A ratiometric optical imaging probe for intracellular pH based on modulation of europium emission
作者:Robert Pal、David Parker
DOI:10.1039/b718993a
日期:——
A set of three pH-responsive ratiometric Eu(III)complexes has been synthesised incorporating a coordinated azathioxanthone sensitiser and a pH dependent alkylsulfonamide moiety. Emission properties, anion binding affinities, pH response curves and protein binding constants were studied in detail in aqueous media, and solutions containing various concentrations of interfering anions and protein were also examined. The complex, [EuL3] exhibited some interference from protein and endogenous anions, e.g.lactate and hydrogen carbonate, but possessed a protonation constant of 7.2 in human serum solution. A suitable calibration curve was obtained and was used to determine the local pH using a 680/589 nm intensity ratio vs. pH plot. Confocal fluorescence microscopy images revealed fast uptake of the complex and a well distributed localisation within the cell; fast egress also occurred. Ribosomal localisation, with a high concentration within the protein-dense nucleoli was observed, in a similar manner to structurally related complexes bearing the same coordinated sensitising moiety. An IC50 value of 67 (±20) µM was estimated using an MTT assay. Selected emission band ratio versus pH plots allow pH measurement in the range 6 to 8, enabling intracellular pH to be measured by microscopy. A value of 7.4 was estimated for NIH 3T3 cells in the protein rich regions of the nucleolus and ribosomes.
我们合成了一组三个具有 pH 值响应的比率测量型 Eu(III)络合物,其中包含一个配位的氮氧蒽酮敏化剂和一个与 pH 值相关的烷基磺酰胺分子。在水介质中对发射特性、阴离子结合亲和力、pH 值响应曲线和蛋白质结合常数进行了详细研究,并对含有不同浓度干扰阴离子和蛋白质的溶液进行了检测。复合物[EuL3]受到蛋白质和内源性阴离子(如乳酸盐和碳酸氢盐)的一些干扰,但在人血清溶液中的质子化常数为 7.2。通过 680/589 nm 波长强度比与 pH 值的关系曲线,我们得到了一条合适的校准曲线,用于确定局部 pH 值。共聚焦荧光显微镜图像显示了复合物的快速吸收和在细胞内的良好定位分布;同时还显示了快速排出。观察到核糖体定位,在蛋白质密集的核小体内浓度较高,其方式与含有相同配位敏化分子的结构相关复合物相似。使用 MTT 试验估计 IC50 值为 67 (±20) µM。选择的发射带比率与 pH 值的关系图允许在 6 到 8 的范围内测量 pH 值,从而可以通过显微镜测量细胞内的 pH 值。据估计,NIH 3T3 细胞核和核糖体蛋白质丰富区域的 pH 值为 7.4。