Formononetin-Loaded PLGA Large Porous Microparticles via Intratracheal Instillation for Bleomycin-Induced Pulmonary Fibrosis Treatment.

Idiopathic pulmonary fibrosis (IPF) is a progressive lung disease of unknown cause, with few effective therapies available and high mortality rates. Our preceding research indicated that formononetin (FMN) could improve the symptoms of the bleomycin-induced pulmonary fibrosis and be a promising drug against IPF. In this study, an inhalable formononetin-loaded poly(lactic-co-glycolic) acid (PLGA) large porous microspheres (FMN-PLGA-MSs) was prepared by the method of emulsion solvent evaporation. SEM showed that FMN-PLGA-MSs were loose particles existing many pores on the surfaces, and the measured mean geometric diameter was more than 10 µm. The encapsulation efficiency (EE) and drug loading efficiency (DL) were 87.72 ± 6.34% and 4.18 ± 0.30%. FMN in FMN-PLGA-MSs could be rapidly released within 2 h and sustainably released for 21 d. Cell tests and q-RT-PCR tests showed that FMN could inhibit the activation of fibroblasts and the deposition of extracellular matrix (ECM) by acting on the TGF-β1/Smad3 signaling pathway. FMN-PLGA-MSs showed higher antifibrotic effects than free FMN oral administration in the pulmonary fibrosis models of mice, remarkably improving pulmonary function, decreasing hydroxyproline levels, and attenuating lung injuries. By formulating formononetin into microsphere preparations, its solubility can be significantly enhanced, enabling effective pulmonary drug delivery. This approach not only improves lung targeting but also reduces systemic toxicity. Additionally, it facilitates superior lung deposition and extends the retention time of the formononetin within the lungs. Taken together, FMN-PLGA-MSs may be a promising inhaled medication for the treatment of IPF.