Theranostics 2018; 8(15):4116-4128. doi:10.7150/thno.26539 This issue

Research Paper

Near-infrared fluorescence imaging in the largely unexplored window of 900-1,000 nm

Guanjun Deng1,2, Sanpeng Li1,2, Zhihong Sun1, Wenjun Li1, Lihua Zhou1, Jiali Zhang1,2, Ping Gong1✉, Lintao Cai1✉

1. Guangdong Key Laboratory of Nanomedicine, Shenzhen Engineering Laboratory of Nanomedicine and Nanoformulations, CAS Key Lab for Health Informatics, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, China
2. University of Chinese Academy of Sciences, Beijing 100049, China

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Citation:
Deng G, Li S, Sun Z, Li W, Zhou L, Zhang J, Gong P, Cai L. Near-infrared fluorescence imaging in the largely unexplored window of 900-1,000 nm. Theranostics 2018; 8(15):4116-4128. doi:10.7150/thno.26539. Available from https://www.thno.org/v08p4116.htm

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Abstract

Graphic abstract

Near-infrared (NIR) fluorescence imaging has relied on fluorophores that emit in the 700-900 nm NIR-Ia or 1,000-1,700 nm NIR-II window for generating deep-tissue images. Up until now, there have been few fluorophores developed for the 900-1,000 nm NIR-Ib window. This is largely because NIR-Ib light is thought to be strongly absorbed by water.

Methods: Here we found that six heptamethine dyes had distinct emission peaks in both the NIR-Ia and NIR-Ib window. We tested the performance of these contrast agents by introducing them into the leaves of the common house plant Epipremnum aureum with early stage anthracnose leaf infections from Khaya senegalensis, as well as injecting them into the hind feet of nude mice and tails of tumour-bearing mice in vivo.

Results: Heptamethine dyes yielded superior images of leaf venation, anthracnose infection locations, sentinel lymph nodes, brain tumours and subcutaneous tumours in the NIR-Ib window. We found that NIR-Ib images had markedly enhanced signal-to-background ratio because autofluorescence, scattering and light absorption by biological tissues and water were weaker at longer wavelengths.

Conclusion: NIR-Ib fluorescence imaging was a powerful method for studying sentinel lymph nodes, tumours, leaf veins and early anthracnose infection locations in plant leaves. The findings challenge our current view of NIR fluorescence imaging and may have important implications for biomedical research and image-guided cancer surgery.

Keywords: near-infrared fluorescence imaging, heptamethine dyes, leaf vein imaging, lymphatic imaging, image-guided cancer surgery