Design of a pseudo-color-assisted biocompatible supramolecular sensing probe for "lighting up" endogenous salicylic acid in plants.

The widely recognized phytohormone, salicylic acid (SA), serves not only as an exogenous additive for fruits and vegetables but, more crucially, as an in vivo regulator of the entire plant growth process. Consequently, it is essential to achieve both in vitro detection and in vivo imaging analysis of the plant hormone SA. In this study, a biocompatible supramolecular probe was crafted using a "label-free" SA aptamer as the host for an aggregation-induced emission (AIE) organic small molecule. Upon recognizing the target SA, the aptamer is not readily digested by the exonuclease (Exo.I), which permits the aptamer sequence to be largely preserved. Under these conditions, the aptamer can be further integrated with the AIE organic small molecule, thereby enabling it to produce fluorescence emission due to restricted intramolecular motion. The probe can efficiently accomplish in vitro detection of SA within a linear range of 0.3-70 μM, with a detection limit reaching 0.09 μM. Most importantly, building on the achievement of fluorescence imaging monitoring of SA in plants, this work has developed a fluorescence image processing program utilizing the Java algorithm. This program facilitates the one-click conversion of monochrome images to pseudo-color in conventional fluorescence imaging, thereby enhancing the ability of the naked eye to discern image details.