Coumarin-based acid dye for fluorescent staining of calcium carbonate particles

Abstract

Vital fluorescence staining of calcium-containing structures in calcifying organisms is a powerful tool for the study of biocalcification. The main dyes used in this field have green or red fluorescence, which may be overlapped with the fluorescence of chlorophyll and other organic substances. We synthesized a novel coumarin-based fluorescent dye QA2 that stains calcium carbonate and calcium phosphate. The fluorescence of this dye depends from environment, it is enhanced in non-polar medium with a shift of the emission maximum to the blue spectrum region. Small vaterite and calcium phosphate particles adsorb QA2 on the surface and exhibit predominantly green fluorescence, while low surface area calcite crystals are stained in bulk and show additional intense blue fluorescence. The ability of the QA2 dye to generate blue fluorescence of calcium carbonate may be useful for tracking calcium carbonate formation at living organisms in the presence of green and red fluorescent organic substances.