Self-assembling nanoparticle targets tumours

Researchers at Imperial College London (ICL) have designed a nanoparticle which helps boost the effectiveness of magnetic resonance imaging (MRI) scanners by specifically seeking out receptors that are found in cancerous cells, according to research published today.

The research can be found in the journal Angewandte Chemie.

The nanoparticle, which is coated in a special protein, operates by looking for specific signals transmitted by tumours, the researchers said.

Scientists at ICL told Laboratorytalk.com: “The protein is not actually a whole protein, but a small part of one, a peptide. The one [we] have used to target the tumours is made up of 5 amino acids - the components of all proteins.”

To create these targeted nanoparticles the researchers chemically attached the peptides to the nanoparticle surface in such a way as to control the number of peptides per particle and also the way in which they are displayed.

“By improving the sensitivity of an MRI examination, our aim is to help doctors spot something that might be cancerous

ICL researcher Nicholas Long

Once the particle locates a tumour, it begins to interact with the cancerous cells. This interaction then strips off the protein coating which causes the nanoparticle to self-assemble into a much larger particle so that it is more visible on the MRI scan.

To conduct the study, ICL researchers used cancer cells and mouse models to compare the effects of the self-assembling nanoparticle in MRI scanning against commonly used imaging agents.

Prior to testing in mice, the nanoparticle was injected into a saline solution to make sure that it would not become so big when it self-assembled that it would cause damage. The nanoparticle grew from 100 to 800 nanometres - still small enough to not cause any harm, the researchers said.

Results taken from the study using mouse models suggest that the nanoparticle produced a more powerful signal and created a clearer MRI image of the tumour.

According to the researchers, the improved scanning sensitivity will enable doctors to detect cancerous cells at a much earlier stages of their development.

Nicholas Long, from the Department of Chemistry at ICL, said: “By improving the sensitivity of an MRI examination, our aim is to help doctors spot something that might be cancerous much more quickly. This would enable patients to receive effective treatment sooner, which would hopefully improve survival rates from cancer.”

Added Long: “MRI scanners are found in nearly every hospital up and down the country and they are vital machines used every day to scan patients’ bodies and get to the bottom of what might be wrong.

“But we are aware that some doctors feel that even though MRI scanners are effective at spotting large tumours, they are perhaps not as good at detecting smaller tumours in the early stages.”

Although recently developed, scientists are already conducting new work to improve the effectiveness of the nanoparticle.

“We would like to improve the design to make it even easier for doctors to spot a tumour and for surgeons to then operate on it. We’re now trying to add an extra optical signal so that the nanoparticle would light up with a luminescent probe once it had found its target, so combined with the better MRI signal it will make it even easier to identify tumours,” Long said.

The ICL team is hoping to test its design in a human trial within the next three to five years.

Juan Gallo, from the Department of Surgery and Cancer at ICL, said: “We’re now looking at fine tuning the size of the final nanoparticle so that it is even smaller but still gives an enhanced MRI image. If it is too small the body will just secrete it out before imaging, but too big and it could be harmful to the body.

“Getting it just right is really important before moving to a human trial.”