Long-circulating thiolated chitosan nanoparticles of nintedanib with N-acetyl cysteine for treating idiopathic pulmonary fibrosis: In vitro assessment of cytotoxicity, antioxidant, and antifibrotic potential

Nintedanib (NIN) is one of the FDA-approved tyrosine kinase inhibitor drugs used to treat idiopathic pulmonary fibrosis (IPF). This study aimed to formulate a long-circulating injection of Nintedanib to treat bedridden patients with IPF. Nintedanib was incorporated into chitosan nanoparticles (NIN-NP) via the ionic gelation method, and N-acetyl cysteine (NAC), a known antioxidant and mucolytic agent, was added to the NIN-NP (NAC-NIN-NP). The lyophilized formulation had a particle size of 174 nm, a polydispersity index of 0.511, and a zeta potential of 18.6 mV. The spherical nanoparticles were observed in transmission electron microscopy, whereas field emission scanning electron microscopy showed irregular clusters of NP. The thiolation of the chitosan in NAC-NIN-NP was confirmed by ATR-FTIR and NMR, which improved drug release profiles showing >90 % drug release that was 2.42-folds greater than NIN-NP lasting for five days. The DPPH assay showed that adding NAC increased the % inhibition of oxidation in blank-NP (from 54.59 % to 87.17 %) and NIN-NP (58.65 %-89.19 %). The MTT assay on A549 cells showed 67.57 % cell viability by NAC-NIN-NP with an IC50 value of 28 μg/mL. The NAC formulation reduced hydroxyproline content (56.77 μg/mL) compared to NIN-NP (69.48 μg/mL) in WI-38 cell lines. Meanwhile, the healthy cells count with NAC-NIN-NP was higher (5.104 × 10³) than with NIN-NP (4.878 × 10³). In Hoechst staining, no significant damage to DNA was observed by the drug or formulation. Therefore, NAC-NIN-NP could be a promising treatment option for IPF patients and can be studied further clinically.