Magnetic Nano-bubbles Preparation And Magnetic Hyperthermia Effect In Glioma

The current treatment of glioma has the problem of high death risk and high recurrence rate.Therefore,some new treatment methods and techniques have been proposed.Among them,magnetic nanoparticles are used as a magnetocaloric agent.Combined with an alternating magnetic field,and the temperature is raised to 42°C or more,but not more than 50°C resulting in thermal damage to tumor cells.However,due to limited cell/tumor tissue phagocytosis and short residence time in cells/tumor tissues,the killing efficiency of magnetocaloric tumors is low.Therefore,exploring how to improve the magnetocaloric properties of magnetic nanoparticles is still a hotspot in current research.In this thesis,by loading magnetic nanoparticles on the nanobubble structure,the effect of magnetic nanobubbles on the magnetocaloric effect of gliomas was studied.The main research content of the thesis includes the following three aspects:(1)After chemically coupling magnetic nanoparticles with carboxyl groups and DSPE-PEG2000 with amino groups through amide bonds,the lipid nanobubbles(MNBs)loaded with magnetic nanoparticles(MNPs)were prepared by repeated extrusion,and the physical and chemical properties were characterized.The FT-IR absorption peak at 1635-1660 cm^-1 proved the conjugation between the magnetic nanoparticles and the phospholipid material.The characterization of the physical and chemical properties of the bubbles demonstrates that the prepared MNB has a hydrodynamic mean size of 699.4±48.96 nm with a polydispersity coefficient(PDI)of 0.315.The Zeta potential is-21.2 m V.Scanning electron microscopy(SEM)results show that MNBs are spherical in shape and there are particles on the surface of the membrane shell.Transmission electron microscopy(TEM)results show that the spherical structure of MNBs is divided into a membrane shell and a central gas core region.And the magnetic nanoparticles are combined into the lipid membrane shell to form a granular structure.The enhanced ultrasound imaging results indicate that MNBs can be uniformly distributed in the solution and have a strong ultrasound contrast enhancement effect.The in vitro magnetocaloric results of MNBs further show that when the current of magnetocaloric is 12A and the iron concentration in MNBs is 1.0 mg/m L,it has the optimized magnetic conversion effect.(2)Based on the structure construction and characterization of MNBs,the magnetocaloric effect of the prepared magnetic nanobubbles interacted with the cell was further explored.In terms of cell biocompatibility,the U87MG cytotoxicity of MNBs was tested.The results demonstrate that the cell viability is higher than 80%in the range of 0-0.8 mg/m L iron concentration for U87MG cells.And for brain microvascular endothelial cells(b ENb3 cells),the cell viability is higher than 80%in the range of 0-1.2 mg/m L iron concentration.Based on the results of cytotoxicity experiments,MNBs are more toxic to U87MG glioma cells than MNPs because MNBs can enhance the phagocytosis of MNPs under the same dosage conditions.Based on the optimizing of the cytotoxicity evaluation of MNBs,the cell magnetocaloric effect was studied.First,the U87MG glioma cell phagocytosis experiment of MNBs and MNPs was explored,and the Fe content in the cells was detected by ICP to evaluate the uptake of MNBs and MNPs.The results show that under the same time conditions,the more concentration of MNBs in the U87MG glioma cells are measured.Furthermore,by optimizing the magnetocaloric parameters including the concentration of MNBs,the current of the alternating magnetic field,and the number of magnetocaloric times,the experiment determins that the best magnetocaloric parameters of the MNBs for U87MG cells are:the concentration of iron in the bubble 1.0 mg/m L;the magnetic field Current 12 A;3 times of magnetic heating,30 min each time and 2 h interval.The cell killing efficiency reaches 70%in 30 min,and the magnetic thermal killing efficiency was still 70%after 24 h treatment.(3)Finally,based on the optimized magneto-caloric program at the cellular level,a preliminary study of the in vivo magneto-caloric effect was carried out on the in situ glioma mouse model.Experiments show that the blood flow in the brain of mice injected with MNBs in situ after one time of magnetic heating increased.The growth of tumors is inhibited after repeated magnetic heating for three consecutive days.The T₂ magnetic resonance imaging exhibits that the imaging of the magnetic heating area and the brain glioma area in the mouse brain glioma after.The appearance of dark spots in the imaging area indicates that the magnetic heating causes the loss of water in these parts and weakens the signal.The pathological section results of brain glioma also exhibits that the volume of mouse glioma after magnetothermal treatment is smaller than that of the control group.