Specific near-IR absorption imaging of glioblastomas using integrin-targeting gold nanorods

Molecular imaging using nanoprobes with high resolution and low toxicity is essential in early cancer detection. Here we introduce a new class of smart imaging probes employing PEGylated gold nanorods (GNRs) conjugated to cRGD for specific optical imaging of α_vβ₃ integrins from glioblastoma. GNRs exhibiting an optical resonance peak in the near-infrared (NIR) region were synthesized using the seed-mediated growth method. CTAB (cetyl trimethylammonium bromide) bilayer on the GNRs was replaced with a biocompatible stabilizer, heterobifunctional polyethyleneglycol (COOH-PEG-SH). Further, the carboxylated GNRs (PGNRs; PEG-coated GNRs) were functionalized with cRGD using EDC-NHS chemistry to formulate cRGD-conjugated GNRs (cRGD-PGNRs) for α_vβ₃ integrins. In order to assess the potential of the cRGD-PGNRs as a targeted imaging probe, we investigated their optical properties, biocompatibility, colloidal stability and in vitro/in vivo binding affinities for cancer cells. Consequently, cRGD-PGNRs demonstrated excellent tumor targeting ability with no cytotoxicity, as well as sufficient cellular uptake due to stable and prolonged blood circulation of cRGD-PGNRs.