title: Development of Ultrasound-switchable Fluorescence Imaging Contrast Agents based on Thermosensitive Polymers and Nanoparticles.
abstract: In this work we first introduced a recently developed high-resolution, deep-tissue imaging technique, ultrasound-switchable fluorescence (USF). The imaging principles based on two types of USF contrast agents were reviewed. To improve USF imaging techniques further, excellent USF contrast agents were developed based on high-performance thermoresponsive polymers and environment-sensitive fluorophores. Herein, such contrast agents were synthesized and characterized with five key parameters: (1) peak excitation and emission wavelengths (λexand λem), (2) the fluorescence intensity ratio between on and off states (IOn/IOff), (3) the fluorescence lifetime ratio between on and off states (τOn/τOff), (4) the temperature threshold to switch on fluorophores (Tth), and (5) the temperature transition bandwidth (TBW). We mainly investigated fluorescence intensity and lifetime changes of four environment-sensitive dyes [7-(2-Aminoethylamino)-N,N-dimethyl-4-benzofurazansulfonamide (DBD-ED), St633, Sq660, and St700] as a function of temperature, while the dye was attached to poly(N-isopropylacrylamide) linear polymers or encapsulated in nanoparticles. Six fluorescence resonance energy transfer systems were invented in which both the donor (DBD-ED or ST425) and the acceptor (Sq660) were adopted. Our results indicate that three Förster resonance energy transfer systems, where both IOn/IOffand τOn/τOffare larger than 2.5, are promising for application in future surface tissue bioimaging by USF technique.
authors.affiliation: Ultrasound and Optical Imaging Laboratory, Department of Bioengineering, The University of Texas at Arlington, Arlington, TX 76010, USA.
authors.forename: Bingbing
authors.initials: B
authors.lastname: Cheng
authors.affiliation: Ultrasound and Optical Imaging Laboratory, Department of Bioengineering, The University of Texas at Arlington, Arlington, TX 76010, USA.
authors.forename: Ming-Yuan
authors.initials: MY
authors.lastname: Wei
authors.affiliation: Ultrasound and Optical Imaging Laboratory, Department of Bioengineering, The University of Texas at Arlington, Arlington, TX 76010, USA.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Joint Biomedical Engineering Program, The University of Texas at Arlington and The University of Texas Southwestern Medical Center at Dallas, TX 75390, USA.
authors.forename: Harish
authors.initials: H
authors.lastname: Pitta
authors.affiliation: Joint Biomedical Engineering Program, The University of Texas at Arlington and The University of Texas Southwestern Medical Center at Dallas, TX 75390, USA.
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Xie
authors.affiliation: Joint Biomedical Engineering Program, The University of Texas at Arlington and The University of Texas Southwestern Medical Center at Dallas, TX 75390, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Hong
authors.affiliation: Joint Biomedical Engineering Program, The University of Texas at Arlington and The University of Texas Southwestern Medical Center at Dallas, TX 75390, USA.
authors.forename: Kytai T
authors.initials: KT
authors.lastname: Nguyen
authors.affiliation: Ultrasound and Optical Imaging Laboratory, Department of Bioengineering, The University of Texas at Arlington, Arlington, TX 76010, USA.
authors.forename: Baohong
authors.initials: B
authors.lastname: Yuan
keywords: Bioimaging; Environment-sensitive; FRET; Nanomaterials; Thermosensitive