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

Abstract

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 (<b>2</b>) and fluorophore (<b>3</b> and <b>4</b>) 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 <i>Escherichia coli</i>.