Dual-reaction triggered sensitivity amplification for ultrasensitive peptide-cleavage based electrochemical detection of matrix metalloproteinase-7.

In this work, a new strategy of dual-reaction triggered sensitivity amplification for ultrasensitive electrochemical detection of matrix metalloproteinase-7 (MMP-7) was developed. The sensitivity of amperometric biosensor relies on the current signal differences (ΔI) caused by per unit concentration target. Benefited from dual-reaction catalytic activities of Pd nanoparticles, dual catalytic reactions were implemented in the biosensor to amplify the ΔI: (1) Fenton-like reaction was triggered by the probes to degrade redox species methylene blue; (2) catalytic precipitation reaction was followed subsequently to generate insoluble precipitation by 4-chloro-1-naphthol oxidation. Dual-enhancement of ΔI triggered by Pd nanoparticle-based catalytic probes significantly improved the detection performance of the biosensor. The peptide-cleavage based biosensor integrated Pd nanoparticle-based catalytic probes with reduced graphene oxide-Au/methylene blue-sodium alginate hydrogel (Au-rGO/MB-SA) nanocomposites substrate for ultrasensitive detection of MMP-7. Under optimal conditions, the proposed biosensor exhibited a wide linear range from 10 fg mL to 10 ng mL with an ultralow detection limit of 3.1 fg mL. This strategy successfully combines the multiple catalytic reactions triggered by nanomaterials with peptide-cleavage pattern in electrochemical biosensor, providing a promising method for detection of other proteases.