A biscoumarinyl hydrazone based nontoxic fluorescent dye for direct binding and imaging of actin in living cells and organism

The filamentous protein ‘actin’ plays an essential role in maintaining a proper cellular health and any disruption in its structure and dynamics may induce the growth and metastasis of cancerous cells. Recent studies have shown that, actin can serve as a potential therapeutic target and an indicator to examine the efficacy of modern chemotherapeutic agents. In this regard, the microscopy imaging of actin using fluorescent dyes can pave the way toward development of efficient drugs for cancer treatment. Herein, we report the synthesis of an organic fluorescent dye (BCH) which shows good selectivity toward F-actin at physiological pH. The dye displays a large Stokes shift (~232 nm), strong emission intensity, good photostability and great sustainability over a wide pH range of 2 to 10. The dye can directly bind and localize in the actin-rich region of gut, testes and eye of a model organism, Drosophila melanogaster in both living and fixed cells and enable their confocal microscopy imaging without using any actin binding domain. Interestingly, the BCH dye is proved to be nontoxic in the tested organism and has been successfully employed as a potential tool to visualize cellular actin in living tissues of larva and pupa of the organism.