Polyethylene glycol functionalized gold nanoparticles: the influence of capping density on stability in various media

Abstract

Thiol-terminated polyethylene glycol (PEG) is commonly used to functionalize the surface of gold nanoparticles (AuNPs) in order to improve their in vivo stability and to avoid uptake by the reticular endothelial system. Although it has been reported that AuNPs functionalized with tethered PEG are stable in biological media, the influence of chain density remains unclear. This study investigates the influence of PEG capping density on the stability of washed and dried AuNPs in: water, phosphate-buffered saline solution (PBS), phosphate-buffered saline solution containing bovine serum albumin (PBS/BSA), and dichloromethane (DCM). PEG coating had a dramatic effect on stability enabling stable suspensions to be produced in all the media studied. A linear relationship was observed between capping density and stability in water and DCM with a somewhat lower stability observed in PBS and PBS/BSA. A maximum PEG loading level of ∼14 wt.% was achieved, equivalent to a PEG surface density of ∼1.13 chains/nm 2 .

Uptake efficiency of surface modified gold nanoparticles does not correlate with functional changes and cytokine secretion in human dendritic cells in vitro

“…Analysis by DLS showed that carboxyl-functional PEG AuNPs display a larger hydrodynamic diameter than aminefunctional PEG AuNPs, despite a similar molecular weight (Mw = 5000) for both PEG polymers. The difference in diameter could be attributed to different PEG surface coverages on AuNPs and was previously described by Manson et al 36 who showed that the hydrodynamic diameter of AuNPs increased from 8 nm to 19 nm as function of capping density. PVA-NH 2 and (PEG + PVA)-NH 2 coated AuNPs showed the largest diameters (Table 1), which can be explained by the presence of amine-PVA with a Mw of 240,000, which is 48 fold higher than the molecular weight of PEG and 4.8-8 fold higher than the corresponding PVA-COOH.…”

“…PVA-NH 2 and (PEG + PVA)-NH 2 coated AuNPs showed the largest diameters (Table 1), which can be explained by the presence of amine-PVA with a Mw of 240,000, which is 48 fold higher than the molecular weight of PEG and 4.8-8 fold higher than the corresponding PVA-COOH. Also, electrostatic repulsion plays an important role: as the number of charges (− NH 3 + ) is higher in the amine-PVA, the electrostatic repulsion between the polymer chains also increases, 36 resulting in a higher hydrodynamic diameter. However, when surface functionalized, AuNPs displayed negative zeta potentials, despite containing positively charged amine groups (− NH 3 + ).…”

Spectroscopy-based study on the interaction between gold nanoparticle and poly(vinylpyrrolidone) molecules in a non-hydrocolloid

“…Interaction of PVP molecules with metal NPs has been studied by various researchers using UV-Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, emission spectroscopy, zeta potential, and X-ray photoemission spectroscopy (XPS) [4][5][6][7]18,19,[25][26][27][28][29][30][31][32][33][34][35][36][37]. Seoudi et al [15] have observed a shift in the band position of C=O and C-N stretching frequencies in the vibrational spectrum of PVP in the presence of Au NPs and ascribed such band shifting to a donor-acceptor-type interaction between the carbonyl group of PVP molecules and Au NP.…”

“…Quenching in the emission intensity of fluorophors (e.g., pyrene, organic dye, amino acids) in the presence of Au NPs was attributed to an interaction between donor and acceptor via charge/energy transfer from the electron donor fluorescent materials to the electron acceptor NP [32][33][34]. An increased zeta value in the Au-PVP colloid as compared to the mother PVP solution (without NP) was ascribed to the accumulating electrons of the O atom of the pyrrolidone group on the surface of the Au NP [19,22,[35][36][37]. Negative shift in the binding energies of the doublet Au4f peak as compared to the bulk Au was ascribed to surface interaction between the Au NP and the capping agent [5,7,19,[30][31][32].…”

Biotinylation of optically responsive gold/polyelectrolyte nanostructures

“…In fact, the surface chemistry of NPs is an area of major interest due to the possibility of controlling the shell composition, charge, thickness, and the ability for surface functionalization using diverse strategies that include attachment of antibodies, fluorophores, and polymers. As a consequence, these functionalized Au NPs have found wide interest in areas such as pharmaceutics, biomedicine, photonics, and new optical materials [17][18][19][20][21][22].…”