Department of Radiology, Shanghai Jiao Tong University Affiliated Sixth People's Hospital , 600 Yishan Road, Shanghai 200233, China.
Key Laboratory for Advanced Materials and Institute of Fine Chemicals, Shanghai Key Laboratory of Functional Materials Chemistry, School of Chemistry and Molecular Engineering, East China University of Science and Technology , Shanghai 200237, China.
ACS Appl Mater Interfaces. 2017 Apr 19;9(15):13029-13036. doi: 10.1021/acsami.7b00936. Epub 2017 Apr 7.
The inflammatory activity of ulcerative colitis plays an important role in the medical treatment. However, accurate and real-time monitoring of the colitis activity with noninvasive bioimaging method is still challenging, especially in distinguishing between chronic and acute colitis. As a good receptor, the oligopeptide transporter (PepT1) is overexpressed in the colonic epithelial cells of chronic ulcerative colitis, which can deliver tripeptide KPV (Lys-Pro-Val, the C-terminal sequence of α-MSH) into cytosol in the intestine. Herein, we report a PepT1 peptide receptor-targeted fluorescent probe, dicyanomethylene-4H-pyran (DCM)-KPV, with the strategy of conjugating the KPV into the DCM chromophore. The diagnostic fluorescent probe bestows a specific receptor-targeted interaction with PepT1 through the KPV moiety, possessing several beneficial characteristics, such as efficient long emission, low photobleaching, negligible cytotoxicity, and high cytocompatibility in living cells. We build the overexpressed PepT1 on the cytomembrane of ulcerative colitis model Caco-2 cell as the efficient receptor to accumulate the targeted tripeptide KPV in the cytoplasm and nucleus. With the co-localization of DCM-KPV and the DNA-specific fluorophore, DAPI, the specifically long emission from chromophore DCM and efficient receptor-targeted peptide KPV, the fluorescent probe of DCM-KPV makes a breakthrough to the direct noninvasive observation of the accumulation in colon inflammation regions via intestinal mucosa, even successfully distinguishing the chronic, acute ulcerative colitis and normal groups. Compared with the traditional unenhanced magnetic resonance imaging and hematoxylin and eosin (H&E) staining, we make full use of exploiting the specific target-receptor interaction between the tripeptide unit, KPV, and the oligopeptide transporter, PepT1, for sensing selectivity. The desirable diagnostic ability of DCM-KPV can guarantee the real-time tracking and visualization of the role of intracellular KPV on ulcerative colitis, which provides an alternative to replace the time-consuming and tissue sampling-invasive H&E staining diagnosis.
溃疡性结肠炎的炎症活动在医学治疗中起着重要作用。然而，用非侵入性生物成像方法准确和实时地监测结肠炎的活动仍然具有挑战性，特别是在区分慢性和急性结肠炎方面。作为一种良好的受体，寡肽转运蛋白（PepT1）在慢性溃疡性结肠炎的结肠上皮细胞中过度表达，它可以将三肽 KPV（Lys-Pro-Val，α-MSH 的 C 末端序列）递送到肠道细胞的细胞质中。在此，我们报告了一种 PepT1 肽受体靶向荧光探针，二氰基乙烯-4H-吡喃（DCM）-KPV，其策略是将 KPV 缀合到 DCM 生色团上。诊断荧光探针通过 KPV 部分与 PepT1 赋予特异性受体靶向相互作用，具有几个有益的特性，例如高效长发射、低光漂白、细胞毒性可忽略不计以及在活细胞中的高细胞相容性。我们在溃疡性结肠炎模型 Caco-2 细胞的质膜上构建过表达的 PepT1，作为有效的受体，将靶向三肽 KPV 积累在细胞质和核内。随着 DCM-KPV 与 DNA 特异性荧光染料 DAPI 的共定位，生色团 DCM 的特异性长发射和高效受体靶向肽 KPV，DCM-KPV 的荧光探针通过肠黏膜实现了对结肠炎症区域积累的直接非侵入性观察的突破，甚至成功地区分了慢性、急性溃疡性结肠炎和正常组。与传统的未增强磁共振成像和苏木精和伊红（H&E）染色相比，我们充分利用三肽单元 KPV 与寡肽转运蛋白 PepT1 之间的特异性靶受体相互作用来实现传感选择性。DCM-KPV 的理想诊断能力可以保证对细胞内 KPV 在溃疡性结肠炎中的作用的实时跟踪和可视化，这为替代耗时和组织采样侵入性 H&E 染色诊断提供了一种选择。
