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Organic polymethine fluorophores with emission in the NIR-II window (1000-1700 nm) are receiving enormous attention in biomolecular medicine and bioimaging, attributed to the high absorption coefficients, bright NIR-II emission, excellent biocompatibility, and molecule adjustability. Recently, researchers have devoted significant effort to designing and improving NIR-II polymethine fluorophores and making notable progress in the NIR-II fluorescence imaging performance. This review summarizes recent developments in the molecular engineering design mentality of polymethine fluorophores and probes and highlights their extensive bioimaging and biosensing applications. Furthermore, we elucidate the potential challenges and perspectives of these NIR-II polymethine dyes in chemical and biomedicine imaging, which may stimulate the further development of high-performance NIR-II polymethine dye contrast agents for their future clinical applications.
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http://dx.doi.org/10.1021/cbmi.3c00040 | DOI Listing |
J Am Chem Soc
June 2025
Department of Applied Chemistry, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan, R.O.C.
NIR-II fluorophores (1000-1700 nm) are pivotal for biomedical imaging, offering deep-tissue penetration and high signal-to-noise ratios but suffer from low quantum yields (QY < 0.01%) beyond 1200 nm. To date, most reported NIR-II small-molecule dyes are derived from polymethine and xanthene frameworks.
View Article and Find Full Text PDFJ Phys Chem A
November 2024
Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea.
Fluorescence imaging is a widely used technique for detecting pathophysiological microenvironments and guiding fluorescence-guided therapy owing to its noninvasiveness, high spatiotemporal resolution, ease of operation, and real-time monitoring capabilities. In particular, NIR-II materials are promising for fluorescence imaging applications because they exhibit reduced light scattering and absorption by biological tissues, enabling deeper imaging with improved spatial resolution and contrast compared to visible or first near-infrared imaging. NIR-II materials refer to those that emit in the second near-infrared region of the electromagnetic spectrum, spanning wavelengths from approximately 1000 to 1700 nm.
View Article and Find Full Text PDFAdv Healthc Mater
August 2024
State Key Laboratory of Medicinal Chemical Biology, Tianjin Key Laboratory of Biosensing and Molecular Recognition, Research Center for Analytical Sciences, College of Chemistry, and School of Medicine, Nankai University, Tianjin, 300071, P. R. China.
Developing small-molecule photothermal agents (PTAs) with good near-infrared-II (NIR-II) response for deeper tissue penetration and minimizing damage to healthy tissues has attracted much attention in photothermal therapy (PTT). However, concentrating ultra-long excitation wavelengths and high photothermal conversion efficiencies (PCEs) into a single organic small molecule is still challenging due to the lack of suitable molecular structures. Here, six polymethine cyanine molecules based on the structure of indocyanine green are synthesized by increasing the conjugated structure of the two-terminal indole salts and the number of rigid methine units, and incorporating longer alkyl side chains into the indole salts.
View Article and Find Full Text PDFAdv Mater
August 2024
College of Pharmaceutical Sciences, Soochow University, Suzhou, 215123, P. R. China.
Fluorescence imaging (FLI)-guided phototheranostics using emission from the second near-infrared (NIR-II) window show significant potential for cancer diagnosis and treatment. Clinical imaging-used polymethine ionic indocyanine green (ICG) dye is widely adopted for NIR fluorescence imaging-guided photothermal therapy (PTT) research due to its exceptional photophysical properties. However, ICG has limitations such as poor photostability, low photothermal conversion efficiency (PCE), short-wavelength emission peak, and liver-targeting issues, which restrict its wider use.
View Article and Find Full Text PDFAdv Healthc Mater
August 2024
Department of Applied Chemistry/Center for Emergent Functional Matter Science, National Yang Ming Chiao Tung University, Hsinchu, 30050, Taiwan.
Emerging organic molecules with emissions in the second near-infrared (NIR-II) region are garnering significant attention. Unfortunately, achieving accountable organic emission intensity over the NIR-IIa (1300 nm) region faces challenges due to the intrinsic energy gap law. Up to the current stage, all reported organic NIR-IIa emitters belong to polymethine-based dyes with small Stokes shifts (<50 nm) and low quantum yield (QY; ≤0.
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