Joint Center of Biomedical Imaging (BMI) of Department of Chemistry & Institute of Biomedical Science & Cancer Hospital, Laboratory of Advanced Materials, Fudan University, Shanghai 200433, P. R. China.
J Am Chem Soc. 2011 Jul 27;133(29):11231-9. doi: 10.1021/ja202344c. Epub 2011 Jul 1.
A nonemissive cyclometalated iridium(III) solvent complex, without conjugation with a cell-penetrating molecular transporter, Ir(ppy)(2)(DMSO)(2)PF(6)(-) (LIr1), has been developed as a first reaction-based fluorescence-turn-on agent for the nuclei of living cells. LIr1 can rapidly and selectively light-up the nuclei of living cells over fixed cells, giving rise to a significant luminescence enhancement (200-fold), and shows very low cytotoxicity at the imaging concentration (incubation time <10 min, LIr1 concentration 10 μM). More importantly, in contrast to the reported nuclear stains that are based on luminescence enhancement through interaction with nucleic acids, complex LIr1 as a nuclear stain has a reaction-based mode of action, which relies on its rapid reaction with histidine/histidine-containing proteins. Cellular uptake of LIr1 has been investigated in detail under different conditions, such as at various temperatures, with hypertonic treatment, and in the presence of metabolic and endocytic inhibitors. The results have indicated that LIr1 permeates the outer and nuclear membranes of living cells through an energy-dependent entry pathway within a few minutes. As determined by an inductively coupled plasma atomic emission spectroscopy (ICP-AEC), LIr1 is accumulated in the nuclei of living cells and converted into an intensely emissive adduct. Such novel reaction-based nuclear staining for visualizing exclusively the nuclei of living cells with a significant luminescence enhancement may extend the arsenal of currently available fluorescent stains for specific staining of cellular compartments.
一种非发光的环金属铱(III)溶剂配合物，没有与穿透细胞膜的分子转运体共轭，Ir(ppy)(2)(DMSO)(2)PF(6)(-)（LIr1），已被开发为第一个基于反应的荧光开启剂，用于活细胞的核。LIr1 可以快速和选择性地使活细胞的核发光，产生显著的发光增强（200 倍），并且在成像浓度下具有非常低的细胞毒性（孵育时间<10 分钟，LIr1 浓度 10 μM）。更重要的是，与基于与核酸相互作用的发光增强的报道的核染料相比，作为核染料的配合物 LIr1 具有基于反应的作用模式，其依赖于其与组氨酸/含组氨酸的蛋白质的快速反应。已经在不同条件下详细研究了 LIr1 的细胞摄取，例如在不同温度下、高渗处理下以及存在代谢和内吞抑制剂的情况下。结果表明，LIr1 通过几分钟内的能量依赖性进入途径穿透活细胞的内外膜。通过电感耦合等离子体原子发射光谱法（ICP-AEC）测定，LIr1 积累在活细胞的核中，并转化为强发光加合物。这种用于可视化活细胞的核并显著增强发光的新型基于反应的核染色方法，可能会扩展当前用于特定染色细胞区室的荧光染料的武器库。
