Single-frequency impedance analysis of biofunctionalized dendrimer-encapsulated Pt nanoparticles-modified screen-printed electrode for biomolecular detection

We report the fabrication of polyamidoamine (PAMAM) dendrimer with 128 carboxyl group-encapsulated Pt nanoparticle-modified screen-printed carbon electrode, as an impedimetric biosensor, for the quantitative detection of human cardiac biomarker troponin-I (cTnI). PAMAM-Pt was electrochemically deposited over SPCE and its 128 terminal carboxyl groups were used as anchors for the site-specific biomolecular immobilization of protein antibody, anti-cTnI. The biosensor was characterized by contact angle measurements, transmission electron microscopy, UV-visible spectroscopy, and electrochemical techniques. A single-frequency impedance analysis study was utilized for the biomolecular sensing by monitoring the changes in the phase angle obtained at an optimized frequency resulting from antigen-antibody interactions. An optimized frequency of 100 Hz was obtained at which maximum changes in the phase angle were observed after immunoreactions for a given concentration of analyte. A concentration-dependent increase in the phase angle of the biosensor was observed with increasing cTnI concentration in the range of 1 pg mL(-1) to 100 ng mL(-1). Based on the concentration response data, the dissociation constant was found to be 0.51 pM reflecting high affinity of biosensor towards cTnI analyte arising due to high anti-cTnI loading with a better probe orientation on the 3-dimensional PAMAM-Pt structure.