Whole-cell biosensing by siderophore-based molecular recognition and localized surface plasmon resonance

A siderophore-based active bacterial pull-down strategy was integrated in a localized surface plasmon resonance (LSPR) sensing platform and subsequently tested by detecting whole-cell Acinetobacter baumannii . The LSPR-based whole-cell sensing approach was previously demonstrated with aptamer-based molecular recognition motifs, and here it is extended to the powerful siderophore system, which exploits the natural bacterial need to sequester Fe( iii ). Specifically, a biscatecholate–monohydroxamate mixed ligand siderophore linked to a biotin via three polyethylene glycol repeating units was synthesized and immobilized on Au trigonal nanoprisms of an LSPR sensor. The resulting surface-confined biotinylated siderophore subsequently chelated Fe( iii ), forming a siderophore–Fe( iii ) complex which was shown to be competent to recognize A. baumannii . Target bacteria were captured and then detected by measuring wavelength shifts in the LSPR extinction spectrum. This siderophore pull-down LSPR biosensor approach is rapid (≤3 h detection) and sensitive – with a limit of detection (LOD) of 80 bacterial cells and a linear wavelength shift over the range 4 × 10 2 to 4 × 10 6 cfu mL −1 . As intended by design, the siderophore-based biosensor was selective for A. baumannii over Pseudomonas aeruginosa , Escherichia coli , and Bacillus cereus , and was stable in ambient conditions for up to 2 weeks.