Bio Meets Nano: Protein Exchange in Saline Biocoronae on Magnetic Nanoparticles.

When iron oxide nanoparticles are incubated together with a biological broth, the biomolecules compete for the binding sites at the solid-liquid interface. At the same time, the biomass rearranges in suspension, building agglomerated structures. Despite general knowledge of the forces involved in bio-nano interactions, gaps remain in the understanding of how biomolecules organize themselves in solution and onto surfaces. This work examines biomolecule adsorption onto metal oxide surfaces with the goal of strengthening this understanding, essential in industrial and natural processes. We demonstrate nearly complete separation of proteins from a biotechnological suspension for non-oxidized and highly oxidized magnetic nanoparticles. Varying the nanoparticle-to-biomass ratio, we find, can lead to different separation patterns, i.e., that selectivity using bare, low-cost materials is possible. Furthermore, we explore how preliminary "passivation" with a biological corona only partially reduces the ability to separate total protein mass from a new suspension in subsequent incubation steps. The study underscores the crucial role of concentration gradients with regard to targets and binding sites as the primary determinant of separation capacity and of biomolecule behavior in solution, highlighting the potential for using bio-nano coronae as biomolecule carriers across diverse fields, including environmental, biomedical, pharmaceutical and nutritional applications.