Targeting infected host cells in vivo via responsive azido-sugar mediated metabolic cell labeling followed by click reaction.

The early in vivo diagnosis of infectious disease foci is largely hindered by invasion and concealment of pathogens in host cells, making it difficult for conventional probes to detect and analyze intracellular pathogens. Taking advantage of the excessively produced reactive oxygen species (ROS) within host cells, herein we report the design of thiol-hemiketal blocked N-azidoacetyl galactosamine (Ac3GalNAzSP), an azido unnatural sugar bearing an unprecedent designed ROS-responsive moiety for targeted labelling of infected host cells. Ac3GalNAzSP showed great stability under physiological conditions, specifically released active unnatural sugar in host cells overproducing ROS, metabolically labeled infected host cells with azido groups, and enabled targeting in vivo infection sites by subsequent Click Chemistry reactions, substantiating an unprecedented approach for targeting infected host cells. This technique could be a powerful tool for early in vivo diagnosis and targeted treatment of infectious disease.