The Role of Onium Salts in the Pro-Oxidant Effect of Gold Nanoparticles in Lipophilic Environments

Andrea Baschieri; Benedetta Del Secco; Nelsi Zaccheroni; Luca Valgimigli; Riccardo Amorati

doi:10.1002/chem.201801110

The Role of Onium Salts in the Pro-Oxidant Effect of Gold Nanoparticles in Lipophilic Environments

Chemistry. 2018 Jun 26;24(36):9113-9119. doi: 10.1002/chem.201801110. Epub 2018 Jun 6.

Authors

Andrea Baschieri¹, Benedetta Del Secco², Nelsi Zaccheroni², Luca Valgimigli¹, Riccardo Amorati¹

Affiliations

¹ Department of Chemistry "G. Ciamician", University of Bologna, Via S. Giacomo 11, 40126, Bologna, Italy.
² Department of Chemistry "G. Ciamician", University of Bologna, Via F. Selmi 2, 40126, Bologna, Italy.

PMID: 29689123
DOI: 10.1002/chem.201801110

Abstract

Metal nanoparticles are reported to be toxic due to the generation of free radicals at their surface. Relatively inert thiol-capped gold nanoparticles (AuNPs) have been reported to induce radical formation in the presence of hydroperoxides, which would conflict with their potential use as inert scaffolds for the design of novel nano-antioxidants. With the aim of clarifying this aspect, we investigated the pro-oxidant activity of dodecanethiol-capped AuNPs (∼5 nm diameter), prepared through the Brust-Schiffrin synthesis, by oxygen-uptake kinetic studies. The pro-oxidant activity was found to be proportional to the impurities of the transfer agent tetraoctylammonium bromide (TOAB) left from the synthesis and decreased on repeated washing of the nanoparticles. Under identical settings similar batches of AuNP (∼9 nm diameter) prepared through the Ulman method without onium salts showed no pro-oxidant behavior. The alternative onium phase-transfer agents Oct₄ NBF₄ (Oct=octyl), Hex₄ NBF₄ (Hex=hexyl), and Hex₄ NPF₆ were comparatively investigated and showed lower pro-oxidant activity depending on the counterion (Br^- >PF₆^- >BF₄^- ).

Keywords: autoxidation; gold; nanoparticles; pro-oxidant activity; radicals.