A Facile Route to Tailoring Peptide-Stabilized Gold Nanoparticles Using Glutathione as a Synthon

Abstract

Abstract:The preparation of gold nanoparticles (AuNPs) of high purity and stability remains a major challenge for biological applications. This paper reports a simple synthetic strategy to prepare water-soluble peptide-stabilized AuNPs. Reduced glutathione, a natural tripeptide, was used as a synthon for the growth of two peptide chains directly on the AuNP surface. Both nonpolar (tryptophan and methionine) and polar basic (histidine and dansylated arginine) amino acids were conjugated to the GSH-capped AuNPs. Ultracentrifugation concentrators with polyethersulfone (PES) membranes were used to purify precursor materials in each stage of the multi-step synthesis to minimize side reactions. Thin layer chromatography, transmission electron microscopy, UV-Visible, 1 H-NMR, and fluorescence spectroscopies demonstrated that ultracentrifugation produces high purity AuNPs, with narrow polydispersity, and minimal aggregation. More importantly, it allows for more control over the composition of the final ligand structure. Studies under conditions of varying pH and ionic strength revealed that peptide length, charge, and hydrophobicity influence the stability as well as solubility of the peptide-capped AuNPs. The synthetic and purification strategies used provide a facile route for developing a library of tailored biocompatible peptide-stabilized AuNPs for biomedical applications.

Cadmium sulfide quantum dots induce oxidative stress and behavioral impairments in the marine clam Scrobicularia plana

“…The CdS quantum dots were previously characterized in deionized water and seawater; it was observed that the majority of CdS quantum dots kept their nanoscale dimensions (3-10 nm) in all media tested [12]. The behavior of polypeptide-stabilized NPs is complex, and, depending on the combination of amino acids present, the stability of the resulting particles to aggregation can be very variable, as evidenced recently by Ho Wu et al [29]. However, the CdS quantum dots used in the present study were stabilized by the tripeptide glutathione, which may provide stability in neutral pH saline media by a mechanism derived from the electrostatic repulsion between negatively charged carboxylic groups in the forms of zwitterions.…”

“…However, the CdS quantum dots used in the present study were stabilized by the tripeptide glutathione, which may provide stability in neutral pH saline media by a mechanism derived from the electrostatic repulsion between negatively charged carboxylic groups in the forms of zwitterions. The behavior of polypeptide-stabilized NPs is complex, and, depending on the combination of amino acids present, the stability of the resulting particles to aggregation can be very variable, as evidenced recently by Ho Wu et al [29].…”

The Impact of Surface Ligands and Synthesis Method on the Toxicity of Glutathione-Coated Gold Nanoparticles

“…Although close nanoparticle-nanoparticle interactions are found in solution, the UV-Vis absorbance spectrum of the conjugated Au-GSH NPs showed a surface plasmon resonance (SPR) at λ max at 522 nm ( Figure S2e ) indicating no significant red-shift of the SPR band resulting from aggregation of the materials after surface conjugation of terminal amino acids and purification. Similarly, no significant change in the diameter, hydrodynamic radius, and SPR band of the Au-GSH-(X) 2 -U3 was observed after multiple purification steps ( Figure S3 ) [ 21 ].…”

“…However, it is possible that there is less GSH on the surface than estimated and that Trp is coupling to the amine of GSH to form a GSH-(X) 3 species. While we were not able to confirm the ligand structure of Au-GSH-X 2 -U2 NPs, we were able to confirm the composition of the ligand structure of Au-GSH-X 2 -U3 NPs by 1 H NMR spectroscopy [ 21 ]. Cyanide and HCl etched samples of Au-GSH-X 2 -U3 in methanol showed the presence of only free GSH-X 2 in samples prepared by U3 ligands [ 21 ].…”

“…GSH is found in high intracellular concentrations; thus, on the surface of the NP, this modified peptide sequence might serve as a good biomimic allowing for high NP uptake and potentially increasing bioavailability [ 20 ]. Following conjugation with GSH, NPs were further conjugated with sequences of amino acids (Trp, His or Met) by activating the terminal carboxyl groups of glutamic acid and glycine from GSH via the coupling reagents EDC and NHS [ 21 , 22 ].…”