A dual-functional magnetic microsphere for ICP-MS quantification and fluorescence imaging of matrix metalloproteinase...

Matrix metalloproteinase 2 (MMP2) plays an important role in tumor growth, invasion and metastasis. In this work, a dual-functional magnetic microsphere probe was designed for ICP-MS quantification and fluorescence imaging of MMP2 in cell secretion. In the designed probe, a NH₂-peptide (-FAM)-biotin was used as a bridge for the combination of carboxylated magnetic beads (MBs-COOH) and streptavidin functionalized gold nanoparticle (Au NP-SA). Initially, the fluorescence of FAM was quenched by Au NP. Since the NH₂-peptide (-FAM)-biotin had a MMP2-specifically recognized sequence, the peptide was specifically cleaved in the presence of MMP2, thus releasing Au NP for the ICP-MS quantification of MMP2 and turning on the fluorescence of FAM for the fluorescence imaging of MMP2. Under the optimal experimental conditions, a linear range of 0.05-50 ng mL^-1 and a limit of detection of 0.02 ng mL^-1 were obtained for MMP2. The relative standard deviation (n = 7, c = 0.1 ng mL^-1) of the proposed method was 5.4%. With good sensitivity and good accuracy, the proposed method realized the quantification and imaging of MMP2 in A549 cell secretion. The proposed method was applied to monitor the expression of MMP2 in the A549 cell secretion under the stimulation of Cd²⁺, providing a new detection strategy in the study of MMP2-related life process.