Synthesis, Stability, and Cellular Internalization of Gold Nanoparticles Containing Mixed Peptide−Poly(ethylene glycol) Monolayers

Abstract

Gold nanoparticles have shown great promise as therapeutics, therapeutic delivery vectors, and intracellular imaging agents. For many biomedical applications, selective cell and nuclear targeting are desirable, and these remain a significant practical challenge in the use of nanoparticles in vivo. This challenge is being addressed by the incorporation of cell-targeting peptides or antibodies onto the nanoparticle surface, modifications that frequently compromise nanoparticle stability in high ionic strength biological media. We describe herein the assembly of poly(ethylene glycol) (PEG) and mixed peptide/PEG monolayers on gold nanoparticle surfaces. The stability of the resulting bioconjugates in high ionic strength media was characterized as a function of nanoparticle size, PEG length, and monolayer composition. In total, three different thiol-modified PEGs (average molecular weight (MW), 900, 1500, and 5000 g mol-1), four particle diameters (10, 20, 30, and 60 nm), and two cell-targeting peptides were explored. We found that nanoparticle stability increased with increasing PEG length, decreasing nanoparticle diameter, and increasing PEG mole fraction. The order of assembly also played a role in nanoparticle stability. Mixed monolayers prepared via the sequential addition of PEG followed by peptide were more stable than particles prepared via simultaneous co-adsorption. Finally, the ability of nanoparticles modified with mixed PEG/RME (RME = receptor-mediated endocytosis) peptide monolayers to target the cytoplasm of HeLa cells was quantified using inductively coupled plasma optical emission spectrometry (ICP-OES). Although it was anticipated that the MW 5000 g mol-1 PEG would sterically block peptides from access to the cell membrane compared to the MW 900 PEG, nanoparticles modified with mixed peptide/PEG 5000 monolayers were internalized as efficiently as nanoparticles containing mixed peptide/PEG 900 monolayers. These studies can provide useful cues in the assembly of stable peptide/gold nanoparticle bioconjugates capable of being internalized into cells.

Sensitive Colorimetric Visualization of Perfluorinated Compounds Using Poly(ethylene glycol) and Perfluorinated Thiols Modified Gold Nanoparticles

“…But the molecular weight of these PEGs is usually larger than 1000 Da. 41,42 In this study, the molar mass of PEG units was low (M = 281) and the interactions between water and PEG chains were weak, so the stability of Au@PEG-F NPs was sensitive to solution pH. The sensitivity of the assay to PFCs at different solution pHs was studied with the concentrations of PFOS ranging in 1−1000 μg L −1 .…”

Surface modification, functionalization and bioconjugation of colloidal inorganic nanoparticles

“…in an increased half-life in the blood stream. PEG-modified nanoparticles are more stable at high salt concentrations and in biological environments; they show less non-specific binding to proteins and cells (Gref et al 2000;Ballou et al 2004;Liu et al 2007bLiu et al , 2008van Vlerken et al 2007;Daou et al 2009). …”

“…In addition, examples for particle synthesis (Slocik et al 2005) and phase transfer (Euliss et al 2003) with the help of peptides have been reported. Making use of the biological functionality of certain peptides, the specific uptake of nanoparticles by cells can be optimized by conjugation of nanoparticles with the corresponding peptide, as reported for Au nanoparticles Liu et al 2007b;Nativo et al 2008) or quantum dots (Pinaud et al 2004) by ligand exchange with cysteine-containing peptides, as well as the reaction of the immune system towards nanoparticles may be modulated by the peptide coating (Bastus et al 2009). Also, coating of quantum dots with lipids pre-modified with e.g.…”

Synthesis of oligo(lactose)-based thiols and their self-assembly onto gold surfaces

“…For example, functionalization with nucleic acids or proteins may destabilize AuNPs, and to improve the colloidal stability the biospecific molecule is mixed with filler molecules providing both steric stabilization and biocompatibility. [12][13][14][15] Oligo(ethylene) glycols (OEGs) are commonly used for steric stabilization of particles, [16,17] including stabilization of liposomes used as drug delivery vehicles, where they also prevent the triggering of immune responses. [18] As an alternative, we have synthesized the oligosaccharides 1-3 ( Figure 1) which presumably are rod-like [19] Immobilization of thiol compounds on gold surfaces into self-assembled monolayers (SAMs) is widely used to prepare well-defined and versatile model surfaces for studies of protein adsorption and biofouling.…”