A novel competitive electrochemical impedance biosensor for the ultrasensitive detection of umami substances based on Pd/Cu-TCPP(Fe)

•A competitive impedance biosensor was first developed for detecting MSG.•The composite signal probe was Pd/Cu-MOF combined with T1R1.•Quadruple signal amplification was applied for impedance signals acquisition.•Simple enzyme-free analysis was attained with a portable screen-printed electrode. The development of biosensors capable of assessing umami intensity has elicited significant attention. However, the detection range of these biosensors is constrained by the sensing components and strategies used. In this study, we introduce a novel competitive, ultra-high-sensitivity electrochemical impedance biosensor by utilizing composite nanomaterials and T1R1 as a composite signal probe. Pd/Cu-TCPP(Fe) had a substantial surface area, effectively enhancing the loading capacity of the T1R1 and thus augmenting the biosensor's recognition precision. Furthermore, the Pd/Cu-TCPP(Fe) elevated peroxidase-like activity catalyzed the formation of insoluble precipitates of 4-CN, resulting in cascaded amplification of the impedance signal. The remarkable catalytic activity of the composite signal probe endowed the biosensor with exceptional analytical performance, featuring a detection limit of 0.86 pg/mL and a linear detection range spanning from 10 to 10000 pg/mL. Successful application of the biosensor for umami substance detection in fish was also demonstrated, signifying its substantial potential in food-flavor evaluation.