Surface Labelling of Gold Nanoparticles with Inorganic Lumophores and Targeting Vectors for Cell Imaging Applications

Transition metal complexes are attractive imaging probes as they offer distinctive photophysical, electrochemical and synthetic advantages over organic dyes, quantum dots and fluorescent proteins due to their high photo-stability, long luminescence lifetimes and large Stokes shifts. Gold nanoparticles have also revolutionised the design, delivery and functionality of imaging probes, being attractive scaffolds to bind luminescent complexes, targeting vectors and therapeutic substances. Previous work in the group has demonstrated that gold nanoparticles can be efficiently coated with transition metal complexes, with the resulting coated particles useful in cellular imaging. In this work, a water-soluble luminescent ruthenium complex and pH-low insertion peptides (pHLIPs) were coupled to gold nanoparticles, and these labelled-nanoparticles exhibited enhanced uptake into human cervical adenocarcinoma cells. The mechanism of pHLIP-mediated nanoparticle delivery was investigated, by conducting time and pH resolved experiments, with an interest in contrasting the benefits of two pHLIP variants as nanoparticle delivery vectors. Subsequent investigations revealed the concentration of intracellular glutathione imposed an effect on nanoparticle internalisation efficiency and the colloidal stability of labelled gold nanoparticles, and that providing gold nanoparticles with a hydrophobic lipid coating also enhanced the efficiency of nanoparticle internalisation into cells