing procedure has been developed for determination of the number of red blood cells (RBCs) under physiochemical conditions based on chemometric modeling of hydrodynamic differential pulse voltammetric (HDPV), and amperometric data as responses of a modified edge plane pyrolytic graphite electrode (EPPGE). In order to obtain a good sensitivity from the EPPGE, its surface was modified with a thin layer of multiwalled carbon nanotubes-ionic liquid (MWCNTs-IL). Catalase (CAT) was immobilized onto the surface of MWCNTs-IL/EPPGE with help of nafion. The response of the biosensor was based on electrochemical reduction of oxygen of the blood samples which was enhanced by a trick based on addition of hydrogen peroxide (H2O2) to blood samples which can be reduced by the CAT to produce extra oxygen. Prior to experiments, the solution in electrochemical cell was bubbled with pure N2 to purge the oxygen in the solution, but in order to increase the selectivity of the biosensor towards detection of the oxygen obtained from the red blood cells, voltammetric responses of the biosensor were modeled by multivariate chemometric calibration methods with the help of radial basis function-partial least squares (RBF-PLS), least squares-support vector machines (LS-SVM), recursive weighted partial least squares (rPLS), ant colony optimization-mathematical pre-processing selection by genetic algorithm-sample selection through a distance-based procedure-partial least squares-1 (ACO-GA-SS-PLS1), and radial basis function-artificial neural networks (RBF-ANN) to select the best method for determination of the number of the RBCs. The results confirmed the amperometric methods modeled by RBF-ANN showed the best performance for supporting the biosensor in determination of the number of the RBCs with a performance which had an excellent compatibility with the results of a hemocytometer. The results of this study as the newest application of chemometric-electrochemical methods can make a strong connection among electrochemists, chemometricians and hematologists to expand their collaborations on determination of blood factors.

Electrochemical determination of sorafenib by chronopotentiometry and ASDPV based on novel molecularly imprinted polymer and their applications in oncology patients

A promising selective and sensitive biosensor was fabricated for the first time to monitor trace amounts of sorafenib (SORF), a multi-target kinase inhibitor, based on the electropolymerization of pyrrole on a carbon paste electrode (CPE). To prepare a modified CPE, the prepared metal organic framework (NH2-MIL-101(Fe)) was mixed with graphite powder in the presence of an appropriate amount of paraffin oil before it was packed into a plastic tube containing a copper wire. Computational studies appreciate the use of pyrrole as the functional monomer for electropolymerization at the CPE surface using chronopotentiometry in the presence of SORF as a template. After the leaching of SORF, the imprinted sensor was characterized using FT-IR, SEM, and AFM, while NH2-MIL-101(Fe) was investigated by XRD, XPS, and SEM analysis. Under optimum conditions, SORF was detected using anodic stripping differential pulse voltammetric and chronopotentiometric techniques. High sensitivity (6.40 × 10−12 mol/L), excellent selectivity, and a wide linear range (4.20 × 10−11–7.10 × 10−3 mol/L) were recorded. Furthermore, the proposed sensor exhibited good repeatability (RSD = 2.40 % for n = 7) and high lifetime stability (∼7 weeks). Based on the above-mentioned merits, the designed electrochemical sensor was properly utilized for SORF determination in different oncology patients with satisfactory results (recovery = 94.40–99.90 %).

Zirconium Oxide Nanostructure Integrated Screen-Printed Mirabegron Voltammetric Sensors

The present study introduced the fabrication and electroanalytical characterization of a novel mirabegron (MIR) voltammetric screen-printed sensor. The sensing platform was based on zirconium oxide nanoparticles (ZrO2NPs) integrated printing carbon ink with enhanced electrocatalytic activity towards the electrooxidation of the MIR molecule at the electrode surface. Under the optimum measuring parameters, MIR exhibited an irreversible oxidation peak at 0.922 V with a diffusion-controlled reaction and the participation of one electron/proton in the electrooxidation process. The zirconium oxide nanoparticles based screen-printed electrodes (ZrO2NPs/SPEs) showed improved performance within the linear MIR concentration ranged from 10.0 to 261.8 ng ml−1 and limit of detection (LOD) value of 2.72 ng ml−1. The introduced ZrO2NPs/SPEs offered higher sensitivity with the possibility of mass production and miniaturization compared with other MIR sensors. Based on the achieved selectivity, the presented electrodes can be applied for the simultaneous differential pulse voltammetric (DPV) monitoring of MIR in the presence of various degradation contaminates and excipients. Furthermore, the presented electroanalytical approach was tested for the sensitive quantification of MIR in biological samples and pharmaceutical formulations with acceptable recovery values in agreement with the official method.

Fabrication of a novel molecularly imprinted biosensor assisted by higher-order calibration methods and a computer-generated experimental design for determination of thyroglobulin in the presence of thyroxine and triiodothyronine as uncalibrated interference

In this work, a novel electrochemical biosensor was fabricated by modification of a rotating glassy carbon electrode (GCE) with fullerene C60-ionic liquid (C60-IL), and electrochemical synthesis of molecularly imprinted polymers (MIPs) on its surface for selective and sensitive determination of thyroglobulin (TG) in the presence of thyroxine (T4) and triiodothyronine (T3) as uncalibrated interference. The MIPs were synthesized onto the surface of electrochemically activated C60-IL/GCE by electropolymerization of 4-aminothiophenol, methacrylic acid, ethylene glycol dimethacrylate (as cross linker), and TG (as template molecule). By incubation of the biosensor in TG solution, the TGs were entrapped within the pathways of the MIPs, and by incubation of the biosensor in electrochemical probe solution, the pathways for reaching the probe molecules to biosensor were decreased which caused the hydrodynamic differential pulse voltammetric (HDPV) response of the biosensor to be decreased. The effects of experimental parameters on response of the biosensor were optimized by a quadratic central composite design, and at optimized conditions determination of TG in the presence of T4 and T3 as uncalibrated interference was performed. The selectivity of the biosensor was further assisted by supporting the biosensor response with the help of second-order calibration methods and generation of second-order HDPV data with the aim of exploiting second-order advantage. Second-order calibration models were developed by MCR-ALS, PARAFAC2, N-PLS/RBL, and U-PLS/RBL with the aim of choosing the best model for assisting the biosensor for selective determination of the TG in the presence of T4 and T3 as uncalibrated interference. The results confirmed the best performance was observed for the biosensor assisted by PARAFAC2 in both synthetic and real matrices which was comparable with HPLC-UV as the reference method, and can be suggested as an alternative method for chromatographic methods.

Electrochemical Sensor Based on N–Doped Carbon Nanodots Derived from the Agro-Waste Cotton Boll Peel Extracts for Nano Molar Determination of an Anti-Cancer Drug, Pemetrexed

A green and facile one-step synthetic route was proposed for the synthesis of nitrogen-doped carbon nanodots (N-CDs) from agro-waste cotton boll peel extract as a natural carbon source and glycine as a nitrogen source. The prepared N-CDs were utilized further in the fabrication of an electrochemical sensor for the nanomolar determination of an anti-cancer drug, pemetrexed (PMT). The electrode material was characterized by XRD, FTIR, TEM, Raman, EDX, UV–vis, fluorescence, cyclic voltammetric and electrochemical impedance spectroscopic studies. The N-CDs drop-casted on the surface of glassy carbon electrode (GCE) served as a good sensing material and exhibited electrocatalytic activity as evident from ∼20-fold enhancement in the oxidation peak current of PMT at N-CDs/GCE with 130 mV lesser positive oxidation peak potential than that at bare GCE. This was attributed to excellent conductivity, higher electroactive surface area, graphitic cores of N-CDs besides the interactions between PMT and N-CDs via hydrogen bonding and π–π stacking. The sensing performance of the demonstrated electrode was optimized by varying the peak current dependant parameters and also by investigating the influence of interfering substances in the determination of PMT. The electrochemical behaviour of PMT at different pH revealed the adsorption controlled electrode process with the involvement of protons. Under optimized conditions, differential pulse voltammetric (DPV), square wave voltammetric (SWV) and adsorptive differential pulse voltammetric (AdSDPV) methods were developed for sensitive determination of PMT at nano molar level. Further, these developed analytical methods were applied successfully for the determination of PMT in analyte fortified human urine samples and pharmaceutical formulations.

Non-targeted and targeted analytical approaches for estimating the features of wine spirits

Non-targeted UV–Vis/synchronous fluorescence (SF) spectroscopic and differential pulse voltammetric (DPV) fingerprinting have been tested to discriminate between caramel-containing and caramel-free wine spirits using partial least squares-discriminant analysis (PLS-DA), variable importance in projection (VIP)-PLS-DA, VIP-principal component analysis-linear discriminant analysis (PCA-LDA) and VIP-support vector machine (SVM). A 96 % total correct classification in VIP-PLS-DA and VIP-PCA-LDA was achieved using, among others, of 115 variables corresponding to a potential range from 0.43 to 1.00 V in DPV, or 45 variables selected from SF spectra recorded at a difference between the emission and excitation wavelengths of 100 nm for diluted samples. The conclusions resulting from the non-targeted methods were verified and confirmed by the targeted quantitative analysis of the samples using the HPLC-DAD method, focused on 5-hydroxymethylfurfural, furfural, syringaldehyde and vanilline. In targeted SF spectroscopic quantitative analysis, the PLS regression model based on 21 variables selected from SF spectra recorded at a difference between the emission and excitation wavelengths of 100 nm was suitable for the determination of caramel in the range from 0.1 to 4.0 g/L. High coefficients of determination R2 and small root mean squared error (RMSE) values for both cross-validation and prediction (R2 = 0.9811 and 0.9736, respectively, and RMSE = 0.046 and 0.047, respectively) prove good quantitative properties of the VIP-PLS regression model.

A novel and intelligent molecularly imprinted enzymatic biosensor for biosensing of human serum albumin in the presence of gamma-globulin, and glucose as uncalibrated interference

Human serum albumin (HSA) is not electroactive, because the electroactive amino acids have been buried in its structure. Therefore, direct electrochemical determination of the HSA as the most abundant protein in human plasma cannot be performed. In this work, a novel electrochemical biosensor has been developed based on synthesis of dual templates molecularly imprinted polymers (DTMIPs) having trypsin (TRP) and HSA as template molecules onto the surface of a glassy carbon electrode (GCE) modified with graphene-ionic liquid (Gr-IL). By incubation of the biosensor with TRP, and HSA, tryptic hydrolysis of the HSA is occurred which breaks the HSA down into free amino acids. The HSA involves five electroactive amino acids including cysteine, tryptophan, tyrosine, methionine and histidine whose differential normal pulse voltammetric (DNPV) responses are overlapped and generated a single peak. In order to increase the sensitivity of the DTMIP/Gr-IL/GCE for determination of the HSA, hydrodynamic DNPV (HDNPV) data were generated, and used for analytical purposes. The second-order HDNPV data were generated at different pulse amplitudes and used to develop four second-order calibration models by multivariate curve resolution-alternating least squares (MCR-ALS), parallel factor analysis2 (PARAFAC2), multi-way partial least squares/residual bilinearization (N-PLS/RBL), and unfolded partial least squares/residual bilinearization (U-PLS/RBL) to select the best procedure for determination of the HSA in the presence of gamma-globulin and glucose as uncalibrated interferences. The results confirmed the best performance for the biosensor assisted by MCR-ALS for ultrasensitive and selective determination of the HSA in both synthetic and real matrices which was comparable with HPLC-UV as a reference method.

Thioglycolic acid-capped gold nanoparticle/cytochrome P450-2E1 electrochemical biosensor for isoniazid

Tuberculosis (TB) is one of the deadliest diseases in Africa and it is classified as a serious global health problem. A new threat associated with the disease is the emergence of multidrug-resistant TB (MDR-TB), which results from improper dose or non-compliance with a treatment regime. It is, therefore, important to determine a patient’s rate of TB drug metabolism at a point-of-care, in order to enable appropriate dose prescription. This work presents a novel enzymatic nanobiosensor for real-time determination of isoniazid (INH), which is a highly prescribed drug for TB treatment. The nanobiosensor consists of a cytochrome P450-2E1 (CYP2E1) isoenzyme covalently attached to a screen printed or disk gold electrode (Au), functionalized with thioglycolic acid-capped gold nanoparticle (TGA-AuNP). The nanomaterial was green-synthesized with banana peel extract (BPE) as the reducing agent. It exhibited an ultraviolet-visible spectroscopy (UV–Vis) signature absorption band for AuNP at 536 nm and a direct bandgap energy (Eg) value of 2.00 eV. Fourier transform infra-red spectroscopy (FTIR) was used to confirm the reduction of Au3+ to Au0. High-resolution transmission electron microscopy (HR-TEM) and high-resolution scanning electron microscopy (HR-SEM) studies indicated that TGA-AuNPs were polydisperse and exhibited spherical morphology. Bovine serum albumin (BSA) and CYP2E1 were attached to the TGA-AuNPs-modified Au electrode using glutaraldehyde (Glu) as binder, to form the nanobiosensor (BSA/CYP2E1/Glu/TGA-AuNPs/Au). Differential pulse voltammetric (DPV) responses of the nanobiosensor for INH were determined in 10 mM phosphate buffer (pH 7.4). The limit of detection (LOD) and the limit of quantification (LOQ) values of the nanobiosensor were 0.0556 μM INH and 0.1683 μM INH, respectively.

Voltammetric determination of sulfamethoxazole using commercial screen-printed carbon electrodes

A differential pulse voltammetric (DPV) method using commercial screen-printed carbon electrodes (SPCE) is developed for a fast and cost-effective determination of the antibiotic sulfamethoxazole (SMX). Optimal measurements are carried out at pH 5.5 in acetate buffer and yield a detection limit of 15 µg/L and a linearity range of 50 – 600 µg/L with good repeatability (1.1%) and reproducibility (2.5%). The method is successfully applied to the analysis of a spiked tap water sample with very high reproducibility (0.4%) and good trueness (Recovery 95.2%).Additional considerations are made about the irreversible electrochemical oxidation of SMX, which is notoriously pH-dependent according to a process involving 2e- and 2H+, in agreement with several reported mechanisms in the literature. Besides, the analysis of other sulfonamide antibiotics is discussed, showing the key role of the free terminal amino group in oxidation, which makes almost undistinguishable voltammetric signals from different molecules sharing this moiety. In contrast, the acetylation of the mentioned group (e.g., in sulfonamide metabolites) drastically reduces the sensitivity of voltammetric measurements.

Determination of Dipyridamole Using a MIP-Modified Disposable Pencil Graphite Electrode

A new method for the determination of the antiplatelet drug dipyridamole (DIP) in pharmaceuticals using a molecularly imprinted polymer (MIP)-modified pencil graphite electrode (PGE) is proposed. The modified electrode was prepared simply and rapidly by electropolymerization of caffeic acid (CA) in the presence of DIP and subsequent DIP extraction with ethanol, resulting in a cost-effective, eco-friendly disposable modified electrode (MIP_PGE). Several working conditions (monomer and template concentration, number of voltametric cycles, scan rate extraction time, and solvent) for the MIP_PGE preparation were optimized. The differential pulse voltammetric (DPV) oxidation signal of DIP obtained at MIP_PGE was 28% higher than that recorded at bare PGE. Cyclic voltammetry emphasized DIP irreversible, pH-dependent, diffusion-controlled oxidation at MIP_PGE. Differential pulse and adsorptive stripping voltammetry at MIP_PGE in phosphate buffer solution pH = 7.00 were applied for the drug quantitative determination in the range of 1.00 × 10−7–1.00 × 10−5 and 1.00 × 10−8–5.00 × 10−7 mol/L DIP, respectively. The obtained limits of detection were at the tens nanomolar level.