6-CFDA is fluorescent polyanionic probe, and its derivatives such as 2′,7′-bis (2-carboxyethyl)-5(6)-carboxyfluorescein are used to measure changes in intracellular pH (pHi) and processes such as dendrimer aggregation and absorption.
[1]. Babcock DF. Examination of the intracellular ionic environment and of ionophore action by null point measurements employing the fluorescein chromophore. J Biol Chem. 1983 May 25;258(10):6380-9. [2]. Graber ML, et al. Characteristics of fluoroprobes for measuring intracellular pH. Anal Biochem. 1986 Jul;156(1):202-12. [3]. Bonizzoni M, et al. PAMAM dendrimer-induced aggregation of 5(6)-carboxyfluorescein. J Org Chem. 2012 Feb 3;77(3):1258-66.