Stability of the Disulfide Bond in Cystine Adsorbed on Silver and Gold Nanoparticles As Evidenced by SERS Data

Abstract

In relation with the difficulties encountered in previous works concerning the preservation of the S–S linkage in cystine (Cys-Cys dimer) on Ag nanoparticles (NPs), we present here a systematic investigation on both cysteine and cystine as a function of various parameters governing the preparation of metal substrates. Surface-enhanced Raman scattering (SERS) was used as a probe for analyzing (i) the integrity of the disulfide bonds of the adsorbed dimers, (ii) the influence of the metal nature, the reduction protocol as well as the Cys-Cys concentration on the adsorption, (iii) the terminal groups through which the interaction with metal surfaces take place, and (iv) the side chain conformation of the adsorbed molecules. From the whole set of experimental data collected in this work, it appears that large size Au NPs, prepared at low citrate concentration, can be considered as the most appropriate substrates for ensuring the integrity of disulfide linkages. Although Ag NPs prepared with hydroxylamine lead to the cleavage of dimers at low concentration, they have shown their adequacy to keep intact S–S bonds beyond a concentration threshold of ∼200 μM. Based on the examination of the SERS data recorded as a function of dimer concentration, we can now assume that this effect is mainly due to the bidentate and monodentate binding of Cys-Cys dimers at low and high concentrations, respectively, facilitating or not their cleavage on Ag surfaces.

The role of adatoms in chloride-activated colloidal silver nanoparticles for surface-enhanced Raman scattering enhancement

“…This feature was observed also for zwitterionic L-cysteine [34–36]. In view of the results presented here, L-cysteine is chemisorbed via its COO − group to the silver surface at Ag + SERS-active sites when using cit-AgNPs as a SERS substrate.…”

Nitroxide-coated silver nanoparticles: synthesis, surface physicochemistry and antibacterial activity

“…40,47,51 On the other hand, the presence of intact disulphide 70 bonds in organic layer on silver nanoparticles surface was also reported. 18,52 Our quantitative XPS results (presented in Table 3) show that during the chemisorption process ca. 80% of disulphide bonds are cleaved and attached to the resulting monoradicals are attached to the silver surface as thiolate moieties (ca.…”

Anchoring Sites of Fibrillogenic Peptide Hormone Somatostatin-14 on Plasmonic Nanoparticles

“…To preserve the structural integrity of this peptide, a special attention was paid to avoid the breakdown of this S−S bond, particularly on Ag NPs, by following the procedure described recently. 24 To establish our nanofabrication protocol, the main parameters to be adjusted were (i) the metal nature and reduction protocol, and (ii) the adequate size of Ag and Au NPs for SERS experiments. Here, the SERS sensitivity was maximized by tuning the excitation wavelength over the plasmon resonance band, which depends on the size of elaborated NPs.…”

“…A total of 50 mL of HAu Cl 4 2% (by weight) was heated to boiling before addition of a variable volume (V) of Na 3 -citrate 1% (by weight). 24 Au NPs with approximate diameters ranging between 15 and 150 nm (15,50, 100, and 150 nm) were prepared by using the following citrate solution volumes: V = 1.00, 0.50, 0.20, and 0.15 mL. Finally, they were aged 2 weeks before use.…”