Dipolar Nanoparticle Interacting with a Lipid Membrane

Understanding the specifics of how nanoparticles interact with biological membranes is essential for the development of nanoparticles designed for drug delivery, biosensing, and nanomedicine. The role of electric dipole moment of conductive nanoparticles in nanoparticle-membrane interactions remains insufficiently studied. Using molecular dynamics simulation, we investigate the interactions of a dipolar nanoparticle with a lipid bilayer. Our results show that the electric dipole moment induces stronger electrostatic attraction between the dipolar nanoparticle and the membrane than that of the non-dipolar nanoparticle, making penetration slightly easier. Steered molecular dynamics force profile shows that the electric dipole moment reduces mechanical resistance by about 440 pN. Fast Fourier Transform analysis shows stronger low-frequency fluctuations of the dipole, when the nanoparticle exits the center of membrane, indicating dynamic polarization. Correlation Width and Correlation Fraction of the membrane's leaflets vary between the dipolar and non-dipolar cases, which shows in the dipolar case lipid-lipid coupling is lower. Our simulations show that excessive per-bead charge suppresses dipole fluctuations due to strong core coupling and lateral repulsion. Tuning surface charge distribution can improve dipolar dynamics, and lower penetration force. The study also suggests experimentally testable hypotheses on how electric dipole moment affects nanoparticle uptake.