Uranyl-binding proteins on silica nanoparticles for repeatable capture of uranyl ions

Successful protein-based enrichment of uranyl, the predominant form of uranium from seawater, relies not only on selective binding of uranyl with a high affinity but also on the reusability of protein binder and a supporting matrix that is abundantly available at low cost. In this work, we propose a silica-binding peptide-enabled approach that allows the non-covalent immobilization of super uranyl-binding protein (SUP) onto silica nanoparticles for their repeated use. We first thoroughly examined solution conditions that affect the stability of uranyl-binding proteins and identified suitable physical conditions that are beneficial for the non-covalent SUP immobilization and subsequent capture of uranyl. We found that the molecular linker between SUP and silica binding peptide plays an important role in improving interaction strength between the silica nanoparticles and the engineered proteins. Consequently, we have demonstrated repeatable recovery and enrichment of uranyl ions from synthetic seawater using the engineered protein on silica nanoparticles. Our approach does not require chemical modification of silica nanoparticles, yet offers strong attachment of SUP to the silica interface and thus attractive reusability of protein-silica nanomaterials.