(T1030-07-39) Development, Characterization and Stability Studies of Amphotericin B and Nonadecanoic Acid loaded Nanostructured Lipid Carriers for Fungal Keratitis

Purpose: Amphotericin B (AMB) in the presence of the natural compound nonadecanoic acid (NDA) has shown a synergistic effect in antifungal activity. As AMB has a toxic effect at higher concentrations. A stable formulation consisting of both compounds showing antifungal action at lower AMB concentrations would reduce the risk of toxicity. The objective of the present study is to formulate a stable formulation consisting of AMB and NDA in a nanostructured lipid carrier (NLC) system for the treatment of fungal keratitis.

Methods: Lipid Screening was done to check the solubility of the drugs in the oil. The lead liquid oils were selected to prepare AMB-NDA-NLC and AMB-NLC. The lipid phase consisted of Oleic acid/castor oil, Precirol™ ATO 5, AMB, and NDA. The aqueous phase consisted of Tween® 80, glycerin, poloxamer 188, benzalkonium chloride, and hydroxypropyl beta cyclodextrin. The lipid phase and aqueous phase were heated to 80°C following which the aqueous phase was slowly introduced into the lipid phase in a drop wise fashion under constant stirring at 2000 rpm. This mixture was then subjected to hot homogenization and probe sonication to obtain the final formulation. The AMB-NLC and AMB-NDA-NLC were prepared with the lead oils (castor oil, oleic acid, and combination of oils) and were put on stability for 14 days at room temperature and evaluated for physicochemical characteristics. The lead formulation was then prepared and put on stability at 4, 25, and 40°C and evaluated for particle size, zeta potential (ZP), polydispersity index (PDI), assay, and entrapment efficiency (EE), pH and viscosity. The formulation was then subjected to lyophilization.   

Results: The lipid screening results showed Castor oil and Oleic acid to have the highest solubilization power (visual examination). The average particle size, PDI, ZP, and assay for AMB-NDA-NLC and AMB-NLC prepared with castor oil, oleic acid or combination of oleic acid and castor are shown in table 1. The average particle size, PDI, ZP, assay, and EE of AMB-NDA-NLC and AMB-NLC at 4, 25, and 40°C are shown in table 2. The pH was found to be 4.15 ± 0.08 and the viscosity was found to be 20.4 ± 4.9 centipoise at room temperature for AMB-NDA-NLC. The formulation was found to be stable for the time period studied, except for those at accelerated condition.

Conclusion: The lead NLC formulations prepared showed desirable physicochemical properties. The stability of the reconstituted lyophilized formulation will be a critical aspect to study in the future. In-vitro studies of the lead formulation would help us to determine the antifungal activity at minimum concentration of AMB in presence of NDA.

Table 1. Day 14 stability of AMB-NLC and AMB-NDA-NLC



Table 2. Day 15 stability of AMB-NLC and AMB-NDA-NLC