Design,Synthesis And Medical Imaging Applications Of New PH Fluorescent Probes

The stability of the human body's pH is closely related to the normal physiological function of life maintenance.If the pH of the body is abnormal,it will lead to cell disorder in the body.This situation will lead to some physiological diseases such as stroke,Alzheimer's disease,cardiovascular and cerebrovascular diseases and even cancer.In eukaryotic cells,various organelles correspond to different pH values.For example,pH in cytoplasm is weakly alkaline,while the lysosomes are weakly acidic(pH 4.0-6.0).Under acidic pH condition,the lysosomes(such as proteases,phosphatases,lipases,nucleases,etc.)are activated.The stable pH ensures the normal operation of lysosomes.Therefore,the cells and the changes in the pH of organelles are monitored in real time,which is great scientific value for the disease diagnosis and metabolic activity of organisms.In the detection methods for detecting the pH value of the biological samples,the fluorescent probes are widely applied to detect the pH in biological samples because of their strong visibility,simple operation,good selectivity,small amount of required sample,high temporal and spatial resolution,and small side effects on cells.According to the research status of pH fluorescent probes,the efficiency of specific detection of pH by fluorescent probes is improved.Different pH fluorescent probes have been designed and studied in this paper.(1)In the second chapter,we designed a ratiometric pH fluorescent probe,which can be used to detect the lysosomal targeting in two-site detection.It is composed of the coumarin and naphthalimide fluorophore with excellent fluorescence properties.It is named probe CN-pH.The Probe CN-pH are respectively connected on the pH response sites in the two fluorophores.Under alkaline conditions,the hydroxyl coumarin group will become negative oxygen ions,and it has strong electron donating ability to strong fluorescent of the coumarin group.Under acidic conditions,the N atom of the morpholine group of the naphthalimide will be protonated so that the PET mechanism is limited.coumarin group hydroxyl becomes negative oxygen ions,with strong electron donating ability to strong fluorescent coumarin group,under acidic conditions,naphthalimide morpholine group N atoms will be the PET of the proton the mechanism is limited.The energy resonance of the coumarin is transferred to the naphthalimide group to form a large push-pull system.The probe CN-pH can detect awide range of pH,showing dual-mode fluorescence signal changes.We successfully used CN-pH to perform pH fluorescence imaging of organelle lysosomes and real-time monitoring of pH changes in cells and lysosomes.(2)We have designed a two-photon pH fluorescent probe by using naphthalimide as a fluorophore,which can be used for double site detection of lysosome targeting.It is named probe MP-Lys.The probe MP-Lys is designed with two pH response sites and two lysosomal targeting sites.The pH of the organelle lysosomes is about 4.0-6.0.Therefore,the N atom of the two pH-responsive sites of morpholine and piperazine on the naphthalimide group will be protonated so that the PET mechanism is limited,and the probe MP-Lys is detected as a change in fluorescence signal.The naphthalimide fluorophore has a two-photon property,so the probe MP-Lys has little damage to the cell.We successfully used MP-Lys to perform pH fluorescence imaging of organelle lysosomes and real-time monitoring of pH changes in cells and lysosomes.(3)Using naphthalimide as a fluorophore to design a two-photon fluorescent probe that targets the detection of lysosome's internal pH in tumor cells,which is named as probe BN-Lys.The probe BN-Lys uses naphthalimide as a fluorophore,and the morpholine group and D-biotin group are designed to be pH-responsive sites and tumor-targeting sites,respectively.The expression or activity of lysosomal cathepsin is involved in the apoptosis of tumor cells and is closely related to the invasion and metastasis of tumors.During this process,the lysosomal pH of tumor cells will increase.Therefore,the probe BN-Lys is great significance for pathological research of tumor and cancer.The N atom of the pH-responsive sites will be protonated so that the PET mechanism is limited,and the probe BN-Lys is detected as a change in fluorescence signal.It has good selectivity for tumor cells and lysosomes.We successfully used BN-Lys to perform pH fluorescence imaging of lysosomes in tumor cells and real-time monitoring of pH changes in cells and lysosomes.