Red- and Far-Red-Emitting Zinc Probes with Minimal Phototoxicity for Multiplexed Recording of Orchestrated Insulin Secretion.

Zinc biology, featuring intertwining signaling networks and critical importance to human health, witnesses exciting opportunities in the big data era of physiology. Here, we report a class of red- and far-red-emitting Zn2+ probes with Kd values ranging from 190 nM to 74 μM, which are particularly suitable for real-time monitoring the high concentration of Zn2+ co-released with insulin during vesicular secretory events. Compared to the prototypical rhodamine-based Zn2+ probes, the new class exploits morpholino auxochromes which eliminates phototoxicity during long-term live recording of isolated islets. A Si-rhodamine-based Zn2+ probe with high turn-on ratio (>100), whose synthesis was enabled by a new route featuring late-stage N-alkylation, allowed simultaneous recording of Ca2+ influx, mitochondrial signal, and insulin secretion in isolated mouse islets. The time-lapse multicolor fluorescence movies and their analysis, enabled by red-shifted Zn2+ and other orthogonal physiological probes, highlight the potential impact of biocompatible fluorophores on the fields of islet endocrinology and system biology.