Tools for Intersectional Optical and Chemical Tagging on Cell Surfaces.

We present versatile tools for intersectional optical and chemical tagging of live cells. Photocaged tetrazines serve as "photo-click" adapters between recognition groups on the cell surface and diverse chemical payloads. We describe two new functionalized photocaged tetrazine structures which add a light-gating step to three common cell-targeting chemical methods: HaloTag/chloroalkane labeling, nonspecific primary amine labeling, and antibody labeling. We demonstrate light-gated versions of these three techniques in live cultured cells. We then explore two applications: monitoring tissue flows on the surface of developing zebrafish embryos, and combinatorial multicolor labeling and sorting of optically defined groups of cells. Photoclick adapters add optical control to cell tagging schemes, with modularity in both tag and cell attachment chemistry.