The ability to effectively detect bacterial infection
in human
tissues is important for the timely treatment of the infection. However,
traditional techniques fail to visualize bacterial species adhered
to host cells in situ in a target-specific manner.
Dihydropteroate synthase (DHPS) exclusively exists in bacterial species
and metabolically converts p-aminobenzoic acid (PABA)
to folic acid (FA). By targeting this bacterium-specific metabolism,
we have developed a fluorescent imaging probe, PABA-DCM, based on the conjugation of PABA with a long-wavelength fluorophore,
dicyanomethylene 4H-pyran (DCM). We
confirmed that the probe can be used in the synthetic pathway of a
broad spectrum of Gram-positive and negative bacteria, resulting in
a significantly extended retention time in bacterial over mammalian
cells. We validated that DHPS catalytically introduces a dihydropteridine
group to the amino end of the PABA motif of PABA-DCM,
and the resulting adduct leads to an increase in the FA levels of
bacteria. We also constructed a hydrogel dressing containing PABA-DCM and graphene oxide (GO), termed PABA-DCM@GO, that achieves target-specific fluorescence visualization of bacterial
infection on the wounded tissues of mice. Our research paves the way
for the development of fluorescent imaging agents that target species-conserved
metabolic pathways of microorganisms for the in situ monitoring of infections in human tissues.