LAUSR

Abstract The involvement of biologically active nitrogen heterocycles in the construction of conjugated structures was important to improve the biocompatibility and optical properties of fluorescent probes. Herein, six pyrazolo [1, 5-a] pyrimidine derivatives (1a–f) were prepared by aldol or Suzuki reaction with the C-5 or C-7 sites of bioactive pyrazolo [1, 5-a] pyrimidine and different fluorophores. The optical properties in eight organic solvents were investigated; they showed excellent solvatochromism and the maximum emission wavelength range was from 443 nm to 678 nm. Besides, all of them exhibited high fluorescence quantum yields (0.44–0.98) in small polar solvents and they also exhibited excellent photostability. Subsequently, the fluorescent imaging experiments indicated that probes 1a–f could be used as lipid droplets (LDs) biomarkers for HeLa cells (cancer cells) and L929 cells (normal cells); moreover, the number of LDs in HeLa cells was found to be obviously more than in L929 cells, so probes 1a–f possessed great potential in distinguishing between normal cells and cancer cells, even in imaging and diagnosis of LDs-related diseases.