Nav: Home

DNA: The next hot material in photonics?

October 02, 2017

WASHINGTON -- Using DNA from salmon, researchers in South Korea hope to make better biomedical and other photonic devices based on organic thin films. Often used in cancer treatments and health monitoring, thin films have all the capabilities of silicon-based devices with the possible added advantage of being more compatible with living tissue.

A thin film is just what it sounds like, a layer of material only nanometers or micrometers thick that can be used to channel light. If the film is a dielectric--that is, an insulator such as glass--it can be used without worrying that it might conduct electricity.

"DNA is the most abundant organic material, and it is a transparent dielectric, comparable to silica," said Kyunghwan "Ken" Oh, of the Photonic Device Physics Laboratory at Yonsei University, Seoul, South Korea. In the journal Optical Materials Express, from The Optical Society (OSA), Oh and his colleagues lay out their method for fabricating the thin films in a way that gives them fine control over the material's optical and thermal properties.

As the basis for the silica glass that makes up optical fibers, silicon has long been a dominant material in inorganic photonic devices because it's readily available and easy to work with from the materials perspective. Oh argues that DNA can play the same role in organic photonic devices because it can be found throughout the living world. It could, for instance, be used to make waveguides similar to silica fibers to carry light within the body. Organic devices should also be easy to manufacture, more flexible than silicon and environmentally friendly.

'A sharper arrow'

One key property of materials used in photonic devices is the refractive index, which determines how light is directed. An optical fiber requires a core with one index, wrapped in a cladding with a different enough index so that when light hits the interface between core and cladding, it is forced back into the core instead of leaking away. Makers of optical fiber not only need material with two different refractive indexes, they need to control the magnitude of that difference to get the desired effects.

In fine-tuning a method for using DNA to create thin films that could be used in photonic devices, Oh's team was able to get a range of refractive indexes four times greater than that available in silicon. With a greater index difference between core and cladding, they can make much thinner optical fibers, as low as 3 microns in diameter, compared to a minimum of 10 in silicon. This allows for a smaller spot size for the light coming out of the fiber, which could be useful in applications that must carefully target light. "If you have a small target, you should have a sharper arrow," said Oh.

Potential applications could include photodynamic therapy, where a cancer patient is given a drug or other substance that binds to cells in a tumor and light activates the drug and destroys the cancer cells, leaving healthy tissue untouched. The films may also be useful in optogenetics, in which light is used to control the activity of specific brain cells, or to make sensors to measure the pressure or oxygen content of blood pressure that could be worn for a long time without causing irritation because they are organic.

Grappling with inconsistent results

To make a thin film, which can be used as the basis for photonic devices, researchers have to dissolve DNA in water, and then dissolve that mixture into an organic solvent. The liquid is placed on a surface, which spins so the material spreads evenly. The solvent then evaporates to leave the film behind. Because DNA doesn't readily dissolve, researchers first mix it with a solution of water and cetyltrimethylammonium (CTMA), a soap-like surfactant. The mixture produces a precipitate, which can then be dissolved into the solvent and spin-coated.

While researchers have used this procedure for several years, their results have been inconsistent. "We noticed that, depending on the papers, the refractive index and material properties varied in a wide range, so we were very curious about it," said Oh. "And we found out the fabrication process was a little bit different from research group to research group."

Controlling the process

Three graduate students in Oh's lab--Woohyun Jung, Hwiseok Jun and Seongjin Hong--found that by controlling the amount of water and CTMA in their mixture, they could fine-tune the refractive index of the thin film. Testing revealed different mixtures, depending on whether they added droplets of water and DNA into the CTMA solution, or water and CTMA into the DNA bath. Oh describes the strand of DNA as a rope, with sites along it to which the CTMA can bind. "If you drop this rope into a CTMA bath, there are tons of CTMA available, so you can soak the rope with the CTMA," said Oh. On the other hand, if you drop CTMA onto a large batch of DNA, the "rope" may not get completely wet; that is, there are areas of DNA without CTMA attached.

The more water the mixture contained, the less CTMA there was, and vice versa. By carefully controlling the amount of both, the team could achieve the desired index of refraction. The same approach provided control over the thermal properties of the film, allowing the researchers to control how much the refractive index changed when the film was heated or cooled. That could allow the film to be used as a temperature sensor, as changes in the light passing through it would be linked to changes in temperature.

Oh's lab is also exploring other methods to control the optical properties of DNA. His hope is to develop a set of fundamental principles and processes that will allow manufacturers to build a wide range of optical devices, including a new generation of wearable sensors.
-end-
Paper: W. Jung, H. Jun, S. Hong, B. Paulson, Y. S. Nam, K. Oh, "Cationic lipid binding control in DNA based biopolymer and its impacts on optical and thermo-optic properties of thin solid films,"Opt. Mater. Express, Volume 7, Issue 11, 3796-3808 (2017).

DOI: 10.1364/OME.7.003796

About Optical Materials Express

Optical Materials Express (OMEx) is an open-access journal focusing on the synthesis, processing and characterization of materials for applications in optics and photonics. OMEx, which launched in April 2011, primarily emphasizes advances in novel optical materials, their properties, modeling, synthesis and fabrication techniques; how such materials contribute to novel optical behavior; and how they enable new or improved optical devices. It is published by The Optical Society and edited by Alexandra Boltasseva. For more information, visit: OSA Publishing.

About The Optical Society

Founded in 1916, The Optical Society (OSA) is the leading professional organization for scientists, engineers, students and business leaders who fuel discoveries, shape real-life applications and accelerate achievements in the science of light. Through world-renowned publications, meetings and membership initiatives, OSA provides quality research, inspired interactions and dedicated resources for its extensive global network of optics and photonics experts. For more information, visit osa.org.

Media Contacts:

Rebecca B. Andersen
The Optical Society
randersen@osa.org
+1 202.416.1443

Joshua Miller
The Optical Society
jmiller@osa.org
+1 202.416.1435

The Optical Society

Related Dna Articles:

Zigzag DNA
How the cell organizes DNA into tightly packed chromosomes. Nature publication by Delft University of Technology and EMBL Heidelberg.
Scientists now know what DNA's chaperone looks like
Researchers have discovered the structure of the FACT protein -- a mysterious protein central to the functioning of DNA.
DNA is like everything else: it's not what you have, but how you use it
A new paradigm for reading out genetic information in DNA is described by Dr.
A new spin on DNA
For decades, researchers have chased ways to study biological machines.
From face to DNA: New method aims to improve match between DNA sample and face database
Predicting what someone's face looks like based on a DNA sample remains a hard nut to crack for science.
Self-healing DNA nanostructures
DNA assembled into nanostructures such as tubes and origami-inspired shapes could someday find applications ranging from DNA computers to nanomedicine.
DNA design that anyone can do
Researchers at MIT and Arizona State University have designed a computer program that allows users to translate any free-form drawing into a two-dimensional, nanoscale structure made of DNA.
DNA find
A Queensland University of Technology-led collaboration with University of Adelaide reveals that Australia's pint-sized banded hare-wallaby is the closest living relative of the giant short-faced kangaroos which roamed the continent for millions of years, but died out about 40,000 years ago.
DNA structure impacts rate and accuracy of DNA synthesis
DNA sequences with the potential to form unusual conformations, which are frequently associated with cancer and neurological diseases, can in fact slow down or speed up the DNA synthesis process and cause more or fewer sequencing errors.
Changes in mitochondrial DNA control how nuclear DNA mutations are expressed in cardiomyopathy
Differences in the DNA within the mitochondria, the energy-producing structures within cells, can determine the severity and progression of heart disease caused by a nuclear DNA mutation.
More DNA News and DNA Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Clint Smith
The killing of George Floyd by a police officer has sparked massive protests nationwide. This hour, writer and scholar Clint Smith reflects on this moment, through conversation, letters, and poetry.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Dispatch 6: Strange Times
Covid has disrupted the most basic routines of our days and nights. But in the middle of a conversation about how to fight the virus, we find a place impervious to the stalled plans and frenetic demands of the outside world. It's a very different kind of front line, where urgent work means moving slow, and time is marked out in tiny pre-planned steps. Then, on a walk through the woods, we consider how the tempo of our lives affects our minds and discover how the beats of biology shape our bodies. This episode was produced with help from Molly Webster and Tracie Hunte. Support Radiolab today at Radiolab.org/donate.