Ultrasensitive Imaging Method

Using Gold-silver 'Nanocages'

New research findings suggest that an experimental ultrasensitive imaging technique that uses a ... more

New research findings suggest that an experimental ultrasensitive medical imaging technique that uses a pulsed laser and tiny metallic "nanocages" might enable both the early detection and treatment of disease. The system works by shining near-infrared laser pulses through the skin to detect hollow nanocages and solid nanoparticles - made of an alloy of gold and silver - that are injected into the bloodstream.
Unlike previous approaches using tiny metallic nanorods and nanospheres, the new technique does not cause heat damage to tissue being imaged. Another advantage is that it does not produce a background "auto fluorescent" glow of surrounding tissues, which interferes with the imaging and reduces contrast and brightness, said Ji-Xin Cheng, an associate professor of biomedical engineering and chemistry at Purdue University.
The improved performance could make possible early detection and treatment of cancer. The tiny gold-silver cages also might be used to deliver time-released anticancer drugs to diseased tissue, said Younan Xia, the James M. McKelvey Professor for Advanced Materials in the Department of Biomedical Engineering at Washington University in St. Louis. His team fabricated the nanocages and nanoparticles used in the research.
The gold-silver structures yielded images 10 times brighter than other experimental imaging research using gold nanospheres and nanorods. The new imaging approach uses a phenomenon called "three-photon luminescence," which provides higher contrast and brighter images than conventional fluorescence imaging methods. Normally, three-photon luminescence is too dim to be used for imaging. However, the presence of gold and silver nanoparticles enhances the brightness, overcoming this obstacle. The ultrafast laser also is thought to possibly play a role by causing "third harmonic generation," which increases the brightness. The three-photon effect might enable scientists to develop advanced "non-linear optical techniques" that provide better contrast than conventional technologies.

Original publication:
Tong L. et al.: Bright Three-photon Luminescence from Au-Ag Alloyed Nanostructures for Bioimaging with Negligible Photothermal Toxicity, Angewandte Chemie, published online April 6.

http://www.purdue.edu

Authors:
Emil Venere

Keywords: Auto-Fluorescent Fluorescence Imaging Imaging Ji-Xin Cheng Ling Tong Medical imaging Nanocages Pulsed Laser Purdue University Three-Photon-Luminescence

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