Understanding the Adsorption of Peptides and Proteins onto PEGylated Gold Nanoparticles

Abstract

Polyethylene glycol (PEG) surface conjugations are widely employed to render passivating properties to nanoparticles in biological applications. The benefits of surface passivation by PEG are reduced protein adsorption, diminished non-specific interactions, and improvement in pharmacokinetics. However, the limitations of PEG passivation remain an active area of research, and recent examples from the literature demonstrate how PEG passivation can fail. Here, we study the adsorption amount of biomolecules to PEGylated gold nanoparticles (AuNPs), focusing on how different protein properties influence binding. The AuNPs are PEGylated with three different sizes of conjugated PEG chains, and we examine interactions with proteins of different sizes, charges, and surface cysteine content. The experiments are carried out in vitro at physiologically relevant timescales to obtain the adsorption amounts and rates of each biomolecule on AuNP-PEGs of varying compositions. Our findings are relevant in understanding how protein size and the surface cysteine content affect binding, and our work reveals that cysteine residues can dramatically increase adsorption rates on PEGylated AuNPs. Moreover, shorter chain PEG molecules passivate the AuNP surface more effectively against all protein types.

The Impact of PEGylation on Cellular Uptake and In Vivo Biodistribution of Gold Nanoparticle MRI Contrast Agents

“…The role of PEG in protein adsorption is controversial in the literature, where many studies have shown that PEG provides a steric barrier that mitigates protein binding to nanoparticles [ 32 , 35 ] while others have reported that some proteins bind to PEGylated particles that do not adsorb to non-PEGylated particles [ 50 , 51 ]. Here, we suggest that the surface chemistry of GNPs plays a crucial role in the ability of PEG to impact protein corona formation, as the difference in the DNA sequence and the length of PEG together dictate the number of adsorbed proteins [ 52 , 53 ]. In addition, the density/conformation of PEG has been reported as an important factor, along with the gold core size, for determining the number of proteins bound to the nanoparticle [ 35 , 36 , 54 , 55 ].…”

Iodination of PEGylated Polymers Counteracts the Inhibition of Fibrinogen Adsorption by PEG

“…Poly­(ethylene glycol), PEG, which is known to inhibit nonspecific protein adsorption and thereby reduce bacterial and cell adhesion, is widely used as one of the blocks in copolymers to reduce biofilm formation on polymeric biomedical devices, such as ophthalmic lenses . PEG is also used to reduce the toxicity of certain drugs and surface passivation of nanoparticles to avoid phagocytosis . In fact, the covalent attachment of PEG is the current gold standard in many drug delivery devices .…”

“…4 PEG is also used to reduce the toxicity of certain drugs and surface passivation of nanoparticles to avoid phagocytosis. 5 In fact, the covalent attachment of PEG is the current gold standard in many drug delivery devices. 6 The details of how the distribution of PEG affects protein adsorption and thereby cell fate are not completely understood, and is still being actively investigated using techniques, such as vibrational sumfrequency generation (SFG) spectroscopy, 7 X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), 8 and molecular dynamics simulations.…”

Protein Adsorption and Conformational Changes

“…Moreover, nanoparticle surface curvature has a profound influence on the adsorption process. Thus, protein-nanoparticle interactions have been extensively investigated, and it is not surprising that they are discussed in a number of reports in this Special Issue [ 12 , 13 , 14 , 15 ]. Lipid surfaces are instead the subject of another contribution in this issue [ 16 ].…”

“…In this Issue, Perera et al [ 12 ] describe a systematic study of peptide and protein adsorption to PEGylated gold nanoparticles. PEGylation is a universally adopted strategy for the passivation of nanoparticles, which reduces unintended protein adsorption and extends the lifetime of gold nanoparticles in biofluids.…”