Visualizing intracellular milieu and electric field-induced cell responses by fluorescence lifetime imaging microscopy

Fluorescence-based optical techniques have significantly advanced our comprehension of living systems, providing invaluable insights into cellular intricacies and facilitating fundamental research and practical diagnostic applications. To explore intracellular environments and the communication among intracellular organelles, we utilized fluorescence lifetime imaging microscopy with exogenous fluorophores of Oregon Green 488 BAPTA-1 AM and Fluovolt and endogenous fluorophores of NAD(P)H and FAD in breast carcinoma MCF7 and MDA-MB-231 and normal MCF10A cells. Fluorescence lifetime images have uncovered a characteristic triangular interrelationship among intracellular calcium ion concentration (Ca²⁺), mitochondrial function, and membrane electric potential in cancerous and normal cells. To delve deeper into the effects of electric field stimulation on intracellular conditions, the nanosecond pulsed electric field (nsPEF) was applied to the breast cancerous and normal cells. Our findings revealed a unique electric field modulation pattern across breast cells; MCF7 cells exhibited initial modulation in cytosolic Ca²⁺ levels, followed by changes in mitochondrial function, whereas MDA-MB-231 and MCF10A cells mostly remained unaffected, demonstrating that intracellular conditions and the effect of nsPEF are different not only between cancerous and normal cells but also between subtypes of cancerous cells.