Tricarbocyanine N-triazoles: the scaffold-of-choice for long-term near-infrared imaging of immune cells in vivo.

Richard J Mellanby,Monica Moral,Iris Mair,Marc Vendrell,Antonio Fernandez,Louise Saul,Jochen Arlt,Jamie I Scott

doi:10.1039/c8sc00900g

Abstract

Herein tricarbocyanine N-triazoles are first described as a rationally-designed near-infrared (NIR) structure overcoming the brightness and photostability limitations of tricarbocyanines for long-term in vivo imaging. The straightforward synthetic approach and the wide availability of alkynes makes this strategy a versatile methodology for the preparation of highly stable N-substituted tricarbocyanines. Furthermore, we validated CIR38M as a non-transferable marker to monitor the fate of therapeutic T cells non-invasively in vivo, showing enhanced performance over conventional NIR fluorophores (i.e. DiR, IR800CW and indocyanine green) as well as compatibility with human cells for translational studies. CIR38M is able to track over time smaller numbers of T cells than current NIR agents, and to visualise antigen-driven accumulation of immune cells at specific sites in vivo. This chemical technology will improve longitudinal imaging studies to assess the efficacy of cell-based immunotherapies in preclinical models and in human samples.

Highlights

In vivo optical imaging has revolutionised our ability to visualise biological processes with high resolution in intact organisms
We addressed these shortcomings by rationally designing tricarbocyanine N-triazoles as a new family of bright, photostable and cell-permeable NIR uorophores containing neutral triazole groups
Triazole derivatives display superior spectral properties when compared to their isosteric tricarbocyanine N-amines, despite only differing in two nitrogen atoms being replaced by methylene groups

Summary

Introduction

In vivo optical imaging has revolutionised our ability to visualise biological processes with high resolution in intact organisms. Flow cytometry analysis a er 3 days under stimulatory conditions con rmed the intracellular retention of CIR38M, as labelled cells expressed the CD45.2 marker but not the CD45.1 marker (Fig. 3d). We examined the properties of CIR38M for tracking CD4+ T cells in vivo using whole-body NIR uorescence imaging.

Results

Conclusion