Definition of fluorescein in US English:



  • An orange dye with a yellowish-green fluorescence, used as an indicator and tracer.

    A derivative of resorcinol and phthalic anhydride; chemical formula: C₂₀H₁₂O₅

    • ‘To this purpose we have considered four dyes, namely: indo - 1, rhodamine 6G, fluorescein, and pyrene.’
    • ‘Anole splenocytes were phagocytically active and produced copious amounts of nitric oxide following exposure to fluorescein labeled E. coli bioparticles.’
    • ‘Rhodamine and fluorescein signals were observed using a fluorescence microscope with the appropriate filters.’
    • ‘A generation - 5 dendrimer platform with fluorescein, folic acid, and methotrexate on its surface may be better at killing tumor cells in vitro than a free drug.’
    • ‘Quinine bisulfate was used as the standard for the bisbenzimide dyes, for PIH and ethidium bromide the standard used was rhodamine 101 and fluorescein was used for the cyanine dyes.’


Late 19th century: from fluorescence + -in.