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Director's Seminar: Harnessing Intrinsic Fluorophore Chemistry to Build Better Imaging Agents (NIH Only)

Air date: Friday, November 15, 2019, 12:00:00 PM
Time displayed is Eastern Time, Washington DC Local
Description: Director's Seminar Series

Existing fluorescent probes derive from a small set of core scaffolds initially developed for various abiological dye applications, and subsequently applied for biomedical research with minimal synthetic modification. Consequently, there exists a significant opportunity to develop molecules specifically tailored for use in modern imaging applications. Cyanine fluorophores are among the most broadly used fluorescent probes, despite poor chemical stability and modest photon output. To address these limitations, we develop new synthetic transformations that modify the core polymethine chromophore unit. We have discovered a novel class of near-IR emitting heptamethine cyanines containing a C4’-O-alkyl substituent. These molecules are readily synthesized through an N- to O- transposition reaction. The new fluorophores exhibit excellent labeling properties, no covalent reactivity, and improved in vivo tumor uptake and signal compared to existing near-IR cyanines. These probes are also being using as organ-specific probes with direct application in certain abdominal surgical procedures. We have also shown that conformationally restrained pentamethine and heptamethine cyanines can be accessed through a multiple ring forming cascade reaction. The resulting far-red fluorophores exhibit improved fluorescence quantum yield (3- to 4-fold) and extended lifetime relative to typical pentamethine cyanines. Moreover, these fluorophores recover from hydride reduction with improved efficiency. These observations enable efficient single-molecule localization microscopy in oxygenated buffer without addition of conventional blinking buffers. Overall, these efforts involve a feedback loop between chemical studies focused on the design and synthesis of novel compounds and biological applications in advanced microscopy and in vivo imaging settings.
Author: Martin J. Schnermann, Ph.D, NCI, NIH
Runtime: 1 hour