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By Sara Elizabeth Cody
On Thursday, April 14, Professor M. Selim Ünlü (ECE, BME, MSE), recipient of the 2016 Charles DeLisi Award and Distinguished Lecture, presented “Optical Interference: From Soap Bubbles to Digital Detection of Viral Pathogens” to a packed room of students, faculty and researchers.
The first named endowed lecture in the history of the College of Engineering, the Charles DeLisi Award and Distinguished Lecture recognizes faculty members with extraordinary records of well-cited scholarship, and outstanding alumni who have invented and mentored transformative technologies that impact our quality of life.
When Ünlü arrived at BU in 1992, he was inspired by the collegial interdisciplinary environment, which led him to apply his background in electrical engineering and electromagnetic waves to developing innovative methods for biological imaging and sensing. His presentation, peppered with video and audio messages from past students and mentors who have contributed to his work, chronicled his career path from graduate school to present day and centered on his current research in optical sensing and developing new bioimaging technologies that address the obstacles that currently plague the field of diagnostics.
“When you are trying to look at pathogens, the most distinguishing thing is to look at its genome, but obstacles like logistics and cost are prohibitive and drive scientists to find more compact and affordable ways that have the same functionality,” said Ünlü. “Single particle detection has been the physicist’s dream of addressing these issues, so that’s what we set out to explore.”
Synergy between Engineering and Medicine
In developing his optical detection technology, he drew inspiration from, of all places, a soap bubble. Specifically, the patterns of colors that develop on the surface when light is being reflected through it. According to Ünlü, the same interference phenomenon that gives rainbow colors to soap bubbles can also provide extremely high sensitivity as illustrated by the recent news on detection of gravity waves by optical interferometry.
“Most people don’t realize that just by calling out a certain color, you are making a measurement in the order of nanometers,” said Ünlü.
Ünlü extended this idea to develop his optical detection technology for single nanoscale particles, where the interference of light reflected from the sensor surface is modified by the presence of nanoparticles, producing a distinct signal that reveals the size of the particle that is otherwise not visible under a conventional microscope. Using this technology, Ünlü and his research team demonstrated label-free identification of some of the most deadly viruses in the world, including hemorrhagic viruses like Ebola, Lassa and Marburg, at a high sensitivity on par with state-of-the-art laboratory technologies. They have even been able to detect particles as small as individual protein and DNA molecules by labeling them with gold nanoparticles to provide sufficient visibility.
“Proteins are too small. We can’t see them directly so we decorate them with gold nanoparticles, which are not much bigger than the proteins themselves,” said Ünlü. “Decorating them with gold nanoparticles increases visibility of the molecules bound on the sensor surface, and we are able to count them in serum or whole blood.”
The resulting technological development in biomarker analysis that Ünlü has spearheaded is digital detection, an approach that counts single molecules, which provides resolution and sensitivity beyond the reach of ensemble measurements. Digital detection for medical diagnostics not only provides very high sensitivity, but also has the potential of making the most advanced molecular diagnostic tools broadly accessible at low cost.
Digital detection captures images of individual viruses in real time
“Optical interference is a very powerful sensing technique,” summed up Ünlü. “With this biological imaging technology, we can detect single particles if they are large enough on the nanoscale, such as viruses, and see them directly. If they are proteins or DNA molecules we have to label them with a small, metallic nanoparticle to see them.”
In terms of next steps, Ünlü and his team will continue to refine the technology for commercialization, including applying some of these findings to produce microarray chips that provide calibration and quality control in industry. His laboratory will continue to work on advancing the technology further and gaining a deeper understanding of the theoretical basis in order to enhance the methodology. In particular, they are looking into applying the technology to such areas as real-time DNA detection, rare mutations, and most recently a project to characterize viruses that target cancer cells.
To conclude his presentation, Ünlü expressed his appreciation of the support he received from the College to foster collaboration, and to his students, mentors and family who helped him along the way.
“I’m very thankful to Boston University for providing an incredibly rich environment for research because there are no barriers between disciplines,” said Ünlü. “Multidisciplinary innovation is the driving force of discovering new things and making society better, and ultimately that is my motivation.”
The DeLisi Lecture continues the College’s annual Distinguished Lecture Series, initiated in 2008, which has honored several senior faculty members. The previous recipients are Professors John Baillieul, (ME,SE), Malvin Teich (ECE) (Emeritus), Irving Bigio (BME), Theodore Moustakas (ECE, MSE), H. Steven Colburn (BME), Thomas Bifano (ME, MSE), Christos Cassandras (ECE, SE) and Mark Grinstaff (BME, MSE, Chemistry, MED).