Effect of AFM-based electrical stimulation on the electrophysiological and mechanical characteristics of cardiomyocytes

Electrical stimulation (ES) is widely used in the field of myocardial tissue engineering. By ES and improving various parameters of conductive substrates, it is possible to change the differentiation and mechanical and electrophysiological characteristics of a single cardiomyocyte, thereby alleviating or curing diseases. In this paper, the mechanical and electrophysiological characteristics of cardiomyocytes under ES were studied by atomic force microscopy (AFM), and the electrical and mechanical characteristics of cardiomyocytes under ES were evaluated. The height change of the piezoelectric actuator along the <i>z</i> axis during the contraction-relaxation cycle was recorded so as to quantify the contractile force of cardiomyocytes in the constant force contact mode. The results showed that the height and action potential (AP) amplitude of cardiomyocytes increased with the increase of the electric field when the electric field intensity was less than 0.8 V cm^-1, but when the electric field intensity was greater than 0.8 V cm^-1, the trend was opposite. The statistical diagram of the relationship between the height and frequency of cardiomyocytes measured by experiments was inverted U-shaped, reaching the peak at about 2 Hz. In addition, with the increase of frequency, the action potential duration (APD) gradually shortens. The results show that when the current was less than 0.28 nA, the amplitude of the height and AP of cardiomyocytes increased with the increase of the current, but when the current was greater than 0.28 nA, the trend was opposite. At the same time, it was found that with the increase of the current intensity, the time for cardiomyocytes to produce the first action potential was shortened, and it tended to be consistent when the current was greater than 0.24 nA. By studying the effects of ES on the electrophysiological and mechanical properties of cardiomyocytes, we can better understand the mechanism and biological effects of ES on the organism. It is helpful for us to study and simulate the electric environment suitable for the growth and maturation of cardiomyocytes and tissues <i>in vitro</i> and provide a basic platform for further cell experiments such as establishing myocardial tissue models and drug screening in the future.