One of the key steps in the development of any drug or imaging agent intended for human use is measurement of the adsorption, metabolism, and excretion of the drug.
Quantifying this collection of pharmacological properties, known as ADME, is a challenging and time-consuming process that is even more difficult when the drug or imaging agent includes a nanoparticle as one of its components. But by taking advantage of the magnetic properties of one kind of nanoparticle, a team of investigators at Washington University in St. Louis has demonstrated that they can measure ADME quickly using magnetic resonance imaging (MRI).
Reporting its work in the journal Magnetic Resonance in Medicine, a team of investigators led by Samuel Wickline, M.D., and Gregory Lanza, M.D., members of the Siteman Cancer Center for Nanotechnology Excellence, describe how it used MRI to measure the ADME properties in rabbits of a nanoparticle designed to bind to a molecule known as avb3, which is found on newly growing blood vessels such as those that surround most solid tumors and around atherosclerotic plaques. For comparison purposes, they also measured ADME for an untargeted but otherwise identical nanoparticle. In both cases, the nanoparticles were loaded with up to 90,000 gadolinium molecules, a number that is easily detected by MRI.
Prior to scanning, the animals had been fed a cholesterol-rich diet designed to spur atherosclerosis. After injecting the nanoparticles into the animals, the investigators scanned the animals using a research MRI instrument every 30 minutes for the next 2.5 hours and then at 8.5, 12.5, and 24 hours. These scans focused on the animals' aortas to determine ADME properties at the site that these nanoparticles were intended to target. The researchers also took blood samples at the time of imaging for calculating ADME using traditional methods.