生物谷报道：肿瘤细胞与正常细胞的耐热程度不同，因此采用热疗治疗肿瘤，一直是科学家探索的方法之一，传统的方法采用加热等方式，均无法达到有效的靶向治疗。实际上，50年前，科学家也发现另外一个现象，磁性纳米颗粒在改变磁场的情况下，能实现颗粒加热的现象，称为特别吸引率（SAR）。但是具有磁性的纳米颗粒都是由金属氧化物组成的，如铁的氧化物，但这些氧化物无法被探测到，因此，使研究成为难题！
最新美国Dartmouth大学科学家巧妙构思，在磁性的金属氧化纳米颗粒表面再覆盖一层金属离子，形成一个复合的纳米粒子，通过磁性分子的导引，使纳米颗粒集中到肿瘤位置，然后改变磁场，使粒子发热，杀死肿瘤细胞。
Nanocomposite turns up the heat on cancer
Iron/iron oxide nanocomposite particles could be used to heat tumours and destroy them say scientists in the US. Ian Baker of Dartmouth College in New Hampshire and colleagues have found that iron particles have a large "specific absorption rate" and so produce lots of heat. The iron particles are then coated with iron oxide, which allows the nanoparticles to be observed using magnetic resonance imaging (MRI).
Scientists have known for 50 years that magnetic nanoparticles can heat up in an alternating magnetic field. However, the nanoparticles need to have a high specific absorption rate (SAR) if they are to be used for destroying tumours. A large SAR not only reduces the dose of nanoparticles required but also minimizes the region treated, so that the heat from the nanoparticles does not affect surrounding healthy tissue.
Iron oxide particles have been used to induce hyperthermia because of their excellent biocompatibility and their good SAR, which results in efficient heating. For clinical applications, scientists also need to be able to observe the nanoparticles in vivo before starting treatment. Superparamagnetic iron nanoparticles typically 4?nm across are used for imaging using MRI but the problem is that these particles are not very efficient for magnetic heating.
Baker and co-workers may now have overcome this dilemma – by using iron particles coated with iron oxide nanoparticles. The saturation magnetization of iron is more than twice that of an iron oxide particle so the SAR also doubles. But, since pure iron cannot be imaged using MRI, the researchers decided to coat it with a thin shell of iron oxide nanoparticles. They therefore have the best of both worlds: the high SAR of iron for heating and the iron oxide film for imaging.
The iron oxide coating also passivates the core iron particles, which are unstable and would otherwise oxidize.
The nanocomposite particles could be used to treat cancer in two ways. The first is to antibody-tag the nanoparticles and inject them into the bloodstream, where they will then find their way to the tumour. The second, which is more suitable for near-surface tumours (like neck tumours), is to directly inject the nanocomposites into the tumour.
Baker told nanotechweb.org that the production method is relatively simple and cheap, and that the nanoparticles produced are fairly uniform in size.
The team now plans to vary the particle size and work on developing different coatings for the particles. Next, the researchers hope to perform in vivo studies by directly injecting the nanoparticles into mice with tumours, as they have already done with iron oxide particles.
The work was published in Appl. Phys. Lett.
