Real-time analysis of glutamate regulated function in neurons using label-free potassium imaging system

In order to develop the novel neuro-imaging technique, we constructed a high resolution type potassium ion (K⁺) image sensor (PIS). A K⁺-sensitive membrane was layered on the ion image sensor of 128 × 128 pixels array. By using the fabricated PIS, the extracellular concentration of the K⁺ ([K⁺]₀) was detectable in the ranges between 10^-3 and 10^-1 M, which was consistent to the physiological ranges, therefore, we successfully detected glutamate-induced changes in [K⁺]₀ associated with gating through K⁺ channel in hippocampal neurons without labeling. The low invasive imaging of [K⁺]₀ in the neurons promises the usefulness for the analysis of neurofunctions and degenerations induced by glutamate.