Synthesis And Magnetic Heating Properties Of Spinel Ferrite Nanoparticles With Self-regulating Temperature

Self-regulating temperature magnetic induction hyperthermia(MIH)is an intelligent hyperthermia technology,realizing self-regulating temperature through magnetic phase transition,which has the good application prospect.For magnetic nanoparticles(MNPs)used in MIH,the synthesis of MNPs with high heating efficiency and low Curie temperature is critical for promoting self-regulating temperature MIH to clinical application.The spinel ferrite nanoparticles are the conventional materials for MIH due to the stable chemical properties and adjustable magnetic properties.Their magnetic properties depend on the types,contents and distribution on A and B sites of metal ions.Here,the self-regulating temperature MNPs with high heating efficiency,which may be used for conventional hyperthermia(42-46?)and hightemperature hyperthermia(46-60?),were synthesized through reducing the ratio of Co2+ions at B sites,tuning the content of doped ions and annealing.The main contents are as follows:The MNPs Zn0.54Coo.46Cro.6Fe1.4O4 with Curie temperature of 48.8? and a heating efficiency of 6.53 W/g(intrinsic loss power:0.255 nH·m2/kg)under clinical alternating magnetic field(16 kA/m,100 kHz)were prepared through reducing the ratio of Co2+ions at B sites.The calculation results based on linear response theory and Stoner-Wohlfarth model suggest that hysteresis loss and relaxation loss are the two major power loss mechanisms of MNPs under the alternating magnetic field,in which the relaxation loss is dominant.The results of magnetic heating experiments show that these nanoparticles can self-regulate temperature at 48.0?,suggesting that these nanoparticles possess self-regulating temperature property.The MNPs ZnxCo1-xCr0.4Fe1.6O4(0.5<?x??0.7)with Curie temperature in the range of 42.6145.0? and heating'efficiency in the range of 9.8-26.8 W/g(intrinsic loss power:0.388-1.05 nH·m2/kg)under clinical alternating magnetic field were synthesized through tuning the content of doped ions.The Curie temperature and heating efficiency of Zno.7Co0.3Cro.4Fe1.6O4 are 42.6? and 9.8 W/g(intrinsic loss power:0.383 nH·m2/kg)respectively,which may be used for conventional hyperthermia.The Curie temperature and heating efficiency of Zn0.65Co0.35Cr0.4Fe1.6O4 are 59.7? and 26.8 W/g(intrinsic loss power:1.05 nH·m2/kg)respectively,which may be used for high-temperature hyperthermia.The results of magnetic heating experiments show that the Zn0.7Co0.3Cr0.4Fe1.6O4 and Zn0.65Co0.35Cr0.4Fe1.6O4 can selfregulate temperature at 42.2? and 59.3?,suggesting that these nanoparticles possess selfregulating temperature property.The Curie temperatures of ZnxCo1-xCr0.4Fe1.6O4(x=0.5,0.55 and 0.6)were reduced from 145.0?,123.8? and 88.8? to 118.5?,94.0? and 52.6? by annealing.The annealing may cause the migration of Co2+ions from B sites to A sites,reducing the Curie temperature.The results of magnetic heating experiments show that the Zn0.7Co0.3Cro.4Fe1.6O4 after annealing could self-regulate temperature at 52.0?,suggesting that these nanoparticles possess selfregulating temperature property.Besides,the heating efficiency of the annealed Zn0.6Co0.7Cr0.4Fe1.6O4 is 28.6 W/g(intrinsic loss power:1.12 nH·m2/kg)under clinical alternating magnetic field.An injectable magnetic hydrogel,which could gel rapidly under body temperature,was prepared through combining the annealed Zn0.6Co0.7Cro.4Fe1.6O4 and an injectable hydrogel.The injectable magnetic hydrogel was injected subcutaneously into the back of mice for magnetic heating experiment to study the heating performance of the annealed Zn0.6Co0.7Cr0.4Fe1.6O4 in vivo.The results show that the temperature of the magnetic hydrogel in mice can be self-regulated in 49.6-50.7? in the three magnetic heating experiments,suggesting that this magnetic hydrogel possesses self-regulating temperature property.