Radiologists regularly employ imaging methods, such as computed tomography (CT) or magnetic resonance imaging (MRI) scans, to help medical teams diagnose and treat disease. Seeing clear images of muscles, organs, and bones inside the body, often times via use of contrast agents, helps physicians diagnose patients earlier and avoid unnecessary surgery and complications. (Contrast agents such as iodine dyes and iron oxides are used to make internal body structures more visible in CT and MRI scans.)
Nanoparticles are used often in medicine. From a biological standpoint, we have lots of nanoparticles in the body, such as lipoproteins. There are already clinically-approved contrast agents that are based on iron oxide nanoparticles.
Now, a new study led by Penn Medicine researchers and published this month online ahead of print in ACS Nano offers insight into how to improve contrast agents for CT and MRI scans—with tiny “disco ball”-like nanoparticles.
The team developed a novel contrast agent in which nanocrystals can be selectively loaded onto the surface of polymer nanospheres as opposed to loading them in the core. This forms a structure reminiscent of a disco ball, inspiring the study’s title: “Nano-Disco Balls: Control Over Surface Versus Core Loading of Diagnostically Active Nanocrystals into Polymer Nanoparticles.” Researchers from Penn found that the ability to control the location of nanocrystals within a delivery vehicle can produce greater contrast, and therefore, more accurate imaging scans.
“The disco ball-shaped platform maximizes the effectiveness of different crystals that can be loaded onto the particle,” said lead author Peter Chhour, a PhD bioengineering graduate student at the University of Pennsylvania. “In the study, we loaded a model drug inside the carrier and had a different sensor imaging crystal on the outside. The platform can be easily modified by changing the type of crystal added on the outside or the drug on the inside.”
Controlled localization of diagnostic nanocrystals to the surface or core of the nanoparticle
For example, if gold is loaded in the core of a nanoparticle, this maximizes contrast for CT, which requires high payloads of contrast agent. Iron oxide produces contrast for MRI and requires access to water, so surface loading maximizes contrast in these cases.
“The technology we developed may help optimize the contrast generated by the particle structure and their effectiveness,” said David P. Cormode, PhD, assistant professor of Radiology, and co-author of the study. “You can deliver the drug and visualize delivery to the target site at the same time.”
This proposed structure can degrade and be separated, whereas many other agents don’t have that property. Plus, it may lead to more effective imaging.
“The novelty is not in changing the materials, but rather in changing the design of the particle itself,” said Cormode. “There’s never been a contrast agent before that has exclusive loading onto the surface. Almost everything previously has loading inside the core, so when people include two kinds of crystals or drugs, they usually combine them together inside the polymer itself. That can diminish the effectiveness of both. Showing that we can separate them in a controllable way and selectively load them in this architecture can better maximize the efficiency of each crystal type.”
Ultimately, the researchers hope the findings lead to ways of detecting disease earlier to better manage patients’ health and lead to other opportunities in drug delivery.