Bioorthogonal Copper Free Click Chemistry for Labeling and Tracking of Chondrocytes In Vivo

Establishment of an appropriate cell labeling and tracking method is essential for the development of cell-based therapeutic strategies. Here, we are introducing a new method for cell labeling and tracking by combining metabolic gylcoengineering and bioorthogonal copper-free Click chemistry. First, chondrocytes were treated with tetraacetylated N-azidoacetyl-d-mannosamine (Ac4ManNAz) to generate unnatural azide groups (-N3) on the surface of the cells. Subsequently, the unnatural azide groups on the cell surface were specifically conjugated with near-infrared fluorescent (NIRF) dye-tagged dibenzyl cyclooctyne (DBCO-650) through bioorthogonal copper-free Click chemistry. Importantly, DBCO-650-labeled chondrocytes presented strong NIRF signals with relatively low cytotoxicity and the amounts of azide groups and DBCO-650 could be easily controlled by feeding different amounts of Ac4ManNAz and DBCO-650 to the cell culture system. For the in vivo cell tracking, DBCO-650-labeled chondrocytes (1 × 106 cells) see...