Low energy nitrogen ion beam implanted tungsten trioxide thin films modified indium tin oxide electrode based acetylcholine sensor

FAST (Flexible Acetylcholine Sensing Thread): Real-Time Detection of Acetylcholine with a Flexible Solid-Contact Potentiometric Sensor

Acetylcholine (ACh) is involved in memory and learning and has implications in neurodegenerative diseases; it is therefore important to study the dynamics of ACh in the brain. This work creates a flexible solid-contact potentiometric sensor for in vitro and in vivo recording of ACh in the brain and tissue homogenate. We fabricate this sensor using a 250 μm diameter cotton yarn coated with a flexible conductive ink and an ACh sensing membrane that contains a calix[4]arene ionophore. The exposed ion-to-electron transducer was sealed with a 2.5 μm thick Parylene C coating to maintain the flexibility of the sensor. The resulting diameter of the flexible ACh sensing thread (FAST) was 400 μm. The FAST showed a linear response range from 1.0 μM to 10.0 mM in deionized water, with a near-Nernstian slope of 56.11 mV/decade and a limit of detection of 2.6 μM. In artificial cerebrospinal fluid, the limit of detection increased to 20 μM due to the background signal of ionic content of the cerebrospinal fluid. The FAST showed a signal stability of 226 μV/h over 24 h. We show that FAST can measure ACh dynamics in sheep brain tissue and sheep brain homogenate after ACh spiking. FAST is the first flexible electrochemical sensor for monitoring ACh dynamics in the brain.

Significance of an Electrochemical Sensor and Nanocomposites: Toward the Electrocatalytic Detection of Neurotransmitters and Their Importance within the Physiological System

A prominent neurotransmitter (NT), dopamine (DA), is a chemical messenger that transmits signals between one neuron to the next to pass on a signal to and from the central nervous system (CNS). The imbalanced concentration of DA may cause numerous neurological sicknesses and syndromes, for example, Parkinson's disease (PD) and schizophrenia. There are many types of NTs in the brain, including epinephrine, norepinephrine (NE), serotonin, and glutamate. Electrochemical sensors have offered a creative direction to biomedical analysis and testing. Researches are in progress to improve the performance of sensors and develop new protocols for sensor design. This review article focuses on the area of sensor growth to discover the applicability of polymers and metallic particles and composite materials as tools in electrochemical sensor surface incorporation. Electrochemical sensors have attracted the attention of researchers as they possess high sensitivity, quick reaction rate, good controllability, and instantaneous detection. Efficient complex materials provide considerable benefits for biological detection as they have exclusive chemical and physical properties. Due to distinctive electrocatalytic characteristics, metallic nanoparticles add fascinating traits to materials that depend on the material's morphology and size. Herein, we have collected much information on NTs and their importance within the physiological system. Furthermore, the electrochemical sensors and corresponding techniques (such as voltammetric, amperometry, impedance, and chronoamperometry) and the different types of electrodes' roles in the analysis of NTs are discussed. Furthermore, other methods for detecting NTs include optical and microdialysis methods. Finally, we show the advantages and disadvantages of different techniques and conclude remarks with future perspectives.

An overview of recent analysis and detection of acetylcholine

Acetylcholine (ACh), the major neurotransmitter secreted by cholinergic neurons, is widely found in the peripheral and central nervous systems, and its main function is to complete the transmission of neural signals. When cholinergic neurons are impaired, the synthesis and decomposition of ACh are abnormal and the neural signalling transition is blocked. To some extent, the concentration changes of ACh reflects the occurrence and development of many kinds of nervous system diseases, such as Alzheimer's disease, Parkinson's disease, Myasthenia gravis and so on. Thus, researches of the physiological and pathological roles and the tracking of the concentration changes of ACh in vivo are significant to the prevention and treatment of these diseases. In the paper, the pathophysiological functions and the comprehensive research progress on detection methods of ACh are summarized. Specifically, the latest research and related applications of the optical and electrochemical biosensors are described, and the future development directions and challenges are prospected, which provides a reference for the detection and applications of ACh.

Metal-Oxide Based Nanomaterials: Synthesis, Characterization and Their Applications in Electrical and Electrochemical Sensors

Pure, mixed and doped metal oxides (MOX) have attracted great interest for the development of electrical and electrochemical sensors since they are cheaper, faster, easier to operate and capable of online analysis and real-time identification. This review focuses on highly sensitive chemoresistive type sensors based on doped-SnO₂, RhO, ZnO-Ca, Sm_x-CoFe_2−xO₄ semiconductors used to detect toxic gases (H₂, CO, NO₂) and volatile organic compounds (VOCs) (e.g., acetone, ethanol) in monitoring of gaseous markers in the breath of patients with specific pathologies and for environmental pollution control. Interesting results about the monitoring of biochemical substances as dopamine, epinephrine, serotonin and glucose have been also reported using electrochemical sensors based on hybrid MOX nanocomposite modified glassy carbon and screen-printed carbon electrodes. The fundamental sensing mechanisms and commercial limitations of the MOX-based electrical and electrochemical sensors are discussed providing research directions to bridge the existing gap between new sensing concepts and real-world analytical applications.

Nicotinamide adenine dinucleotide immobilized tungsten trioxide nanoparticles for simultaneous sensing of norepinephrine, melatonin and nicotine

Herein, we report the anionic surfactant, ethylene diamine tetraacetic acid (EDTA), mediated synthesis of WO₃ nanoparticles and its subsequent modification through gamma irradiation (GI) and electrochemical immobilization with nicotinamide adenine dinucleotide (NAD). Glassy carbon electrode (GCE) modified with GI-WO₃ NPs and the enzyme NAD exhibited strong electro-oxidation of three important biomolecules such as norepinephrine (NEP), melatonin (MEL) and nicotine (NIC) in 0.1 M phosphate buffer saline (PBS) at physiological pH of 7. Square wave voltammetry (SWV) studies exhibited three well-defined peaks at potentials of 120, 570 and 840 mV, corresponding to the oxidation of NEP, MEL and NIC respectively, indicating that simultaneous determination of these compounds is feasible at the NAD/GI EDTA-WO₃/GCE. The proposed sensor displayed a wide linear range of 0.010-1000 μM with the lowest detection limit of 1.4 nM for NEP, 2.6 nM for MEL and 1.7 nM for NIC respectively. Furthermore, the modified electrode was successfully applied to detect NEP, MEL and NIC in pharmaceutical and cigarette samples with excellent selectivity and reproducibility.