SANS/SAXS Study to Unravel the Protein Corona Dynamics Using Deuterated Human Serum Albumin Interactions with Plasmonic Au Nanostructures

Protein corona (PC) significantly influences the stability and biological interactions of nanoparticles and has a dynamic behavior, particularly with respect to the exchange between the "soft" (loosely bound) and "hard" (tightly bound) PC layers. This study employs small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) to investigate the structural and dynamic aspects of interactions of human serum albumin (HSA) with gold nanoparticles and gold nanostars. We utilized recombinant deuterated human serum albumin (dHSA) to enhance neutron contrast, enabling in situ tracking of protein binding and exchange without altering the protein structure or function. As a control, recombinant nondeuterated HSA (nHSA) was used to assess dynamic protein exchange. Structural characterization confirmed similar interactions of dHSA and nHSA with gold surfaces, ensuring reliability in PC dynamics studies. SAXS characterization revealed minimal protein binding to gold nanostars (AuNSs), suggesting a reduced propensity for PC formation compared with spherical gold nanoparticles (AuNPs). SANS measurements, conducted under contrast matching conditions in deuterated water, allowed precise differentiation between free and nanoparticle-bound proteins, demonstrating that PC molecule exchange occurred homogeneously within 4 h of scattering measurements and remains stable for at least 12 h. These findings provide insights into molecule behavior within PC, with implications for nanoparticle design in biomedical applications.