New technology developed by bioengineers at the University of California, Berkeley, promises to make a workhorse lab tool cheaper, more portable and many times faster by accelerating the heating and cooling of genetic samples with the switch of a light.
This turbocharged thermal cycling, described in a paper to be published Friday, July 31, in the journal Light: Science & Application, greatly expands the clinical and research applications of the polymerase chain reaction (PCR) test, with results coming in minutes instead of an hour or more.
This is an artist's rendering of photonic PCR on a chip using light to rapidly heat and cool electrons at the surface of a thin film of gold. This method yields gene amplification results in mere minutes, and promises to transform point-of-care diagnostics in fields as diverse as medicine, food security and evolutionary biology.
Image courtesy of Luke Lee's BioPOETS lab
The PCR test, which amplifies a single copy of a DNA sequence to produce thousands to millions of copies, has become vital in genomics applications, ranging from cloning research to forensic analysis to paternity tests. PCR is used in the early diagnosis of hereditary and infectious diseases, and for analysis of ancient DNA samples of mummies and mammoths.
The huge impact of the PCR test in modern science was recognized in 1993 with a Nobel Prize in Chemistry for its inventors, Kary Mullis and Michael Smith.
Using light-emitting diodes, or LEDs, the UC Berkeley researchers were able to heat electrons at the interface of thin films of gold and a DNA solution. They clocked the speed of heating the solution at around 55 degrees Fahrenheit per second. The rate of cooling was equally impressive, coming in at about 43.9 degrees per second.
"PCR is powerful, and it is widely used in many fields, but existing PCR systems are relatively slow," said study senior author Luke Lee, a professor of bioengineering. "It is usually done in a lab because the conventional heater used for this test requires a lot of power and is expensive. Because it takes an hour or longer to complete each test, it is not practical for use for point-of-care diagnostics. Our system can generate results within minutes."
The slowdown in conventional PCR tests comes from the time it takes to heat and cool the DNA solution. The PCR test requires repeated temperature changes - an average of 30 thermal cycles at three different temperatures - to amplify the genetic sequence, a process that involves breaking up the double-stranded DNA and binding the single strand with a matching primer. With each heating-cooling cycle, the amount of the DNA sample is doubled.
To pick up the pace of this thermal cycling, Lee and his team of researchers took advantage of plasmonics, or the interaction between light and free electrons on a metal's surface. When exposed to light, the free electrons get excited and begin to oscillate, generating heat. Once the light is off, the oscillations and the heating stop.
Gold, it turns out, is a popular metal for this plasmonic photothermal heating because it is so efficient at absorbing light. It has the added benefit of being inert to biological systems, so it can be used in biomedical applications.
For their experiments, the researchers used thin films of gold that were 120 nanometers thick, or about the width of a rabies virus. The gold was deposited onto a plastic chip with microfluidic wells to hold the PCR mixture with the DNA sample.
The light source was an array of off-the-shelf LEDs positioned beneath the PCR wells. The peak wavelength of the blue LED light was 450 nanometers, tuned to get the most efficient light-to-heat conversion.
The researchers were able to cycle from 131 degrees to 203 degrees Fahrenheit 30 times in less than five minutes.
They tested the ability of the photonic PCR system to amplify a sample of DNA, and found that the results compared well with conventional PCR tests.
"This photonic PCR system is fast, sensitive and low-cost," said Lee, who is also co-director of the Berkeley Sensor and Actuator Center. "It can be integrated into an ultrafast genomic diagnostic chip, which we are developing for practical use in the field. Because this technology yields point-of-care results, we can use this in a wide range of settings, from rural Africa to a hospital ER."
The study lead author is Jun Ho Son, a UC Berkeley postdoctoral researcher in Lee's lab.
The Bill and Melinda Gates Foundation and the National Research Foundation of Korea helped support this research.
Sarah Yang | EurekAlert!
Don't Give the Slightest Chance to Toxic Elements in Medicinal Products
23.03.2018 | Physikalisch-Technische Bundesanstalt (PTB)
North and South Cooperation to Combat Tuberculosis
22.03.2018 | Universität Zürich
Satellites in near-Earth orbit are at risk due to the steady increase in space debris. But their mission in the areas of telecommunications, navigation or weather forecasts is essential for society. Fraunhofer FHR therefore develops radar-based systems which allow the detection, tracking and cataloging of even the smallest particles of debris. Satellite operators who have access to our data are in a better position to plan evasive maneuvers and prevent destructive collisions. From April, 25-29 2018, Fraunhofer FHR and its partners will exhibit the complementary radar systems TIRA and GESTRA as well as the latest radar techniques for space observation across three stands at the ILA Berlin.
The "traffic situation" in space is very tense: the Earth is currently being orbited not only by countless satellites but also by a large volume of space...
An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.
The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...
In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.
Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...
Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.
They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...
A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...
23.03.2018 | Event News
19.03.2018 | Event News
16.03.2018 | Event News
23.03.2018 | Materials Sciences
23.03.2018 | Agricultural and Forestry Science
23.03.2018 | Physics and Astronomy