Gold Nanoclusters Dispersed on Gold Dendrite-Based Carbon Fibre Microelectrodes for the Sensitive Detection of Nitric Oxide in Human Serum

Paper-based Electrochemical Sensor Integrated with Gold Nanoparticle-Decorated Carbon Cloth as a Working Electrode for Nitric Oxide Detection in Artificial Tears

Nitric oxide (NO) in human tears regulates numerous ocular surface processes, such as tear generation, corneal wound healing, conjunctival vascular tone, and so forth. Any deviation from its normal concentration is linked to various ocular syndromes, including microbial keratitis, conjunctivitis, pterygium, dry eye, retinitis, glaucoma, and so forth. Therefore, precise monitoring of NO in tears can be considered as a potential biomarker for ocular diseases. Here, we report a highly sensitive and selective electrochemical NO sensor using carbon ink-based electrodes. Counter, working (WE), and reference electrodes have been designed and painted on a butter paper by using carbon ink. To improve the sensing performance, the WE has been modified with a gold nanoparticle (Au NP)-deposited carbon cloth (CC). Such a paper-based sensor demonstrated high sensitivity of ∼0.34 μA μM-1 cm-2, ultralow detection limit of ∼2.35 nM, wide linear range of 10 nM-0.4 mM, and fast response time (0.35 s). The sensor also showed excellent stability and selectivity toward the interfering agents in human body fluids. Such a low-cost, flexible paper-based sensor was employed for the detection of NO in artificial tears.

Carbon nanotube-interconnected ruthenium phthalocyanine nanoparticles used for real-time monitoring of nitric oxide released from vascular endothelial barrier model

Real-time monitoring of nitric oxide (NO) is of great importance in diagnosing the physiological functions of neurotransmission, cardiovascular, and immune systems. This study reports the carbon nanotube-interconnected ruthenium phthalocyanine nanoparticle nanocomposite and its applicability in construction of an electrochemical platform, which could real-time detect NO released from the vascular endothelial barrier (VEB) model in cell culture medium. The nanocomposite exhibits regular morphology, uniform particle size, and excellent electro-catalytic activity to electrochemical oxidation of NO. Under optimal conditions, the electrochemical device has high sensitivity (0.871 μA μM-1) and can selectively detect NO down to the concentration of 6 × 10-10 M. The human brain microvascular endothelial cells were cultured onto the Transwell support to construct the VEB model. Upon stimulated by L-arginine, NO produced by the VEB diffuses into the bottom chamber of the Transwell, and is real-time monitored by the electrochemical device. Moreover, evaluation of the NO inhibition by drug is realized using the electrochemical device-Transwell platform. This simple and sensitive platform would be of great interesting for evaluating the endothelial function or its pathological states, and screening the related drugs or chemicals.

Enzyme-free electrochemical sensor platforms based on transition metal nanostructures for clinical diagnostics

The detection of emergent biomarkers is of key significance in numerous clinical, biological, and biomedical fields. Specifically, the design and development of potent electrochemical lactic acid and glucose sensing platforms are especially in great demand in a variety of industries, including those involved in clinical analysis, biomedicine, biological, food, cosmetics, pharmaceuticals, leather, sports, and chemical industries. Nanostructured transition metal-derived materials have opened the door to electrochemical sensors and biosensors due to their advantages of high surface-to-volume ratio, surface reaction activity, catalytic activity, and strong adsorption capability. The primary aim of the present minireview is to highlight the advancement of enzyme-free electrochemical sensor platforms based on transition metal-derived nanostructures with high electrocatalytic activity and sensing performance towards lactic acid and glucose in practical samples. The preparation approaches, structural and composition monitoring, fabrication of sensing electrodes, catalytic activity, sensing performance in real samples, and the exploration of sensing mechanisms are majorly concentrated on in most of our recent research studies. Moreover, state-of-the-art transition metal-derived nanostructure-derived electrochemical sensor platforms, critical comparison of the analytical performance of the sensor platforms, and the future perspectives of the enzyme-free electrochemical sensor for clinical diagnostics are described.

Graphene nanocomposites for real-time electrochemical sensing of nitric oxide in biological systems

Nitric oxide (NO) signaling plays many pivotal roles impacting almost every organ function in mammalian physiology, most notably in cardiovascular homeostasis, inflammation, and neurological regulation. Consequently, the ability to make real-time and continuous measurements of NO is a prerequisite research tool to understand fundamental biology in health and disease. Despite considerable success in the electrochemical sensing of NO, challenges remain to optimize rapid and highly sensitive detection, without interference from other species, in both cultured cells and in vivo. Achieving these goals depends on the choice of electrode material and the electrode surface modification, with graphene nanostructures recently reported to enhance the electrocatalytic detection of NO. Due to its single-atom thickness, high specific surface area, and highest electron mobility, graphene holds promise for electrochemical sensing of NO with unprecedented sensitivity and specificity even at sub-nanomolar concentrations. The non-covalent functionalization of graphene through supermolecular interactions, including π-π stacking and electrostatic interaction, facilitates the successful immobilization of other high electrolytic materials and heme biomolecules on graphene while maintaining the structural integrity and morphology of graphene sheets. Such nanocomposites have been optimized for the highly sensitive and specific detection of NO under physiologically relevant conditions. In this review, we examine the building blocks of these graphene-based electrochemical sensors, including the conjugation of different electrolytic materials and biomolecules on graphene, and sensing mechanisms, by reflecting on the recent developments in materials and engineering for real-time detection of NO in biological systems.

Metal Oxides Nanomaterials and Nanocomposite-Based Electrochemical Sensors for Healthcare Applications

Wide-ranging research efforts have been directed to prioritize scientific and technological inventions for healthcare monitoring. In recent years, the effective utilization of functional nanomaterials in various electroanalytical measurements realized a rapid, sensitive, and selective detection and monitoring of a wide range of biomarkers in body fluids. Owing to good biocompatibility, high organic capturing ability, strong electrocatalytic activity, and high robustness, transition metal oxide-derived nanocomposites have led to enhancements in sensing performances. The aim of the present review is to describe key advancements of transition metal oxide nanomaterials and nanocomposites-based electrochemical sensors, along with current challenges and prospects towards the development of a highly durable and reliable detection of biomarkers. Moreover, the preparation of nanomaterials, electrode fabrication, sensing mechanism, electrode-bio interface, and performance of metal oxides nanomaterials and nanocomposite-based sensor platforms will be described.