Molecular fluorophores for in vivo bioimaging in the second near-infrared window

Purpose This systematic review aims to summarize the current developments of fluorescence and chemi/bioluminescence imaging based on the molecular fluorophores for in vivo imaging in the second near-infrared window. Methods and results By investigating most of the relevant references on the web of science and some journals, this review firstly begins with an overview of the background of fluorescence and chemi/bioluminescence imaging. Secondly, the chemical and optical properties of NIR-II dyes are discussed, such as water solubility, chemostability and photo-stability, and brightness. Thirdly, the bioimaging based on NIR-II fluorescence emission is outlined, including the in vivo imaging of polymethine dyes, donor - acceptor - donor (D - A - D) chromophores, and lanthanide complexes. Fourthly, we demonstrate the chemi/bioluminescence in vivo imaging in the second near-infrared window. Fifthly, the clinical application and translation of near-infrared fluorescence imaging are presented. Finally, the current challenges, feasible strategies and potential prospects of the fluorophores and in vivo bioimaging are discussed. Conclusions Based on the above literature research on the applications of molecular fluorescent and chemi/bioluminescent probes in the second near-infrared window in recent years, this review weighs the advantages and disadvantages of fluorescence and chemi/bioluminescence imaging, and NIR-II fluorophores based on polymethine dyes, D - A - D chromophores, and lanthanide complexes. Besides, this review also provides a very important guidance for expanding the imaging applications of molecular fluorophores in the second near-infrared window.