Chitosan-based oral nanoparticles as an efficient platform for kidney-targeted drug delivery in the treatment of renal fibrosis.

There is increasingly keen interest in developing orally delivered targeted drugs, especially for diseases that require long-term medication. Hence, we manufactured nanoparticles derived from methoxypolyethylene glycol-chitosan (PCS) to enhance the oral delivery and kidney-targeted distribution of salvianolic acid B (SalB), a naturally occurring renoprotective and anti-fibrotic compound, as a model drug for the treatment of renal fibrosis. Orally administered SalB-loaded PCS nanoparticles (SalB-PCS-NPs) maintained good stability in the gastrointestinal environment, improved mucus-penetrating capacity, and enhanced transmembrane transport through a Caco-2 cell monolayer. The relative oral bioavailability of SalB-PCS-NPs to free SalB and SalB-loaded chitosan nanoparticles (SalB-CS-NPs) was 367.0 % and 206.2 %, respectively. The structural integrity of SalB-PCS-NPs after crossing the intestinal barrier was also validated by Förster resonance energy transfer (FRET) in vitro and in vivo. Fluorescein isothiocyanate (FITC)-labeled SalB-PCS-NPs showed higher kidney accumulation than free FITC and FITC-labeled SalB-CS-NPs (4.6-fold and 2.1-fold, respectively). Significant improvements in kidney function, extracellular matrix accumulation, and pathological changes were observed in a unilateral ureter obstruction mouse model of renal fibrosis after once daily oral treatment with SalB-PCS-NPs for 14 days. Thus, oral administration of SalB-PCS-NPs represents a promising new strategy for kidney-targeted drug delivery.