| In recent years,magnetic hyperthermia,as one of the treatments for cancer,has been developed and studied intensively.Much effort has been focused on the synthesis,modification of magnetic nanoparticles(MNPs)and their application in hyperthermia.Thus,remarkable progress has been made.However,Some restrictions still hider the application of MNPs in clinical trials.One of the main limitations lies in low specific absorption rate(SAR)or low heating capacity.Additionally,it is required that the MNPs employed in hyperthermia must have regular spherical shape and good dispersibility.Therefore,the preparation of MNPs with regular morphology,good dispersibility,high saturation magnetization(Ms)and high SAR is of great significance.Firstly,MnZn MNPs were synthesized by hydrothermal method and were characterized by XRD,SEM,VSM and other methods,which confirmes that the synthesized MnZn MNPs are high purity,spherical and have a Ms of 36.3 emu/g.Then different reaction conditions such as reaction time,reaction temperature,molecular weight of PEG were investigated to find the effect on the properties of nanoparticles,thus optimizing the experimental conditions of synthesizing MnZn MNPs for previous work of preparation of MnZn/CoZn MNPs.The optimum conditions are: 12 h,180 ?,0.5 g PEG6000.In addition,MNPs should not be annealed in air.However,it is found that the MnZn nanoparticles prepared by this method are not particularly high in Ms and SAR.Therefore,the paper adopted solvothermal method based on ethylene glycol(EG)to synthesize MnZn MNPs and MnZn magnetic microspheres.It demonstrates that MnZn nanospheres with different diameters,assembled from MnZn nano-crystals,exhibit regular shape and show high Ms,up to 80 emu/g,high SAR.And the effects on temperature rise and SAR value were investigated.The Mn Zn MNPs synthesized in EG:H2O=2:1 system(20 mg/m L?480 A)has maximum SAR value,reaching up to 119.7W/g.Furthermore,the effects of concentration and current intensity on the ?T and SAR value of MnZn MNPs synthesized in EG:H2O=2:1 solvent system were studied.The results show that the SAR value decreases with the increase of the concentration while the temperature rise and SAR value increases monotonically with the increase of current intensity.And it is found that the best concentrition is 5 mg/m L and has the largest SAR value of up to 224.84 W/g.At the same time,under the ccondition of low dose(5 mg/m L),low current intensity(380 A),the MNPs with high SAR value of 161.65 W/g were obtained,which is suitable for clinical application of magnetic hyperthermia.The magnetic hyperthermia experiment on the MnZn magnetic nanospheres modified with different types and addition of surface modifiers indicates that the value of SAR and ?T increase with the grain size of MnZn nano-crystals,which bears no relation to the diameters of nanosphere.Finally,the MnZn/CoZn composite MNPs have been prepared via hydrothermal method and MnZn/Co Zn-PVP has the SAR value of up to 52.11 W/g,improving the SAR of MnZn MNPs synthesized via hydrothermal method;Ag@MnZn magnetic nanoparticles and Ag@MnZn/R-GO composites,synthesized by solvothermal method,show high SAR value.Compared with Ag@MnZn composite nanoparticles,the dispersibility,magnetic properties and heat production capacity of Ag@MnZn/R-GO composites have been improved,resulting from the addition of graphene oxide.In addition,due to the two composites also possessing the property of Ag,we speculate that these composites not only can be as heat medium in hyperthermia but also can provide additional fluorescence imaging and photothermal therapy. |
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