Detection of K+ Efflux from Stimulated Cortical Neurons by an Aptamer-Modified Silicon Nanowire Field-Effect Transistor

• Published in: ACS sensors 2017-01, Vol.2 (1), p.69-79
• Main Authors: Anand, Ankur, Liu, Chia-Rung, Chou, Ai-Chuan, Hsu, Wan-Hsuan, Ulaganathan, Rajesh Kumar, Lin, Yi-Cheng, Dai, Chi-An, Tseng, Fan-Gang, Pan, Chien-Yuan, Chen, Yit-Tsong
• Format: Article
• Language: English
• ISSN: 2379-3694; 2379-3694
• DOI: 10.1021/acssensors.6b00505

The concentration gradient of K+ across the cell membrane of a neuron determines its resting potential and cell excitability. During neurotransmission, the efflux of K+ from the cell via various channels will not only decrease the intracellular K+ content but also elevate the extracellular K+ concentration. However, it is not clear to what extent this change could be. In this study, we developed a multiple-parallel-connected silicon nanowire field-effect transistor (SiNW-FET) modified with K+-specific DNA-aptamers (aptamer/SiNW-FET) for the real-time detection of the K+ efflux from cultured cortical neurons. The aptamer/SiNW-FET showed an association constant of (2.18 ± 0.44) × 106 M–1 against K+ and an either less or negligible response to other alkali metal ions. The α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) stimulation induced an outward current and hyperpolarized the membrane potential in a whole-cell patched neuron under a Na+/K+-free buffer. When neurons were placed atop the aptamer/SiNW-FET in a Na+/K+-free buffer, AMPA (13 μM) stimulation elevated the extracellular K+ concentration to ∼800 nM, which is greatly reduced by 6,7-dinitroquinoxaline-2,3-dione, an AMPA receptor antagonist. The EC50 of AMPA in elevating the extracellular K+ concentration was 10.3 μM. By stimulating the neurons with AMPA under a normal physiological buffer, the K+ concentration in the isolated cytosolic fraction was decreased by 75%. These experiments demonstrate that the aptamer/SiNW-FET is sensitive for detecting cations and the K+ concentrations inside and outside the neurons could be greatly changed to modulate the neuron excitability.