A better understanding of biological effects of nanomaterials in organisms requests knowledge of the physicochemical properties of nanomaterials in biological systems. Affected by high concentration salts and proteins in biological medium

nanoparticles are much easy to agglomerate

hence the difficulties in characterizing size distribution of the nanomaterials in biological medium. In this work

synchrotron radiation small angle X-ray scattering (SR-SAXS) was used to determine size distributions of Fe

Fe2O3 and Fe3O4 nanoparticles of various concentrations in PBS and DMEM culture medium. The results show that size distributions of the nanomaterials could perfectly analyzed by SR-SAXS. The SR-SAXS data were not affected by the particle content and types of the dispersion medium. It is concluded that SR-SAXS can be used for size measurement of nanomaterials in unstable dispersion systems.