Anti-HER2 immunoliposomes for selective delivery of electron paramagnetic resonance imaging probes to HER2-overexpressing breast tumor cells
Anti-HER2 immunoliposomes for selective delivery of electron paramagnetic resonance imaging probes to HER2-overexpressing breast tumor cells
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DOI：
10.1007/s10549-009-0715-4
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发表时间：
2010-11-01
影响因子：
3.8
通讯作者：
Kao, Joseph P. Y.
中科院分区：
文献类型：
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作者：
Burks, Scott R.;Macedo, Luciana F.;Kao, Joseph P. Y.
电子顺磁共振（EPR）成像是一种新兴的模式，可以检测和定位顺磁分子探针（所谓的自旋探针）在体内。我们以前证明，氮氧自由基自旋探针可以封装在脂质体中的浓度超过100 mM，在氮氧自由基表现出浓度依赖性淬灭的EPR信号，这是类似于荧光分子的自淬灭。因此，完整的脂质体封装高浓度的氮氧自由基表现出大大衰减的EPR光谱信号，和这种脂质体的内吞作用代表了细胞激活的对比度产生机制。内吞作用后，释放出包裹的氮氧自由基，并在细胞内环境中大大稀释。这使氮氧化物去猝灭以产生稳健的细胞内EPR信号。因此，可以将高浓度的氮氧自由基递送至细胞，同时使来自未内吞脂质体的背景信号最小化。我们在这里报告，细胞内EPR信号可以选择性地产生在一个特定的细胞类型，通过利用其表达的人表皮生长因子受体2（HER2）。当被包封淬灭的氮氧化物的抗HER2免疫脂质体靶向时，与不表达HER2的亲本MCF 7细胞或对照CV 1细胞相比，Hc7细胞（其是源自MCF 7乳腺肿瘤细胞系的新型HER2过表达细胞）大量内吞脂质体。HER2依赖性脂质体递送使Hc7细胞能够在细胞内积累750 μ M氮氧化物。通过使用体模模型，我们验证了氮氧化物的这种浓度对于EPR成像是绰绰有余的，从而为使用EPR成像来可视化动物中HER2过表达的Hc7肿瘤奠定了基础。
Electron paramagnetic resonance (EPR) imaging is an emerging modality that can detect and localize paramagnetic molecular probes (so-called spin probes) in vivo. We previously demonstrated that nitroxide spin probes can be encapsulated in liposomes at concentrations exceeding 100 mM, at which nitroxides exhibit a concentration-dependent quenching of their EPR signal that is analogous to the self-quenching of fluorescent molecules. Therefore, intact liposomes encapsulating high concentrations of nitroxides exhibit greatly attenuated EPR spectral signals, and endocytosis of such liposomes represents a cell-activated contrast-generating mechanism. After endocytosis, the encapsulated nitroxide is liberated and becomes greatly diluted in the intracellular milieu. This dequenches the nitroxides to generate a robust intracellular EPR signal. It is therefore possible to deliver a high concentration of nitroxides to cells while minimizing background signal from unendocytosed liposomes. We report here that intracellular EPR signal can be selectively generated in a specific cell type by exploiting its expression of Human Epidermal Growth Factor Receptor 2 (HER2). When targeted by anti-HER2 immunoliposomes encapsulating quenched nitroxides, Hc7 cells, which are novel HER2-overexpressing cells derived from the MCF7 breast tumor cell line, endocytose the liposomes copiously, in contrast to the parent MCF7 cells or control CV1 cells, which do not express HER2. HER2-dependent liposomal delivery enables Hc7 cells to accumulate 750 mu M nitroxide intracellularly. Through the use of phantom models, we verify that this concentration of nitroxides is more than sufficient for EPR imaging, thus laying the foundation for using EPR imaging to visualize HER2-overexpressing Hc7 tumors in animals.