PEGylated N-Heterocyclic Carbene Anchors Designed To Stabilize Gold Nanoparticles in Biologically Relevant Media

Abstract

N-Heterocyclic carbenes (NHCs) have emerged as versatile ligands for surface functionalization. Their ease of synthesis and ability to form strong bonds with a range of substrates provide a unique complement to traditional surface modification methods. Gold nanoparticles (NPs) are a particularly useful class of materials whose applications intimately depend on surface functionalization. Here we report the development of PEGylated-NHC ligands for Au-NP surfaces and the first example of NHC-functionalized NPs that are compatible with biologically relevant conditions. Our PEGylated-NHC-Au-NPs are stable toward aggregation in aqueous solutions in the pH range of 3-14, in <250 mM electrolyte solutions, at high and low temperatures (95 and -78 °C), in cell culture media, and in aqueous H2O2 solutions. This work demonstrates for the first time that NHCs can serve as anchors for water-soluble Au-NPs and opens the door to potential biomedical applications of NHC surface anchors.

Atomically precise organomimetic cluster nanomolecules assembled via perfluoroaryl-thiol SNAr chemistry

“…Next, to test whether more complex molecular architectures could also be introduced onto the clusters, we turned our attention to poly(ethylene glycol) (PEG) 4,22,45,46 . Complete 12-fold conjugation between 2 and commercially available mPEG-thiol (MW avg = 356 Da) occurred within 24 hours at room temperature, yielding OCN 2i (Table 2, entry 1; Supplementary Information, pages 19–20 and 91–97).…”

“…Hybrid AuNP systems are especially attractive due to the synthetic ease of producing systems that are well-defined and tunable in size. Nevertheless, it is well known that thiolated ligands often can desorb or undergo exchange processes with other surfactants in solution over short periods of time, and furthermore, various electrochemical conditions or elevated temperatures (>60 °C) dramatically accelerate these processes 10,19–22 . These events can be explained primarily by the relatively weak nature of the gold–thiolate bond (40–50 kcal/mol) 19 .…”

Optically active histidin-2-ylidene stabilised gold nanoparticles

“…[21][22][23][32][33][34] Therefore, to form AuNPs, t BuNH 2 ÁBH 3 was used as the reducing agent and added to solutions of either 2(L) or 2(D) in THF which resulted in the formation of a deep red solution, with no signs of aggregate formation. In order to isolate the pure AuNP, excess of reducing agent had to be removed.…”

N-Heterocyclic Carbene Ligands for Au Nanocrystal Stabilization and Three-Dimensional Self-Assembly

“…Recently, NHC-based SAMs and NHC-PEG conjugates were both shown to provide high resistance to hydrogen peroxide treatments to Au(111) surfaces and Au NCs, respectively. 42,47 …”

“…26,32−34,37,39,43 The enhanced stability of NHC-based SAMs and NPs to oxidative treatments was reported very recently. 42,47 …”