A novel in-house built printed circuit board-ceria based electrochemical device for rapid detection of Epithelial Sodium Channel (ENaC), a hypertension biomarker

The Epithelial Sodium Channel (ENaC) is a protein that plays a role in the cellular intake of salt and is known as one of the biomarkers for hypertension in the human body. Higher concentrations of sodium lead to increased activity of the ENaC protein in sodium absorption. In this study, a self-made immunosensor was developed using a homemade Printed Circuit Board-Screen Printed Carbon Electrode (PCB-SPCE) modified with cerium oxide. Anti-ENaC was immobilized on the surface of PCB-SPCE/ceria at pH 7.4, relying on the interaction between carboxyl groups of anti-ENaC and cerium oxide to detect the ENaC protein. Additionally, a portable in-house potentiostat named “UnpadStat” was developed for integration with the immunosensor. UnpadStat features a 5-in. touch screen display to showcase measurement data. Cyclic voltammetry measurements using the redox system of K₃[Fe(CN)₆] were applied to bare PCB-SPCE, PCB-SPCE/Ceria, PCB-SPCE/Ceria/Anti-ENaC, and PCB-SPCE/Ceria/Anti-ENaC/ENaC. Measurement results indicated an increase in current after modification with cerium, reaching 73.805 µA compared to unmodified (63.256 µA). After anti-ENaC immobilization, there was a decrease in current to 64.456 µA, and upon binding with the ENaC protein, a further decrease in current occurred, corresponding to the concentration of the ENaC protein. The detection limit obtained in this study was 0.133 ng/mL, and the quantification limit was 0.444 ng/mL for the concentration range of ENaC protein from 0.375 ng/mL to 6.0 ng/mL. The integration of the PCB-based immunosensor and UnpadStat can be utilized to determine the levels of ENaC protein in non-hypertensive urine samples and hypertensive patients.