Fig. 1: Immunofluorescence micrograph of HeLa cells after magnetism-induced hyperthermia.

Understanding the interactions between nanoparticles and biological systems could lead to new tools for diagnostics, imaging and medical therapies for diseases such as cancer. Iron‑based nanoparticles generate heat when exposed to alternating magnetic fields (AC) and scientists are exploring ways of using this heat to kill cancerous cells by a process call hyperthermia. Dhirendra Bahadur and colleagues at the Indian Institute of Technology Bombay, in Mumbai, recently described the properties of a new biocompatible suspension of magnetic nanoparticles and their interactions with immortalised cancer cells.1

The IIT Bombay group have developed a one‑pot method to synthesize stable monophasic manganese iron oxide nanoparticles. They selected a composition with the highest magnetisation—hence strongest magnetic hyperthermic properties—and suspended the nanoparticles in a viscous non-toxic solution of polyacrylic acid creating a uniform dispersion. As expected, on exposure to an AC magnetic field the temperature of the nanoparticle suspension increased.

When HeLa cells were exposed to suspension‑containing growth medium and the AC field, and then incubated for 24 hours, more of these cells died compared to control cultures. In fact, at constant amplitude and frequency of the field, cell death was proportional to the quantity of magnetic material and duration of exposure to the field. The cells did not uptake substantial quantities of nanoparticles: hyperthermic effects were therefore extracellular rather than intracellular.

Using immunofluorescence microscopy, Bahadur’s group observed that hyperthermic cells showed different morphology compared with cells in control cultures. The microtubule and actin networks of the cells’ cytoskeletons were disrupted following magnetic hyperthermic treatment. The authors observed cell membrane blebbing with accumulation of tubulin in the blebs, and that after 12 hours incubation following exposure the actin cytoskeleton was completely destroyed. The results suggest that disruption of the cytoskeleton as a result of hyperthermia contributed to the death of the cells.

The authors believe that further work to functionalize their magnetic nanoparticles with drugs and targeting molecules could yield a combined hyperthermic chemotherapeutic approach to cancer relief.