John P. Wikswo - Research Interests
I joined Vanderbilt in 1977, fresh from graduate and postdoctoral work studying the cardiac magnetic field at Stanford University in the Division of Cardiology and the physics laboratory of William Fairbank. My goal was to build a program in the measurement of biological magnetic fields and make the first measurement of the magnetic field of an isolated nerve, which John Barach, John Freeman, and I accomplished by 1980. More than a dozen years of support by the Office of Naval Research, the NIH, and the Veterans Administration led to the first measurements of the magnetic field of a single nerve axon and other studies that provided, for the first time, a firm biophysical foundation for the production and detection of the magnetoencephalogram and other biomagnetic signals.
By the late 1980s, I recognized that the holy grail of biomagnetic measurements, biological activity that was detectable magnetically but was electrically silent, would be hard to find in one-dimensional systems. I was the first to recognize that the usually ignored differences in the electrical anisotropy between the intracellular and extracellular spaces of a sheet of cardiac tissue would lead to just such a situation. I had to devise a new class of Superconducting Quantum Interference Device (SQUID) magnetometers that had the spatial resolution and sensitivity required to detect these fields and raise the $300,000 to get the instrument built; by 1991 my group had found the desired field pattern and devised magnetic imaging algorithms that have become the gold standard in the field. We recognized that the same instrumentation, scanning stages, and analysis algorithms could detect flaws in metals and plastics, and we mounted a 10-year program that was funded by the Air Force Office of Scientific Research (AFOSR), private industry, and the German government. This work evolved into an AFOSR-sponsored initiative and produced the only technique yet known that can measure the instantaneous rate of corrosion occurring inside an aging aircraft lap joint. This work in turn attracted long-term support from the Air Force. As our understanding grew, we found that the mathematical models of electrically and magnetically silent fields applied not only to cardiac muscle but also riveted aluminum, with the conclusion that magnetically silent currents in an aircraft lap joint would confound the magnetic imaging of the total current density produced at a corrosion interface.
Meanwhile, with colleagues in the Vanderbilt University Medical Center, I began measuring in vivo the cardiac conduction velocity during ischemia and infarct and in the presence of antiarrhythmic drugs. During one of these experiments, I recognized the existence of virtual cathodes in cardiac tissue, which happened to be related to the same anisotropy differences that produced the magic magnetic fields. The cardiac community paid little notice until my collaborators and I showed that these anisotropy differences and associated virtual cathodes and anodes could explain an old puzzle in cardiac electrophysiology, produce a previously unrecognized form of cardiac reentrant activation, and provide key mechanisms for understanding the success or failure of cardiac defibrillation. This work also led us into the non-linear dynamics of cardiac stimulation. A collaboration with Bradley Roth led to our experimental validation of more than eight of his twenty-one bidomain model predictions, demonstrating the power of his models and our measurements.
The continuing exploration of biomagnetic measurements picked up another first, the magnetic field of intestinal smooth muscle, which has spawned a large, well-funded, and productive collaboration with Bill Richards and Alan Bradshaw that has developed SQUID measurements into the first non-invasive clinical tool for the diagnosis of acute mesenteric ischemia and other gastrointestinal disorders.
The quest for the higher spatial resolution SQUIDs led me to recruit Franz Baudenbacher to lead an NSF- and NIH-funded project that has produced the world’s best SQUID microscope and used it in an experiment, in collaboration with a geobiology group at Caltech, to characterize the thermal history of a Martian meteorite from its magnetic signature and show that material could be transported from Mars to Earth without sterilization. This NanoSQUID has the potential to revolutionize the magnetic measurement of geophysical samples, and it allowed us to record beautiful data of the electrically silent magnetic fields of currents propagating through cardiac tissue, made possible by productive excursions into geophysics and NDE!
In 2000, I decided that I wanted to refocus my interests toward biology, and with the support of a $5 million, five-year grant from the Vanderbilt Academic Venture Capital Fund I founded the Vanderbilt Institute for Integrative Biosystems Research and Education (VIIBRE) to foster and enhance interdisciplinary research in the biophysical sciences, bioengineering, and medicine at Vanderbilt. VIIBRE is an autonomous, self-supporting research institute comprised of multiple of self-governing project teams with independent funding, complementary scientific themes, and shared core technologies and facilities. As soon as a scientific, technical, or funding opportunity is identified, a project team is formed, and the team leaders meet regularly to pursue funding, allocate shared resources, and define and guide the research effort. A team may be as small as a single faculty member guiding an undergraduate and a graduate student with the support of a VIIBRE staff member, or a staff member working with a single undergraduate, or as large as several research groups spanning Arts & Science, Engineering, and Medicine at Vanderbilt, or a multi-investigator project involving large research groups at several different institutions or companies. In each case, the teams are formed and evolve, and resources are allocated in a dynamic fashion, adjusting to individual interests, research results, funding, and the progress of students in the course of their undergraduate or graduate education. Our mission and vision – to invent tools and techniques required to understand biological systems across spatiotemporal scales, and to focus research and education on an integrated multidisciplinary approach to microscale engineering and instrumentation for dynamic control and analysis of cellular systems – is being carried out by a cadre of faculty members at Vanderbilt and other institutions worldwide, postdocs, high school, undergraduate, and graduate students, and staff members, who work together on a broad range of projects that explore the interfaces at the intersections of physics, chemistry, engineering, biology, and medicine.
This effort has been highly successful. By 2020, we had twice accomplished our original ten-year goal of using this investment to bring Vanderbilt to the forefront of cellular instrumentation and control, with the first decade focusing on simple microfluidic instrumentation and, building upon that foundation, a second mounting an intense, multi-institutional effort in organs-on-chips. We have used microfluidics, computer control, analytical chemistry, and mathematical modeling in projects such as cellular biosensors, nanoliter bioreactors, chemotaxis devices, and models for cancer and toxicology research; identification of chemical and biological warfare defense agents and infectious pathogens; new technologies for tracking metabolic and signaling dynamics, particularly using ion mobility-mass spectrometry; biomedical imaging; cellular/tissue bioengineering; development of microfabricated devices for measuring cellular properties and controlling cellular behavior; custom digital and analog electronics; replica casting and injection molding of microfluidic devices; fabrication of large-scale instruments and biomedical devices; data analysis; design of experiments; development and application of mathematical models; and inference of drug mechanism of action. Our group has pioneered the use of microfabricated multitrap nanophysiometers for studying metabolism and signaling in immune cells. We are now concentrating our efforts on organ-on-chip perfusion control systems and instrumented microbioreactors for engineered tissue constructs.
My personal research effort focuses on systems biology, primarily from the perspective of organs-on-chips and optimization of automated systems for combined experimental control and inference of quantitative metabolic and signaling models to better span the spatiotemporal scales of systems biology. For two decades, my group has been developing microfluidic devices to solve problems relevant to human biology, medicine, and environmental toxicology, and miniature, low-cost pumps and valves for maintenance of organs-on-chips. In collaboration with AstraZeneca, we developed a 96-channel MicroFormulator to individually address each well of a 96-well plate so as to deliver drugs and remove metabolites with a realistic pharmacokinetic time course. This “MultiWell Micro-Formulator” received a 2017 R&D 100 award, and it is now licensed to CN Bio Innovations, which released a commercial product, the PhysioMimix™, in 2021. I collaborated with CFD Research Corporation under an NCATS SBIR grant to further refine this MicroFormulator technology and create SmartLids that can either control each well of a 24-Transwell plate for 24 of CFDRC’s micro-organs or provide automated multi-week perfusion of printed tissues in Transwell plates. My group has made substantial progress toward a universal Integrated Organ Microfluidic platform for organs-on-chips that includes sophisticated microfluidic pumps and valves, sensors, and computer control.
My group has been recruited by Ross King, a professor of machine intelligence at Chalmers University of Technology in Gothenberg, Sweden, and an expert in symbolic artificial intelligence, to create Genesis, a microfluidic, fully-automated, third-generation robot scientist, which will operate more than a thousand yeast microchemostats as a self-driving systems biology laboratory. Genesis would enable new types of studies to understand, model, and control microbial populations. King previously developed the Adam and Eve robot scientists, which independently formulated scientific hypotheses about yeast metabolic pathways, designed optimal experiments, conducted the experiments, interpreted the data, and confirmed or refuted the hypotheses, all without human intervention. To create a second Genesis system at Vanderbilt, I have received a $999,810 Major Research Instrumentation grant from the National Science Foundation. The primary objective of the MRI effort is enabling independent, long-duration, machine-guided experiments on the single-cell eukaryotic yeast Saccharomyces cerevisiae. Co-PI Eric Spivey will develop, test, and implement all real-time sensing and lysing systems in the Genesis microchemostats. Co-PI John McLean will guide the use of real-time, on-line mass spectrometry metabolomics to analyze a sample of chemostat effluent every ten seconds. Co-PI Megan Behringer will extend the use of Genesis to study communications in bacterial communities, and Jamey Young, a proposed user of the system, will guide the evolution of Genesis to support the continuous culture of Chinese hamster ovary (CHO) cells used in antibody production. Genesis is a bold step towards addressing one of the most challenging tasks facing 21st-century science: the development of high-fidelity computational models of eukaryotic and prokaryotic cellular biology.