Monodisperse phase transfer and surface bioengineering of metal nanoparticles via a silk fibroin protein corona

Uniform hydrophobic nanoparticles synthesized in nonpolar solvents possess excellent physio-chemical properties, showing great potential in biomedical applications. However, the presence of hydrophobic ligands on their surfaces limits their use under physiological conditions. Inspired by protein coronas present at the nano-bio interface, here we report a facile and universal method for phase transfer and surface bioengineering of hydrophobic nanoparticles using beta-sheet-rich silk fibroin, a FDA-approved natural protein. Due to its amphiphilicity and high mechanical stiffness, the beta-sheet-rich silk fibroin not only readily drags nanoparticles from an organic phase into aqueous media but also endows them with excellent monodispersity and long-term stability. The silk fibroin-coated nanoparticles can retain the magnetic and optical properties of the original nanoparticles, acting effectively as probes for biomedical imaging and biosensing. Furthermore, hydrophobic drugs can be easily adsorbed onto the protein coating via hydrophobic interaction, allowing the construction of promising theranostic nanoagents. Given these unique features, the strategy developed here possesses great promise in facilitating biomedical applications of hydrophobic nanomaterials.