Photochemical transformations of thiolated polyethylene glycol coatings on gold nanoparticles
Stacey M. Louie, Justin M. Gorham, Eric A. McGivney, Jingyu Liu, Kelvin B. Gregory, Vincent A. Hackley
Photochemical reactions can result in significant transformations of manufactured nanomaterials in sunlit environments. While transformations of inorganic nanoparticles (NPs) have been investigated extensively, much less attention has been focused on the direct impact of aqueous photochemical reactions on adsorbed organic macromolecules that form the NP corona and strongly mediate the surface interactions and reactivity that control NP transport, fate, and toxicity in natural and biological environments. Here, we assess the transformations of methoxy polyethylene glycol thiol (mPEGSH) coatings on gold NPs (Au-mPEGSH NPs) under controlled UV irradiation. Physical characterization methods indicated a decrease in the adsorbed layer thickness of polymer within 24 h of UV irradiation, resulting in increased susceptibility of the transformed NPs to aggregation. Surface chemistry analyses, including X-ray photoelectron spectroscopy (XPS), showed loss of the ether groups but persistence of reduced S on the AuNP surface, indicative of a chain scission mechanism that results in different NP surface properties from that of either the native AuNP or the initial Au-mPEGSH NP. UV irradiated solutions of mPEGSH in the presence and absence of the Au-mPEGSH NPs were also evaluated by liquid chromatography mass spectrometry (LC-MS). In contrast to the chemisorbed polymer on the Au NPs, the primary observed transformation of the dissolved mPEGSH was thiol oxidation to disulfides without extensive scission to yield lower molar mass fragments. This study demonstrates that transformations of NP-adsorbed coatings must be considered to accurately predict NP fate in environmental systems. These transformations are not predictable from reactions of the dissolved polymer alone, and hence sensitive surface characterization methods will be required to more directly probe the fundamental reactions involved in the photochemical transformation of the corona and the potential role of ....
Royal Society of Chemistry Journal Environmental Science: Nano
, Gorham, J.
, McGivney, E.
, Liu, J.
, Gregory, K.
and Hackley, V.
Photochemical transformations of thiolated polyethylene glycol coatings on gold nanoparticles, Royal Society of Chemistry Journal Environmental Science: Nano, [online], https://doi.org/10.1039/C6EN00141F
(Accessed November 28, 2023)