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-1 to 10 ng mL-1 with an ultralow detection limit of 3.1 fg mL-1. 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.