Siderophore-inspired nanoparticle-based biosensor for the selective detection of Fe³⁺

Inspired by nature's exploitation of the 1,2-dihydroxybenzene unit (or catechol) in mammalian and bacterial siderophores, we report the first example of a nanoparticle sensing system that utilises the strong catechol-Fe³⁺ binding motif to trigger nanoparticle aggregation, promoting a powerful optical response. Gold nanoparticles are functionalised with RAFT polymerisation-prepared water-soluble poly(N-hydroxyethyl acrylamide) containing a catechol moiety at the α-chain-end. A strong red-to-purple colorimetric response occurs in the presence of Fe³⁺ at serum concentrations (8-25 μM) in saline solution. Sodium chloride is critical in generating a strong optical output, as is the length of polymer used to coat the AuNPs. This behaviour is also demonstrated to be selective for Fe³⁺ over a host of other biologically relevant ions.