Gold-peptide nanoconjugate cellular uptake is modulated by serum proteins

Gold nanoparticles (Au NPs, 20 nm) were conjugated with two different cysteine-terminated peptides. Radio-ligand binding studies were conducted to characterize Au NP-peptide binding, suggesting both covalent and noncovalent interactions. The interactions of serum proteins with Au NP-peptide nanoconjugates were determined using gel electrophoresis and dynamic light scattering. Serum proteins rapidly bound the nanoconjugates (15 minutes). The cellular uptake of free peptides and nanoconjugates into mouse myogenic (Sol8) cells was investigated in the absence or presence of serum. In the absence of serum, peptides presented as nanoconjugates showed significantly higher intracellular fluorescence signals compared to those in the presence of serum (P < 0.05), suggesting that serum proteins inhibit Au NP-mediated peptide delivery. The cellular uptake of nanoconjugates was also confirmed using transmission electron microscopy. These data suggest that Au NP-peptide nanoconjugates are a useful platform for intracellular delivery of therapeutics. However, a deeper understanding of the mechanisms regulating their uptake and intracellular trafficking is needed.From the Clinical EditorGold nanoparticles are very popular as drug delivery systems. This paper scrutinizes a rarely addressed aspect of these nanoparticles, namely that serum protein may result in a partial inhibition in Au NP uptake as a result of serum protein binding to the nanoparticles. This factor has to be considered in future studies of Au NP delivery systems.

Graphical AbstractFetal bovine serum (FBS) affects cellular uptake of nanoconjugates. The figure shows confocal fluorescence images of Sol8 cells incubated with Au NP-peptide A nanoconjugates (2 hours) in the presence (A) or the absence (B) of FBS. Fluorescence images suggest that in the absence of FBS, Au NP-mediated uptake of peptide A is enhanced. FBS proteins overcoat nanoconjugates, and this may lead to alterations to retrograde trafficking pathways.Figure optionsDownload high-quality image (447 K)Download as PowerPoint slide