An enzyme-free ultrasensitive electrochemical immunosensor for calprotectin detection based on PtNi nanoparticles functionalized 2D Cu-metal organic framework nanosheets

In this work, a novel high electro-catalytic material was synthesized using PtNi nanospheres to functionalize two-dimensional (2D) ultrathin Cu-TCPP(Fe) nanosheets (PtNi@Cu-TCPP(Fe)), and was further applied to develop an enzyme-free electrochemical immunosensor for the ultrasensitive determination of calprotectin (CALP). The bimetallic Cu-TCPP(Fe) nanosheets with large surface area and massive accessible active sites permitted multiple PtNi to attach their surface, which not only enhanced the catalytic ability and conductivity for nonenzymatic amplification but also provided the modified active sites for antibody immobilization as signal labels. Upon the dual electro-catalytic activity of Cu-TCPP(Fe) and PtNi towards H2O2 reduction for signal amplification, this proposed sandwich CALP immunosensor exhibited a wide linear range of 200 fg mL(-1)similar to 50 ng mL(-1) and a low detection limit of 137.7 fg mL(-1). The functionalized MOF nanosheets-based biosensing method offered an enzyme-free signal amplification strategy, which provided great promise for further bioanalysis and clinical study.