Internally Self-Assembled Pickering Mesosomes Stabilized by Positively Charged Lactoferrin

TL;DR

Researchers created stable, tiny emulsions using positively charged lactoferrin, which can self-assemble into various liquid crystalline structures.

Contribution

The use of positively charged lactoferrin as a stabilizer for forming diverse lyotropic mesophases is novel.

Findings

Lactoferrin-stabilized mesosomes showed long-term stability with diameters between 187 and 239 nm.

The mesosomes retained their structural hierarchy after stabilization, unlike Pluronic F127 which changes morphology.

Abstract

Mesosomes as sub-micrometer-sized emulsions containing
internally
self-assembled lyotropic liquid crystalline (LLC) mesophases were
engineered using lactoferrin (LF) as a Pickering stabilizer. LF was
pretreated with ultrasonication to prevent agglomeration and applied
under controlled pH conditions during processing, resulting in emulsions
with a positive surface charge and high stability. Glycerol monooleate
(GMO) in mixtures with oleic acid (OA) at varying concentration ratios
were used to produce four different lyotropic mesophases: bicontinuous
cubic (Pn3m), inverse hexagonal
(H2), inverse micellar cubic (Fd3m), and microemulsions (ME). At a preadjusted pH of 4, LF
stabilized all four lyotropic mesophases via a Pickering-type mechanism,
forming mesosomes with hydrodynamic diameters (d
H) ranging from ∼187 to ∼239 nm, as measured
by dynamic light scattering (DLS). High-pressure ultrasonication was
used to drive positively charged LF to adsorb at the LLC–water
interface, confirmed via confocal microscopy. The sonication led to
a distinct positive surface charge on the mesosomes, as evidenced
by the ζ potential of ∼+30 mV, without compromising the
mesosomes’ size and stability. Time-resolved DLS experiments
showed that all mesosomes had long-term stability against coalescence
and aggregation for at least 1 month of storage at room temperature.
Small-angle X-ray scattering was used to study the phase behavior
of GMO/OA mixtures before and after their stabilization by LF. The
results showed that all four bulk mesophases maintained their structural
hierarchy after being homogenized into mesosomes. Notably, pure GMO
stabilized by LF formed cubosomes of diamond Pn3m, the same morphology as GMO in the bulk. This behavior
is different from what has been observed for the commonly used stabilizer
for LLC systems, Pluronic F127, which induces a transition to a primitive Im3m cubic morphology upon stabilization.

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