Impacts of polyethylene glycol (PEG) dispersity on protein adsorption, pharmacokinetics, and biodistribution of PEGylated gold nanoparticles

Abstract

PEGylated gold nanoparticles (PEG-AuNPs) are widely used in drug delivery, imaging and diagnostics, therapeutics, and biosensing. However, the effect of PEG dispersity on the molecular weight (M _W) distribution of PEG grafted onto AuNP surfaces has been rarely reported. This study investigates the effect of PEG dispersity on the M _W distribution of PEG grafted onto AuNP surfaces and its subsequent impact on protein adsorption and pharmacokinetics, by modifying AuNPs with monodisperse PEG methyl ether thiols (mPEG _n -HS, n = 36, 45) and traditional polydisperse mPEG2k-SH (M _W = 1900). Polydisperse PEG-AuNPs favor the enrichment of lower M _W PEG fractions on their surface due to the steric hindrance effect, which leads to increased protein adsorption. In contrast, monodisperse PEG-AuNPs have a uniform length of PEG outlayer, exhibiting markedly lower yet constant protein adsorption. Pharmacokinetics analysis in tumor-bearing mice demonstrated that monodisperse PEG-AuNPs possess a significantly prolonged blood circulation half-life and enhanced tumor accumulation compared with their polydisperse counterpart. These findings underscore the critical, yet often underestimated, impacts of PEG dispersity on the in vitro and in vivo behavior of PEG-AuNPs, highlighting the role of monodisperse PEG in enhancing therapeutic nanoparticle performance.

Fig. 1. Monodisperse PEG-AuNPs in blood vessels can avoid being rapidly cleared by reticuloendothelial system and thus increase the accumulation in tumor tissue.

Fig. 2. TEM images of (a) AuNPs; (b) PEG2k-AuNPs; (c) PEG₃₆-AuNPs; (d) PEG₄₅-AuNPs.

Fig. 3. (a) D_H of PEG-AuNPs modified with different concentrations of mPEG-HS; (b) D_H of AuNPs and PEG-AuNPs; (c) zeta potential of AuNPs and PEG-AuNPs; (d) UV-vis absorption spectra of AuNPs and PEG-AuNPs.

Fig. 4. (a) MALDI-TOF spectra of mPEG2k-SH; FMS spectra of (b) PEG2k-AuNPs; (c) PEG₃₆-AuNPs; (d) PEG₄₅-AuNPs.

Fig. 5. (a) Protein adsorption of PEG-AuNPs (1 mg) with different mPEG-HS concentrations in BSA at 37 °C for 12 h, all data points are mean ± SD of 3 independent replicates; (b) comparison of protein adsorption of 1 mg PEG-AuNPs in BSA, FBS, and human serum at 37 °C for 3 h (n = 3–5), using t-test to compare three PEG-AuNPs in different proteins, **p < 0.01 is significantly different from the PEG2k-AuNPs group; (c) schematic diagram of in vitro protein adsorption of monodisperse PEG-AuNPs and polydisperse PEG2k-AuNPs.

Fig. 6. (a) Amount of gold measured by ICP-MS at various time points in the blood reported as percent injected dose per gram of tissue (n = 5); (b) t_1/2 and (c) clearance were analysed in a single-compartment model; **p < 0.01 is significantly different from the PEG2k-AuNPs group (d) distribution of intravenously injected PEG₃₆-AuNPs, PEG₄₅-AuNPs and PEG2k-AuNPs in CT26 subcutaneous tumor-bearing mice, results are expressed as mean ± SD, (n = 5), letter superscripts (a, b or c) indicate the presence of highly significant differences between the different types of PEG-AuNPs within the respective tissue differences **p < 0.01; letters superscripted with different significant differences *p < 0.05.