Recent years have seen a rise in the number of Japanese allergy patients, especially younger people. It is generally known that allergy symptoms to certain chemicals or foodstuff could be extreme, even life-threatening in some cases. Thus there are increasing calls for efficient methods to test the safety of specific chemicals and other substances. In addition, there are demands concerning the screening for efficacy of chemical compounds under consideration as drug candidates. The so-called “cell-based assays” - testing with cultured human cells - is commonly used in such cases. In 2016 my colleagues and I launched a project to develop a novel sensing system for a particular type of cell-based assays (Fig.1). This project is founded upon the results of our research endeavors over the past decade.
Fig.1. Palm-top chemical imaging system
The project's first key technology is the “miniaturized” chemical imaging sensor . Said sensor utilizes the measurement principal behind light-addressable potentiometry, enabling visualization of ion, pH and impedance distributions. We proposed use of a light spot on a small display panel as light source to replace scanning optics in use with conventional systems. Both the size and costs can be reduced by a factor of nearly 100 (Fig.2 (Left)).
(Left) The core of miniaturized chemical imaging system
(Right) Typical chemical image of the defect of cultured cell layer.
The second key technology is impedance mapping of a cultured cell layer . A cell layer's defect and the recovery process thereof can be monitored by means of impedance distribution as visualized through application of the chemical imaging sensor (Fig. 2 (right)).
Quantitative and label-free monitoring of the cell layer's barrier function would produce useful information for cell-based assays.
By combining the two aforementioned key technologies, our new project aims to realize innovative cell-migration assays using a palm-top chemical imaging system. We foresee this providing a powerful tool for testing and screening of chemicals, drugs and so forth. My dream for the future is that the palm-top chemical imaging sensor will be adopted widely for clinical examinations and pathological diagnosis, among other activities.
 "Miniaturized Chemical Imaging Sensor System Using an OLED Display Panel" K. Miyamoto, K. Kaneko, A. Matsuo, T. Wagner, S. Kanoh, M. J. Schöning and T. Yoshinobu, Sensors and Actuators B, 170 (2012) pp.82-87.
 "Visualization of the Recovery Process of Defects in a Cultured Cell Layer by Chemical Imaging Sensor" K. Miyamoto, B. Yu, H. Isoda, T. Wagner, M. J. Schöning and T. Yoshinobu, Sensors and Actuators B, 236 (2016) pp.965-969.