Novel immunosensor platform based on inorganic barium strontium titanate film for human IgG detection

In this investigation, we report a novel immunosensor platform using sol-gel derived amorphous barium strontium titanate (BST) thin films. The impedimetric immunosensor detection was carried out based on a redox-free system with two electrodes and a very diluted NaCl solution as electrolyte. As a proof of concept, the anti-human IgG, a common biomarker found and associated with many diseases, was firstly immobilized on the immunosensor surface, pre-modified by 3-aminopropyltriethoxysilane (APTS) and then by the coupling agent of glutaraldehyde. The modified sensor surface served as selective sensing probe to capture/conjugate the human IgG, pre-diluted with phosphate buffered saline (PBS). Large detectable impedance shift at the low frequency range was observed in an up-trend on antigen immobilization and antigen-antibody conjugation. The measured signal changes in impedance were attributed mainly to the dipole induced interfacial polarization potential at the film/biomolecules interface. Good and repeatable linear relationship was found between the electrical signal outputs and human IgG concentration in logarithm scale for a wide range of antibody concentrations. A detection limit of around 40 ng/mL was also observed. This BST-based immunosensor platform has proven to be effective and promising for biological detection.