Real-time CARS microspectroscopy to follow changes of membrane associated water molecules induced by the electropulsation of liposomes

To deep more insight into basic phenomena occurring during and after electropulsation of biological membranes, a new experimental modality has been used. It combines a wide field Coherent Anti Stokes Raman Spectroscopy system with a coplanar wave guide able to deliver nanosecond pulsed electric fields to different in vitro samples. The experiments have been conducted on liposome suspensions. These systems well mimic phospholipid double layers. Spectra of liposome suspensions have been acquired immediately after electropulsation. Liposome suspension evidenced an increase of the vibrational modes around 3345 cm-1 for pulsed samples with respect to the non-pulsed ones. These vibrational signatures seem associated to the so called lipid associated water molecules. These molecules represent a water structure in which the intermolecular OH bonds become weak leading to the possibility that single water molecules can interact with the liposome lipidis making the pulsed membranes more permeable. Membranes assumed a less organized structure due to the persistence of these water defects.