Internally Self-Assembled Pickering Mesosomes Stabilized by Positively Charged Lactoferrin

Area of Science:

• Materials Science
• Colloid and Surface Science
• Biophysics

Background:

• Lyotropic liquid crystalline (LLC) mesophases are complex self-assembled structures with potential applications in drug delivery and nanotechnology.
• Stabilizing these delicate mesophases, particularly within emulsion systems like mesosomes, presents significant challenges.
• Lactoferrin (LF), a naturally occurring protein, has emerged as a potential biocompatible stabilizer for colloidal systems.

Purpose of the Study:

• To engineer stable sub-micrometer emulsions (mesosomes) encapsulating diverse LLC mesophases using lactoferrin (LF) as a Pickering stabilizer.
• To investigate the role of LF pretreatment (ultrasonication) and processing conditions (pH) on mesosome formation, surface charge, and stability.
• To characterize the internal LLC structures within the mesosomes and compare LF's performance with conventional stabilizers.

Main Methods:

• Preparation of mesosomes using lactoferrin (LF) as a Pickering stabilizer for glycerol monooleate (GMO)/oleic acid (OA) mixtures.
• Ultrasonication pretreatment of LF to prevent agglomeration and high-pressure ultrasonication during emulsification.
• Characterization using dynamic light scattering (DLS) for size and stability, ζ potential for surface charge, confocal microscopy for LF adsorption, and small-angle X-ray scattering (SAXS) for internal mesophase structure.

Main Results:

• LF successfully stabilized four distinct LLC mesophases (bicontinuous cubic, inverse hexagonal, inverse micellar cubic, microemulsions) within mesosomes.
• Mesosomes exhibited hydrodynamic diameters (d_H) of 187–239 nm with a significant positive surface charge (ζ potential ∼+30 mV) due to LF adsorption.
• The engineered mesosomes demonstrated excellent long-term stability (>1 month) and maintained the structural integrity of the encapsulated LLC mesophases, unlike Pluronic F127 stabilization.
• Pure GMO stabilized by LF formed cubosomes with the native Pn3m morphology, whereas Pluronic F127 induced a phase transition.

Conclusions:

• Lactoferrin is an effective Pickering stabilizer for creating stable, positively charged mesosomes encapsulating various lyotropic liquid crystalline mesophases.
• The LF stabilization method preserves the internal hierarchical structure of the LLC mesophases, offering advantages over conventional stabilizers like Pluronic F127.
• These LF-stabilized mesosomes hold promise for advanced applications in fields requiring stable colloidal delivery systems with controlled internal nanostructures.