We have designed and synthesized a series of novel, supramolecular, long-lived fluorescent probes based on the host-guest inclusion complexes formation between fluorescent indolizinyl-pyridinium salts and β-cyclodextrin. Fluorescence and electrospray ionisation mass spectrometry experiments, supported by theoretical molecular docking studies, were utilized in the monitoring of the inclusion complexes formation, evidencing the appearance of corresponding 1:1 and 1:2 species. Additionally, the influence of the guest molecule over the aggregation processes of the cyclodextrin inclusion complexes was investigated by transmission electron microscopy. The absence of cytotoxicity, cellular permeability, long-lived intracellular fluorescence, and in time specific accumulation within acidic organelles identified the investigated supramolecular entities as remarkable candidates for intracellular fluorescence probes. Co-staining experiments using specific organelle markers revealed the fact that, after a 24-h incubation period, the inclusion complexes accumulate predominantly in lysosomes rather than in mitochondria. This study opens new possibilities for a broad range of fluorescent dyes with solubility and high toxicity issues, able to form inclusion complexes with β-cyclodextrin, to be tested as intracellular fluorescence probes.

中文翻译：

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环糊精封装的 pH 敏感染料作为荧光细胞探针：自聚集和体外评估

基于荧光茚-吡啶盐和β-环糊精之间形成的主客体包合物，我们设计并合成了一系列新颖的、超分子的、长寿命的荧光探针。在理论分子对接研究的支持下，荧光和电喷雾电离质谱实验被用于监测包合物的形成，证明相应的 1:1 和 1:2 物种的出现。此外，通过透射电子显微镜研究了客体分子对环糊精包合物聚集过程的影响。无细胞毒性、细胞通透性、长寿命的细胞内荧光，并且随着时间的推移，酸性细胞器内的特异性积累将所研究的超分子实体鉴定为细胞内荧光探针的显着候选物。使用特定细胞器标记的共染色实验表明，经过 24 小时的潜伏期后，包合物主要在溶酶体中而不是在线粒体中积累。这项研究为广泛的具有溶解性和高毒性问题的荧光染料开辟了新的可能性，能够与 β-环糊精形成包合物，作为细胞内荧光探针进行测试。包合物主要在溶酶体中而不是在线粒体中积累。这项研究为广泛的具有溶解性和高毒性问题的荧光染料开辟了新的可能性，能够与 β-环糊精形成包合物，作为细胞内荧光探针进行测试。包合物主要在溶酶体中而不是在线粒体中积累。这项研究为广泛的具有溶解性和高毒性问题的荧光染料开辟了新的可能性，能够与 β-环糊精形成包合物，作为细胞内荧光探针进行测试。