Abstract:
The purpose of this study was to develop pickering nanoemulsions (NEs) containing amphotericin B (AmB) for fungal keratitis therapy. The phase-solubility profiles of AmB in various aqueous cyclodextrin (CD) solutions were determined. The AmB solubilization in oils and surfactants was also examined. Two CDs i.e., gCD and 2-hydroxypropyl-g-CD (HPgCD), medium-chain triglycerides (MCT oil) and phosphatidylcholine (lecithin) were chosen because of their high solubility increment of AmB. Solution-state by 1H-NMR studies demonstrated the formation of MCT oil/αCD, AmB/gCD and AmB/HPgCD complexes. Some interactions between AmB and CD have been observed by solid-state characterizations (FT-IR, PXRD and DSC). The interfacial tension at oil-water interface, CD analysis and the morphology studies have confirmed the affinity of αCD to MCT oil. Thus, MCT oil/αCD complex was used as solid particle to stabilize pickering NEs. The CD-stabilized pickering and non-pickering NEs loaded AmB were developed by using high pressure homogenizer. The physicochemical and chemical properties i.e., pH, osmolality, viscosity, particle size and size distribution, zeta potential, drug content and entrapment efficiency were within the acceptable range. The developed formulations showed less degree of aggregation of AmB and lower hemolytic activity when compared with commercial product, Amphotericin-B®. In vitro drug release through semipermeable membrane studies revealed that pickering NEs provided the sustained drug release owing to most of drug entrapped in the inner core. For antifungal activity, the AmB formulations were superior to AmB itself but equally and inferior to Amphotericin-B® against C. albicans and filamentous fungi, respectively. The stability studies i.e., freeze-thaw, accelerated and long-term stability have found that CD-based pickering NEs exhibited good physical and chemical stability in contrast to the respective non-pickering NEs that showed instability after storage for 3 months. Therefore, CD-based AmB pickering NEs had the potential formulations for further studies.