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A novel di-functional system was synthesized by encapsulation of superparamagnetic Fe3O4 and a therapeutic agent 5-fluorouracil (5-Fu) with the thermo-responsive poly(N-isopropylacrylamide) (PNIPAM), which was coated with mesoporous SiO2 nanoparticles in a mesoporous core–shell structure. The system featured functionalized magnetic Fe3O4 and a smart thermo-responsive polymer PNIPAM. In an alternating magnetic field (AMF), the magnetic nanoparticles were heated up to 45 °C, which was the cancer treatment temperature. Therefore, it has potential for hyperthermia treatment. The smart polymer PNIPAM has a lower critical solution temperature (LCST), which is representative of a phase transition behavior. Based on it, the thermo-responsive polymer PNIPAM played a role of an on-off trigger switch in the process of drug releasing. The tests of drug releasing were investigated by UV-visible spectrophotometry at 45 °C and 25 °C. The test results showed that there was little drug released at 25 °C (below the LCST) but drug was mainly released at the temperature of 45 °C (above the LCST). In a word, our studies were mainly about the di-function of the composite: magnetic hyperthermia treatment and drug release. It has potential applications for reducing side effects of cancer treatment and achieving controlled drug release in response to variations of temperature. [ABSTRACT FROM AUTHOR]

With a high Curie temperature and low entropy change, the magnetic-field-induced martensitic transformation has been obtained in ferromagnetic shape memory alloys MnNiGa by doping a small amount of Co. Due to the ferromagnetic activation effect of Co, a large amount of antiferromagnetically aligned Mn moments are turned into ferromagnetic ordering, which is verified by our electronic structural calculation and experimental observation. Consequently, the magnetization rises up to 70 emu/g and the magnetization difference between two phases increases about ten times, resulting in a considerable dT/dH of 4 K/T and a well-defined reversed transformation induced by a magnetic field. [ABSTRACT FROM AUTHOR]

Effect of a magnetic field on martensitic transformation in the NiCoMnGa alloys was investigated. A field-induced reversible martensitic transformation from the martensitic phase of low magnetization to the parent phase of high magnetization has been realized. The substitution of Co for Ni atoms has turned the magnetic ordering of the parent phase from partially antiferromagnetic to ferromagnetic, resulting in a large magnetization change across the transformation, which dramatically enhances the magnetic field driving force. The transformation temperature can be downshifted by magnetic field at a rate up to 14 K/T in Ni37Co13Mn32Ga18. Other mechanism details were also discussed. [ABSTRACT FROM AUTHOR]

Magnetic field-induced martensitic transformation was realized in Ni50-xCoxMn39Sb11 alloys. The partial substitution of Co for Ni has turned the antiferromagnetically aligned Mn moments in the starting material Ni50Mn39Sb11 into a ferromagnetic ordering, raising the magnetization at room temperature from 8 emu/g for NiMnSb to ∼110 emu/g for Ni41Co9Mn39Sb11. In the same quaternary sample, a magnetization difference up to 80 emu/g was measured across the martensitic transformation, and the transformation temperature (T0=259 K) could be lowered by 35 K under a field of 10 T. Also a magnetoresistance over 70% was observed through this field-induced transformation. [ABSTRACT FROM AUTHOR]