Synthesis And Performance Evaluation Of Small Organic Fluorescent Probes

Fluorescence imaging technology has become a powerful tool for the visualization of life processes because of its real-time,non-invasive,high spatial resolution and other advantages.In particular,near-infrared fluorescence emission greatly promotes in vivo imaging of molecular processes.Near-infrared fluorescent probes have unique advantages in tracking molecular processes in vitro and in vivo,including deep penetration in tissues,little damage to biological samples,and the ability to effectively avoid the interference of spontaneous background fluorescence of biological molecules.One of the advantages of organically synthesized small molecule fluorescent probes is that they can be combined with organic chemistry strategies to control the properties and positions of fluorophores and adjust the chemical structure of fluorophores.At the same time,chemical reactions can also be used to activate fluorophores.The work of this paper is divided into two parts:(1)A new near-infrared fluorescence probe(DCM-OH)which based on dicyanomethylene-4H-pyrans to detect endogenous ONOO-was designed and synthesized.The two-photon absorption cross sections and large Stokes shift make the probe deeper issue penetration and lower self-absorption.The obtained results demonstrated that probe DCM-OH could sensitively detect ONOO-with a low detection limit(53 nM).What's more,probe exhibited an ultrafast response rate(within 5 s)toward ONOO-,which would be in favor of tracking the highly reactive and short-lived ONOO-in the living systems.Moreover,probe was successfully employed for imaging endogenous ONOO-in HepG2/RAW 264.7 cells and further applied to visualize oxidative stress in mouse model of inflammation.(2)Based on rhodium-catalyzed triazole molecular cyclization,a novel rhodamine analogue fluorophore was designed and synthesized.At the same time,taking rhodamine B as the standard reference,the photophysical properties of the new rhodamine analogue fluorophore were determined,and it was found that the photophysical properties of the new fluorophore were similar to those of rhodamine.It is worth noting that an imine group is exposed in the molecular skeleton of the new fluorescent group,which is very easy to connect the recognition group or targeting group,and it is very convenient to construct a new type of fluorescent probe.In the future,designing new fluorescent probes will focus on how to integrate fluorescent signals with more functions.The functional fluorescent probe will respond to the presence of active small biological species through the fluorescent signal.For example,the probe DCM-OH in this paper responds to ONOO-at the inflammation site to reveal its role in the pathological environment.While traditional fluorescent dyes can no longer meet the increasing demands of scientific researchers,the new fluorescent chromophores constructed in this paper are very easy to chemically modify and facilitate the construction of various small molecular fluorescent probes.