Using gold and light to study molecules in water

Jul 31, 2013
This is an infographic drawing showing how the new detection device works. Credit: EPFL/Pascal Coderay

Thanks to a new device that is the size of a human hair, it is now possible to detect molecules in a liquid solution and observe their interactions. This is of major interest for the scientific community, as there is currently no reliable way of examining both the behavior and the chemical structure of molecules in a liquid in real time.

Developed at Boston University by Hatice Altug and her student Ronen Adato, the process brings together infrared detection techniques and . It could potentially make a whole new class of measurements possible, which would be a critical step in understanding basic as well as key aspects of and treatment. "Our technology could prove useful for studying the behaviour of proteins, medicines and cells in the blood or pollutants in water", says Hatice Altug.

Now a researcher at EPFL Dr. Altug has had her results published in Nature Communications.

Like a guitar string

The device is based on a well-known detection technique called infrared absorption spectroscopy. Infrared light can already be used to detect elements: The beam excites the molecules, which start to vibrate in different ways depending on their size, composition and other properties. "It's like a guitar string vibrating differently depending on its length," explains Hatice Altug. The unique vibration of each type of molecule acts as a signature for that molecule.

This technique works very well in but not at all well in . "A large number of molecules need to be present for them to be detected. It's also more difficult to detect molecules in water, as when the beam goes through the solution, the vibrate as well and interfere with the 's signature," explains Dr. Altug.

Using nanoparticles to capture and illuminate molecules

To get around these obstacles, the researchers have developed a system capable of isolating the target molecules and eliminating interferences.

The size of a penny, the device is made up of miniature fluidic chambers, which are covered on one side with nano-scale gold particles with surprising properties. "We cover the surface of the nanoparticles with, for example, antibodies, in order to make a specific protein or chemical stick to them," explains the researcher. "Once the solution containing the targeted elements is introduced into the chamber, the nanoparticles act as molecule catchers." This technique makes it possible to isolate the target molecules from the rest of the liquid.

But this is not the only role the nanoparticles play. They are also capable of concentrating light in nanometer-size volumes around their surface as a result of plasmonic resonance.

In the chamber, the beam doesn't need to pass through the whole solution. Instead, it is sent straight to the nanoparticle, which concentrates the light. Caught in the trap, the target molecules are the only ones that are so intensely exposed to the photons.

The reaction between the molecules and the infrared photons is extremely strong, which means they can be detected and observed very precisely. "This technique enables us to observe molecules in-situ as they react with elements in their natural environment. This could prove extremely useful for both medicine and biology," states Dr. Altug.

Use in medical research

Another advantage is that the chip is extremely compact and can be connected to microscopes already in use. "We don't need large sample sizes to conduct our analyses," says Ronen Adato.

Going forward, Hatice Altug intends to continue her research with a focus on medical applications. The first tests have been conducted with ordinary antibody , and the analyses now need to be fine-tuned. "I'd really like to work with other life-science researchers, hospitals and biologists. I'm especially interested in using my method in the study of diseases, including cancer and neurological disorders, to observe the effect of certain medicines on diseased cells or to detect disease biomarkers, for example."

Explore further: Nanocontainers for nanocargo: Delivering genes and proteins for cellular imaging, genetic medicine and cancer therapy

More information: www.nature.com/ncomms/2013/130… /abs/ncomms3154.html

Related Stories

A new dimension for 3-D protein structures

May 13, 2013

(Phys.org) —3D structures of biological molecules like proteins directly affect the way they behave in our bodies. EPFL scientists have developed a new infrared-UV laser method to more accurately determine ...

Recommended for you

Engineers show light can play seesaw at the nanoscale

12 hours ago

University of Minnesota electrical engineering researchers have developed a unique nanoscale device that for the first time demonstrates mechanical transportation of light. The discovery could have major ...

Engineered proteins stick like glue—even in water

Sep 21, 2014

Shellfish such as mussels and barnacles secrete very sticky proteins that help them cling to rocks or ship hulls, even underwater. Inspired by these natural adhesives, a team of MIT engineers has designed ...

Smallest possible diamonds form ultra-thin nanothreads

Sep 21, 2014

For the first time, scientists have discovered how to produce ultra-thin "diamond nanothreads" that promise extraordinary properties, including strength and stiffness greater than that of today's strongest ...

A nanosized hydrogen generator

Sep 20, 2014

(Phys.org) —Researchers at the US Department of Energy's (DOE) Argonne National Laboratory have created a small scale "hydrogen generator" that uses light and a two-dimensional graphene platform to boost ...

User comments : 0