Nanoparticle colloidal stability investigated by small-angle x-ray scattering

Full text: An evaluation of nanoparticle colloidal stability in the presence of protein is essential to understand the nanoparticle behavior in a biological medium. Frequently, dynamic light scattering (DLS) is the main technique used to make this kind of evaluation. However, we have found out that small-angle X-ray scattering (SAXS) is also an interesting technique to study colloidal stability and protein corona. The SAXS results were evaluated by the variation in the extrapolated intensity at zero scattering angle [I (0)] of the nanoparticles as a function of protein concentration. This work uses these two techniques to study the adsorption of bovine serum albumin (BSA) and fetal bovine serum (FBS) on bare silica nanoparticles (Bare) and silica nanoparticle-modified by zwitterionic (ZW) and polyethylene glycol (PEG). While the hydrodynamic diameter of the nanoparticles shifted to smaller values due to the contribution of free proteins on DLS results, the evaluation of protein corona by SAXS did not have this artifact. In addition, the SAXS technique was able to detect a thin corona protein that did not affect the colloidal stability, as well a system of pair of nanoparticles having interaction, as confirmed by cryo-em. (author)