Synthesis And Application Of Fluorescent Probes For Hypoxia Detection And Imaging

Hypoxia is a one of the utmost important indicators for diseases such as malignant tumor,inflammation,stroke,and cardiac ischemia,and often,worsens the diseases.Therefore the hypoxia status is of great significance for understanding the disease.Nitroreductase(NTR)is a representative biomarker for endogenous hypoxia detection because its reduction activity is closely related to the oxygen concentration.As a consequence,evaluation of NTR level can be a method to determine hypoxia,and can also provide a strategy for the targeted therapy,which is crucial for diagnosis and drug development.However,it’s still a challenge to develop NTR fluorescent probes with properties such as selectivity,high sensitivity,precise targeting,and water solubility.In this paper,OFF-ON molecule fluorescent probes Naphthalimide Nitroreductase Probe(NNP)and c RGD-Naphthalimide Nitroreductase Probe(c RGD-NNP)were developed for the detection of nitroreductase.Both of the probes exhibited excellent photostability,not easy to bleach,stable to p H and high fluorescence quantum yield.The probe NNP was designed by a naphthalimide derivative as a fluorophore,and 2-nitroimidazole was used as a recognition group.The OFF-ON of the fluorescent probe was designed to achieve lower fluorescence background to improve the signal-to-noise ratio by the d-PET effect.When NNP was used to detect nitroreductase in solution,the fluorescence enhancement was 108 times higher than that of the blank.The NNP shows high selectivity,rapid response and low detection limit(3.6 ng/m L).Due to the tumor targeting ability of the hydrophilic c RGD,the probe c RGD-NNP has high specificity,good water solubility,biocompatibility and targeting ability.Experiments show that it was effective to detect nitroreductase activity in MCF-7 breast cancer cells under different hypoxic conditions,and targeted to tumor sites of mice and be reduced.In additional,it is successful to use the liposomeencapsulated NNP to visualize nitroreductase in liver of hepatitis mice.This work also proposes a new method for the detection of nitroreductase that NNP is modified on the optical fiber to realize the excitation and collection of fluorescent signals through the optical fiber,so as to realize the rapid detection of nitroreductase in deeper position.