Blue emission of carbamic acid oligooxazoline biotags

The blue emission of a carbamic acid oligo(2-methyl-2-oxazoline) synthesized by a cationic ring-opening polymerization in supercritical carbon dioxide under controlled conditions is reported. The increase of the light-emission intensity of oligo(2-oxazoline)s was achieved by carbamic acid insertion at the oligomer starting end during the polymerization. Successful labeling of gram-positive S. aureus bacterial cells with carbamic acid ammonium-quaternized oligo(2-oxazoline)s turn these materials into promising blue fluorescent markers for imaging and bioanalytical assays.

► Synthesis of carbamic acid enriched oligo(2-oxazoline)s (OOXs) in scCO2 is reported.
► Fluorescence of enriched carbamic acid OOXs is reported for the first time.
► Light-emission properties can be tuned by scCO2 synthetic route.
► Purely intrinsic blue emission of OOXs results from carbamic acid endcapping.
► Ammonium-quaternized OOXs can be used as blue markers for S. aureus cells.