Ultra-sensitive electrical immunoassay biosensors using nanotextured zinc oxide thin films on printed circuit board platforms

• An electrical sensor is presented that detects troponin-T at 10 fg/mL.
• Enhanced detection was accomplished using impedance spectroscopy with nanotextured ZnO films.
• Columnar growth of ZnO provides physical confinement for molecules.
• A thiol cross-linker was used to functionalize immunoassays to Zn-terminated sites.
• ZnO films grown under argon plasma without oxygen show enhanced biosensing.

This study demonstrates the development of nanotextured zinc oxide (ZnO) thin films sputter deposited on printed circuit boards (PCB) to enhance the capability in detecting low concentrations of the protein troponin-T. The presence of this particular biomarker in the bloodstream is a direct indicator of current and/or future risk of various forms of cardiovascular diseases. Electrical transduction through impedance spectroscopy was used to detect troponin-T functionalized immunoassays on nanotextured ZnO surfaces. Calibration of the immunoassay was performed by measuring the impedance changes resulting from the binding of increasing concentrations of troponin-T to the immobilized antibodies on the ZnO surface in (i) phosphate buffered saline (PBS) and (ii) human serum. The limit of detection achieved using this platform was 10 fg/mL and 100 fg/mL in PBS and human serum, respectively. Enhanced detection of troponin-T was found to correlate to the oxygen vacancies in the ZnO thin film. PCB was chosen as the substrate for ease of integration with microelectronic device manufacturing.