Magnetic nanoparticles can be used to destroy cancer cells. The knowledge of the rheological properties of the cancer cells allows to model the motion of the particles at the surface of the membrane and to get a better understanding of the mechanisms. A first approach was to use magnetic microprobes to determine the viscoelastic properties of a gel that represent the tumor cells. Then a more convenient AFM method has been employed. We have carried out a more general analysis of the AFM tip motion which contains both the indentation and relaxation steps, allowing a better determination of the rheological parameters, in particular of cancer cell called Hep-G2. The knowledge of the viscoelastic behavior of these cells allowed us to predict their indentation by magnetic particles submitted to an alternative field gradient. The synthesis of some of these particles such as: spindle-type iron and gold core-shell nanoparticles, and cobalt nanoneedles were carried out in our laboratory. We proved that the application of an alternative magnetic field of low frequency (a few Hertz) in the presence of magnetic microparticles was able "in vitro" to destroy cancer cells, and a constant magnetic field was far less efficient than an oscillating one. Based on the indentation model, we proposed that the magnetic field induces the formation of clusters of particles which are then large enough to damage the membranes of the cells. Besides magnetolysis by mechanical way we have also shown that cobalt nanoneedles presented an important hysteresis cycle which can be used for hyperthermia treatment of cancer cells at frequencies as low as 10 kHz.
