Signal-off electrochemical sensor for matrix metalloproteinase 9 detection based on sacrificial FeMOF and host-guest strategy

Matrix metalloproteinase-9 (MMP-9) has been implicated in various tumor cell invasions and metastases. In light of the limitations of traditional methods for MMP-9 detection, we have constructed a novel biosensor depending on cucurbit[8]uril (CB[8]) -mediated host-guest interactions and a sacrificial iron metal-organic framework (FeMOF). Herein, MMP9-specific peptides modified on the gold bare electrode are bonded to the FeMOF@AuNPs@peptide complex through CB[8] addition. The connection between MMP9-specific peptides and signal peptides via CB[8] provides stability as well as enables the immobilization of FeMOF on the electrode surface. When Fe3+ from the FeMOF interacts with electrochemical buffer K4Fe(CN)6, Prussian blue will be generated on the gold electrode surface, and a significantly enlarged current response can be detected. However, in the presence of MMP-9, their peptide substrates are specifically cleaved at the site between serine (S) and Leucine (L), which causes an abrupt decrease in the electrochemical signal. The change of signal can reflect MMP-9 concentration. This sensor can reach an ultrahigh sensitivity with a wide detection range of 0.5 pg⋅mL-1 to 500 ng⋅mL-1 and a low detection limit of 1.30 pg⋅mL-1. Importantly, this sensor is very simple, relying solely on self-sacrificial label of FeMOF, rather than complex functional materials. Additionally, it has been well used in serum samples, showing attractive potential for practical applications.