A Novel and Robust Series of Organelle Fluorescent Probes

We have developed and tested a series of organelle‐specific fluorescent probes based on the aminonaphthalimide fluorophore. The three probes presented here redistribute according to transmembrane voltage, pH or high cholesterol lipid domains. We have successfully used them to image mitochondria, lysosome/acidic endosomes and Golgi apparatus in multiple live mammalian cell lines as well as fungi including Candida biofilms by confocal microscopy. Compared to some of the most popular commercial probes, our probes possess several advantages: 1) they utilize the increasingly available but little used 405 nm laser for excitation yet due to a large Stokes shift can be visualized with green filter sets such as those used with GFP, 2) they equilibrate rapidly (seconds to minutes) with target organelles and respond rapidly to changing conditions such as mitochondrial depolarization, 3) they are extremely chemically stable and photostable allowing long‐term monitoring of live cell organelles and 3D confocal imaging as well as having a long shelf life, 4) they have low toxicity toward mammalian and fungal cells and, 5) they have high quantum yields with little self quenching allowing for quantitative and qualitative imaging in complete culture media with minimal interference from background and autofluorescence. These probes have the potential to be very useful in long‐term microscopic cell biology studies and other methods using live cells such as flow cytometry. Support or Funding Information Office of Research and Sponsored Programs‐ UW‐Eau Claire