Adsorption of model proteins and physiologically most relevant SP-A to metal oxide nanoparticles

Einleitung: Engineered metal oxide nanoparticles are produced at tons scale already. Since the miniaturization of materials into the nano-size range may dramatically change physical and chemical properties, nanomaterials will obviously also interact in a different way with biological systems. Once they entered the body, the can interact with the physiological surroundings, i.e. also with proteins. This particle-protein interaction might lead to altered reactions, hence, the investigation of protein adsorption to those particles is of great importance.

Methoden: We quantified and compared the protein adsorption of Bovine Serum Albumin to eight metal oxide nanoparticles of five different bulk materials with BCA-assay. Also, we investigated the adsorption of Surfactant-Protein A (SP-A) with Immunoblot.

Ergebnisse: All adsorption processes could be fitted to a sigmoidal mathematic model, revealing differences in half-maximal adsorption for particles of the same bulk material. After that, we tested the adsorption of those particles to SP-A, a component of the Alveolar Lining Fluid (ALF) covering the respiratory epithelium of the deep lung. The ALF is the first biological barrier encountered by nanoparticles after inhalation. SP-A is a physiologically most relevant protein and provides important biological signals. Moreover, it is involved in the lung's immune defence, controlling e.g. particle binding, uptake or transcytosis by epithelial cells and macrophages. In our study, we could prove different particle-protein interactions for the eight different nanoparticles, whereas particles of the same bulk material revealed different adsorption patterns.

Diskussion: Hence, a prediction of protein adsorption due to particle properties only was not possible. The adsorption pattern for protein from fetal calf serum (FCS) differs significantly from that of SP-A, indicating different adsorption mechanisms. These findings may have important consequences for biological fate and toxicological effects of inhaled nanomaterials.