Two-photon Fluorescent Probes Based On Coumarin

Fluorescent probes can detect the concentration of small molecules, metal ions, proteins, DNA, etc in vivo, thereby establishing a relationship between the concentration and the physiological state. Fluorescent probes have the advantages such as high selectivity, high sensitivity, in-situ real-time detection and expedience of operation. The results of chemical reactions or binding interaction involving in fluorescent probes and biological active substances in vivo can quantify the concentration of active substances and help us to understand life activities from the microscopic point of view better. Compared with single-photon fluorescent probes, two-photon fluorescent probes own lower phototoxicity, better penetration ability and lower auto-fluorescence. In this paper, a series of coumarin-based fluorescent probes were designed and synthesized. The optical properties of probes had been studied and the cell image experiments had been made.1. To improve the two-photon properties of fluophore, two kinds of^-conjugated electron donor were introduced at 6-position (OC6, NC6) and 7-position (OC7, NC7) of coumarin framework. The compounds feature a β-keto acid as a high selective binding site for Mg2+, and OC7 and NC7 show significant "off-on" detecting signals upon addition of Mg2+. From the X-ray crystal structures and DFT calculations, the results indicated that modification of coumarin at 7-position rather than at 6-position will be an efficient way to enhance the two-photon optical properties of the fluorophore.2. Fluorescent probe PC was obtained by linking 2-(aminomethyl)-pyrodine to 7-position coumarin. PC can detect copper ions in the pure buffer solution. When addition of copper ions, the fluorescence of PC was quenched completely, and the complex can further detect PPi. Upon addition of PPi, the fluorescence recovered the 90% fluorescence of PC.3. The two-photon absorption cross section of the fluorescent probes were tested. The results indicated that the two-photon absorption cross section of the fluorescent probes were enlarged by introducing π-conjugated electron donor. They can be applied two-photon confocal laser scanning technology. The responses of probes to pH and the cell toxicity have been tested to prove that the probes have a good biological adaptation.