| Abstract
| - We demonstrate the use of self-assembled luminescent semiconductor quantum dot (QD)−peptide bioconjugatesfor the selective intracellular labeling of several eukaryotic cell lines. A bifunctional oligoarginine cell penetratingpeptide (based on the HIV-1 Tat protein motif) bearing a terminal polyhistidine tract was synthesized and usedto facilitate the transmembrane delivery of the QD bioconjugates. The polyhistidine sequence allows the peptideto self-assemble onto the QD surface via metal-affinity interactions while the oligoarginine sequence allows specificQD delivery across the cellular membrane and intracellular labeling as compared to nonconjugated QDs. Thispeptide-driven delivery is concentration-dependent and thus can be titrated. Upon internalization, QDs display apunctate-like staining pattern in which some, but not all, of the QD signal is colocalized within endosomes. Theeffects of constant versus limited exposure to QD−peptide conjugates on cellular viability are evaluated by ametabolic specific assay, and clear differences in cytotoxicity are observed. The efficacy of using peptides forselective intracellular delivery is highlighted by performing a multicolor QD labeling, where we found that thepresence or absence of peptide on the QD surface controls cellular uptake.
|
