Heavily Labeled Signal Probe for Electrogenerated Chemiluminescence Peptide‐Based Biosensing of Matrix Metalloproteinase 2

The field of electrogenerated chemiluminescence (ECL) biosensing has witnessed remarkable growth, emphasizing the need for precise detection of biomarkers. The synthesis approach of peptide-based signal probe with high recognition ability and high ECL efficiency is a significant issue in the ECL biosensing. Here, a heavily labeled signal probe was synthesized for ECL peptide-based biosensing tactic by using a new aldehyde bearing cyclometalated Ir(III) complex ([Ir(bt)₂(bpy-CHO)PF₆ (bt=2-phenylbenzothiazole, bpy-CHO=4'-methyl-[2,2'-bipyridine]-4-carbaldehyde, denoted as Ir1) as ECL signal reagent and streptavidin (SA) as carrier protein. One ECL peptide-based biosensing method was exemplified for the detection of matrix metalloproteinase 2 (MMP-2) by using Ir1 labeled SA (SA-Ir1) as heavily labeled signal probe and biotinylated peptide as molecular recognition substrate. MMP-2 was sensitively detected in the range from 5 to 100 ng/mL with a detection limit of 1.5 ng/mL. Importantly, two detection modes differing in the order of cleavage recognition by MMP-2 and signal transduction with SA-Ir1 were compared for the first time. First cleavage and second signal transduction were proposed to be beneficial to sensitive detection of target, which provides some ideas for biomarker diagnostics in disease screening at an early stage.