Bélanger-Bouliga Marilyne, Mahious Raja, Pitroipa Poulomsongo Iman, Nazemi Ali
Department of Chemistry, Université du Québec à Montréal, C.P.8888, Succursale Centre-Ville, Montréal, QC H3C 3P8, Canada.
Dalton Trans. 2021 Apr 28;50(16):5598-5606. doi: 10.1039/d1dt00064k.
N-Heterocyclic carbenes (NHCs) have recently emerged as viable alternatives to commonly used thiols to stabilize a variety of metal surfaces and nanoparticles. In this context, thanks to their biocompatibility and novel optical properties, NHC-stabilized gold nanoparticles (AuNPs) have been extensively studied. It has been shown that such materials exhibit improved stabilities in acidic and basic solutions, high temperatures, electrolyte solutions, cell culture media, and to some extent to nucleophilic thiols. Despite intense efforts, instability of NHC-functionalized AuNPs to thiols has been an ongoing challenge. In order to circumvent this problem, quantification of NHC desorption from nanoparticle surface by the invading thiols would constitute a necessary first step. To do this, we have first developed water-soluble azide decorated NHC-stabilized "clickable" AuNPs. Optically active perylene diimide (PDI)-tagged AuNP hybrids are then obtained by means of Cu-catalyzed alkyne-azide cycloaddition between these AuNPs and an alkyne-decorated PDI derivative. Investigation of photophysical properties of these AuNP/PDI hybrids revealed that the fluorescence of PDI molecules is effectively quenched by AuNPs in aqueous solution. The extent of NHC desorption from AuNP surface in presence of glutathione (4 mM), as a biologically relevant thiol, is then quantified by means of fluorescence emission restoration of PDI molecules upon detachment from AuNP surfaces. Our results demonstrate that while ∼20% of surface NHCs are displaced by glutathione within the first 24 h of their exposure to the thiol, ligand desorption reaches ∼45% after one week. We believe that these findings will provide more insight on true stability of NHC-stabilized materials.
N-杂环卡宾（NHCs）最近已成为常用硫醇的可行替代品，用于稳定各种金属表面和纳米颗粒。在这种情况下，由于其生物相容性和新颖的光学性质，NHC稳定的金纳米颗粒（AuNPs）已得到广泛研究。已表明，此类材料在酸性和碱性溶液、高温、电解质溶液、细胞培养基中以及在一定程度上对亲核硫醇具有更高的稳定性。尽管付出了巨大努力，但NHC功能化的AuNPs对硫醇的不稳定性一直是一个持续存在的挑战。为了规避这个问题，通过入侵硫醇对纳米颗粒表面NHC解吸进行定量将是必要的第一步。为此，我们首先开发了水溶性叠氮化物修饰的NHC稳定的“可点击”AuNPs。然后通过这些AuNPs与炔烃修饰的苝二酰亚胺（PDI）衍生物之间的铜催化炔烃-叠氮环加成反应，获得了具有光学活性的PDI标记的AuNP杂化物。对这些AuNP/PDI杂化物的光物理性质研究表明，在水溶液中，PDI分子的荧光被AuNPs有效猝灭。然后，通过PDI分子从AuNP表面脱离时的荧光发射恢复，定量测定在存在作为生物相关硫醇的谷胱甘肽（4 mM）时，NHC从AuNP表面的解吸程度。我们的结果表明，虽然约20%的表面NHC在与硫醇接触的前24小时内被谷胱甘肽取代，但一周后配体解吸率达到约45%。我们相信这些发现将为NHC稳定材料的真正稳定性提供更多见解。
