Quartz Crystal Microbalance Immunoassay for the Cardiac Myoglobin Detection in the Plasma Samples

Abstract

A mass-sensitive method for the detection of cardiac myoglobin (cMb), based on direct monitoring the immunochemical reaction between the cardiac myoglobin and monoclonal antibodies (anti-cMb) using quartz crystal microbalance, was developed. The monoclonal antibodies were immobilized directly onto a gold surface of quartz crystal electrode due to Au-S bond formation by drop casting. The proposed immunosensor provides one-step online analysis in real time, without multiple labeling procedures and without additional chemical modifications of electrode surface. In this work, it was possible to measure specific binding events in plasma samples in short time (30–120 s). This approach was based on the differences of the kinetics of specific interactions and nonspecific sorption and permitted the exclusion of separation steps. The affinity binding was characterized by the association (k a) and dissociation (k d) kinetic rate constants and by the equilibrium association constants (K) all of which were obtained from the experimental frequency vs. time curves. The monitoring of cMb was performed using plasma samples of healthy donors and patients with acute myocardial infarction. Immunosensor had a detection limit of 34.2 ng mL−1 (2 nM) in plasma and a broad range of the (34.2–394.2) ng mL−1 (2–23 nM) working concentrations.