Preparation of a pH-responsive controlled-release electrochemical immunosensor based on polydopamine encapsulation for ultrasensitive detection of alpha-fetoprotein.

To accomplish ultra-sensitive detection of alpha-fetoprotein(AFP), a novel electrochemical immunosensor using polydopamine-coated Fe3O4 nanoparticles (PDA@Fe3O4 NPs) as a smart label and polyaniline (PANI) and Au NPs as substrate materials has been created. The sensor has the following advantages over typical immunoassay technology: (1) The pH reaction causes PDA@Fe3O4 NPs to release Prussian blue (PB) prosoma while also destroying the secondary antibody label and immunological platform and lowering electrode impedance; (2) PB has a highly efficient catalytic effect on H2O2, allowing for the obvious amplification of electrical impulses; (3) PANI was electrodeposited on the electrode surface to avoid PB loss and signal leakage, which effectively absorbed and fixed PB while considerably increasing electron transmission efficiency. The sensor's detection limit was 0.254 pg·mL-1 (S/N = 3), with a detection range of 1 pg·mL-1 to 100 ng·mL-1. The sensor has a high level of selectivity, repeatability, and stability, and it is predicted to be utilized to detect AFP in real-world samples.