Coordination-Based\nSite-Specific Labeling Strategy\nfor Electrogenerated Chemiluminescence Biosensing of Matrix Metalloproteinase\n2

Matrix metalloproteinase\n2 (MMP-2) is an important biomarker for\nsome diseases. Herein, one first-case coordination-based site-specific\nlabeling strategy is proposed for electrogenerated chemiluminescence\n(ECL) biosensing of MMP-2 by employing an iridium(III) solvent complex\nas a signal reagent and a histidine (His)-containing peptide as a\nmolecular recognition substrate. One ECL probe was prepared via coordination\nlabeling of the His-containing peptide with one iridium(III) solvent\ncomplex ([(3-(2-pyridyl)benzoic acid)<sub>2</sub>Ir(DMSO)Cl], Ir1-DMSO).\nHigh ECL efficiency and good cleavage ability by MMP-2 were obtained\nfor the ECL probe. By combining the high sensitivity of the ECL method,\nthe good specificity of the peptide, and the simpleness of the magnetic\nbead-based assay, one “cleavage-magnetic enrichment type”\nECL biosensing method was developed to detect MMP-2. MMP-2 can be\nsensitively detected in the linear range of 1.0–10 ng/mL with\na limit of quantification of 1.0 ng/mL and a limit of detection of\n0.3 ng/mL. Moreover, the ECL biosensing method was successfully applied\nfor the determination of MMP-2 in serum samples with recoveries from\n98.0% ± 8.0% to 108.0% ± 6.0%. Further, high affinity (<i>K</i><sub>d</sub> = 0.11 nM) was obtained for the Ir1-DMSO-labeled\nHis-containing peptide and MMP-2. This work may pave the way for the\nlabeling of His-containing biomolecules with an iridium(III) solvent\ncomplex and provides a promising method in point-of-care testing of\nMMP-2.