Surface Of Screen-printed Carbon Electrode Research Articles

Fast and sensitive diagnosis of autoimmune disorders through amperometric biosensing of serum anti-dsDNA autoantibodies

This work reports the first amperometric biosensor involving the use of neutravidin-functionalized magnetic microbeads (NA-MBs) modified with a biotinylated-anti-dsDNA (b-dsDNA) as efficient magnetic microcarriers to selectively capture anti-dsDNA autoantibodies (IgG, IgA and IgM AAbs) present in the sera of patients with rheumatoid arthritis (RA). Subsequently, the attached anti-dsDNA AAbs are detected with a mixture of conventional HRP-labeled secondary antibodies (HRP-anti-human IgG/IgM/IgA mixture). The biorecognition event is monitored by amperometric transduction using the hydroquinone (HQ)/H2O2 system upon capturing the modified MBs on the surface of screen-printed carbon electrodes (SPCEs). The developed bioplatform exhibits a linear calibration plot ranging from 1 to 200 IU mL−1 with a LOD of 0.3 IU mL−1 for anti-dsDNA AAbs standards. In addition, the biosensor allows performing the determination of the anti-dsDNA AAbs levels directly in 100-times diluted serum samples from patients diagnosed with RA and in just 75 min. The obtained results are in agreement with those provided by an ELISA kit and allow discrimination between positive and negative samples.

Architecting of a biodevice based on a screen-printed carbon electrode modified with the NiONP nanolayer and aptamer in BCM-7 detection

In this study, an ultrasensitive and robust biodevice implemented on a screen-printed carbon electrode (SPCE) surface is introduced. The β-casomorphin-7 (BCM-7) peptide as an early warning sign of autism disorder is distinguished in this system. The SPCE surface was directly electrodeposited with a nanolayer of the nickel oxide nanoparticles (NiONP). In next step, an Apt sequence as a capture of the BCM-7 was strongly attached on this surface. The embedded sensing interface offered some admirable characterizes to detect the BCM-7. The obtained DPV signals were reversely proportional to the concentrations of the BCM-7 through a stable binding reaction in two working linear ranges from 0.5 × 10−9-1.5 μmol l-. Also, an unrivaled limit of detection (LOD) value of 166.6 aM was achieved that is so superior by other reported methods in the BCM-7 sensing. This hand-held biodevice was satisfactorily tested for the BCM-7 detection in human urine and blood sample with an average recovery rate of ∼101.87 %. More importantly, this strategy is free from labeling steps, complex sample processing and interference from common biomolecules in blood or urine. Due to the inherent advantages of the SPCE and the NiONP, utilizing this facile sensing interface may be an ideal choice in constructing of the ultrasensitive biodevice with low cost for distinguishing of the autism disorder.

AFM VISUALIZATION OF PHYTOPLASMA DNA IMMOBILIZATION AND HYBRIDIZATION EVENT ON CHITOSAN MODIFIED SPCE SURFACE

The evidence of DNA immobilization and hybridization on a functional surface is demonstrated in this presentation following the high-resolution atomic force microscopic (AFM) direct observation. A planar functional surface was fabricated by self-assembly of a biopolymer chitosan onto screen-printed carbon electrode (SPCE) concerning to its excellent covalent bonding binding of biomolecules. The target DNA molecules were extracted from important phytoplasma diseased plants such as sugarcane white leaf (SCWL), burmuda grass white leaf (BGWL) and sesame phyllody (SP). The real image in actual posture of long chain natural DNA and the well-known structure of the DNA double helix were obviously visualized following the DNA immobilization and subsequent transitional hybridization with their complementary DNA. The coordinate quantitative parameters of AFM images such as line profile analysis, surface roughness, power spectrum density (PSD) algorithm and fractal dimension were also determined. The width size of double stranded DNA and the specific hybrid DNA were apparently almost 2 folds bigger than their single stranded DNA. Whereas an aggregation and growth mechanism of those DNAs on chitosan modified SPCE surfaces were mainly stacked in vertical direction and grown beyond a diffusion limited model as indicated by their fractal dimension values around 2 to 3. This phenomenon is hence valuable for the verification and the efficient development of diagnostic DNA-based devices.

Single step preparation of platinum nanoflowers/reduced graphene oxide electrode as a novel platform for diclofenac sensor

A single step preparation of platinum nanoflowers and reduced graphene oxide nanocomposite (PtNFs/rGO) modified electrode was accomplished using cyclic voltammetry (CV). A flower-like platinum structure with the homogeneous distribution of PtNFs/rGO on the screen-printed carbon electrode surface was clearly observed by scanning electron microscopy (SEM). The electrochemical behaviors of PtNFs/rGO electrode were systematically investigated by CV. Comparing with an unmodified electrode, PtNFs/rGO electrode provided 5-fold increase in anodic peak current. This newly fabricated electrode not only accelerated the electron transfer between diclofenac and the electrode surface but also promoted the accumulation of diclofenac on electrode surface leading to enhanced electrochemical sensitivity for the quantitative analysis of diclofenac. By using differential pulse voltammetry (DPV), a calibration curve of diclofenac was linear in a range of 0.1−100 µM, and a limit of detection was found to be 40 nM (S/N = 3). Eventually, this system was successfully applied for the determination of diclofenac in human urine samples.

Electrochemical quantification of Ag2S quantum dots: evaluation of different surface coating ligands for bacteria determination.

In this work, novel silver sulphide quantum dots (Ag2S QD) are electrochemically quantified for the first time. The method is based on the electrochemical reduction of Ag+ to Ag0 at -0.3V on screen-printed carbon electrodes (SPCEs), followed by anodic stripping voltammetric oxidation that gives a peak of currents at +0.06V which represents the analytical signal. The optimized methodology allows the quantification of water-stabilized Ag2S QD in the range of approximately 2 × 109-2 × 1012 QD·mL-1 with a good reproducibility (RSD: 5%). Moreover, as proof-of-concept of relevant biosensing application, Ag2S QD are evaluated as tags for Escherichia coli (E. coli) bacteria determination. Bacteria tagged with QD are separated by centrifugation from the sample solution and placed on the SPCE surface for quantitative analysis. The effect of two different Ag2S QD surface coating/stabilizing agents on both the voltammetric response and the bacteria sensing is also evaluated. 3-mercaptopropionic acid (3-MPA) is studied as model of short length coating ligand with no affinity for the bacteria, while boronic acid (BA) is evaluated as longer length ligand with chemical affinity for the polysaccharides present in the peptidoglycan layer on the bacteria cells surface. The biosensing system allows to detect bacteria in the range 10-1-103 bacteria·mL-1 with a limit of detection as low as 1 bacteria·mL-1.This methodology is a promising proof-of-concept alternative to traditional laboratory-based tests, with good sensitivity and short time and low cost of analysis. Graphical abstractNovel silver sulphide quantum dots (Ag2S QD) are electrochemically quantified for the first time. Moreover, Ag2S QD are evaluated as tags for Escherichia coli bacteria determination. The effect of two different QD surface coating ligands is also evaluated.

Anti-human albumin monoclonal antibody immobilized on EDC-NHS functionalized carboxylic graphene/AuNPs composite as promising electrochemical HSA immunosensor

Diagnosis and treatment of some important diseased and metabolic disorders is based on successful detection of albumin. In this work, we aim to develop a simple immunosensor for the detection of human serum albumin in biological fluids. Anti-human albumin antibody was covalently attached to the activated surface of screen-printed carbon electrodes enriched with carboxyl graphene/gold nanoparticles composite. Microstructure (TEM, FE-SEM, XRD) and electrochemical (CV, EIS) characterization methods were used to investigate composite properties and to confirm the successful modification of the electrodes. Under the optimal conditions, linear working range and limit of detection were 2.5–500 μg/mL and 1.55 μg/mL, respectively. Additionally, the effect of some possibly interfering compounds was investigated and the immunosensor was used for real sample analysis. The results showed that the sensor exhibited accurate, precise and sensitive characteristics and can be promising replacement to the convention methods for albumin detection in clinical practice.

Electrochemical Sensing for Examining Vitamin D3 based on MIP using NOVA 1.7 and Autolab PGSTAT 302N

Introduction: An electrochemical sensor has the ability to transform the associated data containing electrochemical reactions into a reliable representative signal. The electrochemical sensors can be classified into potentiometric, conductometric, and ampere-metric or Volta-metric. Although, there are various electrochemical techniques for the detection of Vitamin D3, there is still a need for a simplified and cost-effective method. An electrochemical sensor provides great sensitivity towards the detection of the analyte. Aim: To fabricate an electrochemical sensor for the detection of Vitamin D3. The sensor used Molecular Imprinted Polymer (MIP) based Screen Printed Carbon Electrode (SPCE). Materials and Methods: The SPCE used was a three-electrode system consisting of silver working electrode, silver reference electrode and a counter carbon electrode. The reagents used in the experiment was p-Phenylenediamine, resorcinol and Vitamin D3 that were applied in a particular amount onto the SPCE. The process of electropolymerisation was carried out in order to form a non-conductive layer. Cavities were gradually formed on the surface of SPCE. A mediator was used to obtain reliable results for the detection of Vitamin D3. It is evident from the existing literature that the number of scans of electropolymerisation holds a significant role in this process. The procedure was applied for the formation of non-imprinted electrode in the absence of the analyte. Results: The presence of the template i.e., Vitamin D3 was recorded using the developed electrochemical sensor. The current decreased on rebinding of Vitamin D3 which resulted in the change of redox peak of ferricyanide. This signified the sudden increase in concentration of Vitamin D3 specifying its presence. Conclusion: The results obtained specifies the great sensitivity of the electrochemical sensor towards the template i.e., vitamin D3. The clinical relevance of such electrochemical sensors is that they produce simple, accurate and reproducible results which can be used to optimise the care of patients.

Nanocomposites of poly(l-methionine), carbon nanotube-graphene complexes and Au nanoparticles on screen printed carbon electrodes for electrochemical analyses of dopamine and uric acid in human urine solutions.

A sensitive electrochemical sensor featuring novel composites of gold and carbon nanocomplexes alongside a polymerized amino acid was developed for the determination of uric acid (UA) and dopamine (DA) concentrations in both buffer and human urine sample solutions. The sensor was fabricated by electropolymerization of l-methionine (l-Met) followed by coating of carbon nanotube-graphene complexes and electrodeposition of gold nanoparticles on a screen printed carbon electrode surface. The electrode surfaces were characterized by field emission scanning electron microscopy and energy dispersive spectroscopy, and the electrochemical properties were investigated by cyclic voltammetry and differential pulse voltammetry. Linear ranges of 0.05-3 μM and 1-35 μM with limits of detection of 0.0029 and 0.034 μM were achieved for DA and UA, respectively. In addition, the developed sensor was applied for the analysis of native UA and DA concentrations in undiluted and diluted human urine samples. The UA analysis results were compared to those obtained using high performance liquid chromatography and a fluorometric assay kit while the DA analysis results were compared to those obtained using liquid chromatography-tandem mass spectrometry.

Highly Sensitive Phenol Biosensor Utilizing Selected Bacillus Biofilm Through an Electrochemical Method

An eco-friendly phenol biosensor from Bacillus biofilm was prepared and investigated. The biofilm, which produced tyrosinase enzyme, was successfully immobilized on a screen-printed carbon electrode surface. A total of 72 Bacillus isolates were utilized because of their capability to produce tyrosinase enzyme in tyrosine media. Among them, Bacillus isolate code 100 was selected because it produced an adequate amount of tyrosinase enzyme and a high potentiostat current. The response surface methodology was also used to optimize the phenol sensing condition through an electrochemical method. Results showed that the optimum condition was achieved after 6 days on a phosphate buffer solution (pH of 8), with an optical density of 0.33. Furthermore, the limits of detection and quantification were 3.0 and 13 ng/L, respectively. The measurements of precision yielded a relative standard deviation of < 5%, which is remarkable. Although the biosensor material was used for 35 days, the current throughout was still maintained at 90%, indicating that the evaluated biosensor material has the potential to be used for phenol monitoring on environmental samples in the near future.

Designing of an ultrasensitive BCM-7 aptasensor based on an SPCE modified with AuNR for promising distinguishing of autism disorder

Abstractly, in this study, an aptasensor is introduced based on a platform consisting of the gold nanorod (AuNR) on a screen printed carbon electrode (SPCE) surface. The aptasensor is applied for detection of the β-casomorphin (BCM-7) as a promising biomarker of autism disorder. The NH2-Apt sequence is directly immobilized onto the AuNR/SPCE surface by formation of a chemisorption bond between the amine-Au groups. By incubation of the BCM-7 onto the aptasensor surface, the aptasensor directed against BCM-7 and cleverly formed a target/Apt complex to produce a measurable electrical current change. The aptasensor shows linearity over the range of 1 fmol L−1 to 25 nmol L−1 with a limit of detection (LOD) of 334 amol L−1. Furthermore, the function of the aptasensor in real samples such as human urine and plasma samples is evaluated. The achieved satisfactory results are mainly due to three main reasons including (1) the large specific surface area of the AuNR which forms a 3D network on the SPCE surface to capture more Apt sequences at the sensing interface, (2) utilizing Apt as the BCM-7 receptor with inherent unique properties to produce a synergetic effect with the AuNR, and finally, (3) effective using screen printing technology with the fantastic capability to less cost of the aptasensor preparation. There is hope that miniaturization of the proposed aptasensor may aid future efforts to detect autism symptoms as early as infancy under clinical conditions in real-world.

Etlingera elatior-Mediated Synthesis of Gold Nanoparticles and Their Application as Electrochemical Current Enhancer.

This work presents a simple green synthesis of gold nanoparticles (AuNPs) by using an aqueous extract of Etlingera elatior (torch ginger). The metabolites present in E. elatior, including sugars, proteins, polyphenols, and flavonoids, were known to play important roles in reducing metal ions and supporting the subsequent stability of nanoparticles. The present work aimed to investigate the ability of the E. elatior extract to synthesise AuNPs via the reduction of gold (III) chloride hydrate and characterise the properties of the nanoparticles produced. The antioxidant properties of the E. elatior extract were evaluated by analysing the total phenolic and total flavonoid contents. To ascertain the formation of AuNPs, the synthesised particles were characterised using the ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray (EDX) microscopy, and dynamic light scattering (DLS) measurement. The properties of the green synthesised AuNPs were shown to be comparable to the AuNPs produced using a conventional reducing agent, sodium citrate. The UV-Vis measured the surface plasmon resonance of the AuNPs, and a band centered at 529 nm was obtained. The FTIR results proved that the extract contained the O-H functional group that is responsible for capping the nanoparticles. The HRTEM images showed that the green synthesized AuNPs were of various shapes and the average of the nanoparticles’ hydrodynamic diameter was 31.5 ± 0.5 nm. Meanwhile, the zeta potential of −32.0 ± 0.4 mV indicates the high stability and negative charge of the AuNPs. We further successfully demonstrated that using the green synthesised AuNPs as the nanocomposite to modify the working surface of screen-printed carbon electrode (SPCE/Cs/AuNPs) enhanced the rate of electron transfer and provided a sensitive platform for the detection of Cu(II) ions.

Correlative Voltammetric Microscopy: Structure-Activity Relationships in the Microscopic Electrochemical Behavior of Screen Printed Carbon Electrodes.

Screen-printed carbon electrodes (SPCEs) are widely used for electrochemical sensors. However, little is known about their electrochemical behavior at the microscopic level. In this work, we use voltammetric scanning electrochemical cell microscopy (SECCM), with dual-channel probes, to determine the microscopic factors governing the electrochemical response of SPCEs. SECCM cyclic voltammetry (CV) measurements are performed directly in hundreds of different locations of SPCEs, with high spatial resolution, using a submicrometer sized probe. Further, the localized electrode activity is spatially correlated to colocated surface structure information from scanning electron microscopy and micro-Raman spectroscopy. This approach is applied to two model electrochemical processes: hexaammineruthenium(III/II) ([Ru(NH3)6]3+/2+), a well-known outer-sphere redox couple, and dopamine (DA), which undergoes a more complex electron-proton coupled electro-oxidation, with complications from adsorption of both DA and side-products. The electrochemical reduction of [Ru(NH3)6]3+ proceeds fairly uniformly across the surface of SPCEs on the submicrometer scale. In contrast, DA electro-oxidation shows a strong dependence on the microstructure of the SPCE. By studying this process at different concentrations of DA, the relative contributions of (i) intrinsic electrode kinetics and (ii) adsorption of DA are elucidated in detail, as a function of local electrode character and surface structure. These studies provide major new insights on the electrochemical activity of SPCEs and further position voltammetric SECCM as a powerful technique for the electrochemical imaging of complex, heterogeneous, and topographically rough electrode surfaces.

Batch Injection Analysis with Amperometric Detection for DNA Biosensing Applications

AbstractIn this work, batch injection analysis with the amperometric detection (BIA‐AD), employing a detection cell designed to adapt a screen‐printed carbon electrode (SPCE) was used for the first time as a robust electroanalytical system for DNA biosensing applications. The sensitive amperometric detection was used to evaluate the structural changes in double‐stranded DNA (dsDNA) after UV‐C irradiation of its solution for a given time. Batching of DNA samples was performed by precise electronic pipette microinjection of an irradiated sample aliquot onto the unmodified activated SPCE surface incorporated in the BIA‐AD system. Using the optimized experimental conditions (40 μL of 1 mg mL−1 dsDNA in a 0.1 M phosphate buffer of pH 7.4 sampled at the injection speed degree of 6 and detected at the potential of +1.5 V vs silver pseudo‐reference electrode), a time‐dependent response (gradual decrease of amperometric signal up to 58 % after 10 min of the irradiation) was found for the detection of damage to low molecular weight salmon sperm dsDNA. The advantages of this low‐dimensional and cost‐effective measuring system can be utilized not only for the quantification of DNA damage/degradation by UV irradiation, but they are also promising for studying other types of DNA interactions.

A Novel Electrochemical Sensor Based on Plastic Antibodies for Vitamin D3 Detection in Real Samples

A highly sensitive voltammetric sensor for vitamin D3 is designed and build by the electropolymerization of molecularly imprinted polymer (MIP). Vitamin D3 selective MIP is synthesized by the electropolymerization of p-phenylenediamine–resorcinol mixture on the screen-printed carbon electrode (SPCE) surface in the presence of the vitamin D3 molecules. The electropolymerization of monomers made a film deposition on electrode surface which absolutely suppressed the reduction of ferricyanide. The removal of the vitamin D3 creates the cavities which caused noticeably increased ferricyanide signal, which was again suppressed after the rebinding of vitamin D3. It was shown that the decrease of the ferricyanide peak of the MIP electrode was affected linearly by vitamin D3 concentration. Various factors, by which the response current of the electrode is mainly affected, were studied and optimized. This sensor shows a linear response range of $1 \times 10^{-11}$ – $2 \times 10^{-9}$ M and lower detection limit of $1 \times 10^{\mathbf {-12}}$ M. The sensor was successfully applied for the detection of vitamin D3 in human plasma samples.

Electrochemical sensing of ecstasy with electropolymerized molecularly imprinted poly(o-phenylenediamine) polymer on the surface of disposable screen-printed carbon electrodes

This study demonstrates the ability of an electrochemical sensor based on molecularly imprinted polymers (MIPs) to selectively quantify 3,4-methylenedioxymethamphetamine (MDMA), also known as ecstasy, in biological samples. The device was constructed using ortho-phenylenediamine (o-PD) as the MIP’s building monomer at the surface of a screen-printed carbon electrode (SPCE). The step-by-step construction of the SPCE-MIP sensor was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Density functional theory (DFT) calculations and modelling were performed not only to understand template-monomer interaction but also to comprehend which possible polymer structure - linear or ramified poly(o-PD) – indeed interacts with the analyte. The prepared sensor worked by directly measuring the MDMA oxidation signal through square-wave voltammetry (SWV) after an incubation period of 10 min. Several parameters were optimized, such as the monomer/template ratio, the number of electropolymerization scanning cycles, and the incubation period, to obtain the best sensing efficiency. Optimized sensors exhibited suitable selectivity, repeatability (2.6%), reproducibility (7.7%) and up to one month of stable response. A linear range up to 0.2 mmol L−1 was found with an r2 of 0.9990 and a limit of detection (LOD) and quantification (LOQ) of 0.79 and 2.6 μmol L−1 (0.15 and 0.51 μg mL−1), respectively. The proposed sensor was successfully applied to human blood serum and urine samples, showing its potential for application in medicine and in forensic sciences.

High performance of electrochemical and fluorescent probe by interaction of cell and bacteria with pH-sensitive polymer dots coated surfaces

Using pH-switchable fluorescent polymer dots (PD) by means of fluorescent, colorimetric, and electrochemical signals generated from surfaces coated with PD of zwitterionic structure provided a fast and easy method to assess their performance in mammalian cell and bacterial interactions. The PD-coated surfaces showed high sensitivity over a broad range of pH levels by switching reversibly zwitterionic states, which led to an excellent cellular resistance effect by inhibiting the attachment of nearly 95% of mammalian cells. Similarly, they exhibited a strong interaction with the negatively charged surfaces of bacteria, as observed in the fluorescence ON/OFF system. In addition, PD were employed to detect the attachment of mammalian and bacterial cells: we deposited PD on a screen-printed carbon electrode for cyclic voltammetry analysis. Notably, the presence of cells remarkably interfered with the current flow between the PD and the screen-printed carbon electrode surface by causing an impressive decline in both reduction-oxidation signals, implying the high sensitivity of the PD-coated surfaces to cells and bacteria in different pH environments. Therefore, as smart materials with high sensitivity, biocompatibility, selectivity, and accuracy, PD-coated surfaces represent a promising approach to visualizing and controlling biological cell attachment, thereby helping to avoid contamination in biomedical applications.

A catholically pre-treated low cost screen-printed carbon electrode surface for metal compounds electrocatalyst like hydrogen evolution activity

Search for simple and economical electrocatalyst for the hydrogen gas evolution reaction (HER), which can resemble to the performance of Pt and other precious metals, is a challenging research interest. In this work, a systematic effect of pre-treatment potential of screen-printed carbon (SPCE) surface on the HER performance in 0.5 M H2SO4 was carried out. A new observation of a low potential HER (onset potential, Eonset = −0.02 V vs. RHE) at a cathodic potential, −0.5 V vs. Ag/AgCl on 1 hr pre-treated screen-printed carbon electrode (SPCE*, * = pre-treated) was observed. Physicochemical and electrochemical characterizations of the SPCE* by field emission scanning electron-microscope, Raman, IR and X-Ray photoelectron spectroscopes reveals specific generation of carboxylic acid functionalized carbon surface and in turn for the enhanced HER on the modified electrode surface. Electrochemical characterization of SPCE* with Fe(CN)63− support the observation. A marked decrement in the peak current and significant increase in the peak-to-peak separation potential response due electrostatic repulsion between the anion sites of Fe(CN)63− and –COO– were noticed. This observation is in parallel with the reduced electrical double layer capacitance value of the SPCE* system. The Eonset and Tafel value (54.7 mV dec−1) obtained here are comparable to those at Pt, MoS2, MoSe2 and superior over the N- and P-doped graphene/carbon electrocatalysts for HER. A prototype HER system was developed and demonstrated for H2 gas production at a rate of 0.0053 μM s−1 (Operating potential = −0.5 V vs Ag/AgCl), which is comparable to that of precious metal and metal compound electrocatalysts based HER performance.

Electrochemical aptasensor based on one step co-electrodeposition of aptamer and GO-CuNPs nanocomposite for organophosphorus pesticide detection

In this work, aptamer (Apt) immobilized on sensing interface utilizing one step co-electrodeposition technology was first proposed and applied in an electrochemical aptasensor to detect organophosphorus pesticide. This method was simple and facile, solving the complicated problem of aptasensor preparation process. Specifically, in the preparation of the electrodeposition solution, graphene oxide (GO) was used to connect aptamer modified with NH2, offering the basis for aptamer fixation. And, the introduction of Cu nanoparticles (CuNPs) into the Apt-GO mixed solution enhanced the conductivity of the electrodeposition film, leading to superior electrochemical performance. In addition, during electrodeposition of the prepared solution on screen-printed carbon electrode (SPCE) surface by CV technology, GO was electrochemically reduced to reduced graphene oxide (rGO), providing better electrical conductivity. The Apt/rGO-CuNPs composite coating was characterized using SEM and CV technique. Under the optimal experimental conditions, the low detection limit of 0.003 nM for profenofos, 0.3 nM for phorate, 0.03 nM for isocarbophos and 0.3 nM for omethoate were obtained. The aptasensor was also successfully applied for the analysis of phorate in vegetables. Because the developed aptasensor with simple preparation process had extremely good stability, high selectivity and great sensitivity, it would show great potential for other fields.

Electrochemical determination of antihypertensive drugs by employing costless and portable unmodified screen-printed electrodes

Hypertension increases the risk of heart disease and stroke, is commonly known as a silent killer disease and considered as one of the key risk factor for premature death and disability over the world. Herein, we report for the first time a sensitive, costless and reproducible voltammetric method for individual determination of five antihypertensive drugs namely, propranolol (PRO), timolol (TIM), amlodipine (AML), amiloride (AMI) and triamterene (TRI) using differential pulse voltammetry at bare/unmodified screen-printed carbon electrodes (SPEs) in presence of sodium dodecyl sulfate (SDS). Each drug exhibits an electrochemical signal in aqueous media which is significantly enhanced in presence of optimized concentration of SDS due to accumulation of the protonated drug molecules and electrostatically interaction with negatively charged micellar structures. As a result, the spherical micellar orientation of SDS onto the graphitic surface of SPEs offered the analytically sensitive determination of the target drugs over a wide linear concentration range with nano-molar detection limits possible negating the need for any complicated surface modifications. Finally, the proposed voltammetric method was successfully utilized in the individual determination of the target antihypertensive drugs in pharmaceutical formulations and human urine samples.

Surface Modification of Screen-Printed Carbon Electrode (SPCE) with Calixarene-Functionalized Electrochemically Reduced Graphene Oxide (ERGO/C4) in the Electrochemical Detection of Anthracene

In this study, electrochemically reduced graphene oxide (ERGO) and 4-tertbutylcalix[4]arene (C4) were deposited on the surface of screen-printed carbon electrodes (SPCE) to detect anthracene in aqueous solution. The formation of electrochemically reduced graphene oxide/calix[4]arene (ERGO/C4) on SPCE was characterized using Raman spectroscopy, FTIR, and FESEM. Electrochemical properties of the modified electrode were investigated by means of CV and DPV. The electrochemical response of anthracene was greatly improved on ERGO/C4-SPCE compared to bare SPCE. Under optimized condition, the anthracene peak showed a good linear relationship at a concentration ranging from 2–8 nM and a detection limit of 0.016 nM. The developed sensor was able to conserve its performance in the presence of various organic compound and inorganic metal ions and also yielded a good comparable result to the conventional method which is HPLC in real sample with acceptable recovery of 96–97%; thus proving to be a promising candidate for rapid, inexpensive, and sensitive determination of anthracene in real samples.