Gold nanoparticles could be used as a “test bed” to explore how the tiny particles behave in biological systems, according to a new report. It also suggests a new model for the characterization of nanoparticle formulations to determine just what materials scientists are working with. The report was produced by the National Institute of Standards and Technology (NIST) and the National Cancer Institute’s Nanotechnology Characterization Laboratory (NCL). Nontoxic gold can be fashioned into particles in a range of shapes and sizes. Alone, gold has no biological implications, but it becomes functionalized when it is attached to protein-based drugs along with targeting molecules that cluster preferentially around cancer cells. The nanoparticles generally are coated to prevent clumping and also to avoid rapid clearance by the body’s immune system. A single sulfur atom at the “root” of each multiply branched dendron anchors it to the gold nanoparticle at the center. Researchers at NIST and NCI/NCL are studying the tiny constructs as a test bed for possible biomedical applications. Courtesy of Cho, NIST. The density, stability and coating composition have an impact on the nanomaterial’s safety, the efficacy of the delivery system, and biocompatibility – how well the nanoparticles distribute in the body. Scientists believe that thorough characterization of these parameters will enable them to develop better nanomaterials. The team created a nanoparticle test bed to facilitate its studies. The test bed was a uniform, controllable core-shell nanoparticle that could be made to order with precise shape and size, and to which could be attached nearly any potentially useful functionality. With this information, the researchers could study how controlled variations fared in a biological system. The trial system was based on dendrons, regularly shaped branching molecules that were suitable for the study because individual dendrons are always the same size and can readily be modified to carry “payload” molecules. In addition, the tip of the structure is designed to bond easily to the surface of a gold nanoparticle. The experiment resulted in an exhaustive set of measurements, which the team used to thoroughly describe its custom-made dendron-coated nanoparticles. The scientists established a basic series of measurement protocols that could be applied to any gold-based nanoparticles. The paper, which appeared online April 26 in Chemistry of Materials (doi: 10.1021/cm200591h), outlines the commencement of a catalog of analysis techniques for gathering a detailed description on nanoparticles. The techniques include dynamic light scattering; matrix-assisted laser desorption/ionization mass spectrometry; and ultraviolet/visible, nuclear magnetic resonance and x-ray photoelectron spectroscopy. The dendron-coated nanoparticles were tested also for stability under “biologically relevant” conditions of acidity, temperature and some recognized forms of chemical attacks that could occur within the bloodstream. In vitro biological tests are pending. Possible applications include high-precision drug-delivery systems and diagnostic image enhancers, and chemists are hopeful that gold nanoparticles will be the new gold standard for medical use.