A common problem with chemotherapy is that it works too well: in fact, so well that it kills not only cancer cells but also the body’s other cells. Nanoparticles have turned out to be fantastic guides in the quest to target specific cancer cells with chemotherapy. An international research team with Danish participation has now developed a system that can measure whether the cure will succeed or will be stopped along the way.
Hair loss is one of the first effects of chemotherapy because hair cells divide more quickly than many of the body’s other cells. This side-effect is therefore a first indication that both the cancer cells and the body’s other cells are under a powerful chemical attack. In recent years, researchers have examined the possibility of attaching the chemical compounds to miniscule nanoparticles measured in billionths of a metre.
Nanoparticles can be targeted passively or actively. Passive targeting uses the fact that the blood vessels in tumour tissue are more porous than the blood vessels in healthy tissue, and the particles can therefore diffuse more easily, whereas nanoparticles can actively transport other substances to the target tissue. A team of researchers from the United States, the Netherlands and Denmark has developed nanoparticles that have peptides attached to their surfaces that make them bind to breast cancer cells rather than to other cells.
Unfortunately, the human immune system recognizes the peptides attached to the nanoparticles and destroys them in the bloodstream before they reach the tumour. However, the researchers have now found a clever countermeasure: coating the peptide with polyethylene glycol.
When the particles reach the target site, the enzymes known to be present in tumours cleave away the polyethylene glycol coating. The peptides attached to the particles then bind firmly to and invade the tumour cells. This enables the chemotherapy to be released inside the tumour cells without harming other healthy cells.
The new study shows that this works well. Using fluorescent molecules, for example, enabled researchers to monitor the nanoparticles and the chemotherapy on their respective journeys through a mouse. They could therefore confirm that the nanoparticles remained longer in the mouse’s blood and that several of the nanoparticles reached the tumours.
“Investigating the cellular specificity in tumors of a surface converting nanoparticle by multimodal imaging” has been published in Bioconjugate Chemistry. In 2016, the Novo Nordisk Foundation awarded a grant to Jørgen Kjems, Professor, Interdisciplinary Nanoscience Center, Aarhus University for the project Modular Nanodevice for Personalized Theranostic Medicine.
