Fluoroquinolone-derived fluorescent probes for studies of bacterial penetration and efflux

Fluorescent probes derived from the fluoroquinolone antibiotic ciprofloxacin were synthesised using a Cu( i )-catalysed azide-alkyne cycloaddition (CuAAC) to link a ciprofloxacin azide derivative with alkyne-substituted green and blue fluorophores. The azide ( 2 ) and fluorophore ( 3 and 4 ) derivatives retained antimicrobial activity against Gram-positive and Gram-negative bacteria. The use of confocal fluorescent microscopy showed intracellular penetration, which was substantially enhanced in the presence of carbonyl cyanide 3-chlorophenylhydrazone as an efflux pump inhibitor in Escherichia coli . Fluorescent probes derived from the fluoroquinolone antibiotic ciprofloxacin were synthesised using a Cu( i )-catalysed azide-alkyne cycloaddition (CuAAC) to link a ciprofloxacin azide derivative with alkyne-substituted green and blue fluorophores.