Preparation Of ZIF-8 Drug Delivery Mediated By NTR Fluorescent Probe And Its Tumor Cell Imaging And Cytotoxicity Study

Hypoxia,a common feature of solid tumors,promotes the formation of abnormal blood vessels,which accelerate the growth and metastasis of tumors.And hypoxic tumors may lead to adverse consequences such as drug resistance to chemotherapy drugs.Nitroreductase（NTR）is the most typical reductase that is overexpressed in hypoxic tumor cells.Therefore,it is of great significance for the diagnosis and treatment of tumors to monitor the hypoxia status of tumors by detecting the activity of nitroreductase.As the research progresses,tracer materials with single-function are increasingly unable to meet the research object and practical application,so development of dual-functional nanomaterials with diagnosis and treatment,or even multifunctional nanomaterials are of great importance.In this study,multi-functional metal organic frameworks（MOFs）composite drug carrier with NTR detection,tumor imaging and drug delivery and release was designed and prepared for the first time,providing a new method and idea for tumor hypoxia monitoring and treatment.The main research works are as follows:（1）Fluorescent probes of 2-（5-fluoro-2-nitrophenyl）benzoxazole-5-carboxylic acid was synthesized and used for NTR detectionThis probe was synthesized according to the previous literature,and its structure and optical properties were characterized by hydrogen nuclear magnetic resonance（¹H-NMR）,fourier transform infrared spectrum（FT-IR）,UV-visible spectrophotometer（UV-vis）and fluorospectro photometer.In order to explore optimal reaction conditions,we optimized reaction parameters such as pH value of the solution and reaction time.Under the optimized condition,linear rang of NTR detection was 1.2-15μg/mL with a low detection limit（LOD=3N/S）of 260 ng/mL,and this probe showed good selectivity and stability.（2）The DOX@ZIF/SiO₂-Probe composite fluorescent probe based on 2-（5-fluoro-2-nitrophenyl）benzoxazole-5-carboxylic acid was synthesized and used for NTR detectionDoxorubicin（DOX）was encapsulated in situ into zeolitic imidazolate framework-8（ZIF-8）to obtain DOX@ZIF-8.Then DOX@ZIF/SiO₂-Probe with a size of about 300nm was obtained by wrapping and modifying with SiO₂ membrane and 2-（5-fluoro-2-nitrophenyl）benzoxazole-5-carboxylic acid.Prepared materials were characterized by scanning electron microscope（SEM）,X-ray diffraction（XRD）,FT-IR and X-ray photoelectron spectroscopy（XPS）.By optimizing the detection conditions,the optimal reaction parameters were 30 min for reaction time and 7 for pH.Under the optimited conditions,linnear rang of NTR detection of composite probe was 0.1-5μg/mL with a low detection limit（LOD=3N/S）of 60 ng/mL,and this composite probe showed good selectivity and stability.（3）DOX@ZIF/SiO₂-probe composite fluorescent probe in tumor imaging and cytotoxicity studyZIF-8 is a good drug carrier in response to acid stimulation.The drug release of DOX@ZIF/SiO₂-NH₂ and DOX@ZIF-8 were investigated in sodium acetate buffer（pH=5）.Results showed that the drug release rate of DOX@ZIF/SiO₂-NH₂ was 65%in35 hours,while DOX@ZIF-8 was 78%,indicating that the SiO₂ membrane may reduce the release of DOX from ZIF-8.Cytotoxicity of probe were not obvious on HUVEC and A549 cells when its concentration no more than 30μg/mL.And cytotoxicity of DOX@ZIF/SiO₂-NH₂（≤10μg/mL）was also not significant to HUVEC and A549 cells,indicating its good biocompatibility within this concentration range.When the concentration of the composite probe was 10μg/mL,cytotoxicity of HUVEC cells were not significant,while the cell viability of A549 cells was 68%,indicating that this material had significant cytotoxicity on A549 cells.In addition,the imaging application of composite probe in A549 cells would provide some references for monitoring hypoxia status of cancer cells in the future.