An electrode-separated piezoelectric immunosensor array with signal enhancement based on enzyme catalytic deposition of palladium nanoparticles and electroless deposition nickel-phosphorus

Abstract

A differential piezoelectric immunosensor array was reported with signal enhancement based on the biometallization of palladium nanoparticles (Pd NPs) and successive electroless deposition Ni-P layer. In this strategy, the primary antibody probes were immobilized on the aminated quartz surface in an electrode-separated piezoelectric sensor (ESPS). After bounding with the corresponding antigen and alkaline phosphatase (ALP) conjugated second antibody, the ALP in the sandwich-type immunocomplex can catalyze the substrate of p-aminophenyl phosphate to generate p-aminophenol, which reduces Pd(II) in solution to Pd NPs onto the quartz surface. A successive signal amplification was performed by Pd NPs- promoted catalytic electroless deposition of Ni-P layer. A differential measurement mode was employed to eliminate the influence of non-mass effects, including the changes in conductivity, viscosity, density and temperature of the solution, as well as the baselines draft of piezoelectric sensors. The responses of the differential ESPS in fundamental frequency, third and fifth overtones were compared. The proposed method was applied to the determination of human IgG with a detection limit of 1pg/mL. Compared with biometallization of Pd NPs, the sensitivity is enhanced further by three orders of magnitude due to high activation energy in Ni-P deposition reaction and low baseline draft in differential measurement mode.