Despite significant efforts have been made to prevent paraquat (PQ)-induced pulmonary fibrosis,including corticosteroids and immunomodulatory agents, sufficient therapeutic method has remained underdeveloped.Here, we report a fluorofenidone (AKF)-loaded PEG-PLGA nano drug delivery system (Fig.1.A).Taking advantage of the high expression of polyamine transport system (PTS) in lung cell, the nanoparticle surface was modified with spermidine (SPD) (SPD-NPs), aiming to increasing its intracellular drug delivery efficiency.