Adsorption/Desorption Behaviors and SERS Chemical Enhancement of 6-Mercaptopurine on a Nanostructured Gold Surface: The Au20 Cluster Model

Abstract

Computational approaches are employed to elucidate the binding mechanism and the SERS phenomenon of 6-mercaptopurine (6MP) adsorbed on the tetrahedral Au20 cluster as a simple model for a nanostructured gold surface. Computations are carried out in both vacuum and aqueous environments using a continuum model. In the gaseous phase and neutral conditions, interaction of 6MP with the gold cluster is mostly dominated by a covalent Au−S bond and partially stabilized by the Au⋅⋅⋅H−N coupling. However, in acidic solution, the nonconventional Au⋅⋅⋅H−S hydrogen-bond becomes the most favorable binding mode. The 6MP affinity for gold clusters decreases in the order of vacuum > neutral solution > acidic medium. During the adsorption, the energy gap of Au20 substantially declines, leading to an increase in its electrical conductivity, which can be converted to an electrical noise. Moreover, such interaction is likely a reversible process and triggered by either the low pH in sick tissues or the presence of cysteine residues in protein matrices. While N−H bending and stretching vibrations play major roles in the SERS phenomenon of 6MP on gold surfaces in neutral solution, the strongest enhancement in acidic environment is mostly due to an Au⋅⋅⋅H−S coupling, rather than an aromatic ring-gold surface π overlap as previously proposed.

Binding Mechanism and Surface-Enhanced Raman Scattering of the Antimicrobial Sulfathiazole on Gold Nanoparticles

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Binding mechanism and SERS spectra of 5-fluorouracil on gold clusters

“…In fact, gold nanoparticles have been approved as appropriate materials for many essential applications in biomedicine, biosensors and imaging ( Bai et al, 2020 ; Bansal et al, 2020 ; Zhang et al, 2020 ). In this context, it is important to elucidate the interaction mechanism, as well as the binding nature, of the drug and gold nanoparticles ( Sotnikov et al, 2019 ; Taghizadeh et al, 2019 ; Nhat et al, 2020a ; Chen et al, 2021 ; Hang et al, 2021 ). It has been found that the interactions are mainly stabilized by a charge transfer from the electron-rich atoms of ligands to Au metals ( Nhat et al, 2020b ; Si et al, 2021 ).…”

Predicting adsorption behavior of 6-mercaptopurine anticancer drug upon polyaxazoline nanocarrier: A theoretical study

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