Development of a novel fluorescence probe capable of assessing the cytoplasmic entry of siderophore-based conjugates

Abstract

A novel fluorescence probe capable of assessing the cytoplasmic entry of siderophore-based conjugates was synthesized and evaluated by photochemical characterization and cell-based assays. The specific responsiveness to the cytoplasmic entry of the probe was implemented by adopting a disulfide linker, whose cleavage under the reducing conditions of the cytoplasm induced the display of a distinctive fluorescence signal.

Advances in the Chemical Biology of Desferrioxamine B

“…Conjugates of DFOB and the DNA intercalators nalidixic acid ( 34 ) or anthraquinone carboxylic acid ( 35 ) were prepared to examine the potential to induce Fenton-based damage to DNA upon the localization of the Fe­(III)–DFOB intercalator to DNA . A fluorescent moiety appended to DFOB with a linking region containing a cleavable disulfide bond has been prepared ( 36 ) to measure cytoplasmic transport and processing of FOB in vitro and as a xenosiderophore in E. coli …”

“…116 A fluorescent moiety appended to DFOB with a linking region containing a cleavable disulfide bond has been prepared (36) to measure cytoplasmic transport and processing of FOB in vitro and as a xenosiderophore in E. coli. 117 Antibiotic Adducts (37−43). A small suite of siderophore−antibiotic conjugates, classified as sideromycins, exist in nature, including the albomycins, salmycins, microcins, and ferrimycin A1.…”

Evaluation of a reducible disulfide linker for siderophore-mediated delivery of antibiotics

“…This peptide delivered the aminoglycoside into mammalian cells, affording clearance of intracellular pathogenic bacteria after cleavage of the disulfide linker and release of both antibiotics. Recently, the self-immolative disulfide linker was employed for a siderophore–fluorophore conjugate and shown to provide intracellular release of the fluorophore in a Gram-negative strain [55]. Herein, we report that the disulfide-linked conjugate Ent–SS–Cipro 2 exhibits antibacterial activity against E. coli independent of intracellular siderophore hydrolysis, which contrasts the requirements for the activity of the structurally similar alkyl-linked conjugate Ent–Cipro 1 (Scheme 1).…”

Synthetic transport systems in bacteria

“…1-3a). For example, it was demonstrated that the fluorophore 4-amino-1,8-naphthalimide can be attached to desferrioxamine B with a disulfide-containing linker that dissociates once the conjugate enters the cytoplasm and results in release of the fluorophore [71]. To be more flexible regarding the chemical nature of the cargo molecules, linker design in principle offers the potential to release cargo molecules by cellular esterases, phosphatases or reductases [72,73].…”