Selective and efficient detection and imaging of nitroreductase (NTR) overexpressed in hypoxic tissues is of great importance for better understanding its biological functions. The effective optical probes equipped for NTR detection in vivo is still lacking, so we developed an innovative near infrared (NIR) fluorescent on-off probe (Cy-NO₂) composed of fluorescence reporting unit (an aminocyaine dye) and recognition unit (p-nitrobenzylcarbamate group). The response and mechanism of the NTR activated reduction of Cy-NO₂ were evaluated in vitro through kinetic optical studies, mass spectra analysis and docking calculations. The results demonstrated that Cy-NO₂ could rapidly recognize NTR with high selectivity and sensitivity. The efficient NTR detection ability of Cy7-NO₂ was further validated by fluorescence imaging of hypoxic cells (A549, PC-12 and HUVEC cell). Furthermore, the in vivo hypoxia imaging by Cy-NO₂ were evaluated on tumor-bearing mouse, cerebral ischemia (CIS) and deep vein thrombosis models. The results indicated a rapid and distinct enhancement of its NIR fluorescence highly appropriate for in vivomonitoring of NTR in all of the three animal models, which revealed aspiring clinical value of this NIR fluorescent hypoxia probe.

选择性和有效地检测和成像在低氧组织中过表达的硝基还原酶（NTR）对于更好地了解其生物学功能非常重要。仍然缺少可用于体内NTR检测的有效光学探针，因此我们开发了一种创新的近红外（NIR）荧光开关探针（Cy-NO ₂），该探针由荧光报告单元（氨基可卡因染料）和识别单元（p -硝基苄基氨基甲酸酯基）。通过动力学光学研究，质谱分析和对接计算，在体外评估了NTR激活的Cy-NO ₂还原反应和机理。结果表明，Cy-NO ₂可以高选择性和高灵敏度快速识别NTR。通过低氧细胞（A549，PC-12和HUVEC细胞）的荧光成像进一步验证了Cy7-NO ₂的有效NTR检测能力。此外，在荷瘤小鼠，脑缺血（CIS）和深静脉血栓形成模型上评估了Cy-NO ₂在体内的低氧成像。结果表明，在所有三种动物模型中，其NIR荧光都快速而独特地增强，非常适合于体内对NTR的监测，这揭示了这种NIR荧光低氧探针的令人鼓舞的临床价值。