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 alpha(v)beta(3) 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 alpha(v)beta(3) 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.