Analysis of electromagnetic response of cells and lipid membranes using a model-free method

Electromagnetic radiation (EMR) is omnipresent on earth and may interact with the biological systems in diverse manners. But the scope and nature of such interactions remain poorly understood. In this study, we have measured the permittivity of cells and lipid membranes over the EMR frequency range of 20 Hz to 4.35 × 10¹⁰ Hz. To identify EMR frequencies that display physically intuitive permittivity features, we have developed a model-free method that relies on a potassium chloride reference solution of direct-current (DC) conductivity equal to that of the target sample. The dielectric constant, which reflects the capacity to store energy, displays a characteristic peak at 10⁵-10⁶ Hz. The dielectric loss factor, which represents EMR absorption, is markedly enhanced at 10⁷-10⁹ Hz. The fine characteristic features are influenced by the size and composition of these membraned structures. Mechanical disruption results in abrogation of these characteristic features. Enhanced energy storage at 10⁵-10⁶ Hz and energy absorption at 10⁷-10⁹ Hz may affect certain membrane activity relevant to cellular function.