Effect of Substrate Stiffness on Redox State of Single Cardiomyocyte: A Scanning Electrochemical Microscopy Study

Mechanical microenvironment plays a key role in the regulation of the phenotype and function of cardiac cells, which are strongly associated with the intracellular redox mechanism of cardiomyocytes. However, the relationship between the redox state of cardiomyocytes and their mechanical microenvironment remains elusive. In this work, we used polyacrylamide (PA) gels with varying stiffness (6.5-92.5 kPa) as the substrate to construct a mechanical microenvironment for cardiomyocytes. Then we employed scanning electrochemical microscopy (SECM) to in situ characterize the redox state of a single cardiomyocyte in terms of the apparent rate constant (k_f) of the regeneration rate of ferrocenecarboxylic by glutathione (GSH) released from cardiomyocyte, which is the most abundant reactant of intracellular reductive-oxidative metabolic cycles in cells and can represent the redox level of cardiomyocytes. The obtained SECM results show that the cardiomyocytes cultured on the stiffer substrates present lower k_f values than those on the softer ones, that is, the more oxidative state of cardiomyocytes on the stiffer substrates compared to those on the softer ones. It proves the relationship between mechanical factors and the redox state of cardiomyocytes. This work can contribute to understanding the intracellular chemical process of cardiomyocytes during physiopathologic conditions. Besides, it also provides a new SECM method to in situ investigate the redox mechanism of cardiomyocytes at a single-cell level.