Observation of changes in membrane fluidity after infrared laser stimulation using a polarity-sensitive fluorescent probe

摘要

It has been shown that exposure of live neurons to a low-intensity pulsed infrared light can be used to excite action potentials. Infrared pulsed laser coupled to an optical fiber can be utilized to create a rapid localized increase in temperature in the vicinity of the cell. The resulting temperature gradient leads to an increase in membrane fluidity and permeability, causing depolarization of the target cell. In order to characterize the fluidity of the cell membrane at various temperatures with and without pulsed IR light exposure, we used a polarity-sensitive fluorescent probe di-4-ANEPPDHQ. This dye exhibits a fluorescent shift between the disordered and ordered phases of the membrane, and can be used to quantitatively evaluate the state of the membrane by calculating the generalized polarization (GP) value. Using high-speed imaging of cells exposed to a IR light of varying pulse width, it was determined that a longer pulse width leads to a greater change in the GP value. Comparison of GP values of cells at different ambient temperatures without the pulsed IR light exposure and cells exposed to pulsed IR light indicated that a rapid temperature gradient caused by the exposure to pulsed light induces a larger change in GP value than the ambient temperature increase alone, indicating a greater disruption of membrane fluidity and permeability.