Influence of the Spatial Conformation of Charged Ligands on the Optical Properties of Gold Nanoclusters

Abstract

Photoluminescent gold nanoclusters (Au NCs) were synthesized in one step in aqueous conditions using a mixture of glutathione and (mono or multivalent) glutathione modified arginine peptides. By controlling the ratio of co-ligands, we investigated how the multivalency and the amount of arginines influenced the growth of Au NCs, their surface chemistry, their colloidal stability, and their optical properties. We demonstrated using two-dimensional nuclear magnetic resonance spectroscopy that the organisation of the ligand on the Au surface was composed by an inner rigid layer and an outer flexible part via inter-and/or intra-ligand spatial proximity. This directly impacted the structure of the Au NCs, as confirmed by gel electrophoresis, high transmission electron microscopy, diffusion ordered spectroscopy and mass spectrometry. Increasing arginine content also induced an increase of positive surface charge and an enhancement of the near infrared emission intensity at ~670 nm with quantum yield up to 10% validating the significant influence of the ligands to the optical properties of Au NCs.

Augmented interaction of multivalent arginine coated gold nanoclusters with lipid membranes and cells

“…In this case, the uorescence enhancement has been mainly attributed to a rigidication of the ligand shell around the gold core reducing the non-radiative losses. 25 HRTEM pictures (Fig. 1B) showed metal core size below 3 nm for all samples except for AuSG-3Arg which contained larger particles (>10 nm, NPs).…”

“…Au NCs stabilized by SG or SG-XArg (X ¼ 1, 2 or 3) were prepared by wet chemistry as described in our previous study 25 and reported in the ESI † (Section 1). Au NCs were dissolved in PBS (10 mM, pH 7.4) at 4 mgAu mL À1 and ltered through a 0.2 mm syringe lter (PTFE membrane).…”

“…COLO 829 cells were either seeded in a 6-well plate (250 000 cells per well in 5 mL of DMEMc) 1 day before the experiment or used as cell suspension (500 000 cells per Eppendorf). The Au NCs were added at 37 C or 4 C to the cells in DMEMc or DMEM at different concentrations (10,25 or 100 mgAu mL À1 ) for the indicated times (5, 15, 30, 45 min or 1 h). In both cases, the cells were centrifugated before being resuspended in PBS and analyzed.…”

“…The extended optical and physico-chemical characterizations of these Au NCs have been recently reported elsewhere by our team. 25 In this study, we are particularly interested to investigate the behaviour of these positively charged Au NCs with biological barriers in presence of serum using articial phospholipid models integrated in microuidic devices 14,17,26 and then with living cells. We demonstrated how increasing slightly the positive charges on Au NC surface can lead to strong interaction with articial lipid bilayers and cell membrane in the presence of serum.…”

Atomic-level separation of thiolate-protected metal clusters

“…For this reason, PAGE is also often used to examine the distribution of chemical compositions of a product, optimize reaction conditions, elucidate the degraded processes, and track reactions. [102][103][104][105][106][107][108][109][110] For example, Tsukuda and Teranishi et al observed that Au 25 (SG) 18 was a major product when a triphenylphosphine (PPh 3 )-protected Au cluster was mixed with glutathione (GSH). They attempted to optimize the reaction conditions to selectively synthesize such a stable cluster with atomic precision.…”