Visualizing mitochondria and mouse intestine with a fluorescent complex of a naphthalene-based dipolar dye and serum albumin

We have explored a new research field of fluorophores through the manipulation of fluorophore-binding proteins. The development of a new imaging agent for tracing a specific organelle or a particular site within a living organism has been of great interest in the field of basic science as well as translational medicine. In this work and for the first time, we will disclose a new naphthalene-based dipolar dye and its complex, with serum albumin (SA), and show their applicability for the selective imaging of mitochondria in cells and the intestine in a mouse. The SA-binding dipolar dye, IPNHC, was synthesized straightforwardly, and we identified its photophysical properties and binding mode with SA. IPNHC-SA complex showed a bright emission in the blue wavelength range with a high quantum yield and stability. In the fluorescence imaging study, bright fluorescence images of mouse intestines were observed under a UV light, as well as two-photon (TP) deep tissue imaging after intravenous injection of IPNHC and IPNHC-SA complex. The present findings hold great promise for the application of the fluorescent complex for use in the tracing and tracking of intestine-related diseases at clinical sites.