Solvothermal synthesis of two-dimensional graphitic carbon nitride/tungsten oxide nanocomposite: a robust electrochemical scaffold for selective determination of dopamine and uric acid

Nanozyme film with dicopper-coordinated amino-ligands: A dual enzyme-mimic for real-time in situ dopamine sensing in human neuroblastoma cells

Dopamine (DA) is a vital neurotransmitter, and its real-time detection is critical for understanding neurological functions and diagnosing disorders. Integrated sensing platforms with multiple signal outputs enable real-time monitoring of neurotransmitter release, but their development is often limited by material adaptability, signal reliability, and precise analyte detection in complex systems. Nanozyme-based sensors have emerged as a promising alternative, though developing highly active and selective nanozymes remains a key focus. Herein, a dual-mode portable biosensing device using a nanostructured Cu(II)-poly-L-histidine film via simple electropolymerization onto a screen-printed graphitic electrode (PolyCuHis/SPGE) was developed. This film exhibits remarkable laccase-like, catechol oxidase, and electrocatalytic properties, functioning as an electrochemical/colorimetric probe for DA detection. The sensing mechanism relies on electrostatic and π-π interactions between DA and overoxidized imidazole groups, coupled with efficient charge transfer at active sites, ensuring selective and sensitive DA detection in real-world samples. The PolyCuHis/SPGE sensor demonstrated exceptional performance, with linear responses for electrochemical and colorimetric DA detection in the ranges of 10 nM-100 μM and 1-250 μg/mL, and limits of detection (LOD) of 2.8 nM and 0.204 μg/mL, respectively. The system also exhibited robust repeatability, high stability, and excellent selectivity. Additionally, the device was adapted for visual DA quantification using a smartphone, enhancing its practicality for point-of-care testing (POCT) applications. The sensor's effectiveness was validated by accurately quantifying DA in complex samples and successfully tracking DA release from human neuroblastoma SHSY-5Y cells under pharmacological stimulation. This approach provides a powerful platform for early diagnosis of neurological disorders and advanced POCT applications in neuroscience and clinical diagnostics.

Portable Sensing Probe for Real-Time Quantification of Ammonia in Blood Samples

The detection of ammonia levels in blood is critical for diagnosing and monitoring various medical conditions, including liver dysfunction and metabolic disorders. However, traditional diagnostic methods are slow and cumbersome, often involving multiple contact-based steps such as ammonia separation in alkali conditions followed by distillation or microdiffusion, leading to delays in diagnosis and treatment. Herein, we developed a colorimetric assay capable of rapid detection of ammonia in whole blood or plasma samples, utilizing 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO)-oxidized cellulose nanocrystals (TCNC) coupled with gold nanoparticles (AuNPs). The basis of our assay relies on either (i) the interaction between the carboxylate group (-COO) of TEMPO and ammonium ions or (ii) the manipulation of AuNPs surface plasmon resonance (SPR) through the formation of Au(NH3)43+, which displaces a redox mediator, resazurin, resulting in observable multicolor displays at various concentrations of ammonia. The colorimetric assay exhibits a wide linear detection range for dissolved NH4+ (0.1-37 μM) with a low limit of detection (LOD) of 0.1 μM. Additionally, it effectively measures NH3(g) concentrations in the range of 0.5-144 μM. The fabricated electrochemical nose (E-nose) device demonstrates excellent analytical performance for plasma ammonia sensing (0.05-256 μM). Experimental results demonstrate a linear detection range suitable for clinical applications, with excellent correlation to standard laboratory methods, offering a practical solution for point-of-care (PoC) testing. We anticipate that this approach can be applied broadly to improve patient monitoring and treatment by providing immediate and accurate ammonia measurements in a clinical setting.

Ru-W modified graphitic carbon nitride by a monomer complexation synthesis approach from a tailored polyoxometalate: towards electrochemical detection of hydrogen peroxide released by cells

Detection of hydrogen peroxide (H₂O₂) from cell cultures is important for monitoring different diseases. Here, g-C₃N₄ (gCN) was incorporated into well-defined clusters of RuW (RuW-gCN) through monomer complexation of Ru-substituted phosphotungstate and melamine for electrochemical detection of H₂O₂. RuW-gCN exhibited enhanced electrochemical sensing properties in comparison to its constituents due to the synergic effects between RuW and gCN. The characterization of RuW-gCN revealed successful complexation to form the composite in addition to the presence of a layered structure of gCN. The electrochemical sensor made of RuW-gCN was able to detect H₂O₂ with a detection limit of 46 nM in the linear ranges from 100 nM to 50 μM and from 50 μM to 1 mM. The developed sensor was employed for the selective detection of H₂O₂ in the presence of analytes like ascorbic acid (AA), dopamine, and glucose in addition to being stable even after a week of storage at room temperature. It has also been verified for real sample application by detecting H₂O₂ produced by cancer cells as a result of an AA trigger.

A Highly Sensitive Electrochemical Sensor for Cd2+ Detection Based on Prussian Blue-PEDOT-Loaded Laser-Scribed Graphene-Modified Glassy Carbon Electrode

Heavy metal ion pollution has had a serious influence on human health and the environment. Therefore, the monitoring of heavy metal ions is of great practical significance. In this work, we describe the development of an electrochemical sensor to detect cadmium (Cd2+) using a Prussian blue (PB), poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT)-loaded laser-scribed graphene (LSG) nanocomposite-modified glassy carbon electrode (GCE). In this nanocomposite material, we successfully brought together the advantages of an extraordinarily large surface area. The accumulation of PB nanoparticles results in an efficient electrochemical sensor with high sensitivity and selectivity and fast detection ability, developed for the trace-level detection of Cd2+. Electrochemical features were explored via cyclic voltammetry (CV), whereas the stripping voltammetry behavior of modified electrodes was analyzed by utilizing differential pulse voltammetry. Compared with bare GCE, the LSG/PB-PEDOT/GCE modified electrode greatly increased the anodic stripping peak currents of Cd2+. Under the optimized conditions, the direct and facile detection of Cd2+ was achieved with a wide linear range (1 nM–10 µM) and a low LOD (0.85 nM).