Bright Zinc Probes with Thiomorpholine Monoxide Auxochromes for Imaging Insulin Secretion.

Zinc biology significantly impacts human physiological and pathological processes, especially for β-cell endocrinology. In 2021, our group reported the family with minimal phototoxicity and μM affinities for monitoring Zn/insulin corelease during vesicular secretory events on β-cells (Zhang et al. Angew. Chem. Int. Ed.2021, 60 (49), 25846-25855). Here, we synthesized a series of Zn probes () featuring thiomorpholine monoxide auxochromes with values ranging from 160 nM to 94 μM. By inhibiting the twisted intramolecular charge transfer (TICT) state, the fluorescence quantum yields of can be effectively increased to ∼7 times those of . A privileged candidate, , has a high turn-on ratio (∼134), appropriate affinity (340 nM), and excellent hydrophilicity, making it a powerful tool for long-term recording of insulin secretion in mouse islets with minimal phototoxicity.