What do Amazon.com, Netflix, spelunking, bacterial "fight clubs," and "human on a chip" research have in common? They're all connected to the diverse and pioneering work of John McLean and his team at Vanderbilt University's Center for Innovative Technology.
"Vanderbilt is unique amongst universities, in that it has a tremendous amount of mass spectrometry infrastructure, probably more so than any other academic unit in the country," said McLean. "There are about 70 or 80 state-of-the-art performance instruments here on campus which are used by around 2,000 scientists each year."
McLean's group primarily focuses on technology development and dissemination of technologies to the broader scientific community, both in nanotechnology and in life science research. He and his team also have very strong "-omics" capabilities.
Ion mobility is at the core of much of McLean's work. Before the 2006 introduction of the Waters Synapt system, the first commercially available mass spectrometer featuring ion mobility, McLean was using his own homemade ion mobility-mass spectrometers.
McLean's laboratory now boasts five Synapt systems, which are used for an extremely broad array of research activities, including drug discovery, disease diagnostics, and synthetic biology. Much of the work is untargeted analyses.
"The real benefit is being able to do extremely high-throughput, systems-wide experiments," said McLean. "Our capacity to generate data is unprecedented in the course of science. We can generate close to a terabyte of data an hour, because we’re analyzing everything that we possibly can, as quickly as we can, for a long time duration."
As a result, the biggest challenge for McLean and his team is figuring out how to sift through and interpret all the analytical data they produce. That's where Amazon and Netflix come in.
"One of the directions that we’ve taken that’s been extremely valuable is to take the tools that have been developed by Amazon and Netflix for movie or book recommendations," explained McLean."By comparing user records to other customers with similar interests, Amazon and Netflix can make meaningful recommendations.”
McLean's group follows a similar route to zero in on meaningful molecules in disease pathology.
"We’ll take a cancer biopsy, for example, and analyze it in the ion mobility mass spectrometer," said McLean. "Within a couple of minutes, we’ll pull about 30,000 different molecules. At that stage, we don’t care what those molecules are. But if we analyze a normal piece of breast tissue, for example, we can compare the abundance of molecules in the cancerous tissue versus the non-cancerous. Like Amazon, we can then compare the data to see what patterns emerge."
This approach has proven effective for McLean and his team.
"We have developed bioinformatic algorithms to sort through all of that data, to tell us what were the important molecules and which were not," he said. "This has enabled us to publish a number of papers in diabetes, wound healing, and breast cancer."
McLean has applied the same approach to drug discovery.
"There you're looking to coax bacteria and other organisms to synthesize silent gene clusters that have developed through their evolution," said McLean. "These gene clusters produce natural products that are oftentimes extremely valuable as drug targets."
Another technique the Vanderbilt laboratory uses is "host-guest response." The team takes in-vitro cell cultures or 3D tissue cultures and "pokes" them with a drug or toxin.
"You look at how the cells respond by what they release into the background," said McLean. "That means we have to be able to measure all of those different omics with a time resolution of about one or two minutes. And we want to be able to do it from a systems perspective, looking at everything at the same time."
That's why the combination of ion mobility and mass spectrometry is so important.
"Before, people would spend a lot of time before they ran an analysis to purify just the proteins or just lipids, and so forth," noted McLean. "Those purification procedures can take hours or even days. We’re eliminating much of that. With ion mobility, you can take biological goo and sort out all of the proteins and carbohydrates on the fly."
Enter the spelunker.
"When we do drug discovery, our collaborator is a spelunker and mechanistic enzymologist," explained McLean. "He goes down in the caves, collects new bacteria that have never seen humans before, and brings them back to the lab. We then we culture them up and do a full genome sequence on them. And then we start doing the genetic analysis where we’ll find clusters of genes where we can predict what the molecules should look like that the gene would express. And so, in silico, we can figure out which of those genes are making interesting molecules that we’ve never seen before, that look like drugs."
To accelerate the process, McLean and his collaborators developed an approach they call "fight club."
"With fight club, we grow the bacteria as a monoculture and we perform UPLC ion mobility-mass spectrometry," said McLean. "We generate these very complex spectra of, say, 30,000 to 50,000 molecules. We then take another bacteria that we know a lot about, and we do the same experiment as a monoculture, giving us a baseline of all the molecules that those things are expressing under these conditions. Next, we co-culture, so now they’re fighting for resources. This enables us to generate a map corresponding to the co-culture and then subtract from that map everything from the two monocultures. That leaves us with a map of only those molecules that were expressed when the organisms were fighting for resources. Using that approach, we’ve been able to identify a whole cadre of new drug molecules, probably about 15 or 20 new drugs over the past couple years, which is a lot faster than occurs usually in pharma."
McLean has garnered a shelf full of awards for his work, including an ACS teaching award (voted by undergraduate students), a Department of Defense award, the ASMS Research Award, the Gesellschaft Deutscher Chemiker Award, and the Bunsen-Kirchhoff Award for outstanding achievement in analytical spectroscopy.
This is all the more noteworthy, because as McLean confessed, "I never really wanted to be a scientist. I basically had three majors -- economics, political science, and chemistry. I wanted concrete answers, which political science and economics couldn't provide. So I stuck with chemistry. But I didn’t make that decision until my senior year."
An Ohio native McLean attended the University of Michigan. After earning his undergraduate degree in Chemistry, he went to George Washington University, where he earned his PhD in Chemistry and worked with the FBI Academy and USDA. His postdoctoral work included stints in Germany and five years with David Russell at Texas A&M University, where he first became acquainted with ion mobility.
"I think it’s an accurate statement to say that we would not be able to ask the questions we’re asking today without being able to generate such rich datasets so fast, which ion mobility provides," said McLean. "When people are doing LC/MS, they’re getting basically similar data to what you get from an ion mobility-mass spectrometer but the IM-MS is giving it to you five orders of magnitude faster. That means that I can do 100,000 more experiments than my colleague can in the same amount of time. An LC run takes about an hour, and in a typical ion mobility experiment, we’re finished in about 20 milliseconds."
McLean and his team are also exploring analytical techniques beyond ion mobility-mass spectrometry.
"One of the technologies that we’ve been extremely enthusiastic about is convergence chromatography, or SFC, for several reasons," he explained. "One is that we can shorten that 40- to 60-minute separation from the UPLC to about five or six minutes with convergence chromatography."
ACQUITY UPC2 technology has been particularly effective in McLean's drug discovery work, because it eliminates the need to use a rotary evaporator to remove solvents from each analytical run.
"With SFC, the carbon dioxide evaporates quickly," said McLean “That can take days and days out of the drug discovery process. In addition, SFC enables us to get more molecular chemical coverage, because reverse-phase UPLC focuses on the analysis of hydrophobic molecules. SFC lets us retain and measure hydrophilic and hydrophobic compounds at the same time."
In addition to these projects, John McLean is eagerly anticipating a move into new digs that will house The Center for Innovative Technology.
"It's part of a major research effort having to do with the so-called 'human-on-a-chip initiative," said McLean. Initiated three years ago and funded by the U.S. government, the human-on-a-chip project is a collaboration between government agencies and academic research centers designed to reduce the failure rate – currently at 40% - for drug candidates when testing moves from animal to human models. By creating 3D tissue cultures in a microfluidic platform to emulate the organs of the human body, the intent is to enable drug discovery scientists to test compounds early for their impact on human organs without putting real humans at risk.
The initial success of The Center for Innovative Technology will depend on the participants' ability to couple high-content microscopy fluidly with the untargeted analysis of ion mobility mass spectrometry.
In the midst of all these projects, McLean recharges his batteries by spending time with his four-year-old son and six-year-old daughter, reading nonscientific books, and hiking regularly in the natural areas around Nashville.
And where would John McLean be if his scientific career hadn't worked out?
"I would love to try to be a chef," he confessed. "I like the attention to detail and the precision involved. But I also like the pressure. You’re trying to create something out of raw ingredients as quickly as you possibly can, and there’s not a whole lot of room for error. So it’s not too unlike our current jobs!"