• Covalent editing of cell surfaces with synthetic polymers through metabolic oligosaccharide engineering. • Density of azides on the cell surface tuned by use of different glycan probes which are metabolically processed by different pathways. • Impact of polymer size and nature of glycan label on the total grafting density on the surface of cells is determined. • Demonstrates an alternative method to control and modulate polymer-engineered living cells. The covalent engineering of cellular surfaces with synthetic polymers can introduce abiotic functionality, deliver cargoes to cell surfaces and modulate cell–cell interactions. Metabolic oligosaccharide engineering (MOE) has emerged as a particularly versatile and powerful tool to install chemo-selective handles onto the cell-surface glycocalyx to capture macromolecular ligands. Here we explore the impact of both polymer molecular weight and the specific glycan label on the efficiency of the grafting-to reaction of alkyne-terminated polymers to azido-labelled glycans. Azido, N -acetyl −glucosamine/-galactosamine and −mannosamine were used to label both adherent and suspension mammalian cells, to vary the glycan-location of the azide handle at the cellular surface. Using flow cytometry we show that the location of the azide within the glycan impacts the extent of polymer capture, with the more exposed sialic-acid azide labels giving the highest grafting. Higher molecular weight polymers showed less glycan-dependant capture than smaller, suggesting the polymer steric constraints, rather than glycan location, was the limiting factor for larger cargoes. These results will enable the development of cell/polymer hybrids with tuneable function and potentially tuneable lifetimes, unlocking opportunities in cell-based therapies.
Alkosti et al. (Sun,) studied this question.