Molecular Imaging Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892-1088, United States.
Bioconjug Chem. 2011 Dec 21;22(12):2531-8. doi: 10.1021/bc2003617. Epub 2011 Nov 16.
Optical imaging is emerging as an important tool to visualize tumors. However, there are many potential choices among the available fluorophores. Optical imaging probes that emit in the visible range can image superficial tumors with high quantum yields; however, if deeper imaging is needed then near-infrared (NIR) fluorophores are necessary. Most commercially available NIR fluorophores are cyanine based and are prone to nonspecific binding and relatively limited photostability. Silica-containing rhodamine (SiR) fluorophores represent a new class of NIR fluorophores, which permit photoactivation via H-dimer formation as well as demonstrate improved photostability. This permits higher tumor-to-background ratios (TBRs) to be achieved over longer periods of time. Here, we compared an avidin conjugated with SiR700 (Av-SiR700) to similar compounds based on cyanine dyes (Av-Cy5.5 and Av-Alexa Fluor 680) in a mouse tumor model of ovarian cancer metastasis. We found that the Av-SiR700 probe demonstrated superior quenching, enabling activation after binding-internalization to the target cell. As a result, Av-SiR700 had higher TBRs compared to Av-Cy5.5 and better biostability compared to Av-Alexa Fluor 680.
光学成像是一种重要的工具，可以用于可视化肿瘤。然而，在现有的荧光染料中，有许多潜在的选择。发射在可见光范围内的光学成像探针可以用高量子产率对浅层肿瘤进行成像；然而，如果需要更深层的成像，则需要近红外（NIR）荧光染料。大多数市售的近红外荧光染料基于菁染料，容易发生非特异性结合，并且相对稳定性有限。含有硅的罗丹明（SiR）荧光染料代表了一类新的近红外荧光染料，它可以通过 H-二聚体形成进行光激活，并表现出更好的光稳定性。这使得可以在更长的时间内实现更高的肿瘤与背景比（TBR）。在这里，我们在卵巢癌转移的小鼠肿瘤模型中，将与 SiR700 偶联的亲和素（Av-SiR700）与基于菁染料的类似化合物（Av-Cy5.5 和 Av-Alexa Fluor 680）进行了比较。我们发现，Av-SiR700 探针表现出更好的猝灭性能，使其在与靶细胞结合内化后能够被激活。因此，与 Av-Cy5.5 相比，Av-SiR700 具有更高的 TBR，并且与 Av-Alexa Fluor 680 相比具有更好的生物稳定性。
