Short Peptoid Capping Ligands Stabilize Dispersion of Gold Nanospheres in Aqueous Solutions

Surface functionalization of colloidal gold nanoparticles with capping ligands is critical for controlling their dispersive stability and for introducing application-specific moieties. Peptoids (N-substituted glycine oligomers) are useful candidates for study as capping ligands owing to their straightforward preparation and their biocompatibility. In this work, we have prepared a library of five-residue peptoids and evaluated them as capping ligands for 10 nm gold nanospheres. Our findings revealed important sequence features of peptoids that stabilize nanosphere colloidal dispersions in a range of aqueous conditions that vary in ionic strength and pH. We have also characterized the sizes and surface charges of peptoid-capped nanospheres and made direct comparisons between peptide- and peptoid-capped nanospheres. Lastly, we observed that nanospheres capped with one of the peptoids studied here inhibit the enzyme chymotrypsin.