  Membrane phase-separation is a mechanism that biological membranes often use
to locally concentrate specific lipid species in order to organize diverse
membrane processes. Phase separation has also been explored as a tool for the
design of liposomes with heterogeneous and spatially organized surfaces. These
"patchy" liposomes are promising platforms for delivery purposes, however their
design and optimization through experimentation can be expensive and
time-consuming. We developed a computationally efficient method based on the
surface Cahn-Hilliard phase-field model to complement experimental
investigations in the design of patchy liposomes. The method relies on
thermodynamic considerations to set the initial state for numerical
simulations. We show that our computational approach delivers not only
qualitative pictures, but also accurate quantitative information about the
dynamics of the membrane organization. In particular, the computational and
experimental results are in excellent agreement in terms of raft area fraction,
total raft perimeter over time and total number of rafts over time for two
different membrane compositions (DOPC:DPPC with a 2:1 molar ratio with 20% Chol
and DOPC:DPPC with a 3:1 molar ratio with 20% Chol). Thus, the computational
phase-field model informed by experiments has a considerable potential to
assist in the design of liposomes with spatially organized surfaces, thereby
containing the cost and time required by the design process.
