Nano/Bio Chemistry Laboratory, Institut Pasteur Korea, Gyeonggi-do, South Korea.
J Nucl Med. 2013 Jan;54(1):96-103. doi: 10.2967/jnumed.112.108043. Epub 2012 Dec 11.
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 Er(3+)/Yb(3+) co-doped NaGdF(4) upconversion nanophosphors (UCNPs) were synthesized and evaluated as a multimodal PET/MR/optical probe with tumor angiogenesis-specific targeting properties.
A dimeric cyclic RGDyk ((cRGDyk)(2)) peptide was conjugated to polyacrylic acid-coated NaGdF(4):Yb(3+)/Er(3+) UCNPs along with polyethylene glycol molecules and was consecutively radiolabeled with (124)I. 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 (124)I-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.
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. (124)I-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 (124)I-c(RGDyk)(2)-UCNPs was confirmed by inductively coupled plasma mass spectrometry and biologic transmission electron microscopy analysis.
These results suggest that (124)I-labeled RGD-functionalized UCNPs have high specificity for α(v)β(3) 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.
合成放射性标记的精氨酸-甘氨酸-天冬氨酸（RGD）功能化的 Er(3+)/Yb(3+)共掺杂 NaGdF(4)上转换纳米磷光体（UCNPs），并将其作为具有肿瘤血管生成特异性靶向特性的多模态 PET/MR/光学探针进行评估。
二聚环 RGDyk((cRGDyk)(2))肽与聚丙烯酸包覆的 NaGdF(4):Yb(3+)/Er(3+)UCNPs 以及聚乙二醇分子偶联，并与放射性碘(124)I 进行连续标记。对 U87MG 细胞进行为期 3 天的细胞毒性试验。使用实验室自制共聚焦显微镜对 U87MG 细胞进行(cRGDyk)(2)-UCNP 的上转换荧光成像。在 U87MG 肿瘤模型中，在不阻断环状 RGD 肽的情况下，进行放射性碘标记的 RGD 功能化 UCNP 的小动物 PET 和临床 3-T T1 加权 MR 成像。通过电感耦合等离子体质谱和生物传输电子显微镜分别评估钆浓度和 UCNP 定位。
聚合物包覆的 UCNPs 和二聚 RGD 偶联的 UCNPs 均被单分散合成，其水动力尺寸分别为 30±8nm 和 32±9nm。(cRGDyk)(2)-UCNP 对细胞的细胞毒性作用较低。(cRGDyk)(2)-UCNP 的上转换荧光信号特异性定位于 U87MG 细胞表面。(124)I-c(RGDyk)(2)-UCNP 特异性地积聚在 U87MG 肿瘤中（阻断实验中为 2.8±0.8%注射剂量/克与 1.3±0.4%注射剂量/克），T1 加权 MR 图像显示 U87MG 肿瘤的对比增强显著。通过电感耦合等离子体质谱和生物传输电子显微镜分析证实了(124)I-c(RGDyk)(2)-UCNP 的肿瘤定位。
这些结果表明，放射性碘标记的 RGD 功能化 UCNP 对表达α(v)β(3)整合素的 U87MG 肿瘤细胞和异种移植肿瘤模型具有高度特异性。多模态 UCNP 可用作具有癌症特异性诊断的多模态成像的平台纳米颗粒。
