Novel Approaches For Tumor Diagnosis Based On Functionalized ZIF-8 Nanomaterials And DNA Nanoassemblies

Cancer is one of the main causes of human death in the world today.The clinical stage of cancer directly determines the prognosis of the patient.Generally,early-stage patients can obtain a higher survival rate and prognostic quality.However,At present,the traditional tumor diagnosis methods are still more suitable for the diagnosis after the occurrence of tumor lesions or clinical symptoms.By this time the cancer may have progressed to intermediate or even advanced stages,reducing the patient's chances of a cure.Therefore,the development of accurate and effective tumor diagnosis strategies is of great significance for providing relevant information on tumor development and improving the survival rate of patients.Based on ZIF-8nanocomplex and functionalized DNA tetrahedrons,two novel fluorescent sensing platforms for tumor-related RNA markers have been constructed in this paper.The specific contents are as follows:In chapter 2,miR-21 is a kind of non-coding,endogenous RNA with a length of22 nt and its abnormal expression level is indicative of some diseases,especially cancer.Therefore,miR-21 are considered to be reliable biomarkers for cancer diagnosis and prognosis.We developed a miR-21-triggered polymerase/endonuclease synergistic amplification reaction in living cells.The fluorescence signal generated by this amplification strategy in aqueous solution has linear relationship with the concentration of miR-21 within a certain range,and the detection limit was 4 pM.The amplification strategy in living cells was constructed on ZIF-8 nanoparticles,in which enzymes were encapsulated inside the particles and nucleic acid probes were adsorbed on the surface of the particles.The ZIF-8 composite is capable of internalizing cells and achieving pH-responsive degradation into the cytoplasm.In the presence of miR-21,miR-21 will activate the polymerase/endonuclease synergistic amplification reaction to produce amplified fluorescence signal.This amplification strategy can quickly and specifically respond to miR-21,and is successfully used for sensitive imaging of fluctuating miR-21 expression level,providing a new way for the construction of a multi-protein assisted system in living cells.In Chapter 3,the tumor-associated overexpression patterns of miR-21 and Survivin mRNAs make them potential targets for tumor diagnosis and treatment.Based on fuel stimulants-powered nucleic acid reaction,AS1411 sequence and DNA tetrahedron,we assembled a novel nucleic acid fluorescent probe triggered by two tumor markers for intracelluar imaging.The dynamic nucleic acid reaction for markers' recognition parts and the AS1411 sequence for targeting part are simply assembled on the vertices of DNA tetrahedron.Only when miR-21 and survivin mRNAs are present,the crossed chain replacement reaction between the two marker recognition parts can be triggered to isolate the TAMRA/BHQ2-labeled chains,thus restoring TAMRA's fluorescence.The probe achieves impressive cell internalization efficiency through rigid tetrahedral structure and targeting part.The co-expression of miR-21 and Survivin mRNA are evaluated by recovered fluorescence signals.It comes out to show significant differences of fluorescence signals between cancer cells and normal cells,providing a potential method for accurate identification of cancer cells for tumor diagnosis.