"Researchers can now consider the physical and chemical parameters of a nanoparticle to improve cancer targeting in addition to the more commonly used molecular recognition," team leader Warren Chan told nanotechweb.org. "Such a design strategy is unique to using nanostructures as drug-delivery platforms."

The Toronto researchers began by designing a series of nanoparticles with different sizes and surface chemistry – for example, particles containing poly(ethylene glycol). They then injected the particles into an animal with a tumour. Next, they isolated the tumour to measure the concentration of nanoparticles present using immunoassay, silver staining and optical imaging techniques. In this way, the team was able to determine how the nanoparticles' size and surface chemistry affects the pharmokinetic behaviour of the particles, which eventually determines how they accumulate in a tumour.

Chan and co-workers found that the way that nanoparticles permeate a tumour strongly depends on the overall size of the particles. For example, larger particles seem to stay near blood vessels while smaller ones rapidly diffuse throughout the tumour.

Although scientists understand basically how nanostructures interact with biological systems, this knowledge is limited. "It is my group's objective to study all nanostructure parameters – such as shape and surface charge – for in vivo targeting," said Chan. "By doing these fundamental studies, we are developing a framework that will guide nanostructure design for improved cancer therapy."

The team also plans to design better contrast agents as part of its work.

The results were reported in Nano Letters.