Search Results (458)

We developed a novel and portable magnetic nanochannel electrochemical sensor for the sensitive detection of cadmium ions (Cd²⁺), which pose serious risks to food safety and human health. The sensor was fabricated by co-modifying an anodic aluminum oxide (AAO) nanochannel membrane with a composite of glutathione (GSH) and ferric oxide nanoparticles (Fe₃O₄), denoted as GSH@Fe₃O₄. This modified membrane was then integrated with a screen-printed carbon electrode (SPCE) to construct the GSH@Fe₃O₄/GSH@AAO/SPCE sensing platform. The performance of the sensor was evaluated using differential pulse voltammetry (DPV), which demonstrated a strong linear correlation between the peak current response and the concentration of Cd²⁺ in the range of 5–120 μg/L. The calibration equation was I_DPV(μA) = −0.31 + 0.98·C_{Cd²⁺(μg/L)}, with an excellent correlation coefficient (R² = 0.999, n = 3). The calculated limit of detection (LOD) was as low as 0.1 μg/L, indicating the high sensitivity of the system. These results confirm the successful construction of the GSH@Fe₃O₄/GSH@AAO/SPCE portable nanochannel sensor. This innovative sensing platform provides a rapid, sensitive, and user-friendly approach for the on-site monitoring of heavy metal contamination in agricultural products, especially grains. Full article

In this study, a simple and effective approach was developed for the quantitative detection of serotonin. Hexagonal copper selenide nanostructures (CuSe) were employed to modify a disposable screen-printed carbon electrode (SPCE), and their ability to electrochemically detect serotonin in serum samples was investigated. The fabricated CuSe nanostructures exhibited an interconnected, cluster-like morphology composed of irregularly shaped particles with a distinct hexagonal crystal structure. The electrochemical results revealed that the CuSe/SPCE sensor showed better electrochemical activity and good analytical sensing performance towards serotonin detection. The sensor exhibited a linear response in the concentration range of 10 to 1000 nM, with an excellent correlation coefficient (R² = 0.9998) and a low detection limit of 3 nM. Furthermore, the CuSe/SPCE showed better selectivity, impressive sensitivity (12.45 µM/µA cm⁻²), and good reproducibility toward serotonin detection, making it a promising electrochemical biosensor for serotonin detection in various real biological samples. Full article

In this paper, screen-printed ion-selective electrodes combined with single-walled carbon nanotubes (SWCNTs) and gold nanoparticles (AuNPs) were used to rapidly and accurately measure serum Ca²⁺ concentration. Due to the susceptibility of cows to hypocalcemia after delivery, this disease can affect the health of cows and reduce milk production. Therefore, the development of an economical and swift detection method holds paramount importance for facilitating early diagnosis and subsequent treatment. In this study, by combining the high electrical conductivity and large surface area of SWCNTs with the strong catalytic activity of AuNPs, a SWCNTs/AuNPs composite with high sensitivity and good stability was prepared, achieving efficient selective recognition and signal conversion of Ca²⁺. The experimental results indicate that the screen-printed electrode modified with SWCNTs/AuNPs exhibited excellent performance in the determination of Ca²⁺ concentration. Its linear response range is 10^−5.5–10⁻¹ M, covering the normal and pathological concentration range of Ca²⁺ in cow blood, and the detection limit is far below the clinical detection requirements. In addition, the electrode also has good anti-interference ability and fast response time (about 15 s), showing good performance in the range of 5–45 °C. In practical applications, the combination of the electrode and portable detection equipment can realize the field rapid determination of cow blood Ca²⁺ concentration. This method is easy to operate, cost-effective, and easy to promote, providing strong technical support for the health management of dairy farms. Full article

Precision nutrition is an emerging approach that tailors dietary recommendations based on an individual’s unique genetic, metabolic, microbiome, and lifestyle factors. β-hydroxybutyrate (β-HB) is a key ketone body produced during fat metabolism, especially in states of fasting, low-carbohydrate intake, or prolonged exercise. Therefore, monitoring β-HB levels provides valuable insights into an individual’s metabolic state, making it an essential biomarker for precision and personalized nutrition. A smartphone-connected electrochemical biosensor for single-use, rapid, low-cost, accurate, and selective detection of β-HB in whole blood and saliva at the Point-of-Care (POC) is reported. A graphite screen-printed carbon electrode modified with potassium ferricyanide (Fe(III)GSPE) was used as an electrode platform for the deposition of β-hydroxybutyrate dehydrogenase (HBDH), nicotinamide adenine dinucleotide oxidized form (NAD⁺), and chitosan nanoparticles (ChitNPs). An outer poly(vinyl) chloride (PVC) diffusion-limiting membrane was used to protect the modified electrode. The biosensor showed a linear range in the clinically relevant range, between 0.4 and 8 mM, with a detection limit (LOD) of 0.1 mM. The biosensor was tested on human blood and saliva samples, and the results were compared to those obtained with a commercial ketone meter, showing excellent agreement. Full article

Creatinine serves as a crucial diagnostic biomarker for assessing kidney disease. This work developed portable non-enzymatic and multienzyme-modified electrochemical biosensors for the detection of creatinine based on commercial screen-printed carbon electrodes (SPCEs). The non-enzymatic creatinine sensor was constructed by the electrochemical deposition of AuNPs onto the surface of a pre-activated SPCE by electrochemical activation, followed by the surface modification of a Nafion membrane. The developed AuNPs/SCPE exhibited excellent reproducibility, and the proposed Nafion/AuNPs/SPCE sensor showed excellent detection sensitivity and selectivity toward creatinine. In comparison, the enzymatic creatinine biosensor was gradually established by the electrodeposition of a Prussian blue (PB) membrane on the optimal AuNPs/SCPE surface, followed by multi-enzyme cascade modification (which consisted of creatinine amidohydrolase (CA), creatine oxidase (CI) and sarcosine oxidase (SOx)) and drop-casting the Nafion membrane to stabilize the interface. The introduction of a PB interlayer acted as the redox layer to monitor the generation of hydrogen peroxide (H₂O₂) produced by the enzymatic reaction, while the Nafion membrane enhanced the detection selectivity toward creatine, and the multi-enzyme cascade modification further increased the detection specificity. Both non-enzymatic and enzymatic creatinine sensors could detect the lowest concentrations of less than or equal to 10 μM. In addition, the efficiency and reproducibility of the proposed composite biosensor were also confirmed by repetitive electrochemical measurements in human serum, which showed a positive linear calibration relation of peak currents versus the logarithm of the concentration between 10 μM and 1000 μM, namely, i_p (μA) = −7.06 lgC (μM) −5.30, R² = 0.996. This work offers a simple and feasible approach to the development of enzymatic and non-enzymatic creatinine biosensors. Full article

Electrochemical formation of ceria (mixed Ce₂O₃ and CeO₂) coatings on different types of screen-printed carbon electrodes (SPCEs) (based on graphite (C110), carbon nanotubes (CNT), single-walled carbon nanotubes (SWCNT), carbon nanofibers (CNF), and mesoporous carbon (MC)) were studied. Their potential applications as catalysts for various redox reactions and electrochemical sensors were investigated. The ceria oxide layers were electrodeposited on SPCEs at various current densities and deposition time. The morphology, structure, and chemical composition in the bulk of the ceria layers were studied by SEM and EDS methods. XRD was used to identify the formed phases. The concentration, chemical composition and chemical state of the elements on the surface of studied samples were characterized by XPS. It was established that the increase of the concentration of CeCl₃ in the solution and the cathode current density strongly affected the surface structure and concentration (relation between Ce³⁺ and Ce⁴⁺, respectively) in the formed ceria layers. At low concentration of CeCl₃ (0.1M) and low values of cathode current density (0.5 mA·cm⁻²), porous samples were obtained, while with their increase, the ceria coatings grew denser. Full article

Dopamine is a major catecholamine neurotransmitter that plays an essential role in the functioning of the human central nervous system. Imbalances in dopamine levels are associated with neurological disorders and depression. Thus, measuring the concentration of DA in human body fluids is significantly important. In this work, TEMPO-oxidized cellulose nanofibrils (TOCNFs) extracted from marram grass (Ammophilia arenaria), harvested in the central western part of Tunisia, were utilized to modify disposable screen-printed carbon electrodes (SPCEs) for the sensitive detection of dopamine in biological fluids. Differential pulse voltammetry (DPV) measurements displayed a sensitivity of 7.92 µA/µM and a detection limit of 10 nM. The disposable TOCNF-modified SPCE presents a charge transfer coefficient, α, comparable to that of a TOCNF/graphene/AgNP composite-modified GCE. Moreover, it exhibits good repeatability (RSD = 1.9%), good reproducibility (RSD = 2.3%), and appreciable storage stability (91% of its initial response after 3 weeks). The prepared disposable sensor showed satisfactory recovery of dopamine in human urine samples. Full article

Promethazine hydrochloride (PMH) is a first-generation antipsychotic drug created from phenothiazine derivatives that is widely employed to treat psychiatric disorders in human healthcare systems. However, an overdose or long-term intake of PMH can lead to severe health issues in humans. Hence, establishing a sensitive, accurate, and efficient detection approach to detect PMH in human samples is imperative. In this study, we designed orthorhombic copper molybdate microspheres decorated on reduced graphene oxide (Cu₃Mo₂O₉/RGO) composite via the effective one-pot hydrothermal method. The structural and morphological features of the designed hybrid were studied using various spectroscopic methods. Subsequently, the electrochemical activity of the composite-modified screen-printed carbon electrode (Cu₃Mo₂O₉/RGO/SPCE) was assessed by employing voltammetric methods for PMH sensing. Owing to the uniform composition and structural benefits, the combination of Cu₃Mo₂O₉ and RGO has not only improved electrochemical properties but also enhanced the electron transport between PMH and Cu₃Mo₂O₉/RGO. As a result, the Cu₃Mo₂O₉/RGO/SPCE exhibited a broad linear range of 0.4–420.8 µM with a low limit of detection (LoD) of 0.015 µM, highlighting excellent electrocatalytic performance to PMH. It also demonstrated good cyclic stability, reproducibility, and selectivity in the presence of chlorpromazine and biological and metal compounds. Furthermore, the Cu₃Mo₂O₉/RGO/SPCE sensor displayed satisfactory recoveries for real-time monitoring of PMH in human urine and serum samples. This study delivers a promising electrochemical sensor for the efficient analysis of antipsychotic drug molecules. Full article

Hydroxychloroquine (HCQ), a cornerstone therapeutic agent for autoimmune diseases, requires precise serum concentration monitoring due to its narrow therapeutic window. Current HCQ monitoring methods such as HPLC and LC-MS/MS are sensitive but costly and complex. While electrochemical sensors offer rapid, cost-effective detection, their large chambers and high sample consumption hinder point-of-care use. To address these challenges, we developed a microfluidic electrochemical sensing platform based on a screen-printed carbon electrode (SPCE) modified with a hierarchical nanocomposite of gold nanoparticles (AuNPs), copper-based metal–organic frameworks (Cu-MOFs), and multi-walled carbon nanotubes (MWCNTs). The Cu-MOF provided high porosity and analyte enrichment, MWCNTs established a 3D conductive network to enhance electron transfer, and AuNPs further optimized catalytic activity through localized plasmonic effects. Structural characterization (SEM, XRD, FT-IR) confirmed the successful integration of these components via π-π stacking and metal–carboxylate coordination. Electrochemical analyses (CV, EIS, DPV) revealed exceptional performance, with a wide linear range (0.05–50 μM), a low detection limit (19 nM, S/N = 3), and a rapid response time (<5 min). The sensor exhibited outstanding selectivity against common interferents, high reproducibility (RSD = 3.15%), and long-term stability (98% signal retention after 15 days). By integrating the nanocomposite-modified SPCE into a microfluidic chip, we achieved accurate HCQ detection in 50 μL of serum, with recovery rates of 95.0–103.0%, meeting FDA validation criteria. This portable platform combines the synergistic advantages of nanomaterials with microfluidic miniaturization, offering a robust and practical tool for real-time therapeutic drug monitoring in clinical settings. Full article

An electrochemical sensor was developed for the detection of hydrogen peroxide (H₂O₂) based on the in situ formation of a nickel hexacyanoferrate complex on the electrode surface. Screen-printed carbon electrodes were modified with nickel-doped carbon nanodots (Ni-CNDs), and a nickel hexacyanoferrate complex was electrogenerated over the nickel carbon nanodots. Ni-CNDs were synthetized “a la carte” in one step by including nickel (II) acetate as precursor and characterized using different techniques: transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy, atomic force microscopy (AFM), and infrared spectroscopy (FTIR). The electrocatalytic activity toward H₂O₂ reduction and the oxidation of the resulting modified electrodes was studied. The developed sensor had a strong electrocatalytic effect on the oxidation and reduction of H₂O₂, yielding detection limits of 3.22 and 0.49 μM, respectively. The H₂O₂ content of a tap water sample was determined, confirming the viability of the developed electrochemical sensor. Full article

Vitamins are crucial micro-nutrients for overall well-being, making continuous monitoring essential. There are demands to provide an alternative detection, especially using a portable detection or a point-of-care-testing (POCT) device. One promising approach is employing an in situ electro-polymerised MIP (eMIP), which offers a straightforward polymerisation technique on screen-printed electrodes (SPEs). Here, we report a review based on three databases (PubMed, Scopus, and Web of Science) from 2014 to 2024 using medical subject heading (MeSH) terms “electrochemical polymerisation” OR “electropolymerisation” crossed with the terms “molecularly imprinted polymer” AND “vitamin A” OR “vitamin D” OR “vitamin E” OR “vitamin K” OR “fat soluble vitamin” OR “vitamin B” OR “vitamin C” OR “water soluble vitamin”. The resulting 12 articles covered the detection of vitamins in ascorbic acid, riboflavin, cholecalciferol, calcifediol, and menadione using monomers of catechol (CAT), 3,4-ethylenedioxythiophene (EDOT), o-aminophenol (oAP), o-phenylenediamine (oPD), pyrrole, p-aminophenol (pAP), p-phenylenediamine (pPD), or resorcinol (RES), using common bare electrodes including graphite rod electrode (GRE), glassy carbon electrode (GCE), gold electrode (GE), and screen-printed carbon electrode (SPCE). The most common electrochemical detections were differential pulse voltammetry (DPV) and linear sweep voltammetry (LSV). The imprinting factor (IF) of the eMIP-modified electrodes were from 1.6 to 21.0, whereas the cross-reactivity was from 0.0% to 29.9%. Several types of food and biological samples were tested, such as supplement tablets, poultry and pharmaceutical drugs, soft drinks, beverages, milk, infant formula, human and calf serum, and human plasma. However, more discoveries and development of detection methods needs to be performed, especially for the vitamins that have not been studied yet. This will allow the improvement in the application of eMIPs on portable-based detection and POCT devices. Full article

A composite (N-rGO@ppy) of N-doped reduced graphene oxide (N-rGO) coated with polypyrrole (ppy) particles was successfully synthesized. The incorporation of N-rGO significantly mitigates the aggregation of ppy synthesized in situ, and the doped N atoms improve the conductivity of graphene oxide (GO), thereby enhancing N-rGO@ppy’s redox properties. Firstly, a glassy carbon electrode (GCE) modified with N-rGO@ppy (N-rGO@ppy/GCE) was used in combination with a bismuth film and square-wave anodic stripping voltammetry (SWASV) for the simultaneous trace analysis of Pb²⁺ and Cd²⁺. N-rGO@ppy/GCE exhibited distinct stripping peaks for Pb²⁺ and Cd²⁺, with a linear range of 1 to 500 μg L⁻¹. The limits of detection (LODs) were found to be 0.080 μg L⁻¹ for Pb²⁺ and 0.029 μg L⁻¹ for Cd²⁺, both of which are significantly below the standards set by the World Health Organization (WHO). Subsequently, the same electrochemical sensing strategy was adapted to a more portable screen-printed electrode (SPE) to accommodate the demand for in situ detection. The performance of N-rGO@ppy/SPE for analyzing Pb²⁺ and Cd²⁺ in actual samples, such as drinking water, milk, and honey, showed results consistent with those obtained from conventional graphite furnace atomic absorption spectrometry (GFAAS). Full article

This study describes the development of catalytic surface immobilizing dopamine via cross-linking or tyrosinase through covalent bonds on an electrografted screen-printed carbon electrode with a 4-nitrobenzenediazonium ion. A simple electrochemical reduction approach was used to covalently graft aryldiazonium ions onto the surface of commercial electrodes. After functionalization with aminophenyl groups, dopamine, an important neurotransmitter, was immobilized by imine bond formation using glutaraldehyde as a bifunctional cross-linking molecule. The presence of immobilized dopamine was confirmed by cyclic voltammetry following the electrochemical response of the hydroquinone/quinone redox process from catechol functionalities on the surface, which are responsible for the catalytic activity. In addition, the surface was also characterized by cyclic voltammetry using the redox probe, [Fe(CN)₆]^3−/4−, obtaining a signal approximately 14 times higher than that of a bare electrode, achieving a dynamic concentration range spanning three orders of magnitude. Remarkable sensitivity was also obtained by combining the electrografting, in situ diazotation, to generate grafted aryl diazonium ions on the surface, and coupling reaction to anchor the tyrosinase enzyme to the electrode surface. The response of the TYR-biosensor towards catechol, using the redox probe as mediator, was 10 times higher than that obtained with the dopamine modified catalytic surface. These modified surfaces offer promising alternatives for the voltammetric quantification of catechol in environmental fields. Full article

Methicillin-resistant Staphylococcus epidermidis (MRSE) contamination is commonly found on human skin and medical devices. Herein, we present a sensor utilizing molecularly imprinted polymer nanobodies (nanoMIP) for recognition and electrochemical impedance spectroscopy (EIS) to detect S. epidermidis. Sensor manufacturing involves synthesizing nanoMIP via solid-phase synthesis using whole bacteria as templates. Screen-printed gold electrode (AuSPE)-modified 16-mercaptohexadecanoic acid (MHDA) served to immobilize the nanoMIPs on the sensor surface through an amide bond, with the remaining functional groups blocked by ethanolamine (ETA). Scanning electron microscope (SEM) analysis of the modified AuSPE surface reveals immobilized spherical nanoMIP particles of 114–120 nm diameter, while atomic force microscope (AFM) analysis showed increased roughness and height compared to bare AuSPE. The sensor is selective for S. epidermidis, with a remarkable detection limit of 1 CFU/mL. This research demonstrates that the developed nanoMIP-based sensor effectively detects S. epidermidis. Further research will focus on developing protocols to integrate the nanoMIP-based EIS sensor into medical and industrial applications, ultimately contributing to improved safety for both humans and animals in the future. Full article

In the present work, we designed a straightforward and disposable voltammetric sensor utilizing a molybdenum disulfide/multi-walled carbon nanotube nanostructure-modified screen-printed carbon electrode (MoS₂/MWCNTs/SPCE) for 4-nitrophenol (4-NP) determination. The successful synthesis of the MoS₂/MWCNT nanostructure was characterized using Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EXD) mapping. The electrochemical behavior of 4-NP at the MoS₂/MWCNTs/SPCE was examined using differential pulse voltammetry (DPV), cyclic voltammetry (CV), and chronoamperometry techniques. The MoS₂/MWCNTs/SPCE exhibited outstanding electro-catalytic activity for the voltammetric detection of 4-NP. Under optimized conditions, the reduction peak current showed a linear dependence with the concentration of 4-NP in the range of 0.05 to 800.0 µM, and a detection limit (LOD) of 0.01 µM was determined. In addition, the MoS₂/MWCNTs/SPCE sensor has advantages including repeatability, reproducibility, stability, inexpensiveness, and practical application. The MoS₂/MWCNTs/SPCE-based sensor was also utilized for the determination of 4-NP in real water specimens. Full article