posted on 2023-12-21, 13:06authored byJyoti Gupta, Veerendra Kumar Sharma, Harish Srinivasan, Himal Bhatt, Victoria García Sakai, Ramaprosad Mukhopadhyay, Subhankur Mitra
Synthetic
cationic lipids have garnered significant attention as
promising candidates for gene/DNA transfection in therapeutic applications.
The phase behavior of the vesicles formed by these lipids is intriguing,
revealing intricate connections to the structure and dynamics of the
membrane. These phenomena emerge from the complex interplay between
hydrophobic and electrostatic interactions of the lipids. In this
study, we explore the impact of an ionic liquid-based surfactant,
1-decyl-3-methylimidazolium bromide (DMIM[Br]), on the structural,
dynamical, and phase behavior of cationic dihexadecyldimethylammonium
bromide (DHDAB) vesicles. Our investigations indicate that the addition
of DMIM[Br] increases the vesicle size while thinning the membrane.
Further, DMIM[Br] also induces substantial changes in the membrane
phase behavior. At 10 and 25 mol %, DMIM[Br] eliminates the pre-transition
from coagel to intermediate crystalline (IC) phase and decreases the
onset temperature of the main phase transition to the fluid phase.
In the cooling cycle, the addition of DMIM[Br] further induces the
formation of an intermediate gel phase. This behavior is reminiscent
of the non-synchronous ordering observed in the DODAB membrane, a
longer-chain counterpart of DHDAB. Interestingly, at 40 mol % of DMIM[Br],
the formation of the intermediate gel phase is largely suppressed.
Neutron scattering data provide evidence that the addition of DMIM[Br]
enhances lipid mobility in coagel and fluid phases, suggesting that
DMIM[Br] acts as a plasticizer, enhancing membrane fluidity across
all of the phases. Our findings infer that DMIM[Br] modulates the
membrane’s phase behavior and fluidity, two essential ingredients
for the efficient transport of cargo, by controlling the balance of
electrostatic and hydrophobic interactions.