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Sensing Small Stuff for Medicine

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Ryan Bailey
Title: Assistant Professor, University of Illinois, Urbana-Champaign
Education: PhD, Northwestern
University, 2004
Recommended by: Harris Lewin

Ryan Bailey's lab is focused on improving personalized diagnostics by being able to measure gene and protein expression changes from very small amounts of sample. To that end, he's created a new array technology that he's called silicon-on-insulator microring optical resonator arrays, that "can combine the advantages of massively multiplexed detection and label-free operations," he says. With a PhD in chemistry and a postdoc at the Institute for Systems Biology, Bailey is well-equipped to drive the field forward. "We're trying to develop a platform that can eventually be able to measure DNA, RNA, microRNAs, proteins, and possibly post-translationally modified proteins from the exact same sample," he says.

To create the new sensing technology, Bailey worked from the ground up. The silicon photonic microring resonator is based on semiconductor structures and is very small — about 30 microns in diameter. The underpinnings of how it works are built on optical interference at the surface of the array of sensors. "What we're able to do is functionalize one of these rings with a short cDNA strand or an antibody and when the complementary antigen binds to it, we can very sensitively detect that binding event through a change in refractive index at the surface," Bailey says.

The technology is also highly scalable. "The structures we work with are capable of being expanded to tens of thousands of sensors per square centimeter," he says. "So it's actually higher than a cDNA microarray, [and] our sensing elements are about 20 times smaller than a conventional microarray spot."

One of the biggest applications is for personalized medicine — detecting hard-to-find biomarkers in sparse clinical samples. Since limited sample volume has prevented the measurement of the expression of many different genes and proteins that are involved in disease, Bailey says he considers this to be an information problem. "We're developing these sensors to take very, very small amounts of tissue or bodily fluids and try to generate that same level of biomolecular information" that comes out of research-based microarray experiments, for instance, he says.

During his PhD studies in chemistry at Northwestern University, Bailey became interested in chemical sensing and, in general, improving methods of detection. He did two postdocs, one at Caltech and one at ISB, where he "was really interested in familiarizing myself more with real biological problems," he says. Both Jim Heath and Lee Hood influenced how he approaches his work and the way he envisions the future of personalized medicine. "Their vision for personalized medicine being driven by diagnostics — information can drive personalized medicine — is really what got me excited about developing sensors that can be ultra-scalable, very robust, highly multiplexable, ultra-sensitive, things like that," Bailey says.

Looking ahead

One of the biggest challenges Bailey faces is applying his technology in real-world settings. "Solutions to many of these problems are going to come at the interface of chemistry and physics and biology and engineering and materials science, and that's something that's central to my group," he says.

Publications of note

In a recent paper published in Analytical Chemistry, Bailey and team described "using these sensors to do single biomarker detection." In their work, they used their arrays to perform label-free detection of a cancer biomarker, carcinoembryonic antigen, in undiluted serum. Comparing it to ELISA assays, they found a comparable limit of detection and, "in some cases, better precision."

And the Nobel goes to...

Bailey hopes it would be for "improving the way we treat disease — being able to tailor therapeutics to what a patient's disease requires."

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