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Jing Tang,1 Jianming Li,2 Guo Li,2 Haitao Zhang,2 Ling Wang,3 Dai Li,4 Jinsong Ding2 1School of Pharmaceutical Sciences, Changsha Medical University, 2Xiangya School of Pharmaceutical Sciences, Central South University, Changsha, 3Key Laboratory of Drug Targeting and Drug Delivery Systems, West China School of Pharmacy, Sichuan University, Chengdu, 4Xiangya Hospital, Central South University, Changsha, China Abstract: Idiopathic pulmonary fibrosis is a progressive, fatal lung disease with poor survival. The advances made in deciphering this disease have led to the approval of different antifibrotic molecules, such as pirfenidone and nintedanib. An increasing number of studies with particles (liposomes, nanoparticles [NPs], microspheres, nanopolymersomes, and nanoliposomes) modified with different functional groups have demonstrated improvement in lung-targeted drug delivery. In the present study, we prepared, characterized, and evaluated spermidine (Spd)-modified poly(lactic-co-glycolic acid) (PLGA) NPs as carriers for fluorofenidone (AKF) to improve the antifibrotic efficacy of this drug in the lung. Spd-AKF-PLGA NPs were prepared and functionalized by modified solvent evaporation with Spd and polyethylene glycol (PEG)-PLGA groups. The size of Spd-AKF-PLGA NPs was 172.5±4.3 nm. AKF release from NPs was shown to fit the Higuchi model. A549 cellular uptake of an Spd–coumarin (Cou)-6-PLGA NP group was found to be almost twice as high as that of the Cou-6-PLGA NP group. Free Spd and difluoromethylornithine (DFMO) were preincubated in A549 cells to prove uptake of Spd-Cou-6-PLGA NPs via a polyamine-transport system. As a result, the uptake of Spd-Cou-6-PLGA NPs significantly decreased with increased Spd concentrations in incubation. At higher Spd concentrations of 50 and 500 µM, uptake of Spd-Cou-6-PLGA NPs reduced 0.34- and 0.49-fold from that without Spd pretreatment. After pretreatment with DFMO for 36 hours, cellular uptake of Spd-Cou-6-PLGA NPs reached 1.26-fold compared to the untreated DFMO group. In a biodistribution study, the drug-targeting index of Spd-AKF-PLGA NPs in the lung was 3.62- and 4.66-fold that of AKF-PLGA NPs and AKF solution, respectively. This suggested that Spd-AKF-PLGA NPs accumulated effectively in the lung. Lung-histopathology changes and collagen deposition were observed by H&E staining and Masson staining in an efficacy study. In the Spd-AKF-PLGA NP group, damage was further improved compared to the AKF-PLGA NP group and AKF-solution group. The results indicated that Spd-AKF-PLGA NPs are able to be effective nanocarriers for anti–pulmonary fibrosis therapy. Keywords: idiopathic pulmonary fibrosis, fluorofenidone, spermidine, polyamine transport system, nanoparticles