Modular peptide-functionalized gold nanorods for effective glioblastoma multicellular tumor spheroid targeting

Glioblastoma multiforme (GBM) contains a population of tumor initiating stem-like cells, termed cancer stem cells (CSCs). These CSCs, which are resistant to chemo- and radiotherapy, are thought to persist after treatment and drive tumor recurrence. Thus, it is believed that the elimination of CSCs can lead to GBM remission. GBM CSCs express Nestin on their surface, and can be therefore targeted via this protein. Gold nanorods (AuNRs) functionalized with an engineered, modular peptide that recognizes Nestin (NesPEG-AuNRs) were used to target the models of solid tumors originated from human GBM CSC multicellular tumor spheroids (MCTS). In our study, we show that NesPEG-AuNRs have low cytotoxicity, are efficiently taken up by MCTS, and distribute uniformly throughout our tumor models, not only at the periphery as often seen in other nanoparticle systems. NesPEG-AuNR uptake by MCTS appears to be mediated by an energy/caveolae endocytic mechanism. Moreover, plasmon excitation of AuNRs in the near-infrared (NIR) region results in the production of localized heat. Consequently, NesPEG-AuNR cytotoxicity is only observed during NIR-irradiation in MCTS with a high intracellular AuNR content. The intracellular accumulation/diffusion of NesPEG-AuNRs and NIR-irradiation result in photothermally induced GBM CSC apoptosis and MCTS growth inhibition. In summary, these data suggest that the combination of the Nestin recognizing peptide with AuNRs contributes to better tumor accumulation/penetration, and thus in GBM CSC elimination. Moreover, due to the modularity of our peptide design, the Nestin-binding peptide sequence can be exchanged for peptides targeting other surface markers for the treatment of various types of tumors.