Immunoglobulin G-Based Steric Hindrance Assay for Protein Detection

With the imminent needs of rapid, accurate, simple point-of-care systems for global healthcare industry, electrochemical biosensors have been widely developed owing to their cost-effectiveness and simple instrumentation. However, typical electrochemical biosensors for direct analysis of proteins in the human biological sample still suffer from complex biosensor fabrication, lack of general method, limited sensitivity, and matrix-caused biofouling effect. To resolve these challenges, we developed a general electrochemical sensing strategy based on a designed steric hindrance effect on an antibody surface layer. This strategy utilizes the interaction pattern of protein-G and immunoglobulin G (Fc and Fab regions), providing a steric hindrance effect during the target capturing process. The provided steric hindrance effect minimizes the matrix effect-caused fouling surface and altered the path of electron transfer, delivering a low-fouling and high-sensitivity detection of protein in complex matrices. Also, an enzyme-based horseradish peroxidase/hydroquinone/H₂O₂ transduction system can also be applied to the system, demonstrating the versatility of this sensing strategy for general electrochemical sensing applications. We demonstrated this platform through the detection of Tau protein and programming death ligand 1 with a subpico molar detection limit within 10 min, satisfying the clinical point-of-care requirements for rapid turnaround time and ultrasensitivity.