PEGylated gold nanoparticles: polymer quantification as a function of PEG lengths and nanoparticle dimensions

Abstract

Au nanoparticles with diameters ranging between 15 and 170 nm have been synthesised in aqueous solution using a seed-mediated growth method, employing hydroxylamine hydrochloride as a reducing agent. Thiolated polyethylene glycol (mPEG-SH) polymers, with molecular weights ranging from 2100 to 51 000 g mol-1, were used as efficient particle stabilising ligands. Dynamic light scattering and zeta potential measurements confirmed that the overall mean diameter and zeta potential of the capped nanoparticles increased in a non-linear way with increasing molecular weight of the mPEG-SH ligand. Electron microscopy and thermal gravimetric analysis of the polymer-capped nanoparticles, with a mean gold core diameter of 15 nm, revealed that the grafting density of the mPEG-SH ligands decreased from 3.93 to 0.31 PEG nm-2 as the molecular weight of the ligands increased from 2100 to 51 400 g mol-1 respectively, due to increased steric hindrance and polymer conformational entropy with increase in the PEG chain length. Additionally, the number of bound mPEG-SH ligands, with a molecular weight of 10 800 g mol-1, was found to increase in a non-linear way from 278 (σ = 42) to approximately 12 960 PEG (σ = 1227) when the mean Au core diameter increased from 15 to 115 nm respectively. However, the grafting density of mPEG10 000-SH ligands was higher on 15 nm Au nanoparticles and decreased slightly from 1.57 to 0.8 PEG nm-2 when the diameter increased; this effect can be attributed to the fact that smaller particles offer higher surface curvature, therefore allowing increased polymer loading per nm2. Au nanoparticles were also shown to interact with CT-26 cells without causing noticeable toxicity

Effect of PEG Grafting Density and Hydrodynamic Volume on Gold Nanoparticle–Cell Interactions: An Investigation on Cell Cycle, Apoptosis, and DNA Damage

“…The attached PEG amount was calculated as described in Figure S2 and Table S1 in accordance with the protocol published in the literature. 20,69,70 For fluorescence microscopy imaging, the PEG-coated AuNPs were reacted with FITC dye. 19,38 For this reaction, 1 mg of FITC was dissolved in 200 μL of anhydrous dimethylformamide (DMF) and added to 50 μM PEG-coated AuNP solution.…”

“…The mushroom conformation mainly occurs when the distance, D, between the attachment points of PEG to the surface is larger than R F (D > R F ); however, the brush conformation is observed when D < R F . 49,69 Using the thickness of the PEG layer obtained from DLS measurements (t) and the density of PEG (ρ = 1.09 g/mL), the surface concentration (Γ, g/nm 2 ) and the average distance between grafted PEG chains (D, nm) were calculated using eqs 2 and 3, respectively.…”

Modeling of nanoparticle coatings for medical applications

“…giving D 32 = 5.0Å and D 60 = 3.6Å, for N PEG = 32 and 60, respectively -significantly below the Flory radius for the PEG considered in this paper which is R F = 9.2Å using N = 5 and a = 3.5Å [40]. Using equation (5), we can obtain theoretical estimates of the brush thicknesses L 32 = 13.9Å and L 60 = 17.1Å for N PEG = 32 and 60.…”

Bioconjugated gold nanoparticles enhance cellular uptake: A proof of concept study for siRNA delivery in prostate cancer cells

“…The starting materials AuNPs-citrate and AuNPs-PEI were synthesised in water using sodium citrate and ascorbic acid as reducing agents respectively [20,21] (Fig. 1).…”