PH induced protein-scaffold biosynthesis of tunable shape gold nanoparticles

Abstract

In this paper, a pH-inductive protein-scaffold biosynthesis of shape-tunable crystalline goldnanoparticles at room temperature has been developed. By simple manipulation of thereaction solution’s pH, anisotropic gold nanoparticles including spheres, triangles and cubescould be produced by incubating an aqueous solution of sodium tetrachloroaurate withDolichomitriopsis diversiformis biomasses after immersion in ultrapure Millipore waterovernight. A moss protein with molecular weight of about 71 kDa and pI of 4.9 wasthe primary biomolecule involved in the biosynthesis of gold nanoparticles. Thesecondary configuration of the proteins by CD spectrum implied that the mossprotein could display different secondary configurations including random coil,α-helix and intermediate conformations between random coil andα-helix for the experimental pH solution. The growth process of gold nanoparticles furthershowed that the moss protein with different configurations provided the template scaffoldfor the shape-controlled biosynthesis of gold nanoparticles. The constrained shape of thegold nanoparticles, however, disappeared in boiled moss extract. The gold nanoparticleswith designed morphology were successfully reconstructed using the moss protein purifiedfrom the gold nanoparticles. Structural characterizations by SEM, TEM and SAEDshowed that the triangular and cubic gold nanoparticles were single crystalline.