Metabolically Specific <i>In Situ</i> Fluorescent Visualization of Bacterial Infection on Wound Tissues

Abstract

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 <i>in situ</i> in a target-specific manner. Dihydropteroate synthase (DHPS) exclusively exists in bacterial species and metabolically converts <i>p</i>-aminobenzoic acid (PABA) to folic acid (FA). By targeting this bacterium-specific metabolism, we have developed a fluorescent imaging probe, <b>PABA-DCM</b>, based on the conjugation of PABA with a long-wavelength fluorophore, dicyanomethylene 4<i>H</i>-pyran (<b>DCM</b>). 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 <b>PABA-DCM</b>, and the resulting adduct leads to an increase in the FA levels of bacteria. We also constructed a hydrogel dressing containing <b>PABA-DCM</b> and graphene oxide (GO), termed <b>PABA-DCM@GO</b>, 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 <i>in situ</i> monitoring of infections in human tissues.