In Situ One-Step Fluorescence Labeling Strategy of Exosomes via Bioorthogonal Click Chemistry for Real-Time Exosome Tracking In Vitro and In Vivo

• Published in: Bioconjugate chemistry 2020-05, Vol.31 (5), p.1562-1574
• Main Authors: Song, Sukyung, Shim, Man Kyu, Lim, Seungho, Moon, Yujeong, Yang, Suah, Kim, Jinseong, Hong, Yeonsun, Yoon, Hong Yeol, Kim, In-San, Hwang, Kwang Yeon, Kim, Kwangmeyung
• Format: Article
• Language: English
• Subjects: Animals; Biocompatibility; Biological properties; Biomedical materials; Cancer; Cell Line, Tumor; Chemical compounds; Chemical synthesis; Chemistry; Click Chemistry; Cycloparaffins - chemistry; Drug delivery; Drug delivery systems; Dyes; Exosomes; Exosomes - metabolism; Fluorescence; Fluorescent dyes; Fluorescent Dyes - chemistry; Fluorescent Dyes - metabolism; Fluorescent indicators; Humans; I.R. radiation; Incubation; Infrared imaging; Infrared tracking; Labeling; Lipophilic; Mice; Optical Imaging - methods; Pharmacology; Strategy; Time dependence; Ultracentrifugation
• ISSN: 1043-1802; 1520-4812
• DOI: 10.1021/acs.bioconjchem.0c00216

Exosomes are cellular components with promising uses in cancer diagnostics and therapeutics, and their imaging and tracking are essential to study their biological properties. Herein, we report on an in situ one-step fluorescence labeling strategy for exosomes via bioorthogonal click chemistry. First, exosome donor cancer cells were treated with tetraacetylated N-azidoacetyl-d-mannosamine (Ac4ManNAz) to generate unnatural azide groups (−N3) on their surface via metabolic glycoengineering. Then, the azide groups were labeled with near-infrared fluorescent dye-conjugated dibenzylcyclooctyne (DBCO-Cy5) via bioorthogonal click chemistry. After 2 days of incubation, the DBCO-Cy5-labeled exosomes (Cy5-Exo) were successfully secreted from the donor cancer cells and were isolated via classical ultracentrifugation, providing a high-yield of fluorescent dye-labeled exosomes. This in situ one-step bioorthogonal click chemistry offers improved labeling efficiency, biocompatibility, and imaging sensitivy compared to standard exosomes (ST-Exo), purified with classical ultracentrifugation or carbocyanine lipophilic dye (DiD)-labeled exosomes (DiD-Exo) in vitro. In particular, the Cy5-Exo were successfully taken up by A549 cells in a time-dependent manner, and they could escape from lysosome confinement, showing their possible use as a delivery carrier of therapeutic drugs or imaging agents. Finally, intraveneously injected Cy5-Exo were noninvasively tracked and imaged via near-infrared fluorescence (NIRF) imaging in tumor-bearing mice. This new fluorescence labeling strategy for natural exosomes may be useful to provide better understanding of their theranostic effects in many biomedical applications.