title: Photoswitching Near-Infrared Fluorescence from Polymer Nanoparticles Catapults Signals over the Region of Noises and Interferences for Enhanced Sensitivity.
abstract: As a very sensitive technique, photoswitchable fluorescence not only gains ultrasensitivity but also imparts many novel and unexpected applications. Applications of near-infrared (NIR) fluorescence have demonstrated low background noises, high tissue-penetrating ability, and an ability to reduce photodamage to live cells. Because of these desired features, NIR-fluorescent dyes have been the premium among fluorescent dyes, and probes with photoswitchable NIR fluorescence are even more desirable for enhanced signal quality in the emerging optical imaging modalities but rarely used because they are extremely challenging to design and construct. Using a spiropyran derivative functioning as both a photoswitch and a fluorophore to launch its periodically modulated red fluorescence excitation energy into a NIR acceptor, we fabricated core-shell polymer nanoparticles exhibiting a photoswitchable fluorescence signal within the biological window (∼700-1000 nm) with a peak maximum of 776 nm. Live cells constantly synthesize new molecules, including fluorescent molecules, and also endocytose exogenous particles, including fluorescent particles. Upon excitation at different wavelengths, these fluorescent species bring about background noises and interferences covering nearly the whole visible region and therefore render many intracellular targets unaddressable. The oscillating NIR fluorescence signal with an on/off ratio of up to 67 that the polymer nanoparticles display is beyond the typical background noises and interferences, thus producing superior sharpness, reliability, and signal-to-noise ratios in cellular imaging. Taking these salient features, we anticipate that these types of nanoparticles will be useful for in vivo imaging of biological tissue and other complex specimens, where two-photon activation and excitation are used in combination with NIR-fluorescence photoswitching.
authors: School of Chemistry and Chemical Engineering, University of Chinese Academy of Sciences , Beijing 100049, P. R. China.
authors: Jie
authors: J
authors: Wang
authors: School of Chemistry and Chemical Engineering, University of Chinese Academy of Sciences , Beijing 100049, P. R. China.
authors: Yanlin
authors: Y
authors: Lv
authors: Department of Chemistry and Center for Materials Research, Washington State University Pullman, Washington 99164, United States.
authors: Wei
authors: W
authors: Wan
authors: School of Chemistry and Chemical Engineering, University of Chinese Academy of Sciences , Beijing 100049, P. R. China.
authors: Xuefei
authors: X
authors: Wang
authors: Department of Chemistry and Center for Materials Research, Washington State University Pullman, Washington 99164, United States.
authors: Alexander D Q
authors: AD
authors: Li
authors: School of Chemistry and Chemical Engineering, University of Chinese Academy of Sciences , Beijing 100049, P. R. China.
authors: Zhiyuan
authors: Z
authors: Tian
mesh_terms: D001578:Benzopyrans / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry*; D007211:Indoles / Q000737:chemistry; D057054:Molecular Imaging / Q000379:methods*; D053758:Nanoparticles / Q000737:chemistry; D009574:Nitro Compounds / Q000737:chemistry; D017785:Photons; D011108:Polymers / Q000737:chemistry; D059629:Signal-To-Noise Ratio; D013050:Spectrometry, Fluorescence / Q000379:methods*; D019265:Spectroscopy, Near-Infrared / Q000379:methods*
chemical_list: D001578:Benzopyrans; D005456:Fluorescent Dyes; D007211:Indoles; D009574:Nitro Compounds; D011108:Polymers; C088184:spiropyran
keywords: Förster resonance energy transfer; cellular imaging; near-infrared fluorescence; photoswitching; polymer nanoparticles