쌍극자 상호작용에 기인하여 액적 퍼콜레이션 성능을 갖는 회합형 나노에멀젼 제조에 관한 연구
- 쌍극자 상호작용에 기인하여 액적 퍼콜레이션 성능을 갖는 회합형 나노에멀젼 제조에 관한 연구
- Other Titles
- Attractive Nanoemulsions with Dipole-Dipole Interaction-Driven Interdrop Percolation
- Issue Date
- this results in a percolated network of stable drops that exhibit no signs of coalescence or phase separation. We have figured out that this unique rheological behavior is attributed to the dipolar interaction between the phosphorylcholine groups of lecithin and the methoxy end groups of PEO-b-PCL. Finally, we demonstrate that our nanoemulsion system significantly enhances transdermal delivery efficiency due to its favorable attraction to the skin as well as high diffusivity of the nanoscale emulsion drops. In chapter 4, we introduce a useful and promising approach to fabricate extremely stable silicone nanoemulsions of which interface is structured with a thin film of amphiphilic triblock copolymers. For this, two kinds of amphiphilic triblock polymers, poly [2-(methacryloyloxy) ethyl phosphorylcholine]-block-poly (ε-caprolactone)-block-poly [2-(methacryloyloxy) ethyl phosphorylcholine] (PMPC-PCL-PMPC) and poly (2-aminoethyl methacrylate)-block-poly (ε-caprolactone)-block-poly (2-aminoethyl methacrylate) (PAMA-PCL-PAMA), were synthesized by using atom transfer radical polymerization. The use of phase inversion from a water-in-oil emulsion to an oil-in-water emulsion was critical for formation of thin polymer interfaces, of which thickness is less than 10 nm, thus eventually producing structurally stable silicone nanoemulsions. Co-assembly of PAMA-PCL-PAMA with PMPC-PCL-PMPC enabled patching of positive charges on the surface of silicone emulsion drops. We showed that these charged silicon nanoemulsions could form a multilayer emulsion thin film by the layer-by-layer deposition. Finally, we experimentally demonstrated that the silicone nanoemulsions fabricated in this way were highly stable and had the ability to electrostatically interact with hairs, which enables complete coating of the hair surface with silicone oil layer. In chapter 5, we demonstrated that our nanoemulsion system is a powerful vehicle for enhanced cutaneous delivery of luteolin. Luteolin (3',4',5,7-tetrahydroxyflavone), a type of flavonoid found in medicinal herbs and vegetables, has been of great interest due to its anti-oxidative, anti-inflammatory, and anti-carcinogenic effects. Despite these beneficial biological properties, the ease with which luteolin forms molecular crystals in conventional aqueous formulations has hampered much wider applications. In this study, the luteolin-loaded nanoemulsion, which had an average hydrodynamic size of approximately 290 nm, was produced by the assembly of PEO-b-PCL and lecithin at the O/W interface. The luteolin-loaded nanoemulsion showed outstanding stability against drop coalescence and aggregation. This was confirmed from the slight drop size increase after repeated freeze-thaw cycling and long-term storage. Moreover, in vivo hair growth evaluation demonstrated that the luteolin-loaded nanoemulsions fabricated in this study possessed remarkable hair growth-promotion activity, which is comparable with the case of using a luteolin solution in an organic solvent.
Nanoemulsions are emulsions having the droplet size of usually 20 ~ 500 nm in which oil or water droplets are finely dispersed in the opposite phase with the help of suitable emulsifiers to stabilize the system. They can be stable (metastable) for long times due to the extremely small sizes. Moreover, their small size leads to unique properties such as high surface area per unit volume, transparent appearance and tunable rheology. Nanoemulsions also are non-toxic and non-irritant systems and they can be used for skin or mucous membranes, parenteral and oral administration. These properties make nanoemulsions an attractive candidate for applications in the food, cosmetic, pharmaceutical industries and in drug delivery applications. In particular, transdermal delivery induced by nanoemulsions undergoes with quite different manners when compared to the delivery from conventional microscale complex formulations. The main advantages of using nanoemulsoins arise from their peculiar features, such as high diffusivity, high surface energy, and tailored architectures. Despite their great potential as a delivery carrier, transdermal delivery using nanoemulsions has been limitations due to the stability problem inherent to system (i.e. thermodynamically unstable system). Therefore, my major concern for transdermal delivery using nanoemulsions was to create an initial nanoemulsion with sufficiently small droplets, and then to ensure that it has a sufficiently long kinetic stability for commercial applications. For this goal, I have been developed structurally stable nanoemulsions by engineering a robust interface and controlled interdroplet interactions. In chapter 2, we introduce a robust approach for the fabrication of extremely stable oil-in-water nanoemulsions in which the interface is stabilized by assembly of amphiphilic poly(ethylene oxide)-block-poly(ε-caprolactone) (PEO-b-PCL) copolymers. Phase inversion emulsification, induced by variation of the water volume fraction, facilitated effective assembly of the block copolymers at the oil-water interface. Subsequent application of simple probe-type sonication reduced the droplet size of the precursor emulsions to approximately 200 nm. The prepared nanoemulsions were surprisingly stable against drop coalescence and aggregation, as confirmed by analysis of changes in the droplet size after repeated freeze-thaw cycling and by monitoring the creaming kinetics under conditions of high ionic strength and density mismatch. The results highlight that good structural assembly of the PEO-b-PCL block copolymers at the oil-water interface generated a mechanically flexible but tough polymer film, thereby remarkably improving the emulsion stability. In chapter 3, we introduce an extremely stable attractive nanoscale emulsion fluid, in which the amphiphilic block copolymer, PEO-b-PCL, is tightly packed with lecithin, thereby forming a mechanically robust thin-film at the oil-water interface. The molecular association of PEO-b-PCL with lecithin is critical for formation of a tighter and denser molecular assembly at the interface, which is systematically confirmed by T2 relaxation and DSC analyses. Moreover, our suspension rheology studies also reflect the interdroplet attractions over a wide volume fraction range of the dispersed oil phase
- Appears in Collections:
- GRADUATE SCHOOL[S](대학원) > BIONANOTECHNOLOGY(바이오나노학과) > Theses (Ph.D.)
- Files in This Item:
There are no files associated with this item.
- RIS (EndNote)
- XLS (Excel)