Led-mediated instantaneous pore formation in membranes driven by structural transformation and deprotonation of phospholipids

The mechanisms by which molecules can be efficiently delivered directly into cells are of interest for fundamental cell biological research. Light-emitting diodes (LED) can be used to deliver substances into cells, but there is limited information on how LEDs alter the structure of the plasma membrane. In this study, we determined the mechanisms by which LED induces the instantaneous pore formation in the plasma membrane. We manufactured three types of artificial membrane (AM) composed of phosphatidylcholine (PC), phosphatidylethanolamine (PE), or a mixed form of binary PC/PE and investigated the surfaces and internal structural transformation and chemical changes caused by LED stimulation. LED irradiation (blue and near-infrared wavelengths) decreased the size of the three AMs due to the formation of pores on the surface and internal AM. PE and PC/PE AMs underwent LED-mediated structural transformation. In the PE AMs, chemical changes occurred through deprotonation of the ammonia cation (NH3+) located at the terminal of the head group of the phospholipid to an amine group (NH2). Furthermore, pore formation occurred in plasma membranes from cell lines and was used to deliver cell-impermeable molecules. Our study highlights a fundamental mechanism underlying pore formation at the molecular level.