In biochemistry, Ca and K play essential roles to control signal transduction. Much interest has been focused on ion-imaging, which facilitates understanding of their ion flux dynamics. In this paper, we report a calcium and potassium multi-ion image sensor and its application to living cells (PC12). The multi-ion sensor had two selective plasticized poly(vinyl chloride) membranes containing ionophores. Each region on the sensor responded to only the corresponding ion. The multi-ion sensor has many advantages including not only label-free and real-time measurement but also simultaneous detection of Ca and K. Cultured PC12 cells treated with nerve growth factor were prepared, and a practical observation for the cells was conducted with the sensor. After the PC12 cells were stimulated by acetylcholine, only the extracellular Ca concentration increased while there was no increase in the extracellular K concentration. Through the practical observation, we demonstrated that the sensor was helpful for analyzing the cell events with changing Ca and/or K concentration.

Ca2+, Na+ and K+ are very important ions in cells in which several ion channels and ion pumps maintain the concentration of their ions. The dynamic analysis of cells requires the monitor of plural ions rather than only one ion. In this paper, we developed simultaneous Ca2+-K+ image sensor. The change in Na+ concentration is hard to detect because of the high concentration (145 mM) in extracellular fluid. The sensing membranes were prepared with plasticized PVC membranes using an inkjet method. The Ca2+-K+ image sensor had fast and good response in the salt aqueous solution including 145 mM of sodium ion. The real-time bio-images for Hela cells stimulated by Amphotericin B were captured by the multi-ion image sensor. As a result of simultaneous K+ and Ca2+ images, the increase in the K+ concentration was observed without the change in the Ca2+ concentration.