Emodin nanocrystals enhanced mucus penetration and ameliorated bleomycin-induced pulmonary fibrosis by pulmonary delivery

Pulmonary fibrosis (PF) is a progressive interstitial disease characterised by extracellular matrix deposition and destruction of lung tissue structure. Emodin (Emo) is a natural active compound with anti-inflammatory and antioxidant properties. The initiation of PF is prevented by reducing oxidative stress-induced damage to alveolar epithelial cells." to meet the word count requirement. However, Emo is featured low water solubility, a rapid metabolic rate and low oral bioavailability, which limit its application in the treatment of PF. Therefore, this study formulated emodin as nanocrystals (Emo-NCs) and delivered Emo directly to the lesion site <i>via</i> pulmonary delivery to enhance drug efficacy. The Emo-NCs exhibited a square crystal structure with particle sizes suitable for pulmonary absorption and an appropriate polydispersity index. They released 99.38% over 48 h and significantly improved permeability efficiency in simulated pulmonary mucus. The ability of Emo-NCs to inhibit abnormal fibroblast proliferation and oxidative damage was significantly enhanced compared with Emo. In contrast to the BLM group, the inflammatory cells in the lung tissue sections of the Emo-NCs group were significantly reduced, the alveolar structure was largely restored, and no evident collagen fibre deposition was observed. In summary, Emo-NCs could serve as a viable delivery system for site-specific treatment of PF.