Polymethine Thiopyrylium Fluorophores with Absorption beyond 1000 nm for Biological Imaging in the Second Near-Infrared Subwindow

Abstract

Small-molecule fluorescence imaging in the second near-infrared (NIR-II, 1000−1700 nm) window has gained increasing interest in clinical application. Till now, very few studies have been exploited in the small-molecule fluorophores with both excitation and emission in the NIR-II window. Inspired by the indocyanine green structure, a series of polymethine dyes with both absorption and emission in the NIR-II window have been developed for NIR-II imaging, providing the feasibility to directly compare optical imaging in the NIR-IIa (1300−1400 nm) subwindow under 1064 nm excitation with that in the NIR-II window under 808 nm excitation. The signal−background ratio and the tumor− normal tissue ratio achieved great improvement under 1064 nm excitation in the imaging of mouse blood pool and U87 glioma tumors. Our study not only introduces a broadband emission fluorophore for both NIR-II and NIR-IIa imaging, but also reveals the advantages of NIR-II excitation over NIR-I in in vivo imaging.

Molecular Engineering of an Organic NIR‐II Fluorophore with Aggregation‐Induced Emission Characteristics for In Vivo Imaging

“…To date, several types of fluorophores have been designed for NIR‐II fluorescence imaging, including single‐walled carbon nanotubes (SWNTs), semiconducting quantum dots (QDs), rare‐earth doped down‐conversion nanoparticles, organic dyes, organic nanoparticles (NPs), and donor–acceptor–donor (D–A–D)‐structured small molecules . Very recently, several groups have reported that some conventional NIR‐I organic dyes can also be repurposed for NIR‐II imaging, because they have a long emission tail that extends into NIR‐II wavelengths .…”

An IR820 Dye–Protein Complex for Second Near‐Infrared Window and Photoacoustic Imaging

“…In particular, organic fluorophores such as CH1055, which is based on a donor–acceptor–donor structure including a benzobisthiadiazole derivative as the acceptor, demonstrate attractive optical properties (NIR‐II emission spectra, good quantum yield, high photostability) and excellent in vivo performance . Polymethine fluorophores with NIR‐II emission have also been reported . However, these highly novel organic fluorophores suffer disadvantages such as complicated synthesis, low solubility in aqueous solution, and low availability.…”

Advanced Nanotechnology Leading the Way to Multimodal Imaging‐Guided Precision Surgical Therapy

“…[31,33,42,81,[123][124][125][126] Besides the abovementioned CH1055-PEG and CH-4T, [35,81] this team reported a series of other CH1055 derivative materials, including CQS1000, H1, silk xanthan hydrogel (SXH), and succinate dehydrogenase (SDH) NPs ( Figure 5). [31,33,42,81,[123][124][125][126] Besides the abovementioned CH1055-PEG and CH-4T, [35,81] this team reported a series of other CH1055 derivative materials, including CQS1000, H1, silk xanthan hydrogel (SXH), and succinate dehydrogenase (SDH) NPs ( Figure 5).…”