Design And Synthesis Of Near Infrared Fluorescent Probes And Their Applications In In Vivo Imaging Of Tumor Biomarkers

In recent decades,the diagnosis of tumor-related diseases has become a hot research topic,and also faces a huge challenge in the fields of chemistry and biology.It is worth noting that early diagnosis of diseases is particularly important for preventing the deterioration of the disease and improving the effect of clinical treatment.Therefore,disease diagnosis has attracted close attention in related research fields and clinical research.The progress of the development of medical imaging probes severely hinder the detection of early tumors and small lesions,which in turn limits the diagnosis of diseases.Regarding the difficulty of early diagnosis of tumors,innovative medical imaging and diagnosis technologies are urgently in demand.Compared with other imaging technologies,near-infrared imaging has attracted widespread attention due to its high sensitivity and high resolution imaging.Near-infrared imaging can not only visualize cellular processes and quantitatively detect biological functions in vivo,but also can be used to clarify biological processes and understand information in biological systems,which will undoubtedly promote the development of disease diagnosis,therapy and prevention.Therefore,the development of high-performance near-infrared imaging probes has potential prospects in tumor diagnosis.In this study,two different near-infrared fluorescent probes were constructed and successfully applied for in vivo imaging of related tumors.The main research results are summarized as follows:It has been found that quinone oxidoreductase（NQO1）is an important cancer biomarker that plays important roles in many physiological and pathological processes.Near-infrared（NIR）fluorescent probes capable of selectively detecting NQO1 in vivo will become a useful tool for understanding the mechanism of its biological processes.We reported an easy-to-synthesized and stimuli-responsive NIR fluorogenic probe（QCy7-NQO1）for selective evaluation of NQO1 in living cells and mice.In response to the NQO1 stimulus,QCy7-NQO1 is converted to QCy7,and shows a unique off-on NIR fluorescence signal change.The results of selectivity and kinetic studies indicate that the probe has a high NQO1 response capability.The probe can be used to detect NQO1 content in HT-29 cells.In addition,the probe was successfully applied to real-time in vivo imaging of NQO1 in tumor-bearing mice,indicating that the probe can be used as an effective tool for detecting NQO1 activity in vivo.On the other hand,we propose a promising design strategy based on metal cluster probes,which combines bioorthogonal reaction with metal clusters to achieve efficient and rapid preparation of multifunctional metal cluster probes.Taking the rationably designed probe FA-Cu _C@BSA-Cy5 based on azide-functionalized Cu clusters as an example,we demonstrate the design of multifunctional near-infrared fluorescent probes based on metal clusters and in vivo near-infrared imaging applications.Through the strain-promoted azide-alkyne cycloaddition（SPAAC）reaction,the tumor targeting ligand folic acid（FA）and fluorophore（Cy5）can be chemically conjugated with azido-functionalized Cu _C@BSA-N₃ under biocompatible conditions.The prepared probe showed numerous advantages,including good stability,ultra-small size,hypotoxicity and rapid renal clearance.FA-modified FA-Cu _C@BSA-Cy5 can specifically target KB cells with high FR expression,and in vivo imaging shows high tumor accumulation of FA-Cu _C@BSA-Cy5.In summary,the designed azido-functionalized clusters in this study can be efficiently coupled with different functional groups through bioorthogonal chemistry,providing a novel idea for the construction of multifunctional fluorescent imaging probes for future medical diagnosis.On the other hand,through the ingenious design strategy of small molecule probes,the off-on fluorogenic probes that respond to tumor marker stimulation provide a more effective means for the detection of the dynamic changes of analytes and the diagnosis of physiological diseases.Therefore,reasonably designed NIR fluorescent probes capable of detecting tumor-related biomarkers are of great significance for obtaining disease-related physiological and pathological information.