Fabrication of non-spherical Pickering emulsion droplets by cyclodextrins mediated molecular self-assembly

The unique physiochemical properties of non-spherical carriers play a significant role in their functions and offer distinct advantages as drug delivery systems, including drug loading, stability and targeting. Herein, a simple method to fabricate non-spherical Pickering emulsion droplets (NSPEDs) by cyclodextrins (CDs) mediated molecular self-assembly is reported. The non-spherical shapes controlled by the type and content of oils/CDs were evaluated by the average roundness (Rave) figures. The stability and physicochemical properties of castor oil (CO)-CDs emulsions, including creaming, viscosity and size distribution with different Rave values were characterized. The Pickering emulsion droplets with different Rave values were fabricated through mixing CDs with twelve common oils. The type of oils showed varied dependence of Rave on the content of oils/CDs. Rave increased when reducing the content of oils or raising the content of CDs. The CO-CDs emulsions with larger Rave exhibited higher creaming index, stronger viscosity, smaller size, and thus possessed better stability. The size distributions at 1 μm representing the excess oil-CD microcrystals in the continuous phase became larger with increase in Rave values, indicating that the formation of NSPEDs was mainly ascribed to the excess microcrystals in the emulsions. Finally, the formation mechanism of NSPEDs directed by CDs mediated self-assembly was validated by directly dispersing the microcrystals in water and diluting the obtained emulsions. Cryo scanning electron microscope experiments were also carried out to demonstrate the presence of microcrystals at the oil–water interface. The presented work provided an efficient approach to fabricate and control the shape of droplets in Pickering emulsions for potential new applications as a drug delivery system.