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In this study, we employed calcium imaging to investigate the dynamics of intracellular calcium levels in embryonic chicken cardiomyocytes upon extracellular, optoelectronic stimulation. A photovoltaic layer of donoracceptor pigments on a flexible PET substrate was used as a wireless stimulation electrode. Our findings revealed a distinct change in their spontaneous activity pattern in cardiac cells following asynchronous light stimulation. A short pause in cellular activity, indicative of overdrive suppression, was observed in recordings from several different cells. The pause in activity signifies a transient refractory period induced by stimulation of the photovoltaic device with red light. These findings suggest that photovoltaic electrodes can be used to effectively modulate the electrical activity of cardiac cells in a wireless, non-pharmacological manner. This opens new avenues for non-invasive and precise light-modulated control of cellular electrophysiology as well as potential therapeutic applications for cardiac rhythm disorders.

Fluid flow in the human body can be modeled using a water-level tank, a commonly used mechanistic approach in mechanical engineering for fluid transport processes. Postoperative fluid data from patients undergoing cardiac surgery is used to estimate fluid flow dynamics and total body water in the human body. This simplified model provide a basic understanding of the dynamics of fluid flow processes in the human body and could aid in modeling distribution of fluids in compartments.

This paper discusses possibilities to explain which Kv channels can be considered as first-order systems. This means that the dynamic behavior of these channels can be described with a first-order differential equation and are the most straightforward dynamical systems. For example, a typical first-order system is an RC circuit, and analogously, Kv channels can be considered with the dynamic behavior of first-order systems following RC circuits. This work represents a family of KV channels that can be described as first-order systems, providing an efficient method of ion channel modeling in computational electrophysiology.

Objective: This study aims to explore the potential of organic electrolytic photocapacitors (OEPCs), an innovative photovoltaic device, in mediating the activation of native voltage-gated Cav1.2 channels (I Ca,L ) in Guinea pig ventricular cardiomyocytes., Methods: Whole-cell patch-clamp recordings were employed to examine light-triggered OEPC mediated I Ca,L activation, integrating the channel's kinetic properties into a multicompartment cell model to take intracellular ion concentrations into account. A multidomain model was additionally incorporated to evaluate effects of OEPC-mediated stimulation. The final model combines external stimulation, multicompartmental cell simulation, and a patch-clamp amplifier equivalent circuit to assess the impact on achievable intracellular voltage changes., Results: Light pulses activated I Ca,L , with amplitudes similar to voltage-clamp activation and high sensitivity to the L-type Ca 2+ channel blocker, nifedipine. Light-triggered I Ca,L inactivation exhibited kinetic parameters comparable to voltage-induced inactivation., Conclusion: OEPC-mediated activation of I Ca,L demonstrates their potential for nongenetic optical modulation of cellular physiology potentially paving the way for the development of innovative therapies in cardiovascular health. The integrated model proves the light-mediated activation of I Ca,L and advances the understanding of the interplay between the patch-clamp amplifier and external stimulation devices., Significance: Treating cardiac conduction disorders by minimal-invasive means without genetic modifications could advance therapeutic approaches increasing patients' quality of life compared with conventional methods employing electronic devices.