Role of Surfactant Proteins in the interaction of nanoparticles with the air-blood-barrier

Purpose: Pulmonary surfactant (PS) is the first biological matter a nanoparticle (NP) encounters after deposition into the alveolar lumen. This complex mixture of lipids and proteins offers a pool of biomolecules that can undergo bio-nano-interactions. Especially adsorption of the prevailing Surfactant Protein A (SP-A) might lead a NP – protein corona, that probably largely influences further biological effects like translocation or clearance. Therefore we studied the binding of this protein to magnetic NPs (mNPs) coated with different inhalation relevant materials and the impact of this effect on alveolar macrophage (AM) clearance.

Methods: Adsorption of SP-A and other PS components to mNPs was assayed using Western blot and densitometry. Size distribution of mNPs was measured by Dynamic Light Scattering. Macrophage clearance was studied in a mouse AM model using flow cytometry and confocal microscopy.

Results and Conclusion: Adsorption of the lung relevant SP-A occurred with different affinities among the tested mNPs. Comparison with albumin (BSA) revealed differences in the binding behaviour for some mNPs, clearly influencing particle size distribution but also interactions with AMs. Binding of SP-A to mNPs specifically increased AM interaction compared to BSA. These results suggest that in the deep lung, the identity of the adsorbed protein defines what happens after particle deposition, and that here surfactant proteins might play the major role.