We describe hybrid nanoparticles, composed of iron oxide and gold nanoparticles, as potential dual contrast agents for both computed tomography (CT) and magnetic resonance imaging (MRI). The hybrid nanoparticles are synthesized by thermal decomposition of mixtures of Fe-oleate and Au-oleylamine complexes. Using a nano-emulsion method, the nanoparticles are coated with amphiphilic poly(DMA-r-mPEGMA-r-MA) to impart water-dispersity and antibiofouling properties. An in vitro phantom study shows that the hybrid nanoparticles have high CT attenuation, because of the constituent gold nanoparticles, and afford a good MR signal, attributable to the contained iron oxide nanoparticles. Intravenous injection of the hybrid nanoparticles into hepatoma-bearing mice results in high contrast between the hepatoma and normal hepatic parenchyma in both CT and MRI. These results suggest that the hybrid nanoparticles may be useful as CT/MRI dual contrast agents for in vivo hepatoma imaging.

Multimodal nanoparticles have been extensively studied for target-specific imaging and therapy of various diseases, including cancer. In this study, radiolabeled arginine-glycine-aspartic acid (RGD)–functionalized Er³⁺/Yb³⁺ co-doped NaGdF₄ upconversion nanophosphors (UCNPs) were synthesized and evaluated as a multimodal PET/MR/optical probe with tumor angiogenesis–specific targeting properties. Methods: A dimeric cyclic RGDyk ((cRGDyk)₂) peptide was conjugated to polyacrylic acid–coated NaGdF₄:Yb³⁺/Er³⁺ UCNPs along with polyethylene glycol molecules and was consecutively radiolabeled with ¹²⁴I. In vitro cytotoxicity testing was performed for 3 d. Upconversion luminescence imaging of (cRGDyk)₂-UCNP was performed on U87MG cells with a laboratory-made confocal microscope. In vivo small-animal PET and clinical 3-T T1-weighted MR imaging of ¹²⁴I-labeled RGD–functionalized UCNPs was acquired with or without blocking of cyclic RGD peptide in a U87MG tumor model. Inductively coupled plasma mass spectrometry and biologic transmission electron microscopy were done to evaluate gadolinium concentration and UCNP localization, respectively. Results: Polymer-coated UCNPs and dimeric RGD–conjugated UCNPs were monodispersely synthesized, and those of hydrodynamic size were 30 ± 8 nm and 32 ± 9 nm, respectively. (cRGDyk)₂-UCNPs have a low cytotoxic effect on cells. Upconversion luminescence signals of (cRGDyk)₂-UCNP were specifically localized on the surface of U87MG cells. ¹²⁴I-c(RGDyk)₂-UCNPs specifically accumulated in U87MG tumors (2.8 ± 0.8 vs. 1.3 ± 0.4 percentage injected dose per gram in the blocking experiment), and T1-weighted MR images showed significant positive contrast enhancement in U87MG tumors. Tumor localization of ¹²⁴I-c(RGDyk)₂-UCNPs was confirmed by inductively coupled plasma mass spectrometry and biologic transmission electron microscopy analysis. Conclusion: These results suggest that ¹²⁴I-labeled RGD–functionalized UCNPs have high specificity for α_vβ₃ integrin–expressing U87MG tumor cells and xenografted tumor models. Multimodal UCNPs can be used as a platform nanoparticle with multimodal imaging for cancer-specific diagnoses.

Hypoxia stimulates hepatocellular carcinoma (HCC) cell growth via hexokinase (HK) II induction, and alternatively, HK II inhibition induces apoptosis by activating mitochondrial signaling. This study was to investigate whether the induction of HK II by hypoxia is associated with enhanced mitochondrial stability and to confirm the apoptosis-inducing efficacy of HK II inhibitor in an in vivo model of HCC. Mitochondrial stability was examined by treating isolated mitochondria with deoxycholate, a permeability-enhancing agent. Alteration of permeability transition pore complex composition was analyzed by immunoprecipitation and immunoblotting. An in vivo model of HCC was established in C3H mice i.d. implanted with MH134 cells. The antitumor efficacy of i.p. given 3-bromopyruvate (3-BrPA), a HK II inhibitor, was evaluated by measuring tumor volumes and quantifying apoptosis using terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling staining and ^99mTc-hydrazinonicotinamide-Annexin V scans. Hypoxia enhanced mitochondrial stability, and this was inhibited by 3-BrPA treatment. In particular, HK II levels in permeability transition pore complex immunoprecipitates were reduced after 3-BrPA treatment. In mice treated with 3-BrPA, mean tumor volumes and tumor volume growth were found to be significantly reduced. Moreover, percentages of terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling–positive cells were significantly increased in 3-BrPA–treated mice, and this apoptosis-inducing efficacy was reflected in vivo by ^99mTc-hydrazinonicotinamide-Annexin V imaging. Our results show that hypoxia enhances mitochondrial stability via HK II induction and that HK II inhibitor treatment exhibits an in vivo antitumor effect by inducing apoptosis. Therefore, HK II inhibitors may be therapeutically useful for the treatment of advanced infiltrative hypovascular HCCs, which are growing in a hypoxic environment. [Mol Cancer Ther 2007;6(9):2554–62]