Features of Thiolated Ligands Promoting Resistance to Ligand Exchange in Self-Assembled Monolayers on Gold Nanoparticles

Abstract

An important feature necessary for biological stability of gold nanoparticles is resistance to ligand exchange. Here, we design and synthesize self-assembled monolayers of mixtures of small ligands on gold nanoparticles promoting high resistance to ligand exchange. We use as ligands short thiolated peptidols, e.g. H-CVVVT-ol, and ethylene glycol terminated alkane thiols (HS-C 11 -EG 4 ). We present a straightforward method to evaluate the relative stability of each ligand shell against ligand exchange with small thiolated molecules. The results show that a ligand with a 'thin' stem, such as HS-C 11 -EG 4 , is an important feature to build a highly packed self-assembled monolayer and provide high resistance to ligand exchange. The greatest resistance to ligand exchange was found for the mixed ligand shells of the pentapeptidols H-CAVLT-ol or H-CAVYT-ol and the ligand HS-C 11 -EG 4 at 30:70 (mole/mole). Mixtures of ligands of very different diameters, such as the peptidol H-CFFFY-ol and the ligand HS-C 11 -EG 4 , provide only a slightly lower stability against ligand exchange. These ligand shells are thus likely to be suitable for long-term use in biological environments. The method developed here provides a rapid screening tool to identify nanoparticles likely to be suitable for use in biological and biomedical applications.

Ligand Layer Engineering To Control Stability and Interfacial Properties of Nanoparticles

“…14,[27][28][29][30][31] Alternative strategies have also emerged e.g. based on peptides or peptidols, 19,[32][33][34] and on zwitterionic ligands 35,36 or zwitterionic ligand layers i.e. mixed layers from oppositely charged molecules.…”

Enhanced inhibition of influenza virus infection by peptide-noble metal nanoparticle conjugates

“…where A 650nm and A 520nm are the absorbance of gold nanoparticles at 650 nm and 520 nm, respectively, and A ref650nm and A ref520 are the absorbance of water at 650 nm and 520 nm, respectively (Chen et al, 2012). For comparison of results, this primary stability parameter was normalised by dividing the AP value of control ligand capped gold nanoparticles measured in milli Q water where [DTT] = 0.…”

“…The mix matrix ligand shell of 70:30 mole/mole peptidol and alkanethiol ethylene glycol assembled on gold nanoparticles has well characterised stability with respect to ligand exchange and non-specific binding (Duchesne et al, 2008a, Chen et al, 2012, but the effect of incorporating the FluPep amino acid sequence at the Cterminus of the CVVVT matrix sequence is unknown. Since the molecular weight of FluPep ligand (2967 Da) is greater than that required for group separation on Sephadex G25 (1000 Da) additional purification by means of washes on a 10 kDa cut off Nanosep filter were included to ensure removal of any free FluPep ligand.…”

“…This indicates that the FluPep sequence did not reduce the stability of the gold nanoparticles under these standard conditions. A more stressful test is ligand exchange with small thiols (Chen et al, 2012, Duchesne et al, 2008a, Schulz et al, 2016, Schulz et al, 2013. Ligand-exchange results in a ligand shell that is unable to prevent electrolyte-induced aggregation of the nanoparticles, demonstrated by a decrease in the plasmon absorption at 520 nm.…”

Frontiers in Optical Bio-Imaging and Microscopy

“…Paramelle et al [4] describe their work on the stabilisation of gold nanoparticles for use as bio-imaging probes. In particular, they show how the shell design affects the overall stability of the nanoparticle.…”