Construction of a magnetic-fluorescent-plasmonic nanosensor for the determination of MMP-2 activity based on SERS-fluorescence dual-mode signals.

Matrix metalloproteinase 2 (MMP-2) is a crucial biomarker of tumor growth, invasion and metastasis. In the present study, a core-satellite magnetic-fluorescent-plasmonic nanosensor (FMNS@Au) was constructed through biological self-assembly to generate localized SERS "hot spots" and an efficient FRET system for the sensitive determination of MMP-2 activity in a SERS-fluorescence dual-mode assay. In this hybrid nanosensor, a biotin-labeled peptide containing a specific MMP-2 substrate (PLGVR) was employed as a bridge for the assembly of gold nanoparticles (AuNPs) and avidin functionalized fluorescent-magnetic nanospheres (FMNS). The modified RB on FMNS served as a Raman reporter and a donor of FRET, while the AuNPs assembled on FMNS acted as SERS substrates and acceptors of FRET. In the presence of MMP-2, the SERS "hot spot" effect was weakened and the FRET system was disrupted through enzymatic cleavage of PLGVR, resulting in a reduction of SERS signal and the recovery of fluorescence emission. Importantly, this combination of SERS and fluorescence assay methods in the dual-mode nanosensor broadened the detection range for MMP-2 to 1-200 ng mL, with a limit of detection of 0.35 ng mL and a limit of quantitation of 1.17 ng mL. In addition, our novel nanosensor affords semi-quantitative sensing of MMP-2 by naked-eye observation and accurate detection of MMP-2 through dual-mode analysis. The practicality of FMNS@Au was validated by determination of MMP-2 activity in cell secretions and human serum samples. The designed FMNS@Au nanosensor holds great potential for clinical diagnosis of protease-related diseases.