title: (19)F Magnetic Resonance Imaging Signals from Peptide Amphiphile Nanostructures Are Strongly Affected by Their Shape.
abstract: Magnetic resonance imaging (MRI) is a noninvasive imaging modality that provides excellent spatial and temporal resolution. The most commonly used MR probes face significant challenges originating from the endogenous (1)H background signal of water. In contrast, fluorine MRI ((19)F MRI) allows quantitative probe imaging with zero background signal. Probes with high fluorine content are required for high sensitivity, suggesting nanoscale supramolecular assemblies containing (19)F probes offer a potentially useful strategy for optimum imaging as a result of improved payload. We report here on supramolecular nanostructures formed by fluorinated peptide amphiphiles containing either glutamic acid or lysine residues in their sequence. We identified molecules that form aggregates in water which transition from cylindrical to ribbon-like shape as pH increased from 4.5 to 8.0. Interestingly, we found that ribbon-like nanostructures had reduced magnetic resonance signal, whereas their cylindrical counterparts exhibited strong signals. We attribute this drastic difference to the greater mobility of fluorinated tails in the hydrophobic compartment of cylindrical nanostructures compared to lower mobility in ribbon-like assemblies. This discovery identifies a strategy to design supramolecular, self-assembling contrast agents for (19)F MRI that can spatially map physiologically relevant changes in pH using changes in morphology.
authors.affiliation: Departments of Chemistry, Materials Science and Engineering, Medicine, and Biomedical Engineering, and Simpson Querrey Institute for BioNanotechnology, Northwestern University , Evanston, Illinois 60208, United States.|Departments of Chemistry, Molecular Biosciences, Neurobiology and Radiology, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Adam T
authors.initials: AT
authors.lastname: Preslar
authors.affiliation: Departments of Chemistry, Materials Science and Engineering, Medicine, and Biomedical Engineering, and Simpson Querrey Institute for BioNanotechnology, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Faifan
authors.initials: F
authors.lastname: Tantakitti
authors.affiliation: Departments of Chemistry, Molecular Biosciences, Neurobiology and Radiology, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Kitae
authors.initials: K
authors.lastname: Park
authors.affiliation: Advanced Imaging Research Center, University of Texas Southwestern Medical Center , Dallas, Texas 75390, United States.
authors.forename: Shanrong
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Departments of Chemistry, Materials Science and Engineering, Medicine, and Biomedical Engineering, and Simpson Querrey Institute for BioNanotechnology, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Samuel I
authors.initials: SI
authors.lastname: Stupp
authors.affiliation: Departments of Chemistry, Molecular Biosciences, Neurobiology and Radiology, Northwestern University , Evanston, Illinois 60208, United States.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Meade
mesh_terms: D005459:Fluorides; D057927:Hydrophobic and Hydrophilic Interactions; D008279:Magnetic Resonance Imaging; D049329:Nanostructures; D010455:Peptides
chemical_list: D010455:Peptides; D005459:Fluorides
keywords: fluorine; fluorous; magnetic resonance imaging (MRI); nanofiber; pH response; peptide amphiphile; self-assembly