Ultrasensitive label-free electrochemical immunoassay of carbohydrate antigen 15-3 using dendritic Au@Pt nanocrystals/ferrocene-grafted-chitosan for efficient signal amplification

The introduction of advanced nanocrystals and mediator is crucial for signal amplification of electrochemical immunosensors due to trace amounts of analytes in real samples. Herein, a novel ultrasensitive label-free electrochemical immunosensor was constructed to monitor carbohydrate antigen 15-3 (CA15-3) based on dendritic Au@Pt core-shell nanocrystals (Au@Pt NCs) uniformly dispersed with ferrocene-grafted-chitosan (Fc-g-CS), where Au@Pt NCs were prepared with hexadecyldimethyl benzyl ammonium chloride (HDBAC) as the growth-directing agent via a simple one-pot wet-chemical strategy. More notably, Fc grafted with CS would dramatically improve the stability and the Fc-g-CS enlarged specific surface area and behaved as dispersing agent for the Au@Pt NCs to greatly boost the electrochemical signals and improve the biocompatibility. The resulting immunosensor displayed wider linear range of 0.5-200 U mL(-1) and lower detection limit of 0. 17 U mL(-1), which was further explored for detecting CA15-3 in serum sample with highly acceptable results.