Enzyme-nanoparticle conjugates at oil-water interface for amplification of electrochemical immunosensing

In the current research, the preparation of biocatalytic capsule (Ab(2)-catalytic capsule) was based on utilizing oil (organic compound) to entrap the nano-Au/HRP/HAFP bioconjugates, which were produced by horseradish peroxidase (HRP) and HAP labeled anti-AFP (HAFP) co-conjugated on gold nanoparticles (nano-Au). For the first time, a signal amplification strategy was introduced by the prepared biocatalytic capsule as labels for electrochemical immunodetection of alpha-1-fetoprotein (AFP). The transmission electron microscopy (TEM) images indicated that the biocatalytic capsules were successfully synthesized. The cyclic voltammetry (CV) experiments provided the evidence that the prepared capsule exhibited high catalytic activity for the reduction of H2O2. Besides, a biocompatible monolayer (collagen-TiO2) was introduced to immobilize a nano-Au layer to fabricate the primary antibody on the electrode surface. After the prepared biocatalytic capsule was captured to the electrode surface to form the sandwich type immunoassay, the enhanced sensitivity was obtained with a detection limit of 29 pg/mL The proposed immunoassay also presented good stability, selectivity and storage stability. (C) 2012 Elsevier B.V. All rights reserved.