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 (pronounced Gee-Shin), an associate professor of biomedical engineering and chemistry at Purdue University.
"This lack of background fluorescence makes the images much more clear and is very important for disease detection," he said. "It allows us to clearly identify the nanocages and the tissues."
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 imaging technology provides brightness and contrast potentially hundreds of times better than conventional fluorescent dyes used for a wide range of biological imaging to study the inner workings of cells and molecules.
Findings were detailed in a research paper published online April 6 in the journal Angewandte Chemie's international edition. The paper was written by Purdue chemistry doctoral student Ling Tong, Washington University graduate student Claire M. Cobley and research assistant professor Jingyi Chen, Xia and Cheng.
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.
Previous research to develop the imaging system has required the use of "plasmons," or clouds of electrons moving in unison, to enhance brightness and contrast. However, using plasmons generates tissue-damaging heat. The new technique does not use plasmon enhancement, eliminating this heating, Cheng said.
The three-photon effect might enable scientists to develop advanced "non-linear optical techniques" that provide better contrast than conventional technologies.
"The three-photon imaging capability will potentially allow us to combine imaging and therapy for better diagnosis and monitoring," Xia said.
Researchers used a laser in the near-infrared range of the spectrum pulsing at the speed of femtoseconds, or quadrillionths of a second. The laser pulses 80 million times per second to illuminate tissues and organs after nanocages have been injected, Cheng said.
The cages and particles are about 40 nanometers wide, or roughly 100 times smaller than a red blood cell.
The researchers intravenously injected the nanocages into mice and then took images of the tiny structures in tissue samples from organs such as the liver and spleen.
Emil Venere | EurekAlert!
What happens in the cell nucleus after fertilization
06.12.2016 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Researchers uncover protein-based “cancer signature”
05.12.2016 | Universität Basel
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
06.12.2016 | Materials Sciences
06.12.2016 | Medical Engineering
06.12.2016 | Power and Electrical Engineering