© KATRAN/SHUTTERSTOCKNanomedicine is poised to take the clinical world by storm. More than 150 polymers, liposomes, metals, and many other materials, with sizes ranging from 1 nm to 300 nm, are approved or under investigation to enhance drug delivery, as diagnostics and imaging agents, and in radiotherapy treatments for cancer, among other applications. Moreover, the materials are becoming increasingly sophisticated, as researchers learn how to functionalize nanoparticles and create complex multifunctional conjugates. Attaching polymer coatings to nanoparticles can reduce uptake by the immune system, for example, while molecules that target diseased tissue can be affixed to drugs to lower needed dosages. (See “Nanomedicine.”)
As developers engineer and test this “next generation” of better-targeted nanomedicines, they aim to characterize the particles’ physical and chemical properties, including size, charge, purity, and stability. But a nanomedicine is not simply a homogeneous population of identical structures; rather, it is a complex mixture of closely-related structures that vary in size. Nanoparticles contain hundreds to thousands of atoms, and small variations in the associations between those atoms lead to a natural size heterogeneity. My laboratory, the Nanotechnology Characterization Laboratory (NCL), which was launched by the National Cancer Institute in 2004 to accelerate the pace at which cancer nanomedicines get into clinical trials, has tested gold nanoparticles, for example, which the supplier specified as having an “equivalent sphere average diameter.” Our results, in contrast, showed ...
