Fluorescence Sensing of Dopamine

Abstract

Even though boronic acid has been known for almost 50 years to have high affinity for diol-containing compounds such as carbohydrates, Czarnik and his coworker reported 2-anthrylboronic acid as the first example of fluorescent chemosensor in 1992, which displayed chelation-enhanced fluorescent quenching (CHEQ) effects upon the addition of polyols. Most noticeably, the Sinkai group and James group have been leading the field in many regards. Sinkai and his coworkers have reported new series of PET sensors for saccharides bearing boronic acid unite as well as benzyl amine unit. Recently, James group also reported many noticeable results regarding boronic acid-based fluorescent receptors for saccharides. Norrild, Drueckhammer, Wang, Heagy, and Yoon groups have been actively participating in this field. Catecholamines, including dopamines, are involved in a number of biological processes, most of them directly related to central nerve diseases, such as Parkinson’s disease and hypertension. There have been only few reports regarding fluorescence sensing of dopamine and L-DOPA, which utilized the interaction between boronic acid and catechol group. Especially, Glass and his coworker reported coumarin aldehyde as a selective chemosensor for dopamine and norepinephrine. The sensor binds to catecholamines by forming an iminium bond with the amine moiety as well as a boronate ester with the catechol moiety. Herein, we report a new anthracene fluorophore bearing boronic acid and aldehyde group as a fluorescent chemosensor for dopamine. The title compound displayed large fluorescence quenching effects with dopamine, epinephrine and catechol at pH 7.4. Compound 1 containing aldehyde group bound to dopamine in methanol about two times tighter than compound 2 did.