A new near-infrared fluorescent probe Qcy-OH with a turn-on mechanism based on a acceptor-donor-acceptor (ADA) π-electron system that can undergo an internal charge transfer to form new fluorochromes was developed for monitoring pH fluctuations in biological systems. With the pH value increases, Qcy-OH exhibited a strong pH-sensitive response from 1.1 to 9.0 (pKa = 4.41) and a good linear response from pH 3.0 to 5.5 in aqueous solution and in living cells. In addition, based on the phenolic and ketonic structure interconversions of the fluorescent backbone, Qcy-OH showed rapidly and reversibly response to pH with high selectivity. Because the introduce of two benzothiazolium units in the backbone of the probe as the electron-withdrawing group to enhance the selectivity for intracellular lysosomes, the probe had been applied successfully for tracking lysosomal pH changes and the fluorescence changes showed a good linear enhancement from pH 3.0 to 7.4 in living cells. We believe that this sulfur-driving lysosomes-targeting ability of the probe affords a guarantee for achieving long-term monitoring of lysosomal pH biology by the elimination of harmful protonating effects of the probe.

开发了一种新的近红外荧光探针Qcy-OH，它具有基于受体-供体-受体 (ADA) π 电子系统的开启机制，可以进行内部电荷转移以形成新的荧光染料，用于监测生物体内的 pH 值波动。系统。随着 pH 值的增加，Qcy-OH在水溶液和活细胞中表现出从 1.1 到 9.0（p Ka = 4.41）的强烈 pH 敏感响应和从 pH 3.0 到 5.5 的良好线性响应。此外，基于荧光骨架的酚醛和酮结构相互转换，Qcy-OH以高选择性显示出对 pH 值的快速和可逆响应。由于在探针骨架中引入了两个苯并噻唑单元作为吸电子基团以增强对细胞内溶酶体的选择性，因此该探针已成功应用于追踪溶酶体的 pH 变化，并且荧光变化从 pH 3.0 开始呈现出良好的线性增强在活细胞中达到 7.4。我们相信，探针的这种硫驱动溶酶体靶向能力为通过消除探针的有害质子化效应实现对溶酶体 pH 生物学的长期监测提供了保证。