Cubosome and Hexosome Microparticles: Shape, Rheology, and Templating

Cubosomes and hexosomes are soft particles of cubic and hexagonal phases, formed by self-assembled amphiphilic lipids. They have attracted great attention because of applications in drug delivery. Cubosomes and hexosomes have been produced at the nanoscale, exhibiting unique shapes and symmetries, but a better understanding of links between particle shapes and mesoscale structures is needed for controlled production and broader applications. In this thesis, a bottom-up method based on a precursor emulsion is developed to produce microscale cubosomes and hexosomes in a controlled way. Emulsion droplets containing water, ethanol, the lipid glyceryl monooleate, and the desired additives are suspended in a yield stress fluid, and transform into liquid crystals with solid-like rheology and controlled size and shape. Cubosomes are polyhedral particles formed by growing facets on precursor droplets. Hexosomes are bicones and spinning tops with rotational symmetry. Small angle X-ray scattering confirms the particles are cubosomes and hexosomes, and links particle shapes to microstructures. Themicron-scale liquid crystalline particles provide a route to understanding the effects on production of soft particles with ordered microstructure and unique shapes. The produced cubosomes and hexosomes are used as templates to polymerize various monomers and produce polymeric particles with unique micron-scale geometric shapes. The amphiphilicity of particles allows incorporation of various organic monomers. Photopolymerization in the lipid templates creates polymerized particles preserving the shapes of cubosomes and hexosomes. Particle shapes are controlled by varying the structures and hydrophobicity of the monomers. Monomers also control the elasticity of the final particles produced. Although ultrasound is widely used to produce hexosomes in the top-down method, there are no direct studies of the process, and their effects on hexosome properties. We use high-speed microscopic imaging to directly observe bubble formation and degradation of bulk hexagonal phase, forming liquefied precursor materials that disperse and rapidly crystallize into hexosomes. Ultrasonic dispersal of the viscoelastic hexagonal phase is quantitatively related to the liquid crystal rheiology, providing a process design basis as well as awareness of particle intermediate states that could affect short-time retention of solubilized active molecules.

Grantor dc:publisher

UNSW, Sydney

Year dc:date

2019

Author dc:creator

• Wang, Haiqiao

• Polymerization
• Liquid crystal
• Cubosome
• Hexosome
• Shape

Statement dc:rights

• open access
• CC BY-NC-ND 3.0
• free_to_read

Licence

• https://purl.org/coar/access_right/c_abf2
• https://creativecommons.org/licenses/by-nc-nd/3.0/au/

Language dc:language

EN

Identifier

https://doi.org/10.26190/unsworks/21513

OAI identifier oai:identifier

oai:unsworks.library.unsw.edu.au:1959.4/64505