Screen-printed Carbon Electrode Research Articles

Measurement of Human and Bovine Exhaled Breath Condensate pH Using Polyaniline-Modified Flexible Inkjet-Printed Nanocarbon Electrodes.

The collection, processing, and electrochemical analysis of exhaled breath condensate (EBC) from healthy human and animal subjects is reported on. EBC is a biospecimen potentially rich in biomarkers of respiratory disease. The EBC pH was analyzed potentiometrically using a disposable polyaniline (PANI)-modified inkjet-printed (IJP) carbon electrode. Comparison measurements were performed using a commercial screen-printed carbon (SPC) electrode. The PANI-modified electrodes exhibited reproducible and near-Nernstian responses for pH values between 2 and 9 with slopes from -50 to -60 mV/dec. The PANI-modified IJP carbon electrode exhibited a faster response time and superior reproducibility to the modified SPC electrode. In proof-of-concept studies, the healthy human EBC pH was found to be 6.57 ± 0.09 and the healthy bovine EBC pH was 5.9 ± 0.2. All pH determined using the PANI-modified electrodes were in good agreement with the pH determined using a micro glass pH electrode. An RTube device was used to collect EBC from humans while a modified device was used to collect EBC from calves in the field. EBC volumes of 0.5-2 mL for 5-6 min of tidal breathing were collected from healthy animals. The pH of EBC from healthy calves (17 animals) depends on their age from 1 to 9 weeks with values ranging from 5.3 to 7.2. A distinct alkaline shift was observed for many animals around 20 days of age. The bovine EBC pH also depends on the ambient temperature and humidity at the time of collection. The results indicate that the PANI-modified IJP carbon electrodes outperform commercial SPC and provide reproducible and accurate measurement of pH across various biospecimen types.

Surface functionalization of graphene electrode using flavin AuNps for a realtime sensing of asparagine

Asparagine (ASN) is one of the major non-essential amino acids and helps to breakdown the toxic ammonia within the cell. The electrochemical detection of asparagine was performed by the surface functionalized screen-printed carbon (MSPEC) and screen-printed graphene electrodes (MSPEG) through flavin (Quercetin) based gold nanoparticles (AuNps). Cyclic voltammetry (CV) and Differential Pulse Voltammetry (DPV) were performed through MSPEC and MSPEG at single drop of analyte via DROPSENS. SEM and Electrochemical Impedance (EIS) examined for the surface characteristics, enhancement, and functionality of electrodes modified with flavin AuNps. The surface functionalized electrodes revealed excellent electrochemical sensor with high stability, selectivity, repeatability, and have a low limit detection of 0.001 nM. Also, sensors progression was found to occur through adsorption-controlled phenomena. The oxidation peak potential for asparagine in CV and DPV was well-expressed by the MSPEC and MSPEG, with potentials of +0.0881 V and +0.3141 V, respectively. Hence the flavin based AuNps is a new sensing platform for the consistent asparagine real-time sensor and the selective electrochemical detection of asparagine with an exceptionally low detection limit at one drop.

Assessment of a crustacean allergen in fishery products using a nanomodified label-free voltammetric immunosensing approach

In this work, a label-free immunosensor for the rapid analysis of the crustacean allergen tropomyosin (TPM) is presented. A screen-printed carbon electrode (SPCE) was (bio)modified with oxidized carbon nanotube/manganese(II) ferrite nanomaterial (CNT_O@MnFe2O4) and monoclonal antibodies. The immune interaction with the allergenic protein was detected using a redox probe ([Fe(CN)6]3−/4−) by differential pulse voltammetry. The CNT_O@MnFe2O4 led to a 4-fold increase of the analytical signal compared to the unmodified SPCE, indicating the usefulness of this material in TPM analysis. Moreover, the detection potential was reduced (i.e., closer to 0 V), which increased the selectivity of the sensor even further. The immunosensor enabled a fast analysis time (1 h), providing a limit of detection of 1.6 ng mL−1, and precise results (coefficient of variation = 6.5 %). The analysis of ten commercial foodstuffs was accomplished, and the results were validated with an ELISA assay. The highest TPM concentrations were quantified in shrimp species (M. affinis > P. latisulcatus > P. indicus) and low allergen levels were found in surimi lobster, clam, fresh calamari, and mayonnaise. The simplicity of the sensor makes it a good choice for quality control and food safety assessment in industrial settings.

A disposable ultrasensitive immunosensor based on MXene/NH2-CNT modified screen-printed electrode for the detection of ovarian cancer antigen CA125

Cancer antigen 125 (CA125) is the gold standard biomarker for clinical diagnosis of ovarian cancer, with a threshold value of 35 U/mL in serum. In this paper, a disposable ultrasensitive immunosensor based on Ti3C2Tx-MXene/amino-functionalized carbon nanotube (NH2-CNT) modified screen-printed carbon electrode (SPCE) was constructed for the detection of the ovarian cancer antigen CA125. By optimizing the mass ratio of Ti3C2Tx to NH2-CNT, Ti3C2Tx/NH2-CNT composite with excellent electrochemical properties was prepared, which is beneficial for amplifying the initial electrochemical signal. The positively charged NH2-CNT effectively alleviated the stacking problem of Ti3C2Tx, and its amino group also facilitated the covalent immobilization of the capture antibody. Meanwhile, chitosan (CS) with excellent film-forming ability was also used to successfully enhance the adsorption of electrode material, thus improving the stability of the sensor. In addition, CS could further enhance the current signal. The prepared immunosensor exhibited excellent performance in CA125 detection with a wide linear range from 1 mU/mL to 500 U/mL, and good selectivity, reproducibility and lomg-term stability. Furthermore, the immunosensor showed satisfactory results for the detection of CA125 in clinical serum samples, which is promising for the clinical screening, early diagnosis and prognostic examination of ovarian cancer.

Electro-responsive Molecularly Imprinted Polymers (E-MIPs) for Rapid Detection of Progesterone in Human Serum Samples.

Rapid and reagent-free detection of progesterone (P4) is crucial in point-of-care (POC) measurement due to its important role in the human endocrine and central nervous system. Currently available technologies for P4 detection are often not rapid or require reagents, limiting their use in POC settings. In this work, a self-signaling electrochemical sensing platform for rapid detection of P4 is developed by using electroactive molecularly imprinted polymers (E-MIPs). E-MIPs possess the ability to transduce the molecular recognition event into a measurable electrochemical signal. The E-MIPs are prepared by bulk copolymerization of acrylic acid (AA) and ferrocenylmethyl methacrylate (FcMA) in the presence of P4 followed by its removal from the polymer matrix. By incorporation of ferrocene moieties, the MIP gains intrinsic electroactivity, enabling label-free and direct electrochemical detection of P4 levels. Electrochemical techniques, including cyclic voltammetry and electrochemical impedance spectroscopy, were employed to elucidate the electron transport reaction responsible for the MIP's intrinsic electroactivity. Additionally, the predetermined complementary binding sites confined to the small working area of the screen-printed carbon electrode (SPCE) within the E-MIP matrix facilitate rapid P4 binding, achieving completion within 120 s. The developed E-MIP sensing platform was used for the rapid detection of P4 levels in human serum samples. The short incubation times reported for the E-MIP sensing platform would be beneficial in minimizing the nonspecific binding in the real-world samples. We believe that the proposed E-MIP sensing platform can be applied to clinical samples for detecting fluctuations in P4 levels.

Disposable glutamate biosensor based on platinum nanoparticles, carbon quantum dots and poly-L-aspartic acid

This study reports the design and development of a disposable amperometric biosensor for the determination of L-glutamate. Glutamate oxidase (GlOx) was immobilized onto a screen-printed carbon electrode (SPE) modified with poly-L-Aspartic acid (PAsp), carbon quantum dots (CQD), and platinum nanoparticles (PtNP) for the construction of the biosensor. The surface composition of the modified SPE was optimized using the one variable at a time method. The morphological properties of the biosensor were characterized by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The electrochemical behavior of the modified electrodes was studied by cyclic voltammetry. Under the optimized experimental conditions the linear working range, detection limit and sensitivity of the GlOx/PtNP/CQD/PAsp/SPE were found to be 1.0 − 140 µM, 0.3 µM and 0.002 µA µM−1, respectively. The GlOx/PtNP/CQD/PAsp/SPE biosensor also exhibited good measurement repeatability. The as-developed biosensor was applied for the determination of L-glutamate in spiked serum samples and the average analytical recovery of added glutamate was 98.9 ± 3.9%.

Copper(II) oxide-modified screen-printed carbon electrode for electrochemical detection of tuberculosis and mycobacterial infections treating drugs: rifampicin

Copper(II) oxide-modified screen-printed carbon electrode for electrochemical detection of tuberculosis and mycobacterial infections treating drugs: rifampicin

3D inkjet printing of hybrid electroactive ink based on molecularly imprinted polymers for lipopolysaccharides detection

A hybrid electroactive ink based on molecularly imprinted polymer (MIP) hollow microparticles, zinc oxide nanoparticles (ZnO NPs) and conductive carbon paste (CP) is reported herein for the first time. The MIP/ZnO NPs/CP and corresponding non-imprinted NIP/ZnONPs/CP modified inks were screen-printed on plastic substrates via 3D inkjet technology to cover around 40 working screen-printed carbon electrodes (SPCE) pieces in a single batch. The custom-made electrochemical MIP/ZnONPs/CP@SPCE sensor was designed for the detection of bacterial endotoxins, i.e., lipopolysaccharides (LPS), derived from Pseudomonas aeruginosa. Hollow MIP silica microparticles with specific properties for 3D printing application, in terms of granulation and morphology, were synthesized via sol-gel method using tetraethyl orthosilicate and (3-aminopropyl) triethoxysilane as monomers. Following the structural and morphological characterization of microparticles, the evaluation of template rebinding indicated a clear specificity of MIPs for LPS compared to the NIPs. Hybrid MIP/ZnONPs/CP and NIP/ZnONPs/CP inks were characterized using morphological and structural methods, which confirmed a viscosity of 25.000 mPa.s, a granulation of <20 µm, and a solid powder content of <27 %, as well as a homogenous incorporation of MIP particles and ZnONPs in the conductive CP. Finally, the electrochemical evaluation of the modified MIP/ZnONPs/CP@SPCE sensor revealed a good sensitivity to LPS molecules in PBS at pH 7.4, in the linear working range 1 - 100 µM, where a 0.058 µM limit of detection (LOD) and a response time less than or equal to 1 min were determined. The selectivity of the MIP/ZnONPs/CP@SPCE sensor towards LPS from Salmonella enterica and Escherichia coli was also assessed, highlighting a clear difference between these structural resembling species.

Nanoporous Gold-Modified Screen-Printed Electrodes for the Simultaneous Determination of Pb2+ and Cu2+ in Water.

In this study, nanoporous gold (NPG) was deposited on a screen-printed carbon electrode (SPCE) by the dynamic hydrogen bubble template (DHBT) method to prepare an electrochemical sensor for the simultaneous determination of Pb2+ and Cu2+ by square wave anodic stripping voltammetry (SWASV). The electrodeposition potential and electrodeposition time for NPG/SPCE preparation were investigated thoroughly. Scanning electron microscopy (SEM) and energy-dispersive X-ray diffraction (EDX) analysis confirmed successful fabrication of the NPG-modified electrode. Electrochemical characterization exhibits its superior electron transfer ability compared with bare and nanogold-modified electrodes. After a comprehensive optimization, Pb2+ and Cu2+ were simultaneously determined with linear range of 1-100 μg/L for Pb2+ and 10-100 μg/L for Cu2+, respectively. The limits of detection were determined to be 0.4 μg/L and 5.4 μg/L for Pb2+ and Cu2+, respectively. This method offers a broad linear detection range, a low detection limit, and good reliability for heavy metal determination in drinking water. These results suggest that NPG/SPCE holds great promise in environmental and food applications.

A disposable electrochemical sensor for amyloid-β42 protein based on molecular imprinted polymers with nitrogen doped carbon dots-graphene nanohybrid

This work presented a molecularly imprinted polymer (MIP) electrochemical sensor for determination of amyloid-β42 (Aβ42) as an Alzheimer’s disease (AD) biomarker. A nitrogen-doped carbon-dot-graphene (NCD-G) nanohybrid was synthesized through a simple ultrasonic method. Polypyrrole (PPY) was used as an imprinted polymer with an Aβ42 template for the electropolymerization process. The NCD-G and MIP were modified on a screen-printed carbon electrode (SPCE) without binding agent. The morphology and electrochemical properties of MIP/NCD-G modified SPCE were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis spectroscopy, X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and square wave voltammetry (SWV). The developed sensor exhibited good linear response in a range from 5 to 70 pg/mL with a limit of detection (LOD) of 1 pg/mL under optimal conditions. This sensor shows excellent performance due to the enhancement of effective surface area, electrical conductivity, and electrocatalytic activity. This MIP sensor takes advantage of molecularly imprinted technique combined with nanohybrid to achieve high selectivity and sensitivity. Moreover, it possessed good reproducibility and miniaturization that could be applied as a platform for portable devices in healthcare in the future. Novelty statementThis work provides the combination of a zero-dimensional and two-dimensional materials, nitrogen doped carbon dots-graphene nanohybrid (NCD-G) by self-assembly through a simple ultrasonication method and applied as a molecularly imprinted polymer (MIP) sensor for determination of amyloid-β42 protein. We propose a minimum number of preparation steps which NCD-G could enhance the MIP sensor performance, owing to the synergistic effects with high selectivity and sensitivity. The hybrid formation of the carbon dots with graphene using their π-π interactions in carbon nanostructures. NCD-G nanohybrid and MIP modified on screen printed carbon electrode (SPCE) for the determination of amyloid-β42 have not been previously investigated. Moreover, this disposable strip is a single-use tool that might be essential for on-site devices.

Detection of phenolic compounds from olive oil using green extraction with deep eutectic solvent, cyclic voltammetry

In this study, it has been shown that the deep eutectic solvent containing lactic acid, water and glucose can be used to efficiently extract phenolic compounds (PC) from olive oils. No organic solvents were used for the extraction, making the method environmentally friendly. Further, these total PC (TPC) have been electrochemically determined using a novel screen-printed carbon electrode (SPCE) based on carbon nanofibers (CNFs), using cyclic voltammetry (CV) as a electroanalytical technique. Three different PC, namely p-coumaric, chlorogenic and gallic acid were solubilized in deep eutectic solvent (DES) and analyzed with the electrochemical sensor. For the individual PC excellent detection limits were obtained in the range from 0.0105 μM for gallic acid to 0.0253 μM for chlorogenic acid. After that, a series of six extra virgin olive oils (EVOO) samples and six pomace olive oil (POO) samples were used extract PC by liquid–liquid extraction in DES. The signals registered with the sensor by CV immersed in DES extracts were related to the PC amount of the samples. One of the novelties of this work consists in the use of CVs data for the classification of the EVOO and POO samples and to predict the PC content by PLS1 regression model. Furthermore, Folin-Ciocalteu method has been employed to determine the TPC of the DES extracts of olive oils. Excellent correlations between the voltammetric and spectrophotometric methods results have been obtained demonstrating that the applied methodology could be a considered green method for extraction and detection of PC from olive oils.

Eco-Friendly Voltammetric Analysis of Flibanserin with Electropolymerized β-Cyclodextrin on Carbon Sensors

This study developed a cost-effective method to determine flibanserin (FLN) using a screen-printed carbon electrode modified with β-Cyclodextrin polymer (SPCE/β-CD). The electrode was modified in Britton-Robinson buffer at pH 5.0 to enhance FLN’s electrochemical oxidation, with cyclic and differential pulse voltammetry used for detection. Characterization techniques included energy-dispersive X-ray analysis, scanning electron microscopy, and Fourier transform infrared spectroscopy. The method showed a linear response to FLN concentrations ranging from 5.2 to 80.0 ng ml−1, with a detection limit of 0.004 μM and a quantitation limit of 0.014 μM. The modified electrode demonstrated good sensitivity, reproducibility, and was applied successfully to FLN analysis in spiked human serum and urine samples. An environmental impact assessment was conducted using the Green Analytical Procedure Index, which evaluates the green characteristics of the entire analytical methodology from sample collection to final determination. Additionally, the Analytical Eco-Scale, which assesses the use of organic preparations, procedures, and instruments, demonstrated a favorable green analysis profile. This modified electrode provides a convenient, cost-effective, and eco-friendly approach for determining flibanserin in various matrices.

Accurate cadmium (II) detection with single crystalline α-Fe2O3 nano-hexagonal modified screen-printed carbon electrode

Even in small concentrations, toxic metals like lead, cadmium, and mercury are dangerous to the environment and human health. Environmental monitoring depends on precisely identifying these heavy metals, particularly cadmium ions (Cd(II)). In this study, we present a novel screen-printed carbon electrode (SPCE) modified with single crystalline α-Fe2O3 nano-hexagons that functions as a sensor for detecting Cd(II). The performance of the fabricated sensor was thoroughly assessed and compared with unmodified SPCE using the voltammetric method. The crystalline structure of the synthesized α-Fe2O3 nano-hexagons was confirmed through XRD, and surface analysis revealed an average diameter and thickness of 86 nm and 9 nm, respectively. The α-Fe2O3 modified SPCE yields a 7-fold enhanced response (at pH 5.0 vs. Ag/AgCl) to Cd(II) than bare SPCE. The modified electrode effectively detects Cd(II) with a linear response range of up to 333.0 µM and a detection limit of 0.65 nM under ideal circumstances. This newly fabricated sensor offers significant potential for environmental monitoring applications by providing outstanding practicality, anti-interference ability, and repeatability for detecting Cd(II) in water samples.

Fabrication of copper tungstate nanoparticles on screen printed carbon electrode: A disposable strip for the electrochemical detection of the food additive tertiary Butylhydroquinone

Food additives enhance sensory pleasure and improve marketability in food product formulations, yet their potential health risks are highly consequential. Tertiary butylhydroquinone (TBHQ), in this regard, has a controversial reputation owing to its neurotoxic effects, which include convulsions and other chronic issues. This situation underscores the need for an advanced electrochemical sensing platform. The current study advocates the utilization of copper tungstate nanoparticles to enhance the sensitivity, selectivity, and efficiency in TBHQ detection, thus addressing the challenges posed by the excessive use of additives and safeguarding the integrity of the food supply chain. Hydrothermally synthesized CuWO4 nanoparticles exhibited superior physicochemical and morphological characteristics, bringing about wide linear response ranges (0.01 to 789 μM), high selectivity, excellent anti-interference capabilities, and a low detection limit of 0.9 nM (S/N = 3). The CuWO4 modified screen printed carbon electrode (SPCE) presents promising recovery ranges in food samples, facilitating real-time monitoring and streamlining the quality assessment of food additives.

Disposable and flexible screen-printed-carbon electrode modified with Au/poly-beta-cyclodextrin as electrochemical platform for estriol detection

In this work, a screen-printed carbon electrode in polyethylene (SPPE) modified with Au particles and poly-beta-cyclodextrin polymeric film (SPPE/Au/p-beta-CD) was develop as an electrochemical platform to detect estriol (E3) in environmental and biological samples. The stability, reproducibility and sensitivity of the electrode were confirmed via physicochemical and electrochemical characterization. Electrochemical tests demonstrated an increase in the SPPE electroactive area when 70% graphite ink was applied, and transmission electron microscopy revealed an increase in surface complexity compared with that of the unmodified electrode. The electrochemical impedance spectroscopy (EIS) to SPPE/Au/p-beta-CD data indicated a decrease and increase in the Rct (0.096 kΩ cm2) and constant phase element (CPE) (28.34 µF cm−2) values, respectively. The analytical curve was plotted using concentrations ranging from 2.0 to 48.5 µmol/L and the best results were obtained at pH 4.0; a limit of detection (LD) of 1.88 µmol/L was obtained. During a study of interferents, the platform exhibited high selectivity for E3. The SPPE/Au/p-beta-CD exhibited recovery percentages of E3 between 100.32–110.17% in river water, and female urine, saliva, and sweat. The SPPE/Au/p-beta-CD as electrochemical platform proved to be a reproducible, selective, and low-cost sensor for the detection of E3 in different complex matrices. The modification of SPPE with Au and the beta-CD polymer made the electrode more sensitive and the method used is viable for real application.

High aspect ratio copper nanowires modified screen-printed carbon electrode for interference-free non-enzymatic detection of serum creatinine in neutral medium

In this work, the affinity of copper to create a soluble coordination complex with creatinine was exploited for the electrochemical detection of creatinine levels in serum. High aspect ratio copper nanowires were synthesized by controlled hydrothermal method in the presence of dextrose and octadecyl amine. Disposable screen-printed electrode modified with copper nanowires demonstrated excellent sensing towards creatinine in 0.1 M phosphate buffer with a wide detection range of 50–500 µM. The developed sensor was found to be highly selective even in the presence of interfering molecules like glucose, ascorbic acid, urea, uric acid, and chloride. The proposed copper nanowire-based non-enzymatic creatinine sensor is highly promising for point-of-care testing applications.

Atomic layer deposition of NiO-Coated CNT nanocomposites: Tailoring electrochemical properties for salivary lactate detection

NiO-coated stacked-cut carbon nanotubes (NiO/SCCNT) nanocomposites were synthesized via atomic layer deposition (ALD), coating the CNT core walls with a shell of NiO at different thickness varying NiO ALD cycles (0, 50, 200, and 700). The as-prepared core–shell composite nanomaterials were applied as electrode materials for modifying screen-printed carbon electrodes (SPCE) for the non-enzymatic electrochemical detection of lactate (LA). Electrochemical tests performed by CV and EIS demonstrated the reduced charge transfer resistance in NiO(x)/CNT-SPCE compared to pristine CNT-SPCE configuration, and the pronounced dependence of electrochemical behavior on NiO coating thickness. Notably, the NiO/CNT composite with 200 ALD cycles exhibited superior electrochemical properties for the electrooxidation of lactate. The developed sensor showed high sensitivity to LA, (138.44 µA mM−1 cm−2 in the 0–4 mM range). The limit of detection (LOD) values stood at 0.067 mM (considering the signal-to-noise ratio of S/N=3). The sensor showcased several advantages including a conductive supporting carbon material, impressive sensitivity, selectivity, stability, and reproducibility, thereby enabling rapid and precise lactate quantification in salivary real samples.

Gold nanoparticle decorated bismuth vanadate casting on screen-printed electrode for chlortetracycline detection

Chlortetracycline is one of the tetracyclines with broad-spectrum antibacterial activity (CTC). Humans rarely use CTC, but farm animals consume vast quantities of it, which causes the growth of antibiotic-resistant bacteria and environmental contamination. There is no report on the AuNPs and BiVO4 nanocomposite being dropped cast on SPCE for electrochemical monitoring of the CTC, and the most expensive, time-consuming, and expensively equipped method is conventional chromatography. Here, we report a simple method for preparing gold nanoparticle decorated bismuth vanadate (AuNPs@BiVO4), which was dropped cast on a screen-printed carbon electrode (SPCE). The AuNPs@BiVO4 and AuNPs@BiVO4/SPCE materials were characterized using TEM, SEM-EDX, XPS, DLS, ELS, EIS, and CV, showing a consistent nanocomposite and its electrode. The as-prepared AuNPs@BiVO4/SPCE was used to detect and determine chlortetracycline (CTC) by different pulse potentials in phosphate buffer pH 7.0. The electrode possessed a wide linear range of 0.99–19.06 µM, with obtained LOD = 0.15 µM, LOQ = 0.49 µM, and sensitivity = 0.059 μA μM−1 cm−2. It also exhibited good selectivity, stability, and repeatability, recovering 87.14 %–100 % for detecting CTC in Mili Q and tap water. The findings show that the straightforward approach for making AuNPs@BiVO4 nanocomposite and an AuNPs@BiVO4/SPCE electrode is consistent with electrochemical CTC monitoring. Thus, the proposed electrode could be applied for the detection and determination of CTC in water sources and has the potential to be used for real sample analysis.

A dual-targeted electrochemical aptasensor for neuroblastoma-related microRNAs detection

Neuroblastoma (NB) is a significant pediatric cancer associated with high mortality rates, demanding innovative and appropriate approaches for its accurate detection. This paper described the design of a dual-target electrochemical aptasensor capable of simultaneously detecting neuroblastoma-associated microRNAs (miRNA-181 and miRNA-184) with exceptional sensitivity. Screen-printed carbon electrodes (SPCEs) were utilized with gold nanorods (AuNRs), and aptamers functionalized gold nanoparticles (AuNPs) to improve sensitivity, specificity, and portable detection ability. The detection method employed in this study includes differential pulse voltammetry (DPV) and cyclic voltammetry (CV). Our aptasensor exhibited remarkable limits of detections (LODs) of 5.10 aM for miRNA-181 and 9.39 aM for miRNA-184, respectively, along with a broad linear range spanning from 0.1 fM to 100 pM for both miRNAs. The practical significance of neuroblastoma diagnosis was shown through the validation of serum samples and comparison with quantitative polymerase chain reaction (qPCR). Our electrochemical aptasensor is user-friendly, easy to engineer, and offers a promising approach for accurately and selectively detecting important miRNA biomarkers in cancer screening and diagnosis, showing potential application in various clinical scenarios.

Enhancing Heavy Metal Detection through Electrochemical Polishing of Carbon Electrodes.

Our research addresses the pressing need for environmental sensors capable of large-scale, on-site detection of a wide array of heavy metals with highly accurate sensor metrics. We present a novel approach using electrochemically polished (ECP) carbon screen-printed electrodes (cSPEs) for high-sensitivity detection of cadmium and lead. By applying a range of techniques, including scanning electron microscopy, energy-dispersive spectroscopy, Raman spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry, we investigated the impact of the electrochemical potential scan range, scan rate, and the number of cycles on electrode response and its ability to detect cadmium and lead. Our findings reveal a 41 ± 1.2% increase in voltammogram currents and a 51 ± 1.6% decrease in potential separations (n = 3), indicating a significantly improved active electrode area and kinetics. The impedance model elucidates the microstructural and electrochemical property changes in the ECP-treated electrodes, showing an 88 ± 2% (n = 3) decrease in the charge transfer resistance, leading to enhanced electrode electrical conductivity. A bismuth-reduced graphene oxide nanocomposite-modified, ECP-treated electrode demonstrated a higher cadmium and lead sensitivity of up to 5 ± 0.1 μAppb-1cm-2 and 2.7 ± 0.1 μAppb-1cm-2 (n = 3), respectively, resulting in sub-ppb limits of detection in spiked deionized water samples. Our study underscores the potential of optimally ECP-activated electrodes as a foundation for designing ultrasensitive heavy metal sensors for a wide range of real-world heavy metal-contaminated waters.