Distinguishing Protein Corona from Nanoparticle Aggregate\nFormation in Complex Biological Media Using X‑ray Photon Correlation\nSpectroscopy

In\nbiological systems, nanoparticles interact with biomolecules,\nwhich may undergo protein corona formation that can result in noncontrolled\naggregation. Therefore, comprehending the behavior and evolution\nof nanoparticles in the presence of biological fluids is paramount\nin nanomedicine. However, traditional lab-based colloid methods characterize\ndiluted suspensions in low-complexity media, which hinders in-depth\nstudies in complex biological environments. Here, we apply X-ray photon\ncorrelation spectroscopy (XPCS) to investigate silica nanoparticles\n(SiO<sub>2</sub>) in various environments, ranging from low to high\ncomplex biological media. Interestingly, SiO<sub>2</sub> revealed\nBrownian motion behavior, irrespective of the complexity of the chosen\nmedia. Moreover, the SiO<sub>2</sub> surface and media composition\nwere tailored to underline the differences between a corona-free system\nfrom protein corona and aggregates formation. Our results highlighted\nXPCS potential for real-time nanoparticle analysis in biological media,\nsurpassing the limitations of conventional techniques and offering\ndeeper insights into colloidal behavior in complex environments.