Peptidic coating for gold nanospheres multifunctionalizable with photostable and photolabile moieties

A single-step method to coat and trifunctionalize water-dispersed gold nanospheres (AuNss) with carboxylic acids, amines, and alkynes is reported. The coating is based on a mix of two hexa-peptides, differing only in the C-terminal amino acid. The process yields AuNss that are non-cytotoxic, stable in physiological environments, and which present three reactive surface groups allowing rapid, selective, and modular conjugation (click- and peptide-reactions) to virtually any chosen biomolecule or fluorophore. Conjugated nanostructures were analyzed in vitro and in living cells. Confocal imaging and colocalization analyses demonstrate the presence and reactivity of three different types of covalent bonds with payloads: two of these are photostable while one bond is photolabile and can be cleaved by mu W-power irradiation with a 561 nm cw laser.