Probing the Biological Identity of Inorganic Nanoparticles with Anomalous Small Angle X-Ray Scattering

In a biological milieu, nanoparticles (NPs) undergo alterations that go from aggregation or degradation to the adsorption of a corona of proteins. Those changes influence significantly the intrinsic properties and biological capacities of the engineered nanomaterials and need to be fully understood for the successful biomedical use of NPs. Synchrotron anomalous small-angle X-ray scattering (ASAXS) is used to probe the individual small-angle X-ray scattering (SAXS) contributions from the different components of NPs (core, polymeric coating, and protein corona) on several in vitro systems. By applying a model-based fitting approach combined with pair distance distribution analysis, it is possible to investigate whether and to what extent proteins formed a corona around different nanoparticles. The results obtained agree with well-established dynamic light scattering and transmission electron microscopy experiments, confirming the capacity of ASAXS to obtain full information from complex NP samples, and opening for its use in more realistic biological environments.