Pulmonary delivery of silk fibroin peptides dry powder inhalers for idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a common disease of pulmonary fibrosis with an increasing incidence. Silk fibroin peptides (SFPs) are bioactive substances rich in essential amino acids and possess antioxidant and anti-inflammatory properties; however, their application is limited by drawbacks such as low bioavailability and susceptibility to protein degradation. In this study, spray-drying technology was employed to prepare a silk fibroin peptides dry powder inhaler (SFPs-DPI), followed by characterisation of its physicochemical properties and preliminary in vitro and in vivo studies. The results showed that the yield of SFPs-DPI was 56.86 ± 1.80%, the Carr's index was 25.64 ± 1.71%, the aerodynamic diameter was 2.26 ± 0.04 μm, the moisture content of 0.74%, and the emptying rate was 93 ± 1.61%. In vitro studies demonstrated that SFPs-DPI exhibits good cellular biocompatibility and antioxidant activity. In vivo pharmacodynamic results showed that SFPs-DPI reduced inflammatory infiltration and collagen fibre deposition in the lungs of IPF mice and reduced the expression of type I collagen and α-SMA in lung tissue. Therefore, the physicochemical properties of the SFPs-DPI prepared in this study meet the relevant requirements for dry powder inhalation formulations, providing a preliminary reference for research related to IPF treatment.