Quantification and reactivity of functional groups in the ligand shell of PEGylated gold nanoparticles via a fluorescence-based assay.
We present a fluorescence-based assay for the characterization of functionalized gold nanoparticles (AuNPs) capped with a self-assembled monolayer of mixed thiols derived from poly(ethylene glycol) (PEG). These water-soluble AuNPs carry primary amino groups at the solvent-exposed interface, which can be used for further conjugation of biologically active molecules. The reported assay allows quantification of the average number of functionalizable amino groups per particle (N(NH(2))) with a relative uncertainty below or equal to +/-14% (95% confidence interval), thus providing essential information for the successive derivatization of the AuNPs. Here, a fluorescently labeled derivative of peptide-neurotoxin conantokin-G was coupled to the amino groups of the particle ligand shell via a flexible linker. We quantitatively determined the average number of peptides per particle (N(pept)) and the yield of the two-step conjugation strategy. AuNPs carrying 50-70 copies of the peptide were obtained. In addition, we have gained insights into the deterioration of the self-assembled monolayer due to thiol desorption with time. Under ordinary storage conditions in solution and at room temperature, a decrease in N(NH(2)) between 48% and 75% could be observed at the end of the period of investigation (42-56 days). Slow desorption of the conjugated peptides upon storage was also observed and quantified ( approximately 25% in 14 days).
Department of New Materials and Biosystems, Max Planck Institute for Metals Research, Germany.
Lisa
L
Maus
Joachim P
JP
Spatz
Roberto
R
Fiammengo
D005453:Fluorescence; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D008962:Models, Theoretical; D015394:Molecular Structure; D011092:Polyethylene Glycols / Q000737:chemistry*
D011092:Polyethylene Glycols; D006046:Gold