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0Thermal modulation of the electrophysiological properties of neurons and HEK 293 cells using diamond heater-thermometer
A. Romshin1*, N. Aseyev2, O. Idzhilova2, A. Koryagina2, V. Zeeb1'3, I. Vlasov1, P. Balaban2
1-Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia 2- Institute of Higher Nervous Activity and Neurophysiology of the Russian Academy of Sciences, Moscow,
Russia
3- Institute of Theoretical and Experimental Biophysics of the Russian Academy of Sciences,
Moscow, Russia
Pulsed infrared radiation and thermoplasmonics, which enable fast and targeted control of temperature at the microscale, have recently opened a novel chapter in the study of the electrophysiological properties of living cells. It has been demonstrated that local heating at cellular scale elicits depolarizing capacitive currents across the phospholipid membrane [1,2], sufficient for triggering trains of action potentials in neurons [3]. However, the mismatch in spatial and temporal scale between applied heat and electric response of the cell remain the exact mechanisms by which local temperature affects membrane potential incompletely understood.
The present study explores the impact of local heat on the electrophysiological properties of living cells at the subcellular level using the diamond heater-thermometer (DHT) [4], which integrates the functions of a thermometer and a heater within a single microparticle covering less than 3% of the cell surface. Experimentally, the DHT demonstrated the ability to control local temperatures with an accuracy of less than 0.2°C in the vicinity of the cell. Millisecond heat pulses evoked reversible changes in membrane potential and elicited capacitive currents in primary cultured neurons and HEK 293 cells. A typical voltage shift for local temperatures from 25 to 70°C was ~1 mV. Contrary to expectations, at local temperatures around 50°C, an abrupt increase in cellular response by an order of magnitude was observed allowing the cell to be effectively and reproducibly clamped by temperature. Henceforth, even lower temperatures (<35°C) elicited depolarizations up to 10 mV in primary neurons, sufficient to trigger action potentials (AP) at rates up to 40 Hz. Such an irreversible transition to so-called temperature-clamp mode (TCM) was attributed to heat-induced phase changes in the phospholipid membrane at the point where DHT touches the cell. In addition, the effects of high temperatures beyond the physiological range on cellular electrophysiology were assessed, with a focus on action potential formation. These findings enhance our understanding of how local heat influences cellular functions and provide valuable insights into the thermal modulation of cell activity.
This work was supported by Russian Science Foundation, grant No 23-14-00129 (https://rscf.ru/project/23 -14-00129/).
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