Electrochemical detection of glutamate by metal–organic frameworks-derived Ni@NC electrocatalysts

A Paper Strip-Based Photoinduced Electrogenerated Chemiluminescence Platform with CTF/PMo12 Heterojunction-Sensitive Glutamic Acid Detection

Glutamic acid (GA), a crucial neurotransmitter, plays a significant role in brain function, muscle health, and various neurological disorders. Elevated GA levels have been associated with conditions such as stroke, Parkinson's disease, epilepsy, and Alzheimer's disease. Accurate detection of GA levels is paramount for both diagnostic and research purposes. Herein, we develop a photoinduced electrogenerated chemiluminescence (PECL) test strip fiber paper coated with a covalent triazine framework (CTF)/H3PMo12O40 polyoxometalate (PMo12) heterojunction. Under blue-light irradiation, photogenerated carriers were separated by an electric field, π-electron delocalization, and polarization, leaving holes on the surface of PMo12 to drive ECL reactions based on luminol oxidation, enabling the detection of GA. This detection resulted in a PECL signal, and fluorometry information, including RGB values, was captured by using a smartphone. The PECL platform enabled the sensitive detection of GA as a neurotransmitter within a linear range of 0.05-1.7 mM, with a low limit of detection (LOD) of 15 nM. The results validated the safety and feasibility of this approach to detect GA in biological samples with satisfactory selectivity against other molecules. The combination of PECL with a smartphone reader presents an exciting avenue for the development of test strips on-site for visual real-time monitoring. This integration offers a high-throughput approach suitable for applications in point-of-care testing and disease monitoring.

Nanopsychiatry: Advancing psychiatric diagnosis and monitoring through nanotechnology-based detection

Nanopsychiatry, operating at the nanoscale, leverages engineered nanomaterials and nanodevices to revolutionize psychiatric diagnostics and therapeutics. This review systematically analyzes the implementation of advanced nanomaterials, including quantum dots, carbon nanotubes (CNTs), and metal nanoparticles, in neural interface systems for neurotransmitter detection and drug monitoring. We evaluate the integration of nanoscale architectures in developing high-specificity biosensors for key neurotransmitters such as dopamine, serotonin, and glutamate. The review critically examines recent advances in nanomaterial-based electrochemical and optical sensing platforms, incorporating modified electrodes with conducting polymers, metallic nanocomposites, and functionalized graphene derivatives. These systems demonstrate enhanced sensitivity and selective multi-analyte detection capabilities in complex biological matrices. We analyze how these nanosensors complement conventional neuroimaging techniques, enabling monitoring of neurochemical dynamics in psychiatric conditions with improved spatial and temporal resolution. Furthermore, we assess the development of flexible, nanomaterial-enhanced wearable biosensors incorporating screen-printed electrodes and microfluidic systems. These devices achieve continuous monitoring of neurological biomarkers, facilitating quantitative assessment of psychiatric symptoms and treatment responses. The integration of machine learning algorithms with these nanoscale sensing platforms enables data processing and pattern recognition for personalized psychiatric interventions.

Iron/cobalt co-doped boron quantum dots as nanozymes with peroxidase-like activities and the nanozyme-involved cascade catalysis system for ratiometric fluorescence and dual-mode visual detection of glutamate

To further explore the boron-involved nanomaterials toward efficient applications in chemo/bio sensing and detection fields, this work reports facile preparation of the emerging iron/cobalt co-doped boron quantum dots (Fe/Co@BQDs) that were explored as new artificial nanozymes for ratiometric fluorescence (FL) and visual detection of glutamate (Glu). In the presence of glutamate oxidase (GLOD), Glu was oxidized to produce H2O2, and then the H2O2 was catalyzed by Fe/Co@ BQDs nanozymes to produce hydroxyl radical (•OH). Afterwards, the •OH induced FL quenching responses of rhodamine B (RhB) and Fe/Co@BQDs. Therefore, a new nanozyme-assisted cascade catalysis platform was explored, consisting of Fe/Co@BQDs, GLOD, and RhB. The platform was successfully used for ratiometric FL sensing of Glu and liquid/solid dual-channel FL visual semi-quantitative detection of Glu. The platform exhibits a board linear detection range of 1-500 µM, a low limit of detection of 0.3 µM, highly selective ratiometric FL responses on Glu over potential interferents, and high-performance practical detection of Glu in biological samples. Experimental results verify high peroxidase-like activities of Fe/Co@BQDs that enable efficient applications for unique enzymatic reactions and nanozyme-involved cascade catalysis reactions. The platform can facilitate further development of other types of metal-doped nanomaterials with natural biological enzyme-like activities and their promising applications, especially chemo/bio sensing, bioimaging and therapeutics at the levels of living cells and small animals.

Miniaturized Electrochemical Sensing Platforms for Quantitative Monitoring of Glutamate Dynamics in the Central Nervous System

Glutamate is one of the most important excitatory neurotransmitters within the mammalian central nervous system. The role of glutamate in regulating neural network signaling transmission through both synaptic and extra-synaptic paths highlights the importance of the real-time and continuous monitoring of its concentration and dynamics in living organisms. Progresses in multidisciplinary research have promoted the development of electrochemical glutamate sensors through the co-design of materials, interfaces, electronic devices, and integrated systems. This review summarizes recent works reporting various electrochemical sensor designs and their applicability as miniaturized neural probes to in vivo sensing within biological environments. We start with an overview of the role and physiological significance of glutamate, the metabolic routes, and its presence in various bodily fluids. Next, we discuss the design principles, commonly employed validation models/protocols, and successful demonstrations of multifunctional, compact, and bio-integrated devices in animal models. The final section provides an outlook on the development of the next generation glutamate sensors for neuroscience and neuroengineering, with the aim of offering practical guidance for future research.

A modified Prussian blue biosensor with improved stability based on the use of self-assembled monolayers and polydopamine for quantitative L-glutamate detection

A miniature L-glutamate (L-Glu) biosensor is described based on Prussian blue (PB) modification with improved stability by using self-assembled monolayers (SAMs) technology and polydopamine (PDA). A gold microelectrode (AuME) was immersed in NH2(CH2)6SH-ethanol solution, forming well-defined SAMs via thiol-gold bonding chemistry which increased the number of deposited Prussian blue nanoparticles (PBNPs) and confined them tightly on the AuME surface. Then, dopamine solution was dropped onto the PBNPs surface and self-polymerized into PDA to protect the PB structure from destruction. The PDA/PB/SAMs/AuME showed improved stability through CV measurements in comparison with PB/AuME, PB/SAMs/AuME, and PDA/PB/AuME. The constructed biosensor achieved a high sensitivity of 70.683 nA µM-1 cm-2 in the concentration range 1-476 µM L-Glu with a low LOD of 0.329 µM and performed well in terms of selectivity, reproducibility, and stability. In addition, the developed biosensor was successfully applied to the determination of L-Glu in tomato juice, and the results were in good agreement with that of high-performance liquid chromatography (HPLC). Due to its excellent sensitivity, improved stability, and miniature volume, the developed biosensor not only has a promising potential for application in food sample analysis but also provides a good candidate for monitoring L-Glu level in food production.

Highly Efficient Enzyme-Free Glutamate Sensors Using Porous Network Metal-Organic Framework-Ni-NiO-Ni-Carbon Nanocomposites

This study introduces an innovative electrochemical sensor designed to detect glutamate using a nonenzymatic approach. The sensor utilizes a porous network metal-organic framework (Ni-MOF)-NiO-Ni-Carbon nanocomposite (PNM-NiO-Ni-Carbon) as an electrode modifier, which was synthesized and assessed for its effectiveness. Cyclic voltammetry measurements demonstrated that the PNM-NiO-Ni-Carbon nanocomposite, synthesized at 450 °C, displayed remarkable electrocatalytic activity for glutamate oxidation. The linear range for detection spanned from 5 to 960 μmol/L, and the sensor achieved a low detection limit of 320 nmol/L (S/N = 3), which was comparable to previously reported data. Moreover, the sensor exhibited high accuracy and favorable recovery rates when tested with real samples, thus, demonstrating its potential for rapid glutamate detection. The real samples were analyzed using both electrochemical and high-performance liquid chromatography methods, and the results obtained from the two methods did not differ significantly, validating the sensor's excellent practical performance. Based on our findings, the PNM-NiO-Ni-Carbon system exhibits potential for a wide range of biomedical applications.

Metal-organic framework derived FeNi alloy nanoparticles embedded in N-doped porous carbon as high-performance bifunctional air-cathode catalysts for rechargeable zinc-air battery

Developing efficient and durable bifunctional air-cathode catalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is one of the key efforts promoting the practical rechargeable zinc-air batteries (ZABs). In this paper, high-performance bifunctional air-cathode catalysts by a two-step strategy: atomically dispersed Ni on N-doped carbon is first derived from MOF to form uniformly dispersed NiNC, which are pyrolyzed together with Fe source at different high-temperatures to form FeNi@NC-T (T = 800, 900, and 1000 °C) catalysts. The as-synthesized non-noble metal FeNi@NC-900 catalyst exhibits a considerably small potential gap (ΔE) of 0.72 V between ORR and OER, which is as the same as commercial noble metal Pt/C + Ir black mixed catalyst. The performance of the ZABs using FeNi@NC-900 as the air-cathode catalyst displays a power density of 119 mW·cm^-2 and a specific capacity of 830.1 mAh·g^-1, which is superior to that of Pt/C + Ir black mixed catalyst. This work provides a guideline for designing alloy electrocatalysts with uniform size and nanoparticle distribution for metal-air batteries with bifunctional air-cathodes.

Ratiometric electrochemical sensing platform based on N-doped MOF-derived CoNi/C for the determination of p-phenylenediamine in hair dyes

A stable ratiometric electrochemical sensing platform is introduced for the determination of p-phenylenediamine (PPD). Specifically, the proposed sensing platform employs nitrogen-doped MOF pyrolysis-derived CoNi/C (N-CoNi/C) which was deployed as the sensing agent and methylene blue (MB) as the internal reference, and the MB combined with N-CoNi/C nanomaterials by a simple immersion adsorption process. Full characterization of N-CoNi/C was carried out with respect to morphology, composition, and electrochemical behavior, and the sensing performance of the ratiometric electrochemical sensing platform was evaluated. Complete separation of the oxidation peaks of PPD and MB was achieved using the MB/N-CoNi/C composite modified glassy carbon electrode (MB/N-CoNi/C/GCE) and their ratio signals were used for quantitative determination of PPD. The electrical signal was linearly related to the concentration of PPD in the concentration range 0.3-100 μM, with a fitted correlation coefficient of 0.9987 and a detection limit of 0.091 μM (S/N = 3). Additionally, the sensor has been successfully used for the determination of PPD in commercial hair dyes with a recovery rate of over 95%.

Porous Carbon Boosted Non-Enzymatic Glutamate Detection with Ultra-High Sensitivity in Broad Range Using Cu Ions

A non-enzymatic electrochemical sensor, based on the electrode of a chitosan-derived carbon foam, has been successfully developed for the detection of glutamate. Attributed to the chelation of Cu ions and glutamate molecules, the glutamate could be detected in an amperometric way by means of the redox reactions of chelation compounds, which outperform the traditional enzymatic sensors. Moreover, due to the large electroactive surface area and effective electron transportation of the porous carbon foam, a remarkable electrochemical sensitivity up to 1.9 × 10⁴ μA/mM∙cm² and a broad-spectrum detection range from nM to mM scale have been achieved, which is two-orders of magnitude higher and one magnitude broader than the best reported values thus far. Furthermore, our reported glutamate detection system also demonstrates a desirable anti-interference ability as well as a durable stability. The experimental revelations show that the Cu ions chelation-assisted electrochemical sensor with carbon foam electrode has significant potential for an easy fabricating, enzyme-free, broad-spectrum, sensitive, anti-interfering, and stable glutamate-sensing platform.