Metabolic Glycoengineering of Synthetic "Membrane Receptors" via Supramolecular Host-Guest Recognition

Metabolic glycoengineering enables the installation of unnatural chemical motifs on cell-surface glycoconjugates by leveraging endogenous biosynthetic pathways, yet prior efforts have primarily emphasized covalent chemistries. In this work, high-affinity supramolecular recognition motifs are introduced onto mammalian cell surfaces by using N-acyl-modified mannosamine precursors bearing adamantane guests for cucurbit[7]uril (CB[7]) complexation. A series of adamantane-mannosamine derivatives with varied linker lengths are synthesized and evaluated for metabolic incorporation in Jurkat and MCF-7 cells. Efficient conversion to adamantane-modified sialic acids and presentation at the cell membrane is achieved only for the shortest linker architecture, as confirmed by fluorescence labeling, flow cytometry, and direct mass spectrometric detection of modified sialic acids. Incorporation efficiency exhibited a strong dependence on both linker length and incubation time, revealing steric constraints imposed by the sialic acid biosynthetic machinery. Exploiting this supramolecular handle, a CB[7]-drug conjugate showed enhanced cytotoxicity in metabolically labeled cells. These results establish metabolic glycoengineering as a viable strategy for installing noncovalent, high-affinity supramolecular recognition motifs on cell surfaces, expanding the scope of orthogonal targeting approaches in biological environments.