In Situ and Quantitative Monitoring of Cardiac Tissues Using Programmable Scanning Electrochemical Microscopy.

In vitro cardiac tissue model holds great potential as a powerful platform for drug screening. Respiratory activity, contraction frequency, and extracellular H 2 O 2 levels are the three key parameters for determining the physiological functions of cardiac tissues, which are technically challenging to be monitored in an in situ and quantitative manner. Herein, we constructed an in vitro cardiac tissue model on polyacrylamide gels and applied a pulsatile electrical field to promote the maturation of the cardiac tissue. Then, we built a scanning electrochemical microscopy (SECM) platform with programmable pulse potentials to in situ characterize the dynamic changes in the respiratory activity, contraction frequency, and extracellular H 2 O 2 level of cardiac tissues under both normal physiological and drug (isoproterenol and propranolol) treatment conditions using oxygen, ferrocenecarboxylic acid (FcCOOH), and H 2 O 2 as the corresponding redox mediators. The SECM results showed that isoproterenol treatment induced enhanced oxygen consumption, accelerated contractile frequency, and increased released H 2 O 2 level, while propranolol treatment induced dynamically decreased oxygen consumption and contractile frequency and no obvious change in H 2 O 2 levels, suggesting the effects of activation and inhibition of β-adrenoceptor on the metabolic and electrophysiological activities of cardiac tissues. Our work realizes the in situ and quantitative monitoring of respiratory activity, contraction frequency, and secreted H 2 O 2 level of living cardiac tissues using SECM for the first time. The programmable SECM methodology can also be used to real-time and quantitatively monitor electrochemical and electrophysiological parameters of cardiac tissues for future drug screening studies.