(587j) Entropic Pressure on a Fluid Biological Membrane with Surface Tension

Biological membranes exhibit noticeable thermal fluctuations at physiological temperatures. These fluctuations play a crucial role in various biological processes such as exocytosis, endocytosis, membrane fusion, pore formation, cell adhesion, and binding-unbinding transitions, among others. Studying the entropic factors in such biological phenomena has now become a cornerstone of cell mechanics research. The entropic force is based on various physical arguments and mathematical approximations, initiated by Helfrich, who proposed that this force scales as 1/d^3. This power law has been subsequently validated using advanced theoretical and computational techniques. In the majority of previous studies the membrane is assumed to be tension-free. In this work, we acknowledge the fact that biological membranes may experience surface tension in many physiological situations, and the membrane surface tension acts as a driving force for several biological activities. We reformulate the entropic force for a fluctuating membrane with surface tension and show that the entropic pressure decays exponentially with distance d when the surface tension is not small. Our result can explain some experimental observations on how applying surface tension to membranes promotes adhesion and vesicle fusion due to a significant reduction in the entropic repulsive force. We gratefully acknowledge financial support from the New Jersey Institute of Technology and the National Science Foundation, United States through Grants No. CMMI-2237530 and CBET- 2327899.