"We have succeeded in combining two functionalities in the same nanodevice: one able to deliver an anticancer drug very efficiently and the other that allows imaging of the tumour being treated," team leader Patrick Couvreur of the Université Paris-Sud told nanotechweb.org.

Cancer is fast becoming the most frequent cause of death in industrialized nations. Although new anticancer agents have been discovered in recent years, it is still difficult to deliver therapeutic concentrations of these drugs to tumours. In some cases, the drugs are rapidly metabolized by the body, so becoming useless (or even toxic), and in other cases the body becomes resistant to such treatments.

Nanotechnology is promising for the field of drug delivery but progress is being hampered by poor drug loading in nanoparticles (less than 10% by weight of the transported drug compared with the carrier material). This means that the amount of anticancer drug administered is often ineffective. Another major problem is that the cytotoxic drug can rapidly escape from its capsule after it has been injected into the body, before it has time to reach the target tumour. This is called "burst release" and can lead to serious side effects.

Magnetic core-based nanoparticles
Magnetic core-based nanoparticles could come into their own here, thanks to the fact that these particles can effectively be guided by an applied magnetic field to a target tumour site. Couvreur and colleagues now report on such a system containing the anticancer drug squalenoyl gemcitabine (SQgem).

The team, which includes researchers from the Universidad de Granada and the Universita degli Studi di Torino, began by dissolving the SQgem in a small volume of ethanol. They then poured the mix into a water suspension containing nanoparticles of iron oxide. The nanocomposite is seen to spontaneously self-assemble. The ethanol is then evaporated off and the nano-suspension is ready for injecting into cancer-bearing mice.

The nanocomposite is sensitive to an external magnetic field thanks to the presence of the iron oxide core and so an applied magnetic field can effectively guide it to the point of interest, as mentioned. Indeed, such composites are much better than non-magnetic squalenoyl bioconjugates at treating cancers and an added advantage is that they can be observed using magnetic resonance imaging (MRI) at the same time, so killing two birds with one stone. And to top things off, the composite has low burst release.

The team has also experimented with other anticancer squalenoyl bioconjugates, such as doxorubicin, paclitaxel and cisplatin. "By combining different anticancer medicines as well as different contrast imaging agents for MRI, we open the door to generic and flexible personalized medicine," said Couvreur.

He and his colleagues reckon that the technology could be used to treat solid tumours that cannot be easily removed because of where they are located in the body – for example, brain gliomas – or when there is a risk of haemorrhage.

The researchers, who detailed their results in ACS Nano, will now determine how toxic the nanocomposites are. They have also started to prepare clinical samples of the nanomaterials.