Solvent-dependent ratiometric fluorescent merocyanine dyes: Spectral properties, interaction with BSA as well as biological applications

• A series of merocyanine dyes with excellent spectral properties were synthesized.
• Dyes showed solvent-dependent changes on fluorescence spectra in different solvents.
• Interaction of dye 7d with BSA showed ratiometric response to solvent/protein.
• Dyes 7b–7h exhibited almost no cytotoxicity and stained live cell cytoplasm and mice.

A series of merocyanine dyes with excellent spectral properties were synthesized through changing the heterocyclic base structure for protein labeling and imaging in biological science, such as living cells and living mice. Dyes 7c–7h showed solvent-dependent changes on emission wavelength and fluorescence intensity in water and hydrophobic solvents, which were further analyzed by theoretical calculations and absorption spectra. The interaction of dye 7d with bovine serum albumin (BSA) showed an obvious ratiometric fluorescence response to solvent/protein environment, with the potential to report protein conformational changes. Investigation of the cytotoxicity and bioimaging capability displayed that dyes 7b–7h showed low cytotoxicity, and could stain living cell cytoplasm and be used for imaging in living mice with bright fluorescence at the application dose, which was suggested as fluorescent reagents for imaging in biological science.

A series of novel merocyanine dyes 7a–7h were prepared. The interaction of dye 7d with BSA showed an obvious ratiometric fluorescence response to solvent/protein environment. Cytotoxicity and bioimaging capability of the dyes 7b–7h were also investigated.Figure optionsDownload as PowerPoint slide