State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Linggong Road, High-Tech district, Dalian 116024, China.
J Mater Chem B. 2019 Jan 21;7(3):408-414. doi: 10.1039/c8tb02635a. Epub 2018 Dec 19.
The overexpression of nitroreductase (NTR) in hypoxia has been recognized as a biomarker of highly aggressive disease, and the development of a hypoxia-sensitive two-photon (TP) bioimaging probe with both excitation and emission wavelengths in the red-light region provides favorable deep-tissue imaging with a low background fluorescence signal. Although quite a few TP hypoxia-sensitive fluorescent probes have been reported for NTR detection, their short emission wavelength (<550 nm) limits their application. Herein, we report a red light emissive TP hypoxia-sensitive turn-on probe (NRP) by employing Nile Red as a red-emitting fluorophore and p-nitrobenzene as an NTR recognition group with improved sensitivity. The NRP probe showed obvious strong red-fluorescence enhancement in the presence of NTR and high selectivity toward NTR in aqueous solution. Our in vitro experimental results illustrated that the NRP loaded tumor cells treated under hypoxia display remarkably strong fluorescence in both OP and TP microscopy at 655 nm with 45-fold enhancement, which affords deep-tissue penetration ability. The NRP probe was also successfully applied for imaging NTR in liver tissue slices and a 4T1-bearing mice model, which is important for bioimaging applications.
硝基还原酶（NTR）在缺氧条件下的过表达已被认为是高度侵袭性疾病的生物标志物，开发一种具有双光子（TP）生物成像能力的缺氧敏感性探针，其激发和发射波长都在红光区域，这为具有低背景荧光信号的深层组织成像提供了有利条件。尽管已经有相当多的用于 NTR 检测的 TP 缺氧敏感性荧光探针被报道，但其较短的发射波长（<550nm）限制了其应用。在此，我们报告了一种红光发射的 TP 缺氧敏感性开环探针（NRP），它以尼罗红作为红光荧光团，以对硝基苯作为 NTR 识别基团，并具有改进的灵敏度。NRP 探针在存在 NTR 的情况下表现出明显的强红光荧光增强，并且在水溶液中对 NTR 具有高选择性。我们的体外实验结果表明，NRP 负载的肿瘤细胞在缺氧条件下处理后，在 OP 和 TP 显微镜下均显示出极强的荧光，在 655nm 处增强了 45 倍，具有良好的组织穿透能力。该 NRP 探针还成功地应用于肝组织切片和 4T1 荷瘤小鼠模型中的 NTR 成像，这对于生物成像应用非常重要。
