Medical imaging methods may soon have a new contrast agent thanks to a different way of preparing nanoparticles. This simple method developed by Chinese scientists involves heating an iron salt in a polyalcohol to give a water soluble material.

A TEM image of the PBS buffer suspension of the magnetite nanoparticles

Magnetite (Fe₃O₄) nanoparticles are a promising class of materials for improving the contrast in biomedical imaging techniques, such as MRI. To be useful for imaging, the contrast agent should be non-toxic, water soluble and not prone to aggregation. High crystallinity and a uniform size distribution also improve the reproducibility and effectiveness.

Now Wei Cai and co-workers at Harbin Institute of Technology, China, have developed a new synthesis of magnetite nanoparticles using the polyol process. This method involves heating an iron(III) salt in triethylene glycol to give highly crystalline magnetite-based nanoparticles, with a uniform size. The magnetite has a hydrophilic surface which prevents aggregation and ensures solubility in water (or phosphate buffered saline) without requiring any further surface modification.

Wei Cai said that the synthesis 'provides an alternative approach to the traditional coprecipitation method for large scale preparation of magnetic nanoparticles for biomedical applications'. The synthesised magnetite nanoparticles also had high uptake by cancer cells. Preliminary experiments suggest that these nanoparticles could also be useful as a biomarker for imaging cancer cells.

'Using the polyol process provides a convenient way to prepare highly monodisperse and water-soluble Fe₃O₄ nanoparticles,' commented Chen-Sheng Yeh, an expert in nanomaterials at the National Cheng Kung University, Taiwan. 'The strong magnetization and specific targeting to cancer cells from the resulting magnetites are promising for applications in in vivo cancerous studies,' he added.

Russell Johnson