ToF‐SIMS imaging and spectroscopic analyses of PEG‐conjugated AuNPs

Abstract

Gold nanoparticles (AuNPs) and poly(ethylene glycol) (PEG) are known safe materials to be used in vivo, and so, are becoming increasingly important in biomedical applications. Here, the stability of PEG-conjugated AuNPs in an aqueous solution was monitored as a function of time using several techniques, namely dynamic light scattering (DLS)-size analysis, UV-visible absorption spectrometry and ToF-SIMS. Roughly 15-nm-sized AuNPs were synthesized and pegylated with mPEG (MW = 5 kDa). Four different samples were synthesized, depending on whether or not a dialysis procedure was performed right after synthesis of the AuNPs or pegylation of the AuNPs. The DLS results show that size of mPEG-conjugated AuNPs and standard deviation increased in cases where a dialysis procedure was performed after pegylation of the AuNPs, indicating aggregation of the AuNPs due to the detachment of mPEG ligands from the surface of the AuNPs. Also, results from UV-visible absorption spectra and ToF-SIMS images point to the likelihood that free mPEG ligands in solution help prevent aggregation by maintaining a dynamic equilibrium between the conjugated ligands on the surface of the AuNPs and the free ligands in the aqueous solution. Conversely, once free, mPEG ligands were eliminated from the solution by dialysis and conjugated mPEG ligands detached from the surface of AuNPs into the solution, suspension stability lowered and the AuNPs showed signs of aggregation. We believe that the ToF-SIMS imaging analysis with DLS and UV-visible absorption analyses would be useful to study the stability of PEG-conjugated AuNPs in different environmental conditions.

Stable gold nanocolloids with controllable surface modification and functionalization

“…[19][20][21] For example, Whitesides et al have described the aggregation of gold nanoparticle dispersions upon chemisorption of alkanethiols. 19 Since the underlying mechanisms of ligand exchange reaction is very complicated, 22 it is still not clear yet why irreversible aggregation/precipitation occurred during the PEGylation of citrate-capped gold nanoparticles when the ratio of PEG/gold nanoparticles is below a certain number.…”

“…Recent reports used ToF-SIMS imaging data with DLS and UV-visible data to confirm that elimination of free PEG molecules from solvent by a dialysis procedure led to the aggregation of gold nanoparticles by detaching conjugated PEG from the surface of the gold nanoparticles. 21 Free PEG molecules in solution help to prevent nanoparticles from aggregating. Therefore, the excess amount of PEG molecules has to be added to achieve stable and complete ligand exchange as reflected in reported protocols.…”

The electrospinning of a thermo-responsive polymer with peptide conjugates for phenotype support and extracellular matrix production of therapeutically relevant mammalian cells

“…Mass spectrometry peaks of the ion fragments were identified and confirmed through literature (Table S7 †). [26][27][28][29] The ion fragment CH 3 O − attributed to the underivatised PDEGMA was present on the surface, and a decrease in peak intensity of CH 3 O − was observed for all the scaffolds containing PDEGMA/SH co-polymer ( Fig. 2A).…”

Visualization of solute diffusion into cell walls in solution-impregnated wood under varying relative humidity using time-of-flight secondary ion mass spectrometry

“…TOF-SIMS is an analytical technique having high mass and spatial resolution, and provides semi-quantitative information on the chemical features of the surface of untreated solid samples 14 – 19 . TOF-SIMS has been successfully used to visualize the solute distribution in solution-impregnated wood 20 , 21 . The sample preparation process is quite important to visualize the actual distribution of the target chemicals 22 .…”