Napthalimide-based fluorescent probe for selective and sensitive sensing of formaldehyde and biological applications

Formaldehyde (FA) is a colorless, flammable, foul-smelling chemical used in building materials and in the production of numerous household chemical products. To develop a fluorescent chemosensor for FA, a newly prepared probe 1 containing napthalimide as a fluorophore and hydrazine as a binding site of FA was designed and prepared. The amine group of the hydrazine reacts with FA to form an imide bond. Indeed, the absorption band of probe 1 at 438 nm shifted to 443 nm upon the addition of FA, indicating that the condensation reaction occurred. Also, the addition of FA to probe 1 induced a large enhancement of the emission band at 532 nm compared with the relatively very weak fluorescent emission of probe 1 alone. This high specificity toward FA was observed over other competing analytes such as Ca²⁺, Mg²⁺, acetaldehyde, benzaldehyde, salicylaldehyde, glucose, glutathione, Na₂S, NaHS, H₂O₂, and tert-butylhydroperoxy radical. The typical two-photon dye present in probe 1 also afforded intense fluorescence upon excitation, even at 800 nm, demonstrating that probe 1 could be used for a two-photon fluorescent probe for FA sensing. Probe 1 had a quick response time in the sensing of FA at room temperature. In addition, breast cancer cells treated with probe 1 exhibited intense fluorescence imaging upon exposure to FA, indicating that probe 1 could be used for monitoring FA in living cells. This probe can lead to new possibilities for unique interactions with biological molecules for applications.