Engineers turn a drawback - the stickiness of gold nanoparticles - into an advantage

June 11, 2010 Diana LaScala-Gruenewald
An image of gold nanoparticles. Image courtesy Kimberly Hamad-Schifferli

( -- Gold nanoparticles -- tiny spheres of gold just a few billionths of a meter in diameter -- have become useful tools in modern medicine. They've been incorporated into miniature drug-delivery systems to control blood clotting, and they're also the main components of a device, now in clinical trials, that is designed to burn away malignant tumors.

However, one property of these particles stands in the way of many nanotechnological developments: They're sticky. can be engineered to attract specific biomolecules, but they also stick to many other unintended particles — often making them inefficient at their designated task.

MIT researchers have found a way to turn this drawback into an advantage. In a paper recently published in American Chemical Society Nano, Associate Professor Kimberly Hamad-Schifferli of the Departments of Biological Engineering and Mechanical Engineering and postdoc Sunho Park PhD ’09 of the Department of Mechanical Engineering reported that they could exploit ’ stickiness to double the amount of produced during in vitro translation — an important tool that biologists use to safely produce a large quantity of protein for study outside of a living cell.

During translation, groups of biomolecules come together to produce proteins from molecular templates called mRNA. In vitro translation harnesses these same biological components in a test tube (as opposed to in vivo translation, which occurs in live cells), and a man-made mRNA can be added to guarantee the production of a desired protein. For example, if a researcher wanted to study a protein that a cell would not naturally produce, or a mutated protein that would be harmful to the cell in vivo, he might use in vitro translation to create large quantities of that protein for observation and testing. But there’s a downside to in vitro translation: It is not as efficient as it could be. “You might get some protein one day, and none for the next two,” explains Hamad-Schifferli.

With funding from the Institute of Biomedical Imaging and Bioengineering, Hamad-Schifferli and her co-workers initially set out to design a system that would prevent translation. This process, known as translation inhibition, can stop the production of harmful proteins or help a researcher determine protein function by observing cell behavior when the protein has been removed. To accomplish this, Hamad-Schifferli attached DNA to nanoparticles, expecting that the large nanoparticle-DNA (NP-DNA) aggregates would block translation.

She was discouraged, however, to find that the NP-DNA did not decrease protein production as expected. In fact, she had some unsettling data suggesting that instead of inhibiting translation, the NP-DNA were boosting it. “That’s when we put on our engineering caps,” recalls Hamad-Schifferli.

It turns out that the sticky nanoparticles bring the biomolecules needed for translation into close proximity, which helps speed the translation process. Additionally, the DNA part of the NP-DNA complex is designed to bind to a specific mRNA molecule, which will be translated into a specific protein. The binding must be tight enough to hold the mRNA in place for translation, but loose enough that the mRNA can also attach to the other molecules necessary for the process. Because the designed DNA molecule has a specific mRNA partner, that mRNA in a solution of many similar molecules can be enhanced without having to be isolated.

In addition to enhancing in vitro translation, Hamad-Schifferli’s NP-DNA complexes may have other applications. According to Ming Zheng, a research chemist with the National Institute of Standards and Technology, they could be combined with carbon nanotubes — tiny, hollow cylinders that are incredibly strong for their size. They may ultimately be the cornerstone of transport systems that ferry drugs into cells or between cells. The stickiness of the NP-DNA might enhance the speed and accuracy of such a drug-delivery system.

Although Hamad-Schifferli is confident that her discovery will make in vitro translation more reliable and efficient, she is not done. She hopes to tinker with her system to further enhance protein production in vitro, and see if the system can be applied to enhance translation in live cells. To help reach these goals, she must design and conduct experiments to determine which molecules are involved in the enhancement process, and how they interact. “The upside is that we’ve been lucky,” Hamad-Schifferli says, reflecting on her discovery. “The downside is that it will be difficult to tease out exactly how the system works.”

Explore further: Gold nanoparticles for controlled drug delivery

Related Stories

Gold nanoparticles for controlled drug delivery

December 30, 2008

( -- Using tiny gold particles and infrared light, MIT researchers have developed a drug-delivery system that allows multiple drugs to be released in a controlled fashion.

Coral may help block virus replication

March 14, 2006

McGill University scientists say they've discovered a small molecule in coral that can be used to block the replication of certain viruses.

Mechanism of microRNAs deciphered

May 16, 2007

Over 30% of our genes are under the control of small molecules called microRNAs. They prevent specific genes from being turned into protein and regulate many crucial processes like cell division and development, but how they ...

MIT IDs role of key protein in tumor growth

March 15, 2007

MIT researchers have identified how a missing protein causes tissue to become precancerous--a finding that could help doctors identify patients at high risk to develop tumors.

Recommended for you

Testing TVs and tablets for 'green' screens

August 21, 2017

To improve viewing pleasure, companies have developed television—and tablet screens—that include quantum dots to enhance brightness and color. Some quantum dots are made with potentially harmful metals, which could leach ...

Going nano in the fight against cancer

August 17, 2017

Imagine being able to see the signs of cancer decades before we can now. URI Chemical Engineering Assistant Professor Daniel Roxbury and researchers from Memorial Sloan Kettering Cancer Center have invented a technique that ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.