Time-Resolved Study on Self-Assembling Behavior of PEGylated Gold Nanoparticles in the Presence of Human Serum Albumin: A System for Nanomedical Applications

The combination of a microfluidic approach for synchrotron-based dynamic (early structural changes) with lab-based static small-angle X-ray scattering (SAXS) measurements (longer time scale) allows qualifying nanoparticle (NP) systems for their use in nanomedicine. Time-resolved in situ investigations are performed on self-assembly and colloidal behavior of 5 nm PEGylated (polyethylene glycol) gold NPs in different media. SAXS methods combined with a micromixing fluidic system are used to observe the early stage of NP interactions. Dynamic measurements cover a time range from 1 to 100 s after mixing thoroughly, while static measurements complete the study for up to 10 days after sample preparation. These NPs, after mixing with saline solution (0.9% NaCl solution), self-assemble in 3D ordered domains. The NPs also show this ordering in the presence of human serum albumin (HSA) molecules. It is shown that, although the presence of protein molecules slows down the NP self-assembling process, these molecules improve the long-term colloidal stability of the ordered domains probably via interpolymer complexation between PEG and HSA molecules.