A nanofiber-based drug depot with high drug loading for sustained release

Nanostructures and their related structure-performance relationships for "efficacious, safe and convenient" drug delivery are playing a more and more important role in the fast development of nanopharmaceutics. In this study, a core-shell fiber based nano depot (ND) is prepared for achieving a high drug loading and meanwhile ensuring a zero-order drug sustained release profile. With cellulose acetate (CA) as a filament-forming polymeric matrix and ferulic acid (FA) as a model drug, a triaxial electrospinning was implemented to generate the ND. An elaborate strategy was exploited to ensure a continuous, robust and effective preparation. The strategy comprised a solvent mixture as the outer fluid, a mixed solution containing FA and CA with a high CA concentration as the spinnable middle fluid, and a pure drug solution as the inner liquid for loading enough FA in the NDs as much as possible. TEM and SEM demonstrated the core-shell structure of NDs. The NDs had a drug loading of 71.5 ± 4.6%. The in vitro dissolution tests demonstrated that the loaded FA was able to release through a zero-order kinetics of Q (FA released percentage) to t (release time): Q = 12.03 + 1.89 t (R = 0.9928) during the 48 h. Only 3.6% of the loading FA was released during the late tailing-off period. Three different diffusion types about the drug sustained release mechanism are suggested.