Adsorption of immunomodulatory proteins over silica nanoparticles and the in vitro effect

Silica NPs (SiNPs) used as a platform to deliver molecules have huge potential for biomedical applications. In order to generate new immunomodulatory tools, 2 variants of SiNPs were synthesized and 3 proteins were adsorbed over their surface: bovine serum albumin and the cytokines IL-1β and TGF-β. Protein adsorption was analyzed according to Langmuir and Freundlich models. The adsorption isotherm of IL-1β on both SiNP variants had a good fit to the Freundlich model, indicating the formation of a protein multilayer around the NPs. For BSA and TGF-β isotherms, the fit to the Langmuir model was better, evidencing the presence of a protein monolayer on the NPs. SiNPs@TGF-β complexes were tested in THP-1 cells (human monocytes cells). The complexes reduced cellular metabolic activity and did not cause an increase in nitric oxide expression, which is related to the immunosuppressive activity of TGF-β, but was potentiated and prolonged over time compared to the cytokine alone. These nanocomplexes could be important tools for use as nanoinmunomodulators (NIMs) for the therapeutic treatment of inflammatory diseases.