Micropillar Electrode Array for Enhancing the Maturation of Reprogrammed Cardiac Spheroids

To overcome the problems of stem cell therapies, direct reprogramming which means reprogramming the somatic cell into a specific cell directly without passing through another cell stage is a new approach. However, functional maturation still remains challenging. Therefore, the aim in this study is to apply electrical stimulation to promote direct reprogramming with maintaining the three-dimensional spheroid culture of chemically induced cardiomyocytes. To do that, a novel electrode platform was designed with the dimensions in consideration of stability of both micropillar and spheroid. The average size of spheroids is around 230~260 µm, therefore, the diagonal distance between two micropillars was designed at 183.85 µm and the height of the micropillars was designed at 80 µm in order to avoid spheroid attachment on the bottom of the device. The micropillars were fabricated with deep reactive-ion etching (DRIE) and confirmed with scanning electron microscope (SEM). Through computer simulation technology (CST) Studio Suite, the electrical field of micropillar electrode and film electrode was simulated and the electrical stimulation protocol was optimized (biphasic 1V, 10Hz every 10 seconds for 1 hour). The improvement of the electrophysiological properties of reprogrammed spheroids through the highly efficient electrical stimulation by a micropillar electrode arrays was demonstrated through the comparison with the group without the electrical stimulation.