Free-standing electrochemical biosensor for carcinoembryonic antigen detection based on highly stable and flexible conducting polypyrrole nanocomposite

A flexible free-standing electrochemical biosensor to detect carcinoembryonic antigen (CEA) is described based on a conducting polypyrrole (PPy) nanocomposite film electrode. The conducting PPy composite was constructed by the sandwiched structure formed by PPy doped with pentaerythritol ethoxylate (PEE) and 2-naphthalene sulfonate (2-NS-PPy) separately via electropolymerization. Gold nanoparticles (AuNPs) were fixed on the PPy composite film by electrodeposition and then connected to CEA aptamer through self-assembly to construct a free-standing electrochemical biosensor breaking away from additional soft substrates and current collector. This PPy composite film-based electrochemical biosensor exhibits satisfying sensing performance for CEA detection, with a linear range from 10(-10) g/mL to 10(-6) g/mL and a detection limit of 0.033 ng/mL, good specificity and long-term sensing stability (96.8% of the original signal after 15 days). The biosensor also presents acceptable reproducibility with 1.7% relative standard deviation. Moreover, this electrochemical biosensor owns the deformation stability that could bear various deformations (twisting, folding, and knotting) without affecting device's sensing performance. It can even maintain 99.4% of the original signal under 25% strain deformation. Due to the superior sensing performance, high stability (mechanical deformation and long-term storage), and flexibility, this free-standing electrochemical biosensor proves huge potential in application of flexible and wearable electronics.