The Invisible Hand: How Giant Susceptibility Nanomaterials Enable Field-Directed Cell Sorting, Tissue Heating, and Biological Imaging

Date: November 10, 2022, 4:00–5:00 PM
Location: Annenberg 105 (Social to follow the seminar in the Moore Courtyard)
Speaker: Vicki Colvin, Professor of Chemistry and Engineering and Director of the Center for Biomedical Engineering, Department of Chemistry, Brown University

Magnetic fields can penetrate deep into the human body and, if magnetic materials are present, can image, move, and heat tissue with great precision. These extraordinary capabilities have not been easy to translate in biomedical engineering. Conventional magnetic nanomaterials require extremely large magnetic fields for applications and this requirement severely limits how they can be used. Here we show how organized aggregates of superparamagnetic particles, with uniform and tunable dimensions between 50 – 200 nm, can be optimized to respond to field strengths only a hundredfold higher than the earth's magnetic field. Interparticle interactions in these uniform aggregates lead to exchange interactions throughout the clusters which lowers the barriers to the alignment of magnetic dipoles. These systems can be prepared from iron oxide or even more magnetically responsive ferrites, forming clusters with tunable, uniform dimension and high colloidal stability in relevant biological media. Their initial magnetic susceptibilities in liquids are several hundred times larger than conventional nanomaterials. This allows for magnetothermal heating using portable, battery-operated devices. We apply iron oxide clusters in rodents to eradicate tumors using clinically safe applied fields for the first time, and further show how these systems can be used to sort stem cells. Imaging using both MRI and MPI also benefits from higher susceptibility materials. The generation of more susceptible magnetic particles is significant for biomedical engineering. It makes it possible to envision with larger devices selective heating deep within the body and consider applications for wearable field application devices. From cellular therapy to novel imaging modalities, giant susceptibility materials offer a new set of possibilities for magnetic nanoparticles.



Vicki Colvin

Professor of Chemistry and Engineering and Director of the Center for Biomedical Engineering, Department of Chemistry, Brown University

Vicki Colvin Professor Colvin is the Victor Kreible Professor of Chemistry and Engineering at Brown University and Director of its Biomedical Engineering program. Her research explores how complex materials in both composition and dimensions interact with the environment and living systems. This fundamental knowledge lays a foundation for her group's development of technologies which use new materials in both medical and environmental applications. Examples include electromagnetically active particles in treating diseases and the use of perpetual antioxidants for mediating the foreign body response to implanted medical devices. She has published over 200 peer-reviewed papers, holds seven patents, and is a fellow of AIMBE and AAAS. She has been named a Sloan Foundation Fellow, a Chemistry of Materials Highly Cited Researcher, and currently serves as an associate editor for the ACS journal Nano Letters. She received her undergraduate degree in Chemistry and Physics from Stanford University in 1988 and her PhD in Chemistry from U. C. Berkeley in 1994

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