Rational Design of Latent Fluorophores from Water-Soluble Hydroxyphenyltriazine Dyes Suitable for Lipase Sensing

Derivatives of 2-(2-hydroxy-5-dimethylaminobenzyl)-4,6-dimethylamino-1,3,5-triazine were synthesized by an original multistep protocol that afforded, after quaternization of the N,N-dimethylaminobenzyl moiety, water-soluble fluorescent dyes. These fluorophores exhibited excited-state intramolecular proton transfer and large Stokes shifts ((SS) > 10000 cm(-1)). The phenol residue was masked by an enzyme-labile protecting group based on self-immolative para-hydroxybenzyl alcohol. Lipases were used to unveil the fluorescence under physiological conditions (phosphate-buffered saline, pH 7.2) without aggregation or precipitation of the fluorescent dyes.