Protein-mediated autoreduction of gold salts to gold nanoparticles

Here we report for the first time that proteins can function as unique reducing agents to produce gold nanoparticles from gold salts. We demonstrate that three different proteins, namely, bovine serum albumin (BSA), Rituximab (RIT—an anti-CD20 antibody) and Cetuximab (C225—anti-EGFR antibody), reduce gold salts to gold nanoparticles (GNP). Interestingly, among all the three proteins tested, only BSA can reduce gold salts to gold nanotriangles (GNT). BSA-induced formation of GNT can be controlled by carefully selecting the reaction condition. Heating or using excess of ascorbic acid (AA) as additional reducing agent shifts the reaction towards the formation of GNP with flower-like morphology, whereas slowing down the reaction either by cooling or by adding small amount of AA directs the synthesis towards GNT formation. GNT is formed only at pH 3; higher pHs (pH 7 and pH 10) did not produce any nanoparticles, suggesting the involvement of specific protein conformation in GNT formation. The nanomaterials formed by this method were characterized using UV–visible (UV–vis) spectroscopy and transmission electron microscopy (TEM). This is an important finding that will have uses in various nanotechnological applications, particularly in the green synthesis of novel nanomaterials based on protein structure.

[1]  P. Kahn,et al.  Unfolding and refolding of bovine serum albumin at acid pH: ultrasound and structural studies. , 2006, Biophysical journal.

[2]  Absar Ahmad,et al.  Role of halide ions and temperature on the morphology of biologically synthesized gold nanotriangles. , 2006, Langmuir : the ACS journal of surfaces and colloids.

[3]  Catherine J. Murphy,et al.  Fine-tuning the shape of gold nanorods , 2005 .

[4]  Chad A. Mirkin,et al.  Rapid Thermal Synthesis of Silver Nanoprisms with Chemically Tailorable Thickness , 2005 .

[5]  Shiv Shankar,et al.  Controlling the Optical Properties of Lemongrass Extract Synthesized Gold Nanotriangles and Potential Application in Infrared-Absorbing Optical Coatings , 2005 .

[6]  Bo Li,et al.  Synthesis and optical properties of silver nanowire arrays embedded in anodic alumina membrane , 2004 .

[7]  Balaprasad Ankamwar,et al.  Biological synthesis of triangular gold nanoprisms , 2004, Nature materials.

[8]  C. Murphy,et al.  Room temperature, high-yield synthesis of multiple shapes of gold nanoparticles in aqueous solution. , 2004, Journal of the American Chemical Society.

[9]  John Ballato,et al.  Monopod, bipod, tripod, and tetrapod gold nanocrystals. , 2003, Journal of the American Chemical Society.

[10]  C. Mirkin,et al.  Controlling anisotropic nanoparticle growth through plasmon excitation , 2003, Nature.

[11]  Younan Xia,et al.  Shape-Controlled Synthesis of Gold and Silver Nanoparticles , 2002, Science.

[12]  Jinwoo Cheon,et al.  Single-crystalline star-shaped nanocrystals and their evolution: programming the geometry of nano-building blocks. , 2002, Journal of the American Chemical Society.

[13]  L. Dick,et al.  Metal film over nanosphere (MFON) electrodes for surface-enhanced Raman spectroscopy (SERS): Improvements in surface nanostructure stability and suppression of irreversible loss , 2002 .

[14]  C. Mirkin,et al.  Photoinduced Conversion of Silver Nanospheres to Nanoprisms , 2001, Science.

[15]  A. Requicha,et al.  Plasmonics—A Route to Nanoscale Optical Devices , 2001 .

[16]  Catherine J. Murphy,et al.  Seed‐Mediated Growth Approach for Shape‐Controlled Synthesis of Spheroidal and Rod‐like Gold Nanoparticles Using a Surfactant Template , 2001 .

[17]  J. Cheon,et al.  Controlled synthesis of multi-armed CdS nanorod architectures using monosurfactant system. , 2001, Journal of the American Chemical Society.

[18]  M. El-Sayed,et al.  Some interesting properties of metals confined in time and nanometer space of different shapes. , 2001, Accounts of chemical research.

[19]  M. El-Sayed,et al.  Simulation of the Optical Absorption Spectra of Gold Nanorods as a Function of Their Aspect Ratio and the Effect of the Medium Dielectric Constant , 1999 .

[20]  P. Sadler,et al.  pH-induced structural transitions of bovine serum albumin. Histidine pKa values and unfolding of the N-terminus during the N to F transition. , 1993, European journal of biochemistry.

[21]  V. Fencl,et al.  The role of serum proteins in acid-base equilibria. , 1991, The Journal of laboratory and clinical medicine.

[22]  A. Bode,et al.  Spontaneous decay of oxidized ascorbic acid (dehydro-L-ascorbic acid) evaluated by high-pressure liquid chromatography. , 1990, Clinical chemistry.

[23]  Absar Ahmad,et al.  Synthesis of Gold Nanotriangles and Silver Nanoparticles Using Aloevera Plant Extract , 2006, Biotechnology progress.

[24]  D C Carter,et al.  Structure of serum albumin. , 1994, Advances in protein chemistry.