Line tension of the pore edge in phospholipid/cholesterol bilayer from stretch molecular dynamics simulation

The line tension of the pore in a phospholipid bilayer is important for pore-mediated molecular transport techniques. To understand the cholesterol effects on the line tension of the pore edge at the molecular level, we perform molecular dynamics simulations of phospholipid bilayers with a pore containing cholesterol in different concentrations (0, 20, and 40 mol%). The bilayer with a pore is prepared by using an equibiaxial stretching simulation. The stretched bilayer with a pore is subsequently compressed and the pore spontaneously closes when the applied areal strain of the bilayer is below a certain value. Using the pore closure areal strain and a free energy model of a stretched bilayer with a pore, the upper and lower limits of the line tensions for the bilayers containing cholesterol at 0, 20, and 40 mol% are estimated to be 17.0-48.2, 54.5-100, and 170-261 pN, respectively. The increasing tendency of the line tension qualitatively agrees with that observed experimentally. The pores in the cholesterol-containing bilayers are lined with several cholesterol molecules, which might increase the bending rigidity of the pore edge, and result in the higher line tension of the cholesterol-containing bilayer. The considerable dependency of the line tension on the bilayer compositions might be useful to explain the large variations of the transduction efficiency observed with sonoporation treatment. © 2016 The Japan Society of Mechanical Engineers.