Effect of Short PEG on Near-Infrared BODIPY-Based Activatable Optical Probes

Fuyuki F Inagaki; Daiki Fujimura; Sara Ansteatt; Ryuhei Okada; Aki Furusawa; Peter L Choyke; Marcin Ptaszek; Hisataka Kobayashi

doi:10.1021/acsomega.0c01869

Effect of Short PEG on Near-Infrared BODIPY-Based Activatable Optical Probes

ACS Omega. 2020 Jun 16;5(25):15657-15665. doi: 10.1021/acsomega.0c01869. eCollection 2020 Jun 30.

Authors

Fuyuki F Inagaki¹, Daiki Fujimura¹, Sara Ansteatt², Ryuhei Okada¹, Aki Furusawa¹, Peter L Choyke¹, Marcin Ptaszek², Hisataka Kobayashi¹

Affiliations

¹ Molecular Imaging Program, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, United States.
² Department of Chemistry and Biochemistry, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, Maryland 21250, United States.

Abstract

Targeted near-infrared (NIR) fluorescence probes are playing a significant role in biomedical imaging because NIR penetrates deeper into tissues and is associated with reduced autofluorescence compared to visible light fluorescence probes. Long-wavelength emitting 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) is an attractive platform for synthesizing NIR fluorophores because of its high photostability, high molar absorption coefficient, and sharp absorption and emission spectra. However, its lipophilicity hampers the conjugation chemistry necessary to add targeting moieties. In this study, we synthesized a novel NIR BODIPY derivative, NMP14. Substitutions of ethylene-bridged pyrrole units at the 3- or 5-position of the parent BODIPY chromophore result in a red shift of more than 200 nm. However, NMP14 cannot be conjugated to antibodies because of its hydrophobicity. Therefore, we synthesized NMP13 by adding short poly(ethylene glycol) to NMP14 and successfully conjugated NMP13 to cetuximab and trastuzumab. In vitro microscopic studies showed that NMP13 conjugated antibodies were activated after internalization and lysosomal processing, which means that NMP13 acts as an activatable probe only turning on after cellular internalization. After the administration of NMP13 conjugated antibodies, mice tumors were detected with high tumor to background ratios for a long period. These results suggest that NMP13 has potential as an activatable fluorescence probe for further clinical applications.