Visual detection of myoglobin via G-quadruplex DNAzyme functionalized gold nanoparticles-based colorimetric biosensor

Since myoglobin plays a major role in the diagnosis of acute myocardial infarction (AMI), monitoring of myoglobin in point-of-care is fundamental. Here, a novel colorimetric assay for myoglobin detection was developed based on hemin/G-quadruplex DNAzyme functionalized gold nanoparticles (AuNPs). In the presence of myoglobin, the anti-myoglobin antibody, which was modified on the surface of polystyrene microplate, could first capture the target myoglobin. Then the captured target could further bind to DNA1 probe which contained the aptamer sequence through aptamers/myoglobin interaction. Next, as the DNA2 probe modified AuNPs were introduced, DNA2 probe modified AuNPs could hybridize with the captured DNA1 probe. Subsequently, DNA2 probe which was modified on the AuNPs could fold into a G-quadruplex structure and bind to hemin, and then catalyze the oxidation of colorless ABTS2- to green ABTS(+) by H2O2. Consequently, the relationship between the concentration of myoglobin and the absorbance was established. Due to AuNPs amplification, the myoglobin concentration as low as 2.5 nM could be detected, which was lower than clinical cutoff for myoglobin in healthy patients. This assay also showed high selectivity for myoglobin and was used for the detection of myoglobin in the human serum samples. This work may provide a simple but effective tool for early diagnosis of AMI in the world, especially in developing countries. (C) 2015 Elsevier B.V. All rights reserved.