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New gold nanoparticles serve as biomedical “test bed”

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Compiled by BioPhotonics staff

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.

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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.

Published: September 2011
Glossary
nano
An SI prefix meaning one billionth (10-9). Nano can also be used to indicate the study of atoms, molecules and other structures and particles on the nanometer scale. Nano-optics (also referred to as nanophotonics), for example, is the study of how light and light-matter interactions behave on the nanometer scale. See nanophotonics.
nuclear magnetic resonance
A phenomenon, exploited for medical imaging, in which the nuclei of material placed in a strong magnetic field will absorb radio waves supplied by a transmitter at particular frequencies. The energy of the radio-frequency photons is used to promote the nucleus from a low-energy state, in which the nuclear spin is aligned parallel to the strong magnetic field, to a higher-energy state in which the spin is opposed to the field. When the source of the radio waves is turned off, many nuclei will...
AmericasBasic Sciencebiomedical testbedBiophotonicsBioScandendron-coated nanopaticlediagnostic imagingdrug deliverygold nanoparticlesin vitro biological testsionization mass spectrometrylight scatteringMarylandmatrix-assisted laser desorptionnanoNanotechnology Characteriztion LaboratoryNational Cancer InstituteNational Insitute of Standards and TechnologyNCLNewsNISTnuclear magnetic resonanceparticle formulationsspectroscopyTest & Measurementx-ray photoelectron spectroscopy

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