Abstract
Pickering emulsions for drug delivery applications have gained increasing attention over recent
years because of their low toxicity, high stability, and large stabilizer selectivity. However, diverse
drug delivery routes in the human body pose challenges, such as the harsh environment of oral
enzymes or stomach acid for oral therapeutics, unstable controlled drug release in parenteral
drug administration and low bioavailability in topical drug use due to low drug permeability
and retention. This thesis aims to develop and evaluate novel Pickering emulsion systems for
applications in drug delivery. Three novel Pickering emulsion systems have been introduced
using DI-water as the continuous phase and sunflower oil as the dispersed phase.
Pickering emulsions with a narrow size distribution were prepared using biocompatible
carboxylated nanodiamond (ND) nanoparticles for the first time. Membrane emulsification
and probe sonication were utilized to produce oil droplets with various sizes. The resulting
ND-stabilized Pickering emulsions exhibited remarkable stability against mechanical vibrations
and long-term storage for up to one year, and across a broad pH range. These characteristics
make them promising for use in oral drug delivery applications.
Synthetic two-dimensional (2D) peptide assemblies, composed of triblock oligoglycine
(2T), were utilized to stabilize Pickering emulsions. The lamellar structure and thermodynamic
behavior of the assemblies at the oil/water interface and in the liquid phase were investigated.
Because of the protonation and deprotonation of the terminal amino groups of the oligoglycine,
the emulsion remained stable at pH 7 but became destabilized at slightly lower pH levels. The
synthetic peptide amphiphile is a novel stabilizer to stabilize Pickering emulsions, which holds
significant potential for biomedical applications, particularly for the parenteral route.
2T-modified ND particles were fabricated by covalently bonding the carboxyl group on
ND with the terminal amino group of 2T, and were utilized to stabilize Pickering oil-in-water
emulsions. These emulsions exhibit a better stability over three months of storage compared
to ND or 2T emulsions. As a model system, Pickering emulsions were evaluated for the
encapsulation of organic components for ocular drug delivery for the first time. According
to an ex vivo Bovine Corneal Permeability and Opacity test, there is no significant toxicity
difference between the ND-2T Pickering emulsions and PBS buffer. The retention of ND-2T
Pickering emulsions on corneal tissue is significantly strengthened because of the positively charged terminal amino group of 2T. The superior stability and retention of ND-2T Pickering emulsions on corneal tissue demonstrated in this research suggest their potential application in ocular drug delivery, which could improve patient outcomes.