Stabilization of Gold Nanoparticles by 6-Mercaptopurine Monolayers. Effects of the Solvent Properties

Abstract

6-Mercaptopurine-coated gold nanoparticles (6MP-AuNPs) have been prepared by modification of the nanoparticle surface with 6MP upon displacement of the protective layer of citrate anions. The modification has been studied by UV-vis and FTIR spectroscopies. A study of the stability of these 6MP-AuNPs in aqueous solutions as a function of ionic strength and pH has shown the importance of the charges on the stabilization. The protonation of N9 of the 6MP molecules brings about a sudden flocculation phenomenon. However, the flocculation is reversible upon changing the pH to values where the molecules become newly charged. Evidence of the competence between the interaction of capping solvent molecules and the attractive forces between particles is also shown in this paper.

Determination of 6‐mercaptopurine in the presence of uric acid using modified multiwall carbon nanotubes‐TiO2 as a voltammetric sensor

“…Recently, in order to obtain an effective separation and sensitive detection, some coupled methods such as capillary electrophoresis with laser‐induced fluorescence,16 liquid chromatography with electrochemical detection, 17 and liquid chromatography with microdialysis 18 have been used for monitoring 6‐MP. 6‐MP‐coated gold nanoparticles have more recently been prepared with excellent stability and the enhanced spectroscopic signal has also been used for detecting 6‐MP 19–21. However, there still remain certain limitations in spectrofluorimetric and chromatographic methods that include selecting a suitable column or mobile phase, finding a suitable reactant for the post‐column reaction (in order to increase sensitivity) in liquid chromatography, and facing many interfering substances in spectrofluorimetric methods.…”

Voltammetric determination of 6-mercaptopurine using [Co(phen)3]3+/MWNT modified graphite electrode

“…Recently, in order to obtain an effective separation and sensitive detection, some coupled methods have been used to monitor the 6-MP concentration such as CE with laser-induced fluorescence (LIF) [14], liquid chromatography and electrochemical detection (LC-ECD) [15], liquid chromatography and electrochemical detection (LC-ECD) with microdialysis [16]. Recently, 6-MP-coated gold nanoparticles with excellent stability have been prepared and the enhanced spectroscopy was also used for detecting 6-MP [17][18][19]. However, these techniques required the complicated extraction or derivation procedures.…”

Label‐Free, Non‐Derivatization CRET Detection Platform for 6‐Mercaptopurine Based on the Distance‐Dependent Optical Properties of Gold Nanoparticles

“…This hypothesis was supported by the fact that the fluorescence intensity of fluorescein (4.0 μmol L −1 ) decreased remarkably in the presence of AuNPs (4.3 nmol L −1 ; Figure 2 b). The addition of 6‐mercaptopurine (9.0 μmol L −1 ) into a solution of AuNPs (4.3 nmol L −1 ) caused a slight red shift of the absorption peak of the AuNPs, presumably owing to the adsorption of 6‐mercaptopurine onto the surface of the AuNPs through the formation of covalent AuS bonds (Figure 1, d) 45. It has been reported that metal ions can be used as the cross‐linking agents to speed up the aggregation of AuNPs through cooperative metal–ligand interactions 46–48.…”

“…The fluorescein molecules in the excited state transferred their energies to the AuNPs, thereby resulting in a significant decrease in the CL signal of the TCPO–H 2 O 2 –fluorescein reaction. 6‐Mercaptopurine could assemble on the surface of the AuNPs by forming covalent AuS bonds 45. Aggregation of the AuNPs occurred in the presence of Cu 2+ ions through cooperative metal–ligand interactions,46–48 thereby causing a red‐shift in the absorption band of the AuNPs.…”

“…6-Mercaptopurine could assemble on the surface of the AuNPs by forming covalent AuÀS bonds. [45] Aggregation of the AuNPs occurred in the presence of Cu 2+ ions through cooperative metal-ligand interactions, [46][47][48] thereby causing a red-shift in the absorption band of the AuNPs. The absorbance of the AuNPs decreased dramatically at 520 nm, with the concomitant appearance of a new absorption band at around 721.0 nm.…”