Viscosity sensitive fluorescent dyes with excellent photostability based on hemicyanine dyes for targeting cell membrane

In this paper, three viscosity sensitive cell membrane fluorescent dyes (1a-c) were obtained. Dyes 1a-c were linked by benzaldehyde (5) and benzoindole (2a), benzoxazole (2b) and benzothiazole (2c), with double bond, respectively. The optical properties showed that dyes 1a-c had larger molar extinction coefficients (3.34 ? 1042.64 ? 105 M-1 cm-1) and excellent photostability (89?93 %). In particular, dyes 1a-c had obvious specific response to viscosity. More specifically, they indicated significant OFF-ON fluorescent response at 563 nm, 599 nm and 601 nm to the increase of viscosity (0.89?865 cp), respectively, and displayed an excellent linear relationship with viscosity. Further, the excited-state lifetime of dye 1b was evaluated as long as 828 ps in high viscosity environment by transient absorption spectra. The low cytotoxicity of dyes 1a-c, provided the possibility to be used in living cells. Accordingly, laser confocal experiments clearly exhibited that dyes 1a-c could be well located in the cell membrane. The results can assist in our understanding of the functions of cell membrane as well as application in biosensor and diagnostics.

Automated summary

This study obtained three viscosity-sensitive cell membrane fluorescent dyes with excellent optical properties and viscosity response. The dyes showed good location on the cell membrane and low cytotoxicity, making them promising for applications in biosensors and diagnostics.