Research

Molecular Engineering for Non-Invasive Imaging and Control of Biological Systems

Many important biological processes occur deep inside living organisms. Their study requires technologies to image and manipulate cellular and molecular function non-invasively. To develop such technologies, we pursue fundamental advances at the interface of molecular and cellular engineering with various forms of physical energy: magnetic, mechanical, thermal and chemical. Our work takes advantage of naturally evolved biological structures with unique physical properties, which we use as starting points for engineering. Examples of current research include:

Genetically Encoded Reporters for Ultrasound
We are developing the first genetically encoded and engineered imaging agents for ultrasound based on gas vesicles (GVs), a unique class of hollow protein nanostructures from buoyant microbes. Current work is focused on understanding and engineering the acoustic properties and in vivo interactions of GVs as targeted molecular imaging agents, and using them as reporter genes in bacterial and mammalian cell-based therapeutics and diagnostics.
Funding: NIH (NIBIB, NINDS BRAIN, NCI), DARPA, Packard Foundation, Pew Trust
Collaborators: Stuart Foster (U. Toronto), Mickael Tanter (INSERM, Paris), Richard Andersen (Caltech)

Genetically Encoded Reporters, Devices and Basic Mechanisms of MRI and Magnetic Actuation
We are developing next-generation genetically encoded reporters and sensors for MRI. This includes genetically encoded reporters that operate through novel contrast mechanisms, including the first MRI reporter genes for acoustically modulated MRI,  hyperpolarized xenon MRI and diffusion-weighted MRI. We are also making cells strongly paramagnetic to enable MR imaging and magnetic manipulation. Furthermore, we are studying the fundamental mechanisms of MRI contrast using nitrogen vacancy diamond magnetometry and developing addressable transmitters operated as magnetic spins (ATOMS) for microscale device localization in the body.
Funding: Burroughs Wellcome Fund, Dana Foundation, W.M. Keck Foundation, Human Frontiers Science Program
Collaborators: Azita Emami (Caltech), Leif Schroeder (Leibniz Institut, Berlin), Ron Walsworth (Harvard), Jinwoo Cheon (IBS/Yonsei)

Ultrasonic and Thermal Control of Biological Systems
We are interested in controlling the function of cells inside the body using focused ultrasound. For example, we have engineered tunable thermal bioswitches that allow us to control gene expression in engineered microbes and protein association in mammalian cells. These switches can be actuated with ultrasound, providing millimeter spatial precision. In addition, we are interested in using ultrasound to stimulate and inhibit neural activity in animals and humans. We are studying the mechanisms by which ultrasound interacts with the brain and developing technologies that combine the spatial precision of ultrasound with synthetic neurobiology.
Funding: NIH (BRAIN Initiative, NIMH), DARPA, Sontag Foundation, US Army
Collaborators: Doris Tsao (Caltech), Michael Ortiz (Caltech), Mory Gharib (Caltech), Shin Shimojo (Caltech), Viviana Gradinaru (Caltech), Chiara Daraio (Caltech), Charles Caskey (Vanderbilt), Peter Lee (City of Hope)

Additional support acknowledgements: Heritage Medical Research Institute, Jacobs Institute for Molecular Engineering in Medicine, Weston Havens Foundation.

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