(706e) Design and Characterization of Biodegradable Gold Nanoclusters for Optical Imaging

Gold nanoparticles which exhibit surface plasmon resonance in the near-infrared region (NIR) of the optical spectrum have been found to be extremely useful for biomedical imaging applications¹. These imaging agents, however, must eventually be cleared from the body. Clearance has been shown to be highly dependent by the size of imaging contrast agents, and current imaging agents typically exceed the clearance requirement of approximately 5 nm in diameter².

We have developed clusters of 4 nm gold nanoparticles which are less than 100 nm in diameter and possess the ability to biodegrade. UV-visible NIR spectroscopy indicates that these nanoclusters present strong absorbance in the 650 to 900 nm region. The nanoclusters biodegrade over the course of approximately a week into particles small enough for efficient clearance. Cluster formation was induced by the addition of a polymer templating agent, and primary particles were capped with different ligands in order to prevent uncontrolled aggregation. Hyperspectral microscopy, darkfield reflectance imaging and transmission electron microscopy (TEM) confirmed that the nanoclusters biodegrade in macrophage cells as well as in solution. ζ-potential measurements have also been conducted on clusters and deaggregated particles in order to approximate surface charge and electrostatic forces. The results can be described with DLVO theory. In conclusion, biodegradable clusters of gold nanoparticles, which show substantial NIR absorbance, were created and shown to degrade at physiological conditions, providing new opportunities for biomedical imaging without accumulation of toxic nanoparticles in the body.

(1) Anker, J.N., et al. Biosensing with plasmonic nanosensors. Nature Materials 7 (2008) 442-453

(2) Choi, H.S.. et al. Renal clearance of quantum dots. Nature Biotechnology 25 (2007) 1165-1170