Emulsions for Topical Eye Delivery: State of the Art and Future Perspectives

Multiphase Drug Distribution and Exchange in Oil-in-Water Nanoemulsion Revealed by High-Resolution 19F qNMR

“…9 Studies on the manufacturing process, characterization, and delivery of emulsion products have been abundant. 2,9,10 However, the drug distribution in different phases of o/w emulsions has not been explicitly measured noninvasively 11 despite the distribution studies using separation methods such as ultra-centrifugation (UC), 12 ultrafiltration, 7 or dialysis. 8 This is due to the unique challenge of the o/w soft matter nanocore, which is thermodynamically unstable 1,6 and subject to structural changes upon invasive separation.…”

“…Therefore, at least three phases, including water (w), surfactant (s) (i.e., the interface layer), and oil (o), are present in the NE formulation. , One salient feature of an o/w NE is its ability to dissolve hydrophobic drug molecules in nonaqueous phase compartments to achieve better bioavailability . Studies on the manufacturing process, characterization, and delivery of emulsion products have been abundant. ,, However, the drug distribution in different phases of o/w emulsions has not been explicitly measured noninvasively despite the distribution studies using separation methods such as ultra-centrifugation (UC), ultra-filtration, or dialysis . This is due to the unique challenge of the o/w soft matter nanocore, which is thermodynamically unstable , and subject to structural changes upon invasive separation. , …”

“…DFPN contains two fluorine atoms located at positions 28 and 29 (Figure A inset), respectively, where the resolved 19 F NMR peaks were phase-specific probes. The formulation is composed of 5% castor oil, 4% polysorbate-80 (PS-80) as a surfactant, ,, and 500 μg/mL drug DFPN per labeled content (LC) . At an oil/surfactant (o/s) mass ratio of 1.25 (5%/4%), oil molecules are known to form NE globules with a median size of 104 nm. ,, In a previous study, a similar NE size distribution was measured using diffusion-ordered NMR spectroscopy (DOSY-NMR) .…”

“…The formulation is composed of 5% castor oil, 4% polysorbate-80 (PS-80) as a surfactant, ,, and 500 μg/mL drug DFPN per labeled content (LC) . At an oil/surfactant (o/s) mass ratio of 1.25 (5%/4%), oil molecules are known to form NE globules with a median size of 104 nm. ,, In a previous study, a similar NE size distribution was measured using diffusion-ordered NMR spectroscopy (DOSY-NMR) . In certain cases, when the o/s ratio was optimized, the coexistence of the NE and ME in the emulsion could be identified …”