Protein Biomarker Determination Using Versatile Sensing Platform from Electrografting from Diazonium Cations Into Polymelamine-Modified Electrodes

Protein biomarker detection has considerable potential applications in facilitating rapid, low-cost, point-of-care diagnostics. This can be achieved electrochemically via a redox active surface incorporating a recognition site. Polymelamine (pMel) films exhibit a reversible redox couple at a mild potential. Herein we report the fabrication of a pMel film and subsequent functionalization of the interface by the electrografting of a reactive diazonium-derived layer. This allowed for immobilization of protein recognition sites on the interface enabling the selective electrochemical detection of proteins by observing the attenuation of the pMel redox system. Bovine serum albumin and anti-asparaginase were detected in a linear range of 1–10,000 pM, with limits of detection of 0.42 and 0.32 pM, respectively. The latter is a biomarker of clinical importance in the monitoring of chemotherapy treatment—with its detection demonstrated within the clinically relevant concentration range. The sensor response time was 25 minutes, with the results reproducible over three independent electrodes for each target. Sensor construction was verified using voltammetry, electrochemical impedance spectroscopy, x-ray photoelectron spectroscopy, and scanning electron microscopy. Signal transduction of the sensing interface was observed voltametrically, through attenuation of the pMel redox couple. The versatile, novel, and simple strategy outlined herein can be applied to produce pMel interfaces functionalized with a wide range of functionalities to tailor the interfaces for specific sensing applications.