Engineering High-performance Near-infrared Fluorescent Probes For Imaging Research In Disease Model

Early diagnosis of diseases is crucial for disease treatment.Due to the advantages of excellent selectivity,high sensitivity and deeper signal feedback depth,activatable near-infrared（NIR）fluorogenic probes can non-invasively monitor physiological and pathological processes in vivo,which have become an indispensable tool for the early diagnosis of disease.However,it is difficult for small molecular fluorogenic probes to accurately detect and map the early biomarkers with low concentration in the deep microlesion.Therefore,there is in urgent need of high-performance fluorogenic probes that can accurately in vivo detect tiny lesions of early diseases.Notably,thanks to the tailor-made features of small molecular fluorogenic probes,their photophysical properties,responsiveness and biodistribution can be customized systematically for specific purpose by the modification of molecular structure.In this thesis,the imaging performance of molecular probes was improved by different design strategies.We hope that the excellent probes are capable of achieving early diagnosis of the disease and further promote the development of precision medicine.（1）Enzyme-activated liver-targeted NIR fluorogenic probe for visualization of drug-induced liver injuryIn order to improve the insufficient fluorescence signal and low sensitivity caused by the insufficient accumulation of molecular probe in the lesion,active targeting strategies was adopted to promote the ability to target the region of interest.At the same time,by integrating highly targeted accumulation with activatable probe platform,diseased-related biomarker can be detected and mapped with high sensitivity,thereby finally achieving high-sensitive diagnosis of disease in situ.In this section,a LAP-activated hemi-cyanine fluorogenic probe hCy-CA-LAP was designed for the detection of LAP and fluorescence imaging of drug-induced liver injury（DILI）.The hCy-CA-LAP probe was modified with a high-affinity cholic acid to improve the liver-targeting capacity.Then the liver-targeting hCy-CA-LAP was used for in situ imaging of APAP-induced DILI.Compared with the non-targeting probe hCy-LAP,hCy-CA-LAP is able to effectively accumulate in the liver,thereby realizing precise imaging and evaluation of DILI in vivo.This study demonstrated that enzyme-activated fluorescent probes with in situ targeting are the key to improving the imaging performance,then hCy-CA-LAP was applied for accurate in vivo imaging of two different types of DILI（APAP-induced acute liver injury and RFP-induced cholestatic liver injury）.（2）NIR fluorescent/photoacoustic dual-modal probe for accurate imaging of hepatic inflammationFor the insufficient information and poor accuracy of single-modal fluorescence imaging,multi-modal imaging that combines the advantages of different modes was adopted for comprehensive and accurate detection of early lesions.By combining the high sensitivity of fluorescence imaging and the high resolution of photoacoustic imaging,an O₂^·--activated dual-modal probe hCy-Tf-CA was designed,which greatly improved the accuracy of the detection of early biomarker O₂^·-and liver inflammation.NIR fluorescence images showed that hCy-Tf-CA could sensitively detect hepatic O₂^·-in hepatic inflammation mouse modal.At the same time,photoacoustic images exhibited the distribution information of hepatic O₂^·-with high resolution.Therefore,hCy-Tf-CA can achieve more comprehensive and accurate assessment of early hepatic inflammation.Notably,this two-in-one strategy greatly reduce the synthetic workload,providing a promising strategy for precision medicine.（3）Activated NIR probe with hydrophilic modification for the detection and tracking of NQO1 in cells and in vivoIn view of the poor imaging performance of molecular fluorogenic probes in vivo,the physical properties were improved by the modification of probe structure,so as to facilitate the high sensitivity detection of biomarkers and in situ imaging of early lesions.First,QCy7 probe platform with large Stoke’s shift and excellent optical properties was selected to design sensitive imaging probes.Based on this platform,we constructed an early tumor biomarker NAD（P）H:quinone oxidoreductase-1（NQO1）specific activated NIR fluorogenic probe QCy7-NQO1.Then,by introducing two hydrophilic sulfonates,a hydrophilic NIR probe S-QCy7-NQO1 was designed and optimized,which significantly improved its response rate and optical brightness in biological systems,and realized sensitive detection of endogenous NQO1 activity in living cells and tumor-bearing mice.Therefore,S-QCy7-NQO1 not only serves as a practical tool for detecting abnormal NOQ1 levels in early tumor,but also provides a simple way to enhance the imaging performance of fluorogenic probes in vivo.