Tunable and Nontoxic Fluorescent Probes Based on Carbon Dots for Imaging of Indole Propionic Acid Receptor in Plant Tissues in Situ.

Indole propionic acid (IPA) is one of the important plant growth hormones for promoting rooting and fruiting. Labeling IPA receptor in plant tissues is able to further track the signal transduction processes of IPA and uncover the function mechanism of IPA on crop productions. In this paper, a tunable and nontoxic fluorescent probe for IPA receptors was designed and synthetized base on carbon dots (C dots). Firstly carboxyl-modified carbon dots were prepared by high temperature cracking of citric acid. The fluorescence emission wavelengths of C dots varied with the excitation wavelengths change. Then IPA-modified carbon dots (IPA-C dots) were prepared by coupling the amino of tryptophan with the carboxyl of as-prepared carbon dots. Compared with C dots, the fluorescence intensity of IPA-C dots was double and the fluorescence stability was satisfactory under various conditions. This probe retained the biological activity of IPA and acted as target recognition of IPA receptors in plant tissues. The probe could avoid green fluorescence background of plants. The imaging results showed that the IPA receptors mainly existed on the membrane of stele. The toxicity test indicated the probe was less toxic than traditional inorganic semiconductor quantum dots.