The fluorescent probe for the detection of calcium ions is an indispensable tool in the biomedical field. The millimolar order of Ca(II) ions is associated with many physiological processes and diseases, such as hypercalcemia, soft tissue calcification, and bone microcracks. However, the conventional fluorescent probes are only suitable for imaging Ca(II) ions in the nanomolar to micromolar range, which can be because of their high affinities toward Ca(II) ions and aggregation-caused quenching drawbacks. To tackle this challenge, we herein develop an aggregation-induced emission (AIE) probe SA-4CO₂Na for selective and light-up detection of Ca(II) ions in the millimolar range (0.6–3.0 mM), which can efficiently distinguish between hypercalcemic (1.4–3.0 mM) and normal (1.0–1.4 mM) Ca²⁺ ion levels. The formation of fibrillar aggregates between SA-4CO₂Na and Ca(II) ions was clearly verified by fluorescence, scanning electron microscopy, and transmission electron analysis. Moreover, this AIE-active probe can be used for wash-free and light-up imaging of a high concentration of Ca(II) ions even in the solid analytes, including calcium deposits in psammomatous meningioma slice, microcracks on bovine bone surface, and microdefects on hydroxyapatite-based scaffold. It is thus expected that this AIE-active probe would have broad biomedical applications through light-up imaging and sensing of Ca(II) ions at the millimolar level.

中文翻译：

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聚集诱导发射探针，用于高浓度钙离子的照亮和原位检测

用于检测钙离子的荧光探针是生物医学领域必不可少的工具。Ca（II）离子的毫摩尔级与许多生理过程和疾病有关，例如高钙血症，软组织钙化和骨微裂纹。但是，常规的荧光探针仅适用于在纳摩尔至微摩尔范围内成像Ca（II）离子，这可能是因为它们对Ca（II）离子的亲和力高以及聚集引起的猝灭缺陷。为了解决这一挑战，我们在这里开发了一种聚集诱导发射（AIE）探针SA-4CO ₂ Na，用于选择性和照光检测毫摩尔范围（0.6–3.0 mM）中的Ca（II）离子，高钙血症（1.4–3.0 mM）和正常（1.0–1.4 mM）Ca ^2+之间离子水平。通过荧光，扫描电子显微镜和透射电子分析清楚地证实了SA-4CO ₂ Na和Ca（II）离子之间的纤维状聚集体的形成。此外，即使在固体分析物中，该AIE活性探针也可用于高浓度Ca（II）离子的免洗和亮光成像，包括在假性脑膜瘤切片中的钙沉积，牛骨表面的微裂纹以及羟基磷灰石基支架上的微缺陷。因此，可以预期这种AIE活性探针将通过照亮成像和感测毫摩尔水平的Ca（II）离子而具有广泛的生物医学应用。