Illuminating the Surface Corona of Biogenic Silver Nanoparticles

Biogenic nanoparticles are attractive due to their unique surface chemistry compared to chemical counterparts. Underpinning the importance of the surface layer or corona is the interaction between the nanoparticles and the environment. The surface corona provides biological identity, physical structure, colloidal stability and a chemical scaffold for modification. Understanding the structure and composition of the corona that surrounds nanoparticles enables rational design for applications. Previous investigations examining biogenic nanoparticles have purported a coating comprised of biomolecules, however a defined structure is extremely limited. We address this limitation through a detailed examination involving both in situ analyses of silver nanoparticle dispersions (indirect) produced by Fusarium oxysporum and desorbing the surface corona (direct). Using a series of orthogonal characterization techniques we show evidence the surface corona of biogenic silver nanoparticles is comprised of a thin mixed layer of peptides and carbohydrates. We propose the origin of these peptides is from adaptive or protective proteins triggered by environmental stress. The differences and limitations in our two approaches are highlighted. Our findings make it clear that methods used to characterize the inherent surface corona of biogenic silver nanoparticles should be carefully documented for consistent and judicious interpretations.