Bio-orthogonal ligations that crosslink living cells with a substrate or other cells require high stability and rapid kinetics to maintain the nature of target cells. In this study, we report water-soluble cyclooctadiyne (WS-CODY) derivatives that undergo an ion-pair enhanced double-click reaction. The cationic side chain of WS-CODY accelerated the kinetics on the azide-modified cell surface due to proximity effect. Cationic WS-CODY was able to crosslink azide-modified, poorly adherent human lung cancer PC-9 cells not only to azide-grafted glass substrates but also to other cells within 5−30 min. We discovered that cell−substrate crosslinking induced the ITGA5 gene expression, whereas cell−cell crosslinking induced the CTNNA1 gene, according to the adhesion partner. Ionpair-enhanced WS-CODY can be applied to a wide range of cells with established azide modifications and is expected to provide a powerful tool to regulate cell−substrate and cell−cell interactions.

Click reactions are used for chemoselective functionalization in many research fields. Despite the utility of small, bioinert azide groups as a counterpart, applications of strain-promoted alkyne-azide cycloaddition (SPAAC) reactions for...