A team of researchers from Imperial College London has designed a self-assembling nanoparticle that can target tumors, and which could bring earlier diagnoses of cancer through more effective magnetic resonance imaging (MRI) scanning. They sought to improve on current techniques for detecting small tumoral masses by making MRI contrast agents more specific and sensitive, to help doctors identify cancers much quicker.

The non-toxic nanoparticle is coated with a protein that identifies signals given off by tumors by targeting specific receptors located in cancerous cells. On finding a tumor, the nanoparticle interacts with the cancerous cells as the protein coating is stripped off, resulting in the nanoparticle self-assembling into a much larger particle that can be more easily seen by scanning.

The study, which featured in the journal Angewandte Chemie [Gallo et al. Angew Chem. Int. Ed. (2014) DOI: 10.1002/anie.201405442], compared the effects of the self-assembling nanoparticle in MRI scanning against more typical imaging agents, demonstrating that the nanoparticle provided a more powerful signal and clearer MRI image than small molecules. They also had to ensure the nanoparticle did not grow too big to become harmful or too small so that it would be secreted before imaging.

The nanoparticles are functionally versatile and offer interesting physical properties; for instance, their magnetic properties vary depending on whether they are on their own or aggregated, which was used to advantage. Instead of injecting large magnetic particles that could cause serious problems to the patients, they employed tiny nanoparticles that could be combined in specific sites. As researcher Juan Gallo told Materials Today, “We have prepared a probe that not only finds and accumulates in the tumor, but it also responds to it changing its properties (size and magnetic properties through aggregation) to provide a more intense (and then easier to distinguish) signal.”

They also demonstrated that quite complex designs can be achieved on nanoparticulate probes; here, through ligand design, they obtained a probe that reacts to provide an increase in the signal detected by MRI, a design that could find other applications such as in drug release. The team is now looking to fine-tune the size of the final nanoparticle before testing the probes in clinical trials, and also hope to attain an additional signal for a different medical imaging modality in the same probes, including from a fluorescent dye to light up the tumor under specific circumstances to aid surgery.