pH-Dependent Synthesis of Anisotropic Gold Nanostructures by Bioinspired Cysteine-Containing Peptides

pH-Dependent Synthesis of Anisotropic Gold Nanostructures by Bioinspired Cysteine-Containing Peptides

Author Tofanello, Aryane Google Scholar
Miranda, Erica G. A. Google Scholar
Dias, Igor W. R. Google Scholar
Lanfredi, Alexandre J. C. Google Scholar
Arantes, Jeverson T. Google Scholar
Juliano, Maria A. Autor UNIFESP Google Scholar
Nantes, Iseli L. Google Scholar
Abstract In the present study, alkaline peptides AAAXCX (X = lysine or arginine residues) were designed based on the conserved motif of the enzyme thioredoxin and used for the synthesis of gold nanoparticles (GNPs) in the pH range of 2-11. These peptides were compared with free cysteine, the counterpart acidic peptides AAAECE and gamma-ECG (glutathione), and the neutral peptide AAAACA. The objective was to investigate the effect of the amino acids neighboring a cysteine residue on the pH-dependent synthesis of gold nanocrystals. Kohn-Sham density functional theory (KS-DFT) calculations indicated an increase in the reducing capacity of AAAKCK favored by the successive deprotonation of their ionizable groups at increasing pH values. Experimentally, it was observed that gold speciation and the peptide structure also have a strong influence on the synthesis and stabilization of GNPs. AAAKCK produced GNPs at room temperature, in the whole investigated pH range. By contrast, alkaline pH was the best condition for the synthesis of GNP assisted by the AAARCR peptide. The acidic peptides produced GNPs only in the presence of polyethylene glycol, and the synthesis using AAAECE and gamma-ECG also required heating. The ionization state of AAAKCK had a strong influence on the preferential growth of the GNPs. Therefore, pH had a remarkable effect on the synthesis, kinetics, size, shape, and polydispersity of GNPs produced using AAAKCK. The AAAKCK peptide produced anisotropic decahedral and platelike nanocrystals at acidic pH values and spherical GNPs at alkaline pH values. Both alkaline peptides were also efficient capping agents for GNPs, but they produced a significant difference in the zeta potential, probably because of different orientations on the gold surface.
Language English
Sponsor FAPESP [2012/07456-7, 2015/17688-0]
CAPES [5583/2014-04]
Grant number FAPESP:2012/07456-7
Date 2016
Published in Acs Omega. Washington, v. 1, n. 3, p. 424-434, 2016.
ISSN 2470-1343 (Sherpa/Romeo, impact factor)
Publisher Amer Chemical Soc
Extent 424-434
Access rights Open access Open Access
Type Article
Web of Science ID WOS:000391204000013

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