A benzothiazole-based ratiometric fluorescent probe for detection of formaldehyde and its applications for bioimaging.

We presented a new benzothiazole-based fluorescent probe for ratiometric sensing of formaldehyde. Upon treatment with formaldehyde, the alkylamine-functionalized probe can be converted to its aldehyde analogue via the target-mediated 2-aza-Cope rearrangement, which led to significant shifts in both absorption (from 392 to 452 nm) and emission (from 492 to 552 nm) bands. The sensing mechanism was confirmed by HPLC, UV/Vis and fluorescence spectroscopy. The probe is capable of sensing formaldehyde under physiological conditions with high selectivity over potentially competing biological analytes. The probe also displayed sensitive ratiometric fluorescence response (up to 35.7 fold) for formaldehyde with a low limit detection of 0.58 μM. Furthermore, the probe was successfully employed for ratiometric imaging of formaldehyde in living cells as well as in zebrafish.