Navigation Links
Gold nanorods shed light on new approach to fighting cancer
Date:10/16/2007

WEST LAFAYETTE, Ind. - Researchers have shown how tiny "nanorods" of gold can be triggered by a laser beam to blast holes in the membranes of tumor cells, setting in motion a complex biochemical mechanism that leads to a tumor cell's self-destruction.

Tumor cell membranes often have an abnormally high number of receptor sites to capture molecules of folic acid, or folate, a form of vitamin B that many tumor cells crave. The Purdue researchers attached folate to the gold nanorods, enabling them to target the receptors and attach to the tumor cell membranes.

"The cells are then illuminated with light in the near-infrared range," said Ji-Xin Cheng (pronounced Gee-Shin), an assistant professor in Purdue's Weldon School of Biomedical Engineering. "This light can easily pass through tissue but is absorbed by the nanorods and converted rapidly into heat, leading to miniature explosions on the cell surface."

Scientists have recently determined that gold nanorods and other nanostructures can be used to target and destroy tumor cells, but it was generally assumed that cell death was due to the high heat produced by the light-absorbing nanoparticles. The Purdue team discovered, however, that a more complex biochemical scenario is responsible for killing the cells.

"We have found that rather than cooking the cells to death, the nanorods first punch holes in the membrane, and cell death is then chemically induced, in this case by an influx of calcium," said Alexander Wei, an associate professor of chemistry at Purdue.

Findings are detailed in a research paper appearing Oct. 19 in the journal Advanced Materials. The paper, which appeared online last week, was written by doctoral students Ling Tong, Yan Zhao, Terry B. Huff and Matthew N. Hansen, along with Wei and Cheng.

The gold rods are less than 15 nanometers wide and 50 nanometers long, or roughly 200 times smaller than a red blood cell. Their small size is critical for the technology's potential medical applications: the human immune system quickly clears away particles larger than 100 nanometers, whereas smaller nanoparticles can remain in the bloodstream far longer.

Shining light on the gold nanorods causes them to become extremely hot, ionizing the molecules around them.

"This generates a plasma bubble that lasts for about a microsecond, in a process known as cavitation," Wei said. "Every cavitation event is like a tiny bomb. Then suddenly, you have a gaping hole where the nanorod was."

The gold nanorods also are ideal for a type of optical imaging known as two-photon luminescence, used by Cheng and his research group to monitor the position of nanorods in real time during tumor-cell targeting. The imaging technique provides higher contrast and brighter images than conventional fluorescent imaging methods.

In experiments with tumor cells in laboratory cultures, the nanorods attached to the cell membranes and were eventually taken up into the cells. The researchers found that it could take far less power to injure cells by exposing the nanorods to near-infrared light while they are still on the membrane surface instead of waiting until the nanorods are internalized.

"This means that if you wait until the nanorods are inside the cell, then you really have to pump up the laser power, so localizing the nanorods on the cell membrane strongly influences their ability to inflict cell damage," Cheng said.

The findings suggest an optimal window of opportunity for applying near-infrared light to the nanorods for cancer treatment.

"We like to believe this opens the possibility of using nanorods for biomedical imaging as well as for therapeutic purposes," Cheng said.

The Purdue researchers observed that light-absorbing nanorods cause the formation of membrane "blebs, " similar to severe blistering. These blisters, however, are not produced directly by the high heat generated by the nanorods.

"The blebbing is triggered by the nanorods, but it's really caused through a complex biochemical pathway - a chemically induced process," Cheng said. "Extra calcium gets into the cell and triggers enzyme activity, which causes the infrastructure inside the cell to become loose, and that gives rise to the membrane blebs."

Researchers used a calcium-sensitive fluorescent dye to back up their argument that calcium influx caused the tumor cell death. When the nanorod-bearing tumor cells were maintained in a calcium-free nutrient medium, no blisters were formed if the nanorods were exposed to near-infrared light. But when the researchers added calcium to the medium, the blebbing took place immediately.

Although the technique offers promise for a new cancer treatment, it is too early to determine when it could be in clinical use, said Wei, who is collaborating with the National Cancer Institute to determine the suitability of the functionalized gold nanorods for future clinical studies.


'/>"/>

Contact: Emil Venere
venere@purdue.edu
765-494-4709
Purdue University
Source:Eurekalert

Related biology news :

1. Purdues gold nanorods brighten future for medical imaging
2. Researchers discover way to make cells in the eye sensitive to light
3. Recent breakthroughs in common adult leukemia highlighted in New England Journal of Medicine
4. Bacteria collection sheds light on urinary tract infections
5. Sea skate experiment sheds light on human cell transport
6. X-Ray Beams And Fruit Fly Flight Simulator Aid Scientists View Of Muscle Power
7. McGill researchers shed light on formation of carcinogen in food
8. Scientists discover how plants disarm the toxic effects of excessive sunlight
9. Light therapy may combat fungal infections, new evidence suggests
10. Medical molecules designed to respond to visible light that can penetrate tissue
11. Genetic defects give the immune system the green light to attack the pancreas
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:4/26/2016)... and LONDON , April ... part of EdgeVerve Systems, a product subsidiary of ... today announced a partnership to integrate the Onegini ...      (Logo: http://photos.prnewswire.com/prnh/20151104/283829LOGO ) ... their customers enhanced security to access and transact ...
(Date:4/15/2016)... 2016 Research and Markets has ... Market 2016-2020,"  report to their offering.  , ... ,The global gait biometrics market is expected to ... period 2016-2020. Gait analysis generates multiple ... used to compute factors that are not or ...
(Date:3/31/2016)... -- Genomics firm Nabsys has completed a financial  restructuring under ... M.D., who returned to the company in October 2015. ... including Chief Technology Officer, John Oliver , Ph.D., ... Vice President of Software and Informatics, Michael Kaiser ... Bready served as CEO of Nabsys from 2005-2014 and ...
Breaking Biology News(10 mins):
(Date:5/25/2016)... (PRWEB) , ... May 25, 2016 , ... ... Michael Fitzmaurice recently became double board-certified in surgery and surgery of the hand ... Dr. Fitzmaurice is no stranger to going above and beyond in his pursuit ...
(Date:5/25/2016)... (PRWEB) , ... May 25, 2016 , ... Scientists at ... line options being tried for mesothelioma may be hampering the research that could lead ... research. Click here to read it now. , The team evaluated 98 ...
(Date:5/25/2016)... ... 25, 2016 , ... Lady had been battling arthritis since the age of ... left knee. Lady’s owner Hannah sought the help of Dr Jeff Christiansen of ... her cruciate ligament and help with the pain of Lady’s arthritis. Dr Christiansen suggested ...
(Date:5/24/2016)... ... May 24, 2016 , ... Cell therapies for a range ... by research at Worcester Polytechnic Institute (WPI) that yielded a newly patented method ... , The novel method, developed by WPI faculty members Raymond Page, PhD, professor ...
Breaking Biology Technology: