Pentamethinium fluorescent probes: The impact of molecular structure on photophysical properties and subcellular localization

• Fluorescent probes based on pentamethinium salts.
• Influence of structure and medium on photostability of a fluorescent probe.
• Mitochondrial localization based on interaction with cardiolipin.
• Live-cell fluorescence imaging of mitochondrial network.

The performance of fluorescent probes arises from their structural basis. In this study, we report design and synthesis of a series of novel symmetrical γ-substituted pentamethinium fluorescent probes. Relationship between structure, photophysical properties and intracellular localization was explored and structural variations resulting in high photostabillity and selectivity for subcellular localization were obtained. Substitution of benzothiazolium moieties on both sides of the pentamethinium chain for indolium units led to red shift in the absorption and fluorescence emission maxima of the probe and increased photostability. The major advantage of the probes with side indolium units is their mitochondrial specificity, high photostability and synthetic accessibility.

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