Differential Pulse Research Articles

Zirconia nanoparticles/carbon quantum dots modified carbon paste electrode as electrochemical sensor for determination of antiepileptic drug eslicarbazepine acetate in bulk and pharmaceutical dosage form

A new, sensitive and selective electrochemical method has been developed for determination of the antiepileptic prodrug eslicarbazepine acetate (ESL) that is used for the treatment of partial-onset seizures in adults with epilepsy. It belongs to the class of sodium channel blockers called dibenzoazepine family. A novel modified zirconia nanoparticles carbon paste nanocomposite, carbon dots sensor prepared from banana peels by solvothermal method has been fabricated. The voltammetric method is based on the direct anodic oxidation of ESL at the electrode surface using differential pulse voltammetry. Under the optimum experimental conditions, ESL exhibited a linear relationship in the range of 3.04 × 10-8 to 9.66 × 10-5 M with a lower detection limit of 7.57 × 10-9 M and quantification limit of 2.29 × 10-8 M. The proposed method was validated according to ICH guidelines and was applied for estimating ESL in raw material showing high accuracy and precision with successful application on tablet dosage form.

Enhanced modified poly-tyrosine voltammetric sensor for the quantification detection of salivary pepsin

Pepsin as an aspartic acid protease member and one of the three foremost proteolytic enzymes in the digestive system is essential to be detected. An electrochemically polymerized tyrosine film on carbon paste electrode (pTyr/CPE) has been synthesized by electro-polymerization donating an affordable electrochemical sensor to sense salivary pepsin as a diagnostic technique for gastroesophageal reflux disease (GRD) due to saliva collection is non-invasive and relatively comfortable. The pTyr/CPE was applied for Voltammetric sensing of pepsin and its quantification in phosphate buffer solution of pH 2.0 (PBS). Scanning electron microscopy (SEM) was conducted to learn the surface morphology. Cyclic voltammetry (CV), differential pulse voltammetry (DPVs), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) were developed to realize the electrocatalytic activity of the sensor. The pTyr/CPE proceeded as a sensitive detector to pepsin with two linear ranges from 1 to 20 & 20 to 100 ng/mL donating two limits of detection as 0.5 & 0.09 ng/mL, respectively, and high selectivity toward pepsin, as well as stability and fast response of 1.5 s. Consequently, it is guessed that the pTyr/CPE sensor could be supportive for the initial diagnosis of GRD through the detection of pepsin in saliva. Finally, we quantified the pepsin levels in saliva samples of LPR patients (n = 2), showing that the results were agreeable with those from the electrochemical sensor.

Fabrication of flexible Au microsensors by a simple stamping method for the point-of-care direct detection of trace leucomalachite green

Leucomalachite green (LMG) is the metabolic product of malachite green, which is a common aquaculture antimicrobial known for its high toxicity and long persistence. To date, few reports on the direct detection of LMG using electrochemical point-of-care (POC) sensors have been published. In the present work, flexible gold (Au) microsensors were fabricated from nanometer-thin Au leaves for the first time on different substrates, such as polyethylene terephthalate, thermoplastic polyurethane, silicone, polyvinyl chloride wristbands, and nitrile gloves, through simple hot stamping. The entire fabrication process did not involve toxic solvents and complex equipment, and the material cost was only $0.1 per microsensor. The morphology, electrochemical properties, and sensing performance of the microsensors were characterized by scanning electron microscopy, cyclic voltammetry, and differential pulse voltammetry. Benefiting from the excellent catalytic activity and conductivity of Au, the microsensors exhibited outstanding direct sensing capability for LMG with a detection limit of 6.3 nM. Moreover, the microsensors demonstrated excellent recovery rates in real sample analysis, validating their practicality. The technology reported in this work provides a pioneering and effective solution for the sensitive and convenient POC direct detection of LMG and further allows for the fabrication of Au microsensors on different flexible and conformal substrates, offering sensitive solutions for POC detection in environmental, food safety, and healthcare applications.

Manganese tetraphenylporphyrin and carbon nanocoil interface-based electrochemical sensing of tyrosine.

Tyrosine is one of the essential metabolites present in the human body for nutritional maintenance and normal physiological functioning. Its concentration in the body is crucial in predicting various hereditary, emotional, and physiological disorders. Therefore, quantitative monitoring of tyrosine in clinical samples is indispensable. We state the use of carbon nanocoils/manganese tetraphenylporphyrin convened glassy carbon electrode (CNC/MnTPP/GC) for the streamlined electrochemical sensing of tyrosine. Cutting-edge analytical techniques were employed to perform a comprehensive physicochemical analysis of the synthesized materials. To investigate the electrochemical properties, various techniques such as cyclic voltammetry (CV), differential pulse voltammetry (DPV), electrochemical impedance spectroscopy, and chronocoulometry were employed. CNC/MnTPP/GC displayed an optimal response at pH 5 and exhibited remarkable linearity within the concentration range of 0.05 to 100 μM for tyrosine. Using DPV, it demonstrated a low limit of detection (21 nM ± 1.17) and a sensitivity of 0.12 μA μM-1 cm-2. CNC/MnTPP/GC displayed excellent performance in terms of repeatability, reproducibility, and stability for up to 30 days, making it suitable for real-time analysis, particularly in the analysis of tyrosine in blood serum. Notably, CNC/MnTPP/GC showcased a superior detection limit compared to previously reported methods.

Application of two-dimensional zeolitic imidazolate framework-L (Co)/multi-walled carbon nanotube nanocomposite modified electrode as a sensitive voltammetric sensor for determination of cannabidiol

In this study, a two-dimensional (2D) leaf-like zeolitic imidazolate framework-L (Co)/multi-walled carbon nanotubes (2D ZIF-L (Co)/MWCNTs) nanocomposite was synthesized using a simple method and utilized as an effective material for voltammetric determination of cannabidiol (CBD). The morphology, structure, and composition of the synthesized ZIF-L (Co)/MWCNTs were characterized through techniques including field-emission scanning electron microscopy (FE-SEM), X-ray powder diffraction (XRD), and Energy Dispersive X-ray spectroscopy (EDS). The screen-printed electrode (SPE) modified with ZIF-L (Co)/MWCNTs was fabricated by the drop-casting of ZIF-L (Co)/MWCNTs suspension on the SPE surface. To study the electrochemical behavior of CBD, cyclic voltammetry (CV), chronoamperometry, and differential pulse voltammetric (DPV) analysis was performed, and compare the oxidation behavior on ZIF-L (Co)/MWCNTs/SPE and bare SPE. The peak current of the DPV of CBD showed a linear increase with its concentration in the range of 0.5 μM – 280.0 μM, and a low detection limit (LOD) of 0.02 μM was achieved. Moreover, the proposed sensor was successfully used to determine CBD in real specimens.

Graphene oxide/Cu–MOF-based electrochemical immunosensor for the simultaneous detection of Mycoplasma pneumoniae and Legionella pneumophila antigens in water

The combination of copper–metal organic framework (Cu–MOF) with graphene oxide (GO) has received growing interest in electrocatalysis, energy storage and sensing applications. However, its potential as an electrochemical biosensing platform remains largely unexplored. In this study, we introduce the synthesis of GO/Cu–MOF nanocomposite and its application in the simultaneous detection of two biomarkers associated with lower respiratory infections, marking the first instance of its use in this capacity. The physicochemical properties and structural elucidation of this composite were studied with the support of XRD, FTIR, SEM and electrochemical techniques. The immunosensor was fabricated by drop casting the nanocomposite on dual screen-printed electrodes followed by functionalization with pyrene linker. The covalent immobilization of the monoclonal antibodies of the bacterial antigens of Mycoplasma pneumoniae (M. pneumoniae; M. p.) and Legionella pneumophila (L. pneumophila; L. p.) was achieved using EDC-NHS chemistry. The differential pulse voltammetry (DPV) signals of the developed immunosensor platform demonstrated a robust correlation across a broad concentration range from 1 pg/mL to 100 ng/mL. The immunosensor platform has shown high degree of selectivity against antigens for various respiratory pathogens. Moreover, the dual immunosensor was successfully applied for the detection of M. pneumoniae and L. pneumophila antigens in spiked water samples showing excellent recovery percentages. We attribute the high sensitivity of the immunosensor to the enhanced electrocatalytic characteristics, stability and conductivity of the GO–MOF composite as well as the synergistic interactions between the GO and MOF. This immunosensor offers a swift analytical response, simplicity in fabrication and instrumentation, rendering it an appealing platform for the on-field monitoring of pathogens in environmental samples.

Electrochemical sensor based on mesoporous g-C3N4/N-CNO/gold nanoparticles for measuring oxycodone

Oxycodone, often used as an analgesic, is a potent opioid. While its effectiveness has been proven in the control of moderate to acute pain, excessive use of oxycodone imposes heart failure, heart palpitations, reduction of red blood cells, bone pain, and even death. Therefore, monitoring the oxycodone concentration in blood is vital for emergency care. For this purpose, a novel electrochemical sensor was designed based on a glassy carbon electrode modified with mesoporous g-C3N4 (M-C3N4), carbon nano-onions doped with nitrogen (N-CNO), and gold nanoparticles. At first, the SEM and XRD techniques were employed to characterize prepared M-C3N4 and N-CNO samples. The electro-oxidation behavior of the oxycodone was evaluated by cyclic and differential pulse voltammetric methods. Based on the influence of the potential scanning rate and solution pH on the voltammetric response of oxycodone oxidation, a redox mechanism was proposed. A 16 nM detection limit was acquired for the oxycodone analysis with a linear response in the 0.05–150 µM range. This sensor showed a remarkable ability for oxycodone detection in plasma samples. The long-term stability, superior selectivity, and reproducibility of this sensor prove its ability to measure oxycodone accurately and precisely in authentic spices.

An electrochemical/SERS dual-mode immunosensor using TMB/Au nanotag and Au@2D-MoS2 modified screen-printed electrode for sensitive detection of prostate cancer biomarker

This study describes a novel dual-mode immunosensor that combines electrochemical (EC) and surface-enhanced Raman scattering (SERS) techniques for the detection of prostate-specific antigen (PSA), a biomarker associated with prostate cancer. The sensor consists of a nanocomposite of gold nanoparticles (AuNPs) deposited on two-dimensional (2D) molybdenum disulfide (Au@MoS2) modified on a working carbon electrode of a screen-printed electrode (SPE). Subsequently, the primary antibody (Ab1) is immobilized on the modified electrode, creating Ab1/Au@MoS2/SPE for specific recognition of the target PSA. In parallel, AuNPs are conjugated with a secondary antibody (Ab2) and a probe molecule, 3,3′,5,5′-tetramethylbenzidine (TMB), leading nanotags (TMB/Ab2/AuNPs) formation exhibiting strong SERS and EC responses. Upon the presence of the target, sandwich immunocomplexes can be formed through antigen-antibody interactions (Ab1-PSA-Ab2). The differential pulse voltammetry (DPV) technique is employed for EC detection mode, while a handheld Raman spectrometer with a 785 nm excitation laser is utilized to collect SERS signals. The developed system demonstrates excellent selectivity and sensitivity, with low limits of detection (LODs) of 3.58 pg mL−1 and 4.83 pg mL−1 for EC and SERS sensing, respectively. Importantly, the dual-mode immunosensor proves effective quantifying PSA protein in human serum samples with good recovery. Given its high sensitivity and proficiency in analyzing biological samples, this proposed immunosensor holds promise as an alternative tool for the early diagnosis of cancers.

Screen-printed electrode-based sensor for rapid ketamine determination: optimization and on-site application for seized drugs analysis

This study investigates the electrochemical behavior of ketamine using an in-lab fabricated screen-printed electrode system and explores its potential application in quantitative analysis. Cyclic voltammetry and differential pulse voltammetry (DPV) experiments were employed to characterize the oxidation behavior of ketamine. Systematic optimization of DPV parameters, including pulse amplitude, pulse width, potential step, potential, and time accumulation for analyte preconcentration resulted in the selection of optimal conditions for quantitative analysis. The developed DPV method exhibited excellent linearity (R2 = 0.996) over the concentration range of 50–500 µM, with a limit of detection of 15 µM and a limit of quantification of 50 µM. Authentic samples analysis demonstrated the utility of the proposed sensor for quantitative analysis of ketamine in pharmaceutical products and seized drug samples. Overall, the developed sensor offers a promising tool for the rapid and accurate analysis of ketamine in various samples with potential applications in on-site forensic analysis.Graphical abstract

Exploring the interspecific relationships among Dendrobium species via electrochemical fingerprinting techniques

This study investigated the interspecific relationships among 29 Dendrobium species using electrochemical fingerprinting techniques. Differential pulse voltammetry was employed to record species-specific electrochemical profiles in both phosphate buffer solution (PBS) and acetic acid buffer solution (ABS). Distinct voltammetric patterns were observed for each species, with ABS yielding higher peak currents compared to PBS. On average, peak currents in ABS were 37.2 % ± 5.8 % higher than in PBS across all species. For example, D. nobile showed a peak current of 12.3 μA in ABS compared to 8.9 μA in PBS, a 38.2 % increase. Normalized two-dimensional plots of the electrochemical fingerprints served as unique signatures for species differentiation. Cluster analysis of the electrochemical data revealed phylogenetic relationships largely consistent with previous molecular studies, while also highlighting novel groupings. For instance, D. parishii and D. pulchellum formed separate branches, indicating distant relationships with other species. Common species such as D. officinale, D. nobile, D. primulinum, and D. loddigesii clustered together, confirming their close relationships. Interestingly, species from Sect. Dendrobium showed mixed clustering with species from four other sections, reflecting the genus's complex evolutionary history. While some inconsistencies with previous molecular phylogenetic studies were noted, such as the distant relationship between D. parishii and D. anosmum, the overall congruence between electrochemical and molecular data validates the potential of this approach. This study demonstrates that electrochemical fingerprinting, combined with appropriate data analysis techniques, can provide valuable insights into the taxonomic relationships and chemical diversity of Dendrobium species, offering a complementary tool to traditional morphological and molecular methods for plant systematics and conservation efforts.

Highly sensitive electrochemical multimodal immunosensor for cluster of differentiation 5 (CD5) detection in human blood serum for early stage cancer detection based on laser-processed Ti/Au electrodes

In the rapidly evolving field of medical diagnostics, biomarkers play a pivotal role, particularly in the early detection of cancer. Cluster of differentiation 5 (CD5), a cell surface glycoprotein found on T cells and B-1a lymphocytes, is instrumental in immune regulation and is associated with both autoimmune diseases and malignancies. Despite its significant diagnostic and therapeutic potential, CD5 detection has been limited by modern methods in the pg/ml range. This study presents a novel multimodal electrochemical immunosensor that employs laser-processed Ti/Au electrodes for the ultra-sensitive detection of CD5 in human blood serum. The “multimodal” approach combines different analytical techniques - differential pulse volctammetry (DPV) and electrochemical impedance spectroscopy (EIS) - to ensure comprehensive analysis, enhancing both the accuracy and reliability of the sensor. This novel sensor significantly outperforms existing commercial ELISA kits, achieving a limit of detection (LOD) of 1.1 ± 0.2 fg/mL with DPV and 3.9 ± 0.5 fg/mL with EIS in phosphate-buffered saline (PBS) and 6.6 ± 3.1 fg/mL and 15.6 ± 3.1 fg/mL in human serum (HS), respectively. These results highlight the immunosensor's potential for improving early-stage cancer diagnosis and broader medical applications.

Pd nanoparticles supported on Fe3O4 particles grafted with poly(acrylamide) gel brush for simultaneous electrochemical‐sensing of dopamine and paracetamol

AbstractIn the present study, a glassy carbon electrode (GCE) modified with Pd nanoparticles deposited on poly(acrylamide) gel brush‐grafted magnetic particles (Pd/PAAmGB@Fe3O4) with core‐shell structure was fabricated for simultaneous electrochemical detection of dopamine (DA) and paracetamol (PA). Electrochemical performance of Pd/PAAmGB@Fe3O4/GCE was evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). The fabricated sensor exhibited voltammetric sensing with a satisfactory linear determination range from 0.4–41 μM for DA and from 0.5–95 μM for PA. The limit of detection (LOD) was 0.1 μM for DA and 0.17 μM for PA based on signal to noise ratio of 3. The proposed sensor also had excellent reusability and selectivity, good reproducibility and stability, and satisfactory recovery in biomedical examples. It is believed that metal nanoparticles deposited on polymer gel brush composites may offer promising new horizons for sensor growth.

Stable sandwich-type electrochemical lead ions sensor based on bismuth-metal organic framework and Mxene

For electrochemical Pb2+ detection, high sensitivity and stability are essential owing to the mutagenicity, carcinogenicity, and teratogenicity of aqueous Pb2+ ions. Herein, a three-dimensional bismuth-containing metal-organic framework (Bi-MOF) was synthesized using a hydrothermal method, followed by post-synthetic functionalization with thiol (-SH) groups. A sandwich-type Bi-MOF-SH/Mx/Bi-MOF-SH/GCE multilayer sensitive electrochemical sensor was then constructed on the surface of the glassy carbon electrode for Pb2+ detection. Differential pulse anodic stripping voltammetry (DPASV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used to evaluate the performance of the sensor. The developed multilayer sensor demonstrated an exceptionally high current response, good sensitivity (0.03–20.0 μg/L), and an ultra-low level of detection of 0.012 μg/L (S/N=3) towards Pb2+ ions. The as-prepared electrode showed high stability, repeatability, and selectivity among possible interfering ions (Na+, Ca2+, Cu2+, Zn2+, K+, Mg2+, Al3+, and Cd2+), suggesting potential for use in real-world applications.

SIMULTANEOUS DETERMINATION OF ASCORBIC ACID, URIC ACID, AND DOPAMINE ON CARBON NANOTUBE PASTE ELECTRODE

Background: Ascorbic acid (AA), uric acid (UA), and dopamine (DA) play crucial roles in human metabolism. These substances coexist in biological fluids, and their levels are directly associated with various pathologies. A significant problem encountered in the direct and simultaneous electrochemical detection of AA, UA, and DA is that these species present very close oxidation potentials on most electrode materials, leading to an overlap in the voltammetric response. Aim: The main goal of this work was to determine the concentration of AA, UA, and DA in a natural water sample on a carbon nanotube paste electrode (CNTPE). Methods: All voltammetric measurements were performed on a µAutolab potentiostat/galvanostat (Metrohm) connected to an electrochemical cell of three electrodes: working, reference (Ag/AgCl, KCl3.0M), and auxiliary (platinum). The working electrode was handmade in our laboratory. The following proportions were used to prepare the paste: 50% CNT + 50% mineral oil and 65% CNT + 35% mineral oil. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used for the electroanalytical study. Results: The linear ranges for the simultaneous determination of AA, DA, and UA by DPV were: 0.45 – 1.0 mM, 50 – 200 ?M, and 10 – 90 ?M, respectively. The LODs of the proposed method for AA, DA, and UA were: 7.97 mM; 8.57 ?M, and 5.96 ?M, respectively. The relative standard deviations (RSD) were 4.6, 2.8, and 1.6% for 0.45 mM of AA, 50 ?M of DA, and 50 ?M of UA. Discussion: The oxidation mechanism of: AA, UA, and DA is a process that involves two electrons and 2 protons. Electrochemical detection of DA in the presence of high levels of AA on carbon-based electrodes becomes difficult due to the catalytic oxidation of AA by DA. For the three molecules, AA, UA, and DA, it is observed that the oxidation peak currents increased with increasing concentration. Conclusions: CNTPE allowed the separation of the oxidation peaks of the ternary mixture of AA, UA, and DA by cyclic voltammetry and, when associated with DPV allowed the simultaneous quantitative determination of AA, UA, and DA.

A simple eco‐friendly carbon paste modified electrode using chitosan‐CaO nanocomposite for the voltammetric detection of the antibiotic ornidazole in real samples

AbstractHerein, an eco‐friendly, simple, inexpensive electrochemical sensor for the antibiotic ornidazole (ORN) was developed based on a carbon paste electrode modified by chitosan‐CaO nanocomposite (Chi‐CaO‐NC/CPE). Eggshell waste was utilized to prepare CaO‐NPs which were then combined with chitosan (Chi) to obtain Chi‐CaO‐NC/CPE. The prepared Chi‐CaO‐NC/CPE was characterized by different techniques such as XRD, FTIR, SEM, and EDX. The produced sensor showed higher electrocatalytic activity toward ORN in (0.1 M) PBS (pH 7.0) than the unmodified CPE. The influence of pH and scanning rate on the reduction peak of ORN implies that the reduction process of ORN at the Chi‐CaO‐NC/CPE surface was a diffusion‐controlled reaction with four electrons and four protons. Additionally, under ideal conditions, differential pulse voltammetry (DPV) revealed that the cathodic current was directly proportional to ORN concentrations within two various detection ranges of 0.015–0.3 μM and 0.3–4.5 μM. The limit of quantification (LOQ), and the limit of detection (LOD) were 0.0138 μM and 4.13×10−3 μM, respectively. Moreover, the fabricated sensor provided acceptable selectivity towards ORN, good stability, and repeatable response, with recoveries ranging from 95.8 %–102.0 %; this electrode was also successful in detecting ORN in commercial tablets and milk samples.

Highly conductive Ti3C2 MXene-supported CoAl-layered double hydroxide nanosheets for ultrasensitive electrochemical detection of organophosphate pesticide fenitrothion.

A novel electrochemical method is presented for ultrasensitive detection of the organophosphate pesticide (OPP) fenitrothion by using Ti3C2 MXene/CoAl-LDH nanocomposite as the electrode modifier. The Ti3C2 MXene/CoAl-LDH nanocomposite is synthesized by growing CoAl-LDH in situ on MXene nanosheets. The combination of two ultrathin 2D materials provides more active sites, larger specific surface area, superior adsorption properties, and better electrical conductivity, which leads to rapid electron-transfer and mass-transfer between the substrate electrode and analytes when it is acted as the electrochemical sensing material. In addition, through the chelation of phosphate groups with the Ti defect sites enriched in MXene, OPP is adsorbed on the electrode. Consequently, the corresponding modified electrode gives rise to a wide linear response range of 0.03 ~ 120μmol/L for the differential pulse voltammetry detection of fenitrothion with a low detection limit of 5.8nmol/L (3σ). The method offers good repeatability, stability, selectivity, and practicability for real samples. This strategy provides a reference platform for the electrochemical monitoring of trace OPPs residue by using MXene/LDH-based nanocomposites.

Ultrasensitive analyses of zearalenone in grain samples with a catalytic oxidation platform involving gold nanomaterials

Zearalenone (ZEN) contamination in cereals poses a serious threat to human and animal health, yet existing rapid test methods still suffer from poor stability and low sensitivity. The studied sensor reduces inspection time while enabling applications for on-site grain inspection. Specifically, a ZEN detector that can sensitively detect ZEN content in grains was developed. Ion implantation is an effective method for modifying screen-printed electrodes (SPEs). Gold nanoparticles (AuNPs; 5–10 nm) were uniformly implanted using screen-printed electrodes as a catalytic oxidation medium to generate an electrochemical sensor. The surface structure of the modified electrode was characterized using scanning electron microscopy and X-ray photoelectron spectroscopy. The results showed that differential pulse voltammetry had good linear electrochemical response to ZEN at 10 ng/kg to 10 mg/kg, with a detection limit of 1.1 ng/kg. We used AuNP-SPE sensors to detect ZEN in grain samples such as maize and oats.

Surface modification prepared porous copper oxide/(Cu-S)n metal-organic framework/reduced graphene oxide hierarchical structure for highly selective electrochemical quercetin detection.

Electrochemical alkalization of (Cu-S)n metal-organic framework (MOF) and graphene oxide ((Cu-S)n MOF/GO) composite yields a new CuO/(Cu-S)n MOF/RGO (reduced GO) composite with porous morphology on screen printed carbon electrode (SPCE) which facilitated the electron transfer properties in electrochemical quercetin (QUE) detection. A selective QUE detection ability has been demonstrated by the constructed electrochemical sensor (CuO/(Cu-S)n MOF/RGO/SPCE), which also has a broad dynamic range of 0.5 to 115µM in pH 3 by differential pulse voltammetry. The detection limit is 0.083µM (S/N = 3). In this study, it was observed that the real samples contained 0.34mgmL-1 and 27.7µgg-1 QUE in wine and onion, respectively.

Laser-Induced Electrochemical Biosensor Modified with Graphene-Based Ink for Label-Free Detection of Alpha-Fetoprotein and 17β-Estradiol.

In this research, a novel electrochemical biosensor is proposed based on inducing graphene formation on polyimide substrate via laser engraving. Graphene polyaniline (G-PANI) conductive ink was synthesized by planetary mixing and applied to the working zone of the developed sensor to effectively enhance the electrical signals. The laser-induced graphene (LIG) sensor was used to detect alpha-fetoprotein (AFP) and 17β-Estradiol (E2) in the phosphate buffer saline (PBS) buffer and human serum. The electrochemical performance of the biosensor in determining these biomarkers was investigated by differential pulse voltammetry (DPV) and chronoamperometry (CA). In a buffer environment, alpha-fetoprotein (AFP) and 17β-Estradiol detection range were 4-400 ng/mL and 20-400 pg/mL respectively. The experimental results showed a limit of detection (LOD) of 1.15 ng/mL and 0.96 pg/mL for AFP and estrogen, respectively, with an excellent linear range (R2 = 0.98 and 0.99). In addition, the designed sensor was able to detect these two types of biomarkers in human serum successfully. The proposed sensor exhibited excellent reproducibility, repeatability, and good stability (relative standard deviation, RSD = 0.96%, 1.12%, 2.92%, respectively). The electrochemical biosensor proposed herein is easy to prepare and can be successfully used for low-cost, rapid detection of AFP and E2. This approach provides a promising platform for clinical detection and is advantageous to healthcare applications.

Real samples sensitive dopamine sensor based on poly 1,3-benzothiazol-2-yl((4-carboxlicphenyl)hydrazono)acetonitrile on a glassy carbon electrode

Herein, a novel electrochemical sensor that was used for the first time for sensitive and selective detection of dopamine (DA) was fabricated. The new sensor is based on the decoration of the glassy carbon electrode surface (GC) with a polymer film of 1,3-Benzothiazol-2-yl((4-carboxlicphenyl)hydrazono)) acetonitrile (poly(BTCA). The prepared (poly(BTCA) was examined by using different techniques such as 1H NMR, 13C NMR, FTIR, and UV-visible spectroscopy. The electrochemical investigations of DA were assessed using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results obtained showed that the modifier increased the electrocatalytic efficiency with a noticeable increase in the oxidation peak current of DA in 0.1 M phosphate buffer solution (PBS) at an optimum pH of 7.0 and scan rate of 200 mV/s when compared to unmodified GC. The new sensor displays a good performance for detecting DA with a limit of detection (LOD 3σ), and limit of quantification (LOQ 10σ) are 0.28 nM and 94 nM respectively. The peak current of DA is linearly proportional to the concentration in the range from 0.1 to 10.0 µM. Additionally, the fabricated electrode showed sufficient reproducibility, stability, and selectivity for DA detection in the presence of different interferents. The proposed poly(BTCA)/GCE sensor was effectively applied to detect DA in the biological samples.