Multifunctionalized ZIFs nanoprobe-initiated tandem reaction for signal amplified electrochemical immunoassay of carbohydrate antigen 24-2

Based on multifunctionalized zeolitic imidazolate frameworks (ZIFs)-initiated cascade reaction triggered signal amplification strategy, a novel sandwich-type amperometric immunosensor was constructed for ultrasensitive detection of carbohydrate antigen 24-2 (CA 242). The methylene blue-glucose oxidase-ZIF-8/reduced graphene oxide-Au (MB-GOx-ZIF-8/Au-rGO) was synthesized by a facile coprecipitation method for enzyme immobilization and redox species loading. The multifunctionalized ZIFs conjugated with labeling antibodies were employed as immunoprobe. In the presence of glucose, tandem reaction was driven by the immunoprobe to catalyze the glucose oxidation to yield H2O2. Simultaneously, the generated H2O2 induced the decomposition of poly(anilineboronicacid) (PABA)/poly(vinyl alcohol) (PVA) films on substrate, which made the PVA chains breaking away from PABA polymer. Due to the poor conductivity of PVA chains, this decomposition reaction can amplify the current signal. The current difference (ΔI) caused by per unit concentration target with tandem reaction amplification was elevated prominently, resulting in ultrasensitive analytical performance of the immunosensor. Under optimal conditions, the proposed immunosensor displayed wide linear range from 0.001 to 1000 U mL−1 with an ultralow limit of detection 69.34 μU mL−1 (S/N = 3). This method successfully implemented functionalized ZIFs in immunoprobe construction for sensitivity amplification, providing a promising strategy to construct ultrasensitive immunosensing platform for analysis of other tumor marker.