Rational design of oral flubendazole-loaded nanoemulsion for brain delivery in cryptococcosis

Cryptococcal meningitis is caused by Cryptococcus spp. and predominantly affects patients with acquired immunodeficiency syndrome. However, an increase in the number of nonHIV patients diagnosed with cryptococcosis raises concerns worldwide. The current antifungal therapy has some limitations such as being unavailable in some countries, high cost, toxicity, and the need for trained professionals for intravenous administration, which compromises patient compliance, resulting in treatment withdrawal and increased fungal resistance. In this regard, new alternative drugs, especially those administered orally and at affordable cost are desired. However, these drugs face challenges due to the gastrointestinal (GI) and blood-brain barriers (BBB). In this present work, we developed a new oil-in-water nanoemulsion containing flubendazole (FLZ) for oral administration using a unique low-energy process for treating cryptococcosis. The combination of D-phase emulsification (DPE) process and design of experiment (DoE) resulted in a stable FLZ-loaded nanoemulsion with 35-nm mean particle size, 60.0% oil phase with 3.0% surfactant phase (both % w/w), at 25 °C process temperature without using specific equipment. The careful selection of components for developing this nanoemulsion as a drug carrier is thoroughly discussed herein, including the interaction of lipid components with brain transporters, the type of surfactant as a permeability enhancer through BBB, as well as the choice of the drug. The use of statistical design combined with the DPE process, and selection of components, resulted in reducing approximately 30% of fungal burden in mice brain, and safety testing in an invertebrate model showed nontoxicity by this nanoemulsion. This work reports a step-by-step alternative process for designing a nanoemulsion with improved efficacy and safety, even containing a drug at a significantly reduced concentration compared to previously published works. This nanoemulsion provides multiple benefits - overcoming GI and BBB barriers, and affordable production cost - delivering a new antifungal alternative for treating cryptococcosis.