Synthesis Of Multifunctional Ultra-small NaGdF₄ Nanoparticles And The Applications In Magnetic Resonance T1 Imaging And Therapy

Molecular imaging is a current research hotspot in the field of imaging medicine.Research on nanomaterial-based contrast agents?known as nanocontrast agents?has been extensively studied.The early diagnosis and efficacy monitoring of diseases such as tumors through molecular imaging has always been a research hotspot in the field of medical imaging,but substantial progress is slow.Some teams have developed a variety of new nano-contrast agents through biomarkers or signal molecules for in vivo tracking and evaluation of therapeutic effects.However,the study found that the process of transforming nanocontrast agents from preclinical research to clinical application has not been ideal.The reason is that people pay more and more attention to the biological safety of nanomedicines.How to improve the specific identification and shorten the retention time of nano-probs in tumor tissues is very important for the future research and development of nano-drugs.The ability of drugs targeting tumors is divided into passive targeting and active targeting.Passive targeting is the use of the ERP effect?that is,the high permeability and retention effects of solid tumors?to make use of the widened and missing lymphatic reflux system of tumor vessel walls to enrich macromolecular drugs in tumor tissues,while active targeting It is realized by modifying the surface of nanoparticles with specific biomolecules to enhance the ability of tumor cells to absorb nanoparticles.It can be seen that active targeting has more specificity than passive targeting,and it has a significantly superior effect on the enrichment of nano-drugs in tumor tissues.As a powerful tool,magnetic resonance imaging?MRI?has been extensively applied for non-invasive diagnosis of various diseases through producing excellent soft-tissue contrast.In this paper,nano magnetic resonance contrast agents with ultra-small volume are prepared.One has the ability to actively target,which can enhance the contrast of magnetic resonance by the specific recognition via tumors and nanoparticles,and the other one is loaded with the chemotherapy drug DOX and studied its effect in treating cancer in vitro.?objective?To synthesize hyaluronic acid-functionalized NaGdF4 nano-dots?NaGdF₄ ND@HAs?that can be efficiently cleared by the kidney and use it as an MRI contrast agent targeting triple negative breast cancer tumor models.An anti-tumor nano-drug platform?NaGdF₄@tryptone-DOX?with an anti-tumor effect was constructed to explore the use of magnetic resonance to guide tumor chemotherapy.?methods?Hydrophobic NaGdF₄ nanodots were synthesized,and tryptone was used as a phase transfer agent.The hydrophobic oleic acid-coated NaGdF₄ nanodots?NaGdF₄ ND@OA,3.8 nm in diameter?were transformed to a hydrophilic phase by Gd-phosphate coordination reaction.After being activate by NHS and EDC,the HA was coupled to tryptone-coated NaGdF4 nanodots?NaGdF4@tryptone?to modify HA to the surface of NaGdF4 nanodots.The characteristics were characterized by DLS,TEM,HRTEM,XRD,XPS,EDS,FTIR and so on.In vitro cell studies were performed using triple-negative breast cancer?TNBC?cell line MDA-MB-231 cells,which overexpressed CD44 on the cell membrane,non-triple-negative breast cancer cell line MCF-7 cells and normal human kidney tissue cells 293 cells in vitro.The effects of nanodots on the viability of MDA-MB-231,MCF-7 and 293 cells were measured.Cell phagocytosis experiments were performed to detect the uptake of nanoparticles to cells,and in vitro magnetic resonance was used to detect the imaging capabilities of nanoparticles.The researches on the biological safety of nanoparticles were taken.A Balb/c nude mouse model of female subcutaneous breast cancer was constructed,and the in vivo magnetic resonance imaging studies,organ distribution and biological metabolism studies were performed on nude mice.Evaluate the biocompatibility of nanoparticles to live animals through studies on experimental animal growth conditions,daily activities and organ sections,blood routines,etc.A passive targeted magnetic resonance contrast agent NaGdF₄ ND@tryptone-DOX loaded with DOX was constructed,and its release ability under different internal environmental conditions was studied.The killing ability of nano-drugs on tumor cells and the uptake process were measured.In vitro magnetic resonance experiments was taken to detect the imaging capabilities of nanoparticles.The biological safety of nanoparticles to living animals was evaluated through studies on experimental animal growth conditions and blood routines.?results?Hydrophilic hyaluronic acid functionalized NaGdF₄ nanodots were synthesized by a simple method and characterized by various methods.After treating MDA-MB-231,MCF-7 and 293 cells with NaGdF₄ ND@tryptone and NaGdF₄ ND@HAs nanodots for 24 hours,it can be seen that the nanodots are in the concentration range of 6.25-200?g/mL,and the cell survival rate is higher than 90%.There was no significant difference in survival rates between the two groups,indicating that the nanoparticles showed low toxicity.The results of cell phagocytosis test showed that the uptake of NaGdF₄ ND@HAs was higher than that of NaGdF₄@tryptone,indicating that NaGdF₄ ND@HAs has a high affinity with MDA-MB-231 cells.The results of in vivo magnetic resonance experiments showed that at any collection time,the intensity of tumor signal collected by the nude mice in the NaGdF₄ ND@HAs nanoparticle injection group in the tumor area was stronger than that in the NaGdF₄ ND@tryptone group.The content of Gd in each major organ was detected by ICP-MS.It was found that the detection of radon in kidney and tumor tissues was significantly higher than the accumulation of radon in other organs,and the NaGdF₄ ND@HAs nanoparticle injection group was used in tumors.The amount of detection within is 1.87 times that of the NaGdF₄ ND tryptone group.The results of biodistribution experiments showed that the liver signal changed little,and the magnetic resonance signal value detected in the kidney and bladder increased significantly within 24 hours after the nanoparticle injection,and fell back to the pre-injection level after 24 hours.24 hours after the injection,approximately 75%of the Gd were collected from the urine.The morphology and diameter of the nanoparticles collected in urine did not change significantly.The results of the biocompatibility experiment showed that no matter the blood routine or the histological analysis of the main organs,the difference between the experimental group and the control group was almost negligible.The constructed NaGdF₄ ND@tryptone-DOX has a drug loading rate of more than 90%,and the ability of DOX in the weakly acidic internal environment of tumors is much higher than normal pH conditions.With the increase of drug administration,the nanoparticles have a greater effect on tumors,the virulence of the cells was significantly increased,and there was almost no difference from the free DOX.After being stored for two weeks at room temperature,the colloidal stability and imaging ability of the nanoparticles did not change significantly.The results of hemolysis experiments showed that no obvious hemolytic reaction occurred even when the concentration of nanoparticles was as high as 800?g mL-1.During the feeding period,the mice were not affected in terms of their habits and growth.Blood routine results showed that most parameters don't have differences,while the white blood cell content in the acute phase was significantly reduced,but after 10 days,they could basically recover.?conclusion?1.A simple method was used to synthesize hydrophilic hyaluronic acid functionalized NaGdF₄ nanodots.The successful preparation of NaGdF₄ ND@HAs was proved by various characterization methods.2.The in vitro experiments of NaGdF₄ ND@HAs showed that the nanoparticles showed low toxicity and had no effect on the cell morphology distribution.The nanoparticles could specifically recognize MDA-MB-231 cells,and this specific recognition was achieved by the cell surface receptor,CD44 molecule.3.The animal experiment results show that the prepared NaGdF₄ ND@HAs nanoparticles have high MDA-MB-231 tumor targeting ability,good biosafety and can be eliminated by the kidney.This study proves that NaGdF₄ ND@HAs nanoparticles have great potential to be used as an excellent magnetic resonance contrast agent for detection of overexpression CD44 tumor due to their advantages such as efficient kidney clearance,excellent targeting ability and excellent biocompatibility..4.DOX is loaded onr NaGdF⁴ ND@tryptone,because of its high drug loading rate and pH-dependent drug release ability,it has strong killing effect on tumor cells,and at the same time it exhibits excellent magnetic resonance imaging capabilities.It provides ideas for the further construction of a magnetic resonance-guided chemotherapy nanoplatform for tumor chemotherapy.