Nanotechnology Now







Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > Nanoparticles: A golden bullet for cancer

Gold nanocages (right) are hollow boxes made by precipitating gold on silver nanocubes (left). The silver simultaneously erodes from within the cube, entering solution through pores that open in the clipped corners of the cube.
Gold nanocages (right) are hollow boxes made by precipitating gold on silver nanocubes (left). The silver simultaneously erodes from within the cube, entering solution through pores that open in the clipped corners of the cube.

Abstract:
Nanoparticles provide a targeted version of photothermal therapy for cancer

By Diana Lutz

Nanoparticles: A golden bullet for cancer

St. Louis, MO | Posted on March 17th, 2010

In a lecture he delivered in 1906, the German physician Paul Ehrlich coined the term Zauberkugel, or "magic bullet," as shorthand for a highly targeted medical treatment.

Magic bullets, also called silver bullets, because of the folkloric belief that only silver bullets can kill supernatural creatures, remain the goal of drug development efforts today.

A team of scientists at Washington University in St. Louis is currently working on a magic bullet for cancer, a disease whose treatments are notoriously indiscriminate and nonspecific. But their bullets are gold rather than silver. Literally.

The gold bullets are gold nanocages that, when injected, selectively accumulate in tumors. When the tumors are later bathed in laser light, the surrounding tissue is barely warmed, but the nanocages convert light to heat, killing the malignant cells.

In an article just published in the journal Small, the team describes the successful photothermal treatment of tumors in mice.

The team includes Younan Xia, Ph.D., the James M. McKelvey Professor of Biomedical Engineering in the School of Engineering and Applied Science, Michael J. Welch, Ph.D., professor of radiology and developmental biology in the School of Medicine, Jingyi Chen, Ph.D., research assistant professor of biomedical engineering and Charles Glaus, Ph.D., a postdoctoral research associate in the Department of Radiology.

"We saw significant changes in tumor metabolism and histology," says Welch, "which is remarkable given that the work was exploratory, the laser ‘dose' had not been maximized, and the tumors were ‘passively' rather than ‘actively' targeted."

Why the nanocages get hot

The nanocages themselves are harmless. "Gold salts and gold colloids have been used to treat arthritis for more than 100 years," says Welch. "People know what gold does in the body and it's inert, so we hope this is going to be a nontoxic approach."

"The key to photothermal therapy," says Xia, "is the cages' ability to efficiently absorb light and convert it to heat. "

Suspensions of the gold nanocages, which are roughly the same size as a virus particle, are not always yellow, as one would expect, but instead can be any color in the rainbow.

They are colored by something called a surface plasmon resonance. Some of the electrons in the gold are not anchored to individual atoms but instead form a free-floating electron gas, Xia explains. Light falling on these electrons can drive them to oscillate as one. This collective oscillation, the surface plasmon, picks a particular wavelength, or color, out of the incident light, and this determines the color we see.

Medieval artisans made ruby-red stained glass by mixing gold chloride into molten glass, a process that left tiny gold particles suspended in the glass, says Xia.

The resonance — and the color — can be tuned over a wide range of wavelengths by altering the thickness of the cages' walls. For biomedical applications, Xia's lab tunes the cages to 800 nanometers, a wavelength that falls in a window of tissue transparency that lies between 750 and 900 nanometers, in the near-infrared part of the spectrum.

Light in this sweet spot can penetrate as deep as several inches in the body (either from the skin or the interior of the gastrointestinal tract or other organ systems).

The conversion of light to heat arises from the same physical effect as the color. The resonance has two parts. At the resonant frequency, light is typically both scattered off the cages and absorbed by them.

By controlling the cages' size, Xia's lab tailors them to achieve maximum absorption.

Passive targeting

"If we put bare nanoparticles into your body," says Xia, "proteins would deposit on the particles, and they would be captured by the immune system and dragged out of the bloodstream into the liver or spleen."

To prevent this, the lab coated the nanocages with a layer of PEG, a nontoxic chemical most people have encountered in the form of the laxatives GoLyTELY or MiraLAX. PEG resists the adsorption of proteins, in effect disguising the nanoparticles so that the immune system cannot recognize them.

Instead of being swept from the bloodstream, the disguised particles circulate long enough to accumulate in tumors.

A growing tumor must develop its own blood supply to prevent its core from being starved of oxygen and nutrients. But tumor vessels are as aberrant as tumor cells. They have irregular diameters and abnormal branching patterns, but most importantly, they have thin, leaky walls.

The cells that line a tumor's blood vessel, normally packed so tightly they form a waterproof barrier, are disorganized and irregularly shaped, and there are gaps between them.

The nanocages infiltrate through those gaps efficiently enough that they turn the surface of the normally pinkish tumor black.

A trial run

In Welch's lab, mice bearing tumors on both flanks were randomly divided into two groups. The mice in one group were injected with the PEG-coated nanocages and those in the other with buffer solution. Several days later the right tumor of each animal was exposed to a diode laser for 10 minutes.

The team employed several different noninvasive imaging techniques to follow the effects of the therapy. (Welch is head of the oncologic imaging research program at the Siteman Cancer Center of Washington University School of Medicine and Barnes-Jewish Hospital and has worked on imaging agents and techniques for many years.)

During irradiation, thermal images of the mice were made with an infrared camera. As is true of other animals that automatically regulate their body temperature, mouse cells function optimally only if the mouse's body temperature remains between 36.5 and 37.5 degrees Celsius (98 to 101 degrees Fahrenheit). At temperatures above 42 degrees Celsius (107 degrees Fahrenheit) the cells begin to die as the proteins whose proper functioning maintains them begin to unfold.

In the nanocage-injected mice, the skin surface temperature increased rapidly from 32 degrees Celsius to 54 degrees C (129 degrees F).

In the buffer-injected mice, however, the surface temperature remained below 37 degrees Celsius (98.6 degrees Fahrenheit).

To see what effect this heating had on the tumors, the mice were injected with a radioactive tracer incorporated in a molecule similar to glucose, the main energy source in the body. Positron emission and computerized tomography (PET and CT) scans were used to record the concentration of the glucose lookalike in body tissues; the higher the glucose uptake, the greater the metabolic activity.

The tumors of nanocage-injected mice were significantly fainter on the PET scans than those of buffer-injected mice, indicating that many tumor cells were no longer functioning.

The tumors in the nanocage-treated mice were later found to have marked histological signs of cellular damage.

Active targeting

The scientists have just received a five-year, $2,129,873 grant from the National Cancer Institute to continue their work with photothermal therapy.

Despite their results, Xia is dissatisfied with passive targeting. Although the tumors took up enough gold nanocages to give them a black cast, only 6 percent of the injected particles accumulated at the tumor site.

Xia would like that number to be closer to 40 percent so that fewer particles would have to be injected. He plans to attach tailor-made ligands to the nanocages that recognize and lock onto receptors on the surface of the tumor cells.

In addition to designing nanocages that actively target the tumor cells, the team is considering loading the hollow particles with a cancer-fighting drug, so that the tumor would be attacked on two fronts.

But the important achievement, from the point of view of cancer patients, is that any nanocage treatment would be narrowly targeted and thus avoid the side effects patients dread.

The TV and radio character the Lone Ranger used only silver bullets, allegedly to remind himself that life was precious and not to be lightly thrown away. If he still rode today, he might consider swapping silver for gold.




####

About Washington University in St. Louis
Washington University is a medium-sized, independent university dedicated to challenging its faculty and students alike to seek new knowledge and greater understanding of an ever-changing, multicultural world.

The University is highly regarded for its commitment to excellence in learning. Its programs, administration, facilities, resources, and activities combine to further its mission of teaching, research, and service to society.

For more information, please click here

Contacts:
MEDIA CONTACTS
Diana Lutz
Senior Science Editor
(314) 935-5272


EXPERTS @ WUSTL
Younan Xia
The James M. McKelvey Professor
Work: (314) 935-8328


Michael Welch
Professor of radiology and developmental biology
(314) 362-8436

Copyright © Washington University in St. Louis

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

MIG Takes a Roll-Up-Your-Sleeves Approach with Revamped MEMS/Sensors Technical Event -- MIG welcomes technologists to MEMS Technical Congress, emphasizes working groups and breakout sessions on emerging MEMS & sensors, tech transfer and integration March 6th, 2015

Phenom-World announces the Phenom XL, world’s fastest desktop SEM to handle large samples March 6th, 2015

Air Bearing Stage / Systems Introduced by PI at Photonics West March 6th, 2015

Consistent Scalable Functionalised Graphene Capacity March 5th, 2015

Possible Futures

European roadmap for graphene science and technology published February 25th, 2015

Quantum research past, present and future for discussion at AAAS February 16th, 2015

World’s first compact rotary 3D printer-cum-scanner unveiled at AAAS by NTU Singapore start-up: With production funded by crowdsourcing, the first unit will be delivered to the United States in March February 16th, 2015

Nanotechnology Electric Vehicle (EV) Market Analysis Report 2015: According to Radiant Insights, Inc February 13th, 2015

Academic/Education

Get ready for NanoDays! March 5th, 2015

NanoTecNexus Launches New App for Learning About Nanotechnology—STEM Education Project Spearheaded by Interns February 26th, 2015

SUNY Poly CNSE Researchers and Corporate Partners to Present Forty Papers at Globally Recognized Lithography Conference: SUNY Poly CNSE Research Group Awarded Both ‘Best Research Paper’ and ‘Best Research Poster’ at SPIE Advanced Lithography 2015 forum February 25th, 2015

KIT Increases Commitment in Asia: DAAD Funds Two New Projects: Strategic Partnerships with Chinese Universities and Communi-cation Technologies Network February 22nd, 2015

Nanomedicine

Patent for the Novel Cancer Therapies – Ceramide Nanoliposomes March 4th, 2015

Arrowhead to Present at 2015 Barclays Global Healthcare Conference March 4th, 2015

Democratizing synthetic biology: New method makes research cheaper, faster, and more accessible March 3rd, 2015

Pens filled with high-tech inks for do-it-yourself sensors March 3rd, 2015

Announcements

MIG Takes a Roll-Up-Your-Sleeves Approach with Revamped MEMS/Sensors Technical Event -- MIG welcomes technologists to MEMS Technical Congress, emphasizes working groups and breakout sessions on emerging MEMS & sensors, tech transfer and integration March 6th, 2015

Phenom-World announces the Phenom XL, world’s fastest desktop SEM to handle large samples March 6th, 2015

Air Bearing Stage / Systems Introduced by PI at Photonics West March 6th, 2015

Get ready for NanoDays! March 5th, 2015

Grants/Awards/Scholarships/Gifts/Contests/Honors/Records

Anousheh Ansari Wins the National Space Society's Space Pioneer Award for "Service to the Space Community" March 5th, 2015

Enhanced Graphene Components for Next Generation Racing Yacht March 5th, 2015

Rice's Stephan Link honored for nanoscience research: The Welch Foundation honors ‘rising star’ with $100,000 Hackerman Award February 26th, 2015

Cutting-edge technology optimizes cancer therapy with nanomedicine drug combinations: UCLA bioengineers develop platform that offers personalized approach to treatment February 24th, 2015

Nanobiotechnology

Experiment and theory unite at last in debate over microbial nanowires: New model and experiments settle debate over metallic-like conductivity of microbial nanowires in bacterium March 4th, 2015

Untangling DNA with a droplet of water, a pipet and a polymer: With the 'rolling droplet technique,' a DNA-injected water droplet rolls like a ball over a platelet, sticking the DNA to the plate surface February 27th, 2015

Bacteria network for food: Bacteria connect to each other and exchange nutrients February 23rd, 2015

Building tailor-made DNA nanotubes step by step: New, block-by-block assembly method could pave way for applications in opto-electronics, drug delivery February 23rd, 2015

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More










ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







© Copyright 1999-2015 7th Wave, Inc. All Rights Reserved PRIVACY POLICY :: CONTACT US :: STATS :: SITE MAP :: ADVERTISE