Department of Medical Imaging Center, Nanfang Hospital, Southern Medical University, Guangzhou, People's Republic of China.
Int J Nanomedicine. 2013;8:245-55. doi: 10.2147/IJN.S38678. Epub 2013 Jan 11.
Pretargeting of biomarkers with nanoparticles in molecular imaging is promising to improve diagnostic specificity and realize signal amplification, but data regarding its targeting potential in magnetic resonance (MR) imaging are limited. The purpose of this study was to evaluate the tumor angiogenesis targeting efficacy of the anti-αvβ3 antibody guided three-step pretargeting approach with magnetoliposomes.
Polyethylene glycol-modified and superparamagnetic iron oxide-encapsulated magnetoliposomes with and without biotin were synthesized and characterized. The cytotoxicity of both probes was evaluated using the methyl thiazdyl tetrazolium assay, and their cellular uptake by mouse macrophage was visualized using Prussian blue staining. Three-step pretargeting MR imaging was performed on MDA-MB-435S breast cancer-bearing mice by intravenous administration of biotinylated anti-αvβ3 monoclonal antibodies (first step), followed by avidin and streptavidin (second step), and by biotinylated magnetoliposomes or magnetoliposomes in the targeted or nontargeted group, respectively (third step). The specificity of αvβ3 targeting was assessed by histologic examinations.
The developed magnetoliposomes were superparamagnetic and biocompatible as confirmed by cell toxicity assay. The liposomal bilayer and polyethylene glycol modification protected Fe(3)O(4) cores from uptake by macrophage cells. MR imaging by three-step pretargeting resulted in a greater signal enhancement along the tumor periphery, occupying 7.0% of the tumor area, compared with 2.0% enhancement of the nontargeted group (P < 0.05). Histologic analysis demonstrated the targeted magnetoliposomes colocalized with neovasculature, which was responsible for the MR signal decrease.
These results indicate that our strategy for MR imaging of αvβ3-integrin is an effective means for sensitive detection of tumor angiogenesis, and may provide a targetable nanodelivery system for anticancer drugs.
在分子成像中使用纳米颗粒对生物标志物进行 Pretargeting 有望提高诊断的特异性并实现信号放大，但关于其在磁共振（MR）成像中的靶向潜力的数据有限。本研究的目的是评估抗-αvβ3 抗体引导的三步 Pretargeting 方法用磁脂质体对肿瘤血管生成的靶向效果。
合成并表征了聚乙二醇修饰的和超顺磁性氧化铁包被的带有和不带生物素的磁脂质体。使用甲基噻唑四唑测定法评估两种探针的细胞毒性，并使用普鲁士蓝染色观察它们在小鼠巨噬细胞中的摄取情况。通过静脉注射生物素化抗-αvβ3 单克隆抗体（第一步），然后用亲和素和链霉亲和素（第二步），分别在靶向组或非靶向组中用生物素化磁脂质体或磁脂质体进行 MDA-MB-435S 乳腺癌荷瘤小鼠的三步 Pretargeting MR 成像。通过组织学检查评估 αvβ3 靶向的特异性。
所开发的磁脂质体是超顺磁性的且具有细胞相容性，这通过细胞毒性测定得到了证实。脂质双层和聚乙二醇修饰保护了 Fe(3)O(4)核心免受巨噬细胞摄取。三步 Pretargeting MR 成像结果显示，与非靶向组的 2.0%增强相比，肿瘤边缘的信号增强更大，占肿瘤面积的 7.0%（P < 0.05）。组织学分析表明，靶向磁脂质体与新生血管共定位，这是导致 MR 信号下降的原因。
这些结果表明，我们用于 αvβ3-整合素的 MR 成像的策略是敏感检测肿瘤血管生成的有效手段，并且可能为抗癌药物提供一种靶向纳米递药系统。
