title: Engineering Genetically-Encoded Mineralization and Magnetism via Directed Evolution.
abstract: Genetically encoding the synthesis of functional nanomaterials such as magnetic nanoparticles enables sensitive and non-invasive biological sensing and control. Via directed evolution of the natural iron-sequestering ferritin protein, we discovered key mutations that lead to significantly enhanced cellular magnetism, resulting in increased physical attraction of ferritin-expressing cells to magnets and increased contrast for cellular magnetic resonance imaging (MRI). The magnetic mutants further demonstrate increased iron biomineralization measured by a novel fluorescent genetic sensor for intracellular free iron. In addition, we engineered Escherichia coli cells with multiple genomic knockouts to increase cellular accumulation of various metals. Lastly to explore further protein candidates for biomagnetism, we characterized members of the DUF892 family using the iron sensor and magnetic columns, confirming their intracellular iron sequestration that results in increased cellular magnetization.
authors.affiliation: Wyss Institute for Biologically Inspired Engineering, Harvard University, 3 Blackfan Circle, 5th Floor, Boston, MA 02115, USA.|School of Engineering and Applied Sciences, Harvard University, Pierce Hall, 29 Oxford Street, Cambridge, MA 02138, USA.|Department of Systems Biology, Harvard Medical School, 200 Longwood Ave, Alpert 536, Boston, MA 02115, USA.
authors.forename: Xueliang
authors.initials: X
authors.lastname: Liu
authors.affiliation: Graduate Program in Bioengineering UC Berkeley/UCSF, Department of Bioengineering, 306 Stanley Hall #1762, University of California Berkeley, CA 94720-1762, USA.
authors.forename: Paola A
authors.initials: PA
authors.lastname: Lopez
authors.affiliation: Wyss Institute for Biologically Inspired Engineering, Harvard University, 3 Blackfan Circle, 5th Floor, Boston, MA 02115, USA.|Department of Systems Biology, Harvard Medical School, 200 Longwood Ave, Alpert 536, Boston, MA 02115, USA.
authors.forename: Tobias W
authors.initials: TW
authors.lastname: Giessen
authors.affiliation: Harvard College, Harvard University Harvard College, 86 Brattle Street, Cambridge, MA 02138, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Giles
authors.affiliation: Wyss Institute for Biologically Inspired Engineering, Harvard University, 3 Blackfan Circle, 5th Floor, Boston, MA 02115, USA.|Department of Systems Biology, Harvard Medical School, 200 Longwood Ave, Alpert 536, Boston, MA 02115, USA.
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Way
authors.affiliation: Wyss Institute for Biologically Inspired Engineering, Harvard University, 3 Blackfan Circle, 5th Floor, Boston, MA 02115, USA.|Department of Systems Biology, Harvard Medical School, 200 Longwood Ave, Alpert 536, Boston, MA 02115, USA.
authors.forename: Pamela A
authors.initials: PA
authors.lastname: Silver
mesh_terms: D019020:Directed Molecular Evolution; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005293:Ferritins / Q000235:genetics / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D058185:Magnetite Nanoparticles
chemical_list: D058185:Magnetite Nanoparticles; D005293:Ferritins; D007501:Iron