Growth of Highly Fluorescent Polyethylene Glycol- and Zwitterion-Functionalized Gold Nanoclusters

Abstract

We have prepared and characterized a new set of highly fluorescent gold nanoclusters (AuNCs) using one-step aqueous reduction of a gold precursor in the presence of bidentate ligands made of lipoic acid anchoring groups, appended with either a poly(ethylene glycol) short chain or a zwitterion group. The AuNCs fluoresce in the red to near-infrared region of the optical spectrum with emission centered at ∼750 nm and a quantum yield of ∼10-14%, and they exhibit long fluorescence lifetimes (up to ∼300 ns). Dispersions of these AuNCs exhibit great long-term colloidal stability, over a wide range of pHs (2-13) and in the presence of high electrolyte concentrations, and a strong resistance to reducing agents such as glutathione. The growth strategy further permitted the controlled, in situ functionalization of the NCs with reactive groups (e.g., carboxylic acid or amine), making these nanoclusters compatible with common and simple-to-implement coupling strategies, such as carbodiimide chemistry. These properties combined make these fluorescent NCs greatly promising for use in various imaging and sensing applications where NIR and long-lived excitations are desired.

Multivalent Glycosylation of Fluorescent Gold Nanoclusters Promotes Increased Human Dendritic Cell Targeting via Multiple Endocytic Pathways

“…Thioctic-zwitterion (Zw, M ~412 g.mol-1) was synthesized following the protocol described elsewhere 40,53 . Phalloidin (Sigma) and 1 µg/ml Hoechst 33258 (Sigma), respectively.…”

Zwitterion functionalized gold nanoclusters for multimodal near infrared fluorescence and photoacoustic imaging

“…28,30,34 Molar ratio Au:ligand has been modified during the synthesis in order to play both on the final metal core size and on the ligand coverage. Thus, a molar ratio Au > ligand leads to NP for Au:Zw = 2:1 and 5:1 and a molar ratio Au ≤ ligand leads to NCs for Au:Zw = 1:1, 1:2, and 1:5.…”

Ultra-small fluorescent inorganic nanoparticles for bioimaging

“…89,97 In addition to dendrimers, some other polymers such as multiarm star polyglycerol-block-poly(acrylic acid) and DHLA functionalized PEG were used to stabilize metal nanoclusters. 98,99 Recently, we used multidentate thioether-terminated 50 poly(methacrylic acid) (PTMP-PMAA) (Figure 7(a)) as ligand to successfully prepare water-soluble fluorescent Au nanoclusters through reduction of HAuCl 4 with NaBH 4 . 100 Due to the strong steric effect, this polymer ligand has also been used to prepare ultra-small magnetic iron oxide nanoparticles.…”