Electrochemical Immunoassay for Cardiac Markers with Magnetic Particles as a Solid Phase and Silver Nanoparticles as an Electroactive Bio-label

− This paper introduces a novel electrochemical detection method for measuring the formation of an immunological complex. The described electrochemical immunoassay consists of several consecutive steps. First the sample is mixed with silver colloid and magnetic particles both previously conjugated to appropriate antibodies. The analyte from the sample binds to both silver and magnetic beads forming a sandwich immunocomplex: magnetic particle – analyte – silver nanoparticle (Fig. 1). That complex is separated from the sample with the use of magnetic field and then washed to remove any unbound silver nanoparticle. The bound silver nanoparticles are dissolved electrochemically into silver ions. This process is extensively investigated and the detailed mechanism of nanoparticles dissolution is presented. After the silver dissolution the released silver ions Ag are detected with anodic stripping voltammetry (ASV) and the ASV signal of silver oxidation is proportional to the analyte concentration. This approach allows for fast detection of cardiac markers like myoglobin and troponin in low volume, turbid samples with the detection limit of 200 and 150 pg/mL respectively.