Abstract
Towards clarifying the spatio-temporal neurotransmitter distribution, potentiometric redox sensor arrays with 23.5-µm resolution were fabricated. The sensor array based on a charge-transfer-type potentiometric sensor comprises pixels with gold electrodes deposited on the surface of pixels. The sensor output corresponding to the interfacial potential of the electrode changed logarithmically with the mixture ratio of KFe(CN) and KFe(CN), where the redox sensitivity reached 49.9 mV/dec. By employing hydrogen peroxidase as an enzyme and ferrocene as an electron mediator, the sensing characteristics for hydrogen peroxide (HO) were investigated. The analyses of the sensing characteristics revealed that the sensitivity was about 44.7 mV/dec., comparable to the redox sensitivity, while the limit of detection (LOD) was achieved to be 1 µM. Furthermore, the oxidation state of the electron mediator can be the key to further lowering the LOD. Then, by immobilizing oxidizing enzyme for HO and glutamate oxidase, glutamate (Glu) measurements were conducted. As a result, similar sensitivity and LOD to those of HO were obtained. Finally, the real-time distribution of 1 µM Glu was visualized, demonstrating the feasibility of our device as a high-resolution bioimaging technique.
Highlights
Neurotransmitters (NTs) such as acetylcholine (ACh), dopamine (DO), glutamate (Glu), and γ−amino butyric acid (GABA) are chemical messengers for signal transmission between synapses in central nerve systems (CNS), playing an important role in brain function including behavior and cognition [1]
Since the reduction in the signal current is directly linked to the deterioration of limit of detection (LOD), that fact imposes difficulty in achieving a higher spatial resolution to the level required to capture the NT dynamics, which is considered to be the order of 1 μm [4], while keeping low LOD
The redox sensitivity characterized using the mixture of K3Fe(CN)6 and K4Fe(CN)6 was confirmed to reach 49.9 mV/dec., while it was found to be affected by the coverage of the gold electrode on the sensing area
Summary
Neurotransmitters (NTs) such as acetylcholine (ACh), dopamine (DO), glutamate (Glu), and γ−amino butyric acid (GABA) are chemical messengers for signal transmission between synapses in central nerve systems (CNS), playing an important role in brain function including behavior and cognition [1]. Their irregular concentrations that affect the synaptic transmission are considered to be linked to various diseases such as Alzheimer’s, Parkinson’s disease, schizophrenia, and depression [2]. Dudina et al integrated 9216 carbon nanotube field-effect transistors into an array They demonstrated Glu detection down to the concentration 10 μM by a single channel. Since the reduction in the signal current is directly linked to the deterioration of LOD, that fact imposes difficulty in achieving a higher spatial resolution to the level required to capture the NT dynamics, which is considered to be the order of 1 μm [4], while keeping low LOD
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