Strong pulsed electric fields can induce transient perforation of the cell membrane which enables the delivery of exogenous molecules (drugs, proteins, and plasmids) into living cells. The physical mechanisms of this process are poorly understood. This project is centered on the idea that electrohydrodynamic flows exist and play an essential role in the non-equilibrium dynamics of biomembranes. The fluid nature of the membrane allows lipids to flow within it. We hypothesize that electric fields induce lateral redistribution of lipids in the fluid bilayer membranes, which gives rise to the complex dynamics observed in experiments with model membranes.
This project is an integral part of Dartmouth student Paul Salipante's Ph.D. thesis aimed at understanding the shape and stability of interfaces in electric fields. A comparison between two types of interfaces, simple (such as oil/water) and complex (such as lipid membranes), will reveal salient features of the lipid bilayer electromechanics. While the interrogation of simple interfaces involves relatively unsophisticated experimentation, which could be done in the PI's Laboratory, the investigation of the membranes requires equipment which is not available at Dartmouth College. The membrane biophysics lab at the Max Planck Institute of Colloids and Interfaces (MPI-KG) led by Rumiana Dimova possesses state-of-the-art equipment which will enable the membrane experiments. This award will support Mr. Salipante to spend one year at MPI-KG collaborating with Dr. Dimova and her team. The experience in MPI-KG's vibrant, international research environment will contribute to Mr. Salipante's education as a globally-engaged engineer and enhance his skills for international collaboration. This award is funded jointly by the Office of International Science and Engineering and the Division of Chemical, Bioengineering, Environmental, and Transport Systems.
Membranes that encapsulate cells and internal cellular organelles are composed primarily of lipid bilayers. Biomimetic membranes assembled from polymers are used as vectors for targeted drug delivery. We investigate both experimentally and theoretically the deformation and stability of fluid membranes made of lipids or polymers in uniform electric fields. A frequency dependent shape deformation of vesicles (closed membranes) in AC fields elucidates the capacitive nature of the membrane and provides a new experimental method for measuring membrane capacitance. Compared to lipid membranes, we find that polymer membranes have an order of magnitude lower capacitance, which correlates with their larger thickness. Upon application of the electric field, the dynamic response of the vesicle is sensitive to membrane viscosity, while the steady state shape is governed by membrane tension and bending stiffness. Strong DC pulses, typically used in cell electroporation, is shown to induce an instability in both lipid and polymer membranes. The instability leads to vesicle collapse, where the timescale of collapse depends inversely on the square of the electric field strength. The outcomes of this research directly impact biomedical technologies that employ membrane electroporation (e.g. gene transfection) or cell fusion. The interconversion of electric and mechanical energies, one example being the membrane flexoelectricity (bending in response to electric fields), could be exploited for novel micro- and nano-fluidic designs. The transformative nature of the project lies in its exploratory nature, which may lead to unforeseen research directions. This collaboration project engaged a graduate student in research at the forefront of science and immersed him an interdisciplinary international environment. This has contributed to the studentâ€™s education as a globally-engaged engineer.