Promotion and Detection of Cell–Cell Interactions through a Bioorthogonal Approach

Manipulation of cell–cell interactions via cell surface modification is crucial in tissue engineering and cell-based therapy. To be able to monitor intercellular interactions, it can also provide useful information for understanding how the cells interact and communicate. We report herein a facile bioorthogonal strategy to promote and monitor cell–cell interactions. It involves the use of a maleimide-appended tetrazine-caged boron dipyrromethene (BODIPY)-based fluorescent probe and a maleimide-substituted bicyclo[6.1.0]non-4-yne (BCN) to modify the membrane of macrophage (RAW 264.7) and cancer (HT29, HeLa, and A431) cells, respectively, via maleimide–thiol conjugation. After modification, the two kinds of cells interact strongly through inverse electron-demand Diels–Alder reaction of the surface tetrazine and BCN moieties. The coupling also disrupts the tetrazine quenching unit, restoring the fluorescence emission of the BODIPY core on the cell–cell interface, and promotes phagocytosis. Hence, this approach can promote and facilitate the detection of intercellular interactions, rendering it potentially useful for macrophage-based immunotherapy.