Atomic Force Microscopy (AFM) study of elastic modulus of artificial phospholipid membranes*

The study of artificial phospholipid membranes (PMs) on plane substrates has become relevant to gain insights into the physical behaviour of cell membranes. Here, we analyse the temperature dependence of Young’s modulus and adhesion of several PMs (DPPC, DMPC and DSPC) by Atomic Force Microscopy (AFM) and Surface Force Spectroscopy (SFS) measurements. Phospholipids were deposited onto silicon substrates by physical vapour deposition (PVD) in high vacuum. Using Raman spectroscopy, we find that the chemical structure of our phospholipids remains unchanged after PVD. AFM measurements in liquid confirm the self-assembly of the phospholipid bilayer. Young’s modulus and adhesion measurements obtained by SFS show two phase transitions, consistent with the ripple-gel transition and the gel-liquid crystalline phases. With this we have shown that several types of PMs can be vapour deposited in high vacuum, regaining their structure and mechanical properties after proper hydration. This study opens new pathways to assemble phospholipid mixtures by vapour deposition.