Ratiometric fluorescence detection of an anthrax biomarker with Eu3+-chelated chitosan biopolymers

[Display omitted] •A novel bio-based ratiometric fluorescent probe based on europium (Eu3+)-chelated chitosan biopolymer was synthesized.•The chitosan-based sensor selectively and sensitively detected DPA, a biomarker of bacterial spores.•The chitosan-based sensor had detection limit of 10nM for DPA. A novel chitosan-based ratiometric fluorescent probe incorporating an EDTA-Eu3+ complex as the sensing unit and fluorescein dye as the internal standard was designed to detect dipicolinic acid (DPA) as an anthrax biomarker with high sensitivity and selectivity. The fluorescence intensity of fluorescein dye attached to the chitosan backbone remains constant as an internal reference, while the Eu3+ emission increased linearly upon the consecutive addition of DPA. The selectivity studies were performed by adding different competitive aromatic ligands to the sensing environment and no signifacant fluorescence response was observed. The results demonstrated the superior selectivity of the system to DPA. Overall, this novel chitosan-based ratiometric fluorescent probe enables ratiometric and sensitive DPA detection over nanomolar concentrations (as low as 10nM) and displays straightforward selectivity over other competitive aromatic ligands.