Polymeric mixed micelles as nanomedicines: Achievements and perspectives.
The aim of the present work was to prepare and characterize chitosan-stearic acid conjugate nanomicelles for encapsulation of amphotericin B (AmB) and to evaluate the in vitro nebulization of the formulations. Water soluble chitosan was grafted to stearic acid (SA) chains via 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide mediated coupling reaction. The chemical structure of depolymerized chitosan (DC)-SA copolymers and degree of amino substitution was determined by (1)H NMR. AmB was loaded in nanomicelles with a maximal encapsulation efficiency of 97%. The physicochemical properties and formation of polymeric micelles were studied by dynamic light scattering and fluorescence spectroscopy method. Nanomicelles possessed positive charges with mean particle sizes of 101-248 nm. AmB-loaded micelles were also characterized for their antifungal activity, aggregation state of the drug, nebulization efficiency and retention of AmB in the micelles after nebulization. The results indicated that encapsulation of AmB in DC-SA micelles could improve the antifungal activity of the drug in some of the cases. The nebulization efficiency was up to 56% and the fine particle fraction (FPF) varied from 40% to 52%. Since there was only a little change in encapsulation of the drug in micelles after nebulization, DC-SA micellar formulations can be a suitable choice for pulmonary delivery of AmB.