Solution Effects on Peptide-Mediated Reduction and Stabilization of Au Nanoparticles.

Biomimetic methods for the preparation and application of inorganic nanomaterials represent a unique avenue to sustainably generating functional materials with long-term activity. Typically, for the fabrication of these structures, the peptide is mixed with metal ions in solution prior to the addition of an exogenous reductant such as NaBH4, leading to nanoparticle nucleation and growth. In biological systems, strong reductants such as NaBH4 are not available, thus different metal ion reduction methods must be exploited. Recent work has shown that the AuBP1 peptide (WAGAKRLVLRRE), a Au binding peptide with an N-terminal tryptophan, can spontaneously reduce Au3+ without an exogenous reductant. Remarkably, this system initially demonstrated the formation of large Au aggregates that disassemble to form individual Au nanoparticles, stabilized by the peptide bound to the inorganic surface. In this contribution, we demonstrate the significant effects of aqueous solvent-processing conditions (pH, ionic strength, and ion composition) on the rate of particle evolution. Understanding how such effects alter the metal ion reduction process and subsequent nanoparticle fabrication is important in controlling the final structure/function relationship of the resultant peptide-capped materials. This work identifies conditions that may enhance nanoparticle synthesis using biomimetic approaches where the peptide has complete control over the complexation, reduction, nucleation, and growth of nanomaterials.